July 2011
Volume 52, Issue 8
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Clinical and Epidemiologic Research  |   July 2011
What Is Causing Active Trachoma? The Role of Nonchlamydial Bacterial Pathogens in a Low Prevalence Setting
Author Affiliations & Notes
  • Matthew J. Burton
    From the Department of Clinical Research and
    Kilimanjaro Centre for Community Ophthalmology and
  • Victor H. Hu
    From the Department of Clinical Research and
    Kilimanjaro Centre for Community Ophthalmology and
  • Patrick Massae
    Kilimanjaro Centre for Community Ophthalmology and
  • Sarah E. Burr
    From the Department of Clinical Research and
    Medical Research Council Laboratories, Fajara, The Gambia.
  • Caroline Chevallier
    Biotechnology Laboratory, Kilimanjaro Christian Medical Centre, Moshi, Tanzania; and
  • Isaac A. Afwamba
    Biotechnology Laboratory, Kilimanjaro Christian Medical Centre, Moshi, Tanzania; and
  • Paul Courtright
    Kilimanjaro Centre for Community Ophthalmology and
  • Helen A. Weiss
    MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom;
  • David C. W. Mabey
    From the Department of Clinical Research and
  • Robin L. Bailey
    From the Department of Clinical Research and
  • Corresponding author: Matthew J. Burton, International Centre for Eye Health, Department of Clinical Research, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom; matthew.burton@lshtm.ac.uk
Investigative Ophthalmology & Visual Science July 2011, Vol.52, 6012-6017. doi:10.1167/iovs.11-7326
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      Matthew J. Burton, Victor H. Hu, Patrick Massae, Sarah E. Burr, Caroline Chevallier, Isaac A. Afwamba, Paul Courtright, Helen A. Weiss, David C. W. Mabey, Robin L. Bailey; What Is Causing Active Trachoma? The Role of Nonchlamydial Bacterial Pathogens in a Low Prevalence Setting. Invest. Ophthalmol. Vis. Sci. 2011;52(8):6012-6017. doi: 10.1167/iovs.11-7326.

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      © 2015 Association for Research in Vision and Ophthalmology.

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Abstract

Purpose.: In low prevalence settings, clinically active follicular trachoma (TF) is often found in the absence of detectable Chlamydia trachomatis. The reasons for this persistent follicular phenotype are not well understood; one possible explanation is that other bacterial species are provoking the inflammatory response. This study investigated the relationship between TF, C. trachomatis, and nonchlamydial bacterial infection.

Methods.: A cross-sectional survey was conducted in a trachoma endemic village in Tanzania. All available children were examined for trachoma and swabs were collected for microbiologic culture (blood and chocolate agar) and C. trachomatis PCR (Amplicor).

Results.: Four hundred seventy-three children under 10 years of age were recruited for this study. The prevalences of TF and C. trachomatis were 13.7% and 5.3%, respectively, and were not associated. Bacteria were cultured from 305 (64.5%) swab samples; 162 (34.3%) grew a pathogen (with or without a commensal organism) and 143 (30.2%) grew commensal bacteria only. The most common pathogens were Streptococcus pneumoniae and Haemophilus influenzae (type B and non–type B). The presence of bacterial pathogens was associated with TF (odds ratio, 4.68; 95% confidence interval, 2.31–9.50; P < 0.001).

Conclusions.: In regions with low levels of endemic trachoma, it is possible that much of the TF that is observed is attributable to nonchlamydial bacterial pathogens. It is plausible that individuals who have previously developed a follicular conjunctivitis in response to C. trachomatis may more readily reform conjunctival follicles when challenged with certain other bacterial species.

Trachoma remains a leading cause of blindness in many of the world's poorest regions. 1 It is caused by the obligate intracellular bacterium Chlamydia trachomatis, and is characterized by episodes of recurrent, chronic follicular conjunctivitis. In some individuals, this inflammation results in progressive scarring of the tarsal conjunctiva, leading to the blinding complications of trichiasis and corneal opacification. 
The control of blinding trachoma focuses on the implementation of the surgery, antibiotics, facial cleanliness, and environmental improvement (SAFE) strategy. 2 Current World Health Organization (WHO) guidelines recommend annual mass drug administration (MDA) with oral azithromycin or topical tetracycline for 3 years to entire communities where the prevalence of trachomatous inflammation–follicular (TF; Simplified WHO Trachoma Grading System 3 ) in children 1 to 9 years of age (TF%1–9) is greater than 10%. 2 However, it has been recognized for some time that in low prevalence settings, the relationship between the signs of TF and the detection of C. trachomatis infection is variable and at times very weak. 4 7 This relationship becomes even less consistent after the introduction of antibiotic control programs. 8 10  
The discordance between disease and chlamydial infection is an increasingly important issue for trachoma control programs as the prevalence of trachoma declines. When deciding to initiate or stop MDA, programs currently have no practical alternative to assessing the prevalence of clinical signs of active trachoma. There are probably several factors that contribute to the mismatch in signs and infection. First, the temporal sequence for these two events differs: infection probably starts and finishes before the inflammatory response, which can persist for many weeks after the resolution of infection. 11 At a population level, the prevalence of TF appears to take very much longer to decline after the initiation of MDA than the prevalence of chlamydial infection. 8 10 It has been found to stay above the 10% TF treatment threshold for months or years in the absence of detectable chlamydial infection. Second, there are other recognized causes of a follicular conjunctivitis, such as other bacteria and certain viruses. It is plausible that, in an individual who has previously developed a follicular response to C. trachomatis, subsequent nonchlamydial infections causing conjunctival inflammation might be more likely to elicit a follicular reaction that mimics TF. 
To investigate the relationship between the signs of TF and C. trachomatis and other bacterial species, we conducted a cross-sectional survey of the children living in a trachoma-endemic community, relating the clinical phenotype to laboratory evidence of infection. 
Methods
Ethical Approval
This study adhered to the tenets of the Declaration of Helsinki. It was approved by the Tanzanian National Institute of Medical Research Ethics Committee, the Kilimanjaro Christian Medical Centre Ethics Committee, and the London School of Hygiene and Tropical Medicine Ethics Committee. The study was explained to the parents/guardians of potential study subjects. Informed consent was documented in writing by the parent/guardian on behalf of each child before recruitment. 
Study Participants
The study was conducted in a single village in Siha District, Kilimanjaro Region, Northern Tanzania. We carried out a census of the village. All children under 10 years of age who were present and for whom consent was given were enrolled into the study. This district had never received MDA for trachoma control. 
Clinical Assessment and Sample Collection
The left eye of each subject was examined by a single ophthalmologist (MJB) using 2.5× loupes and a bright torch. Clinical signs were graded using the 1981 WHO Trachoma Grading System (FPC). 12 Clinically active trachoma was defined as the presence of either a follicular score of 2 or 3 (F2/3) or a papillary score of 3 (P3), equivalent to TF and trachomatous inflammation–intense (TI) of the WHO Simplified Trachoma Grading System, respectively. 3 The conjunctiva was anesthetized with preservative-free proxymetacaine 0.5% eye drops (Minims; Chauvin Pharmaceuticals, Surrey, UK). A rayon-tipped swab sample was collected from the inferior fornix, placed immediately into Amies–charcoal transport media (Sterilin, Caerphilly, UK) and kept at ambient temperature until processing in the laboratory later the same day. A second, Dacron polyester–tipped swab (Hardwood Products Company, Guilford, Maine) was collected from the left upper tarsal conjunctiva for the detection of C. trachomatis in a standardized manner (passed firmly four times across the conjunctiva with a quarter turn between each pass). The samples for PCR were kept on ice packs until transfer to a –80°C freezer later the same day for storage until processing. The examiner changed gloves before examining and collecting swabs from each child. “Negative field controls” were collected after every 50 subjects by passing the swab through the air a few centimeters in front of a seated study subject. The village was mass treated with single dose oral azithromycin immediately after the survey. 
Laboratory Tests
Microbiology testing was performed at the KCMC Biotechnology Laboratory, Moshi, Tanzania. Microbiology samples were inoculated onto blood and chocolate agar later the same day (usually <6 hours from the collection time) and incubated at 37°C for 48 hours. Culture isolates were identified by standard microbiologic techniques. Testing for C. trachomatis by PCR was performed at the MRC Laboratories, Gambia; samples were transferred there on dry ice. DNA was extracted from the dry swab using an isolation kit (QIAmp DNA mini kit; Qiagen, Crawley, UK). C. trachomatis was detected using a test kit (Amplicor CT/NG kit; Roche Molecular Systems, Branchburg, NJ), with previously described modifications. 5,13  
Data Analysis
Data were entered into a database (Access 2007; Microsoft, Redmond, WA) and analyzed using software (STATA, v 11.0; StataCorp LP, College Station, TX). A nonparametric test for trend was used to examine the relationship between bacterial culture results and the ordered categories of follicular and papillary inflammation severity. χ2 tests were used to determine strength of association for individual bacterial isolates with the TF status, with an exact test used if there were fewer than five expected events in a cell. Odds ratios (ORs) and 95% confidence intervals (CIs) for the univariate associations between TF and each factor were estimated using logistic regression, and P values were estimated using likelihood ratio tests. Factors associated with TF (P < 0.10) were included in a multivariable logistic regression model. Age was considered an a priori confounder because of the known association with TF. Staphylococcus epidermidis, Corynebacterium spp., viridans group streptococci, and Bacillus spp. were designated as commensal organisms for the purposes of this analysis. 
Results
Study Participants and Samples
A total of 700 children under 10 years of age were recorded as living in the study village at the time of this survey. We were able to examine 571 (81.5%) children. Of the 129 children not examined, 58 (45%) had traveled away, 29 (23%) refused, 25 (19%) were too young, and 17 (2%) were not found despite several visits. Bacteriology and C. trachomatis PCR samples were collected from 484 (84.8%) and 557 (97.5%) of the 571 children who were examined, respectively. Both bacteriology and C. trachomatis PCR results were available on a total of 473 of 571 (82.8%) children. Comparing the 473 children for whom results were obtained and all the other 227 children living in the village, there was no difference in either the mean age (P = 0.92) or the proportion who were of male sex (47.6%; P = 0.20). The 98 children who were examined but did not have both microbiology and chlamydial PCR results were slightly older (5.8 vs. 5.0 years; P = 0.01); the proportion that was male was comparable (P = 0.13). All subsequent analyses are limited to the 473 children with both laboratory results. 
Clinical Signs and C. trachomatis Infection
TF was diagnosed in 65 (13.7%) children. The frequencies of the FPC Grading System follicular (F) and papillary (P) inflammation scores are shown in Table 1. C. trachomatis DNA was detected by Amplicor PCR in 25 (5.3%) samples. The frequency of PCR positive samples by clinical grade is shown in Table 1. There was no association between the presence of TF and the detection of C. trachomatis (OR, 1.21; 95% CI, 0.40–3.64; P = 0.74). All “negative field controls” tested negative by Amplicor C. trachomatis PCR. 
Table 1.
 
Clinical Disease and C. trachomatis Infection
Table 1.
 
Clinical Disease and C. trachomatis Infection
Follicular Inflammation Papillary Inflammation
n (%) Infected (%)* n (%) Infected (%)*
FPC score FPC score
    F0 323 (68.3) 13 (4.0)     P0 372 (78.6) 16 (4.3)
    F1 85 (18.0) 8 (9.4)     P1 69 (14.6) 5 (7.3)
    F2 35 (7.4) 2 (5.7)     P2 26 (5.5) 4 (15.4)
    F3 30 (6.3) 2 (6.7)     P3 6 (1.3) 0 (0.0)
TF TI
    No 408 (86.3) 21 (5.1)     No 467 (98.7) 25 (5.4)
    Yes 65 (13.7) 4 (6.1)     Yes 6 (1.3) 0 (0.0)
Conjunctival Bacterial Culture
Bacteria were cultured and identified from 305 (64.5%) swab samples, of which 162 (34.3%) grew a pathogen (with or without a commensal organism) and 143 (30.2%) grew commensal bacteria only. A wide range of organisms was cultured (Table 2). Double infections were found in 107 and triple infection in 20 eyes. Only 11 of these involved combinations of the more common pathogenic organisms. There was no significant difference between the three bacterial infection categories (no growth, commensal only, and pathogen) in the proportion of eyes with C. trachomatis detected (P = 0.21). 
Table 2.
 
Bacteria Cultured from Conjunctival Swabs
Table 2.
 
Bacteria Cultured from Conjunctival Swabs
Name All Eyes (n = 473) No TF (n = 408) TF (n = 65) P *
n (%) n (%) n (%)
Commensal organisms
    Viridans group streptococcus 153 (32.4) 131 (32.1) 22 (33.9) 0.78
    Staphylococcus epidermidis 70 (14.8) 61 (14.9) 9 (13.8) 0.82
    Corynebacterium spp. 45 (9.5) 40 (9.8) 5 (7.7) 0.59
    Bacillus spp. 8 (1.7) 8 (2.0) 0 (0.0) 0.26
Pathogenic organisms
    Streptococcus pneumoniae 48 (10.2) 34 (8.3) 14 (21.5) 0.001
    Haemophilus influenzae, type B 66 (14.0) 50 (12.6) 16 (24.6) 0.008
    Haemophilus influenzae, non–type B 43 (9.1) 28 (6.9) 15 (23.1) <0.001
    Micrococcus spp. 8 (1.7) 8 (2.0) 0 (0.0) 0.30
    Moraxella catarrhalis 3 (0.6) 3 (0.7) 0 (0.0) 1.00
    Haemophilus parainfluenza 2 (0.4) 2 (0.5) 0 (0.0) 1.00
    Branhamella catarrhalis 2 (0.4) 2 (0.5) 0 (0.0) 1.00
    Neisseria spp. 1 (0.2) 1 (0.3) 0 (0.0) 1.00
    Enterobacter spp. 1 (0.2) 1 (0.3) 0 (0.0) 1.00
    Klebsiella spp. 1 (0.2) 1 (0.3) 0 (0.0) 1.00
Clinical Signs and Bacterial Infection
Pathogenic bacteria were grown from samples from 61.1% of eyes with TF compared to 29.9% of eyes without TF. There was no difference in the proportion of eyes with or without TF that had commensal bacteria (Table 2). Streptococcus pneumoniae, Haemophilus influenzae type B, and Haemophilus influenzae non–type B were significantly more frequent in eyes with TF (Table 2). There was an increasing trend in the proportion of eyes with bacterial pathogens cultured with increasing FPC follicular score (P < 0.001; Table 3). There was a similar but less marked increase for FPC papillary inflammation (Table 3). There were also significant univariate associations between TF and being younger than 3 years of age and with having pathogenic bacteria cultured (Table 4). In a multivariable logistic regression model, S. pneumoniae, H. influenzae type B, and H. influenzae non–type B were all independently associated with TF (Table 5). 
Table 3.
 
Clinical Signs of Trachoma and Type of Conjunctival Bacterial Isolates
Table 3.
 
Clinical Signs of Trachoma and Type of Conjunctival Bacterial Isolates
Follicular Inflammation Papillary Inflammation
No Growth Commensal Pathogen No Growth Commensal Pathogen
n (%) n (%) n (%) n (%) n (%) n (%)
FPC score FPC score
    F0 130 (40.3) 99 (30.7) 94 (29.1)     P0 145 (39.0) 114 (30.7) 113 (30.4)
    F1 27 (31.8) 30 (35.3) 28 (32.9)     P1 16 (23.2) 21 (30.4) 32 (46.4)
    F2 6 (17.1) 7 (20.0) 22 (62.9)     P2 6 (23.1) 6 (23.1) 14 (53.9)
    F3 5 (16.7) 7 (23.3) 18 (60.0)     P3 1 (16.7) 2 (33.3) 3 (50.0)
TF TI
    No 157 (38.5) 129 (31.6) 122 (29.9)     No 167 (35.8) 141 (30.2) 159 (34.0)
    Yes 11 (17.0) 14 (21.5) 40 (61.5)     Yes 1 (16.7) 2 (33.3) 3 (50.0)
Table 4.
 
Univariate Associations with Trachomatous Inflammation-Follicular
Table 4.
 
Univariate Associations with Trachomatous Inflammation-Follicular
Variable OR 95% CI P *
Sex, female 1.33 0.79–2.26 0.28
Age group, y
    0–3 1 0.06
    4–6 0.68 0.37–1.25
    7–10 0.46 0.23–0.90
Chlamydia trachomatis 1.21 0.40–3.64 0.74
Bacterial infection
    None 1.00 <0.001
    Commensal only 1.54 0.68–3.53
    Pathogen 4.68 2.31–9.50
Bacterial species
    Viridans group streptococcus 1.08 0.62–1.88 0.78
    Staphylococcus epidermidis 0.91 0.43–1.94 0.81
    Corynebacterium spp. 0.77 0.29–2.02 0.58
    Streptococcus pneumoniae 3.02 1.52–6.01 0.003
    Haemophilus influenzae, type B 2.34 1.24–4.42 0.01
    Haemophilus influenzae, non–type B 4.07 2.04–8.14 <0.001
Table 5.
 
Multivariable Logistic Regression Model for Trachomatous Inflammation-Follicular
Table 5.
 
Multivariable Logistic Regression Model for Trachomatous Inflammation-Follicular
Variable OR 95% CI P *
Age group, y
    0–3 1 0.25
    4–6 0.80 0.42–1.52
    7–10 0.66 0.33–1.35
Bacterial species
    Streptococcus pneumoniae 3.22 1.56–6.66 0.003
    Haemophilus influenzae, type B 2.92 1.47–5.81 0.003
    Haemophilus influenzae, non-type B 5.34 2.57–11.3 <0.001
Discussion
In this study, the prevalence of TF%1–9 was relatively low (13.7%) but was still above the 10% treatment threshold for initiating community level MDA. 2 An additional 18% of the children in this population had a mild follicular conjunctivitis (FPC grade F1). The prevalence of C. trachomatis detected by Amplicor PCR was lower (5.3%) than the prevalence of TF. Overall, we found no association between the signs of active trachoma and chlamydial infection in this community. These observations are consistent with findings from other low prevalence settings and illustrate the difficulty control programs face in determining where to invest resources to distribute antibiotic for trachoma control. 6 9 The weak relationship between the signs of active trachoma and C. trachomatis infection is likely to lead to many communities receiving unnecessary antibiotic treatment. In regions with an initially higher prevalence of disease and chlamydial infection, the relationship between the two weakens markedly after the initiation of MDA. 10  
To develop rational strategies for managing MDA in low and medium prevalence settings, it is necessary to have a better understanding of the causes of follicular conjunctivitis in trachoma endemic communities. Probably part of the explanation for the discordance between episodes of active disease and C. trachomatis infection is their different time course. 11,14 Follicles in children can persist for weeks or months after the chlamydial infection is no longer detectable. In low prevalence settings, C. trachomatis infection prevalence is often so low that it is difficult to imagine that this alone is sufficient to sustain a prevalence of TF above the treatment threshold, and other factors may contribute. 7  
In this population-based survey, we examined the potential contribution of nonchlamydial bacterial species to the presence of a “TF” phenotype. In contrast to C. trachomatis, nonchlamydial bacteria were frequently cultured from the conjunctiva of children. The range of organisms included some that are generally considered commensal and others normally considered to be pathogens. We found no association between the presence of TF and the presence of a commensal organism alone. However, we did find a clear association between TF and pathogenic bacteria, specifically S. pneumoniae and H. influenzae. There was no significant difference in the frequency of bacterial pathogens between individuals with no follicles (F0) and those with very few follicles, below the diagnostic threshold for TF (F1). 
There are little published data on the normal conjunctival bacterial flora in children in Africa. The only recent study comes from a village in Sierra Leone, a country that does not have endemic trachoma, which tested people of all ages. 15 This study found 86% had positive cultures (S. epidermidis 28%, S. aureus 20%, P. aeruginosa 6%, Klebsiella 4%, and H. influenzae 2%). However, there were a number of differences in the range and relative frequencies of organisms cultured in these two studies. For example, the study from West Africa did not identify any S. pneumoniae and only relatively few H. influenzae. These differences could be attributable to differences in sample collection and processing (performed in the United States), population demographics (only 16% under 18 years of age), and the environment (more humid) in the Sierra Leonean study. 
A number of studies have investigated bacterial infection in children living in trachoma-endemic regions (Table 6). 16 21 However, these were mostly conducted before the development of sensitive PCR-based techniques for C. trachomatis detection and the current trachoma grading systems. 3,12 In addition, a number of methodologic variations make it difficult to draw definite conclusions about the contribution of other bacteria to follicular conjunctivitis in trachoma-endemic environments. Several studies were not population-based, only including cases with active trachoma or with a limited selection of unaffected individuals. 16,17,20 Two studies present microbiology results based on microscopy alone (no culture performed). 18,20 In these earlier studies, the range of organisms identified by culture was generally similar to those we found, albeit with some differences in the relative frequency. In the most methodologically comparable studies to ours, S. pneumoniae and H. influenzae were prominent among the pathogens. 16,19,21 In two studies, it is possible to partially evaluate the relationship between active trachoma and bacterial infection. 16,17 In the larger of these, reanalysis of the available data suggests a significant association between active trachoma and conjunctival pathogens, when compared to normal healthy controls. 16 Surprisingly, the authors reached the opposite conclusion—that individuals with trachomatous conjunctivitis were no more likely to grow a pathogen than controls. However, in their analysis, they included within the control group a large number of individuals with “simple bacterial conjunctivitis,” which added to the number of pathogens identified in the control group and probably should not have been regarded as clinically normal. 
Table 6.
 
Studies of Conjunctival Bacterial Infection in Children in Trachoma Endemic Communities
Table 6.
 
Studies of Conjunctival Bacterial Infection in Children in Trachoma Endemic Communities
Country (Year) Study Population and Design Findings Comments
Taiwan (1962) 16 Three separate trachoma endemic areas; conjunctival swab samples from preschool and first-grade children; about half had active trachoma; cultured (blood and chocolate agar) Culture positive; normal, 42/144 (29%); active trachoma, 74/201 (37%); organisms: Staphylococcus pneumoniae, 15.6%; α-streptococci, 11.6%; Haemophilus, 6.4%; Staphylococcus spp., 5.0% Sampling frame not specified, drawn from a number of different settings; variation of MacCallan's trachoma grading system used, making it difficult to relate to current clinical grades (to derive an approximation to active trachoma, Tr-D, Tr-I Tr-II, Tr-III, and CFC have been combined here); no Chlamydia trachomatis test data presented; reanalysis of the data suggests a significant association between active trachoma and bacterial infection (OR, 2.58; 95% CI, 1.6–4.0; P < 0.0010)
USA (1967) 17 School children (140) enrolled in a treatment trial for active trachoma; cultured (blood agar); microbiology results from before and after treatment combined Culture positive; normal/Tr-4, 41%, and Tr-I, Tr-II, and Tr-III, 43% Sampling frame not specified; MacCallan's trachoma grading system used; microbiology results from before and after treatment combined; no C. trachomatis test data presented.
Morocco (1968) 18 Sample from 16 communities enrolled in a trachoma control study; in each community, 160–180 children 0–8 years of age were randomly selected; conjunctival scrapings were Gram stained; no culture Positive slide: Haemophilus, 81%; Moraxella, 20%; S. pneumoniae, 19% MacCallan's trachoma grading system used; denominator not stated; no C. trachomatis test data presented; no analysis of bacterial infection in relation to active trachoma
Tunisia (1974) 19 Two villages—(A) 151 children 6–9 years with active trachoma; (B) 44 children <15 years, randomly selected; conjunctival swab (cultured blood agar); conjunctival smear, Giemsa stain for chlamydial inclusions Culture positive: S. viridans, 65%; Diphtheroids, 52%; Haemophilus spp., 40%; S. epidermidis, 13% The number of children contributing data to the reported culture results was 277, and this is higher than the 195 children described in the subject description; the age and clinical status of the additional 82 children is not presented; Haemophilus was found to be the major cause of mucopurulent conjunctivitis; no analysis of bacterial infection in relation to active trachoma
Tunisia (1975) 20 Single village—151 children initially having active trachoma were enrolled into a treatment trial; conjunctival scraping with Giemsa staining; no culture; each child had both eyes sampled on three occasions Results of 927 slides presented; slides positive for bacteria: 48% (Haemophilus, 25% and Moraxella, 16%) Difficult to interpret, because multiple data from both eyes are presented together; no analysis of bacterial infection in relation to active trachoma
Nepal (1999) 21 Single village—122 children 1–10 years of age; conjunctival swab (cultured blood agar) Active trachoma in 38%; S. pneumoniae, 22%; Haemophilus spp., 7%; Moraxella, 16% The focus of this study was the change in bacterial antibiotic sensitivity patterns after azithromycin treatment; no C. trachomatis test data presented; no analysis of bacterial infection in relation to active trachoma
We have previously found that individuals with established trichiasis and conjunctival scarring are more likely to have nonchlamydial bacterial infections. 22 24 This is often associated with a marked clinically apparent inflammatory reaction in the conjunctiva in the absence of detectable C. trachomatis infection. 22 In addition, after trichiasis surgery, individuals with bacterial infection had significantly increased expression of various factors that could plausibly be involved with the scarring process (interleukin-1β, tumor necrosis factor–α, and matrix metalloproteinases-1 and -9). 25 This raises the possibility that these other bacteria could contribute to stimulating progressive cicatricial disease in conjunctiva that has previously been damaged by the immune response to C. trachomatis
This study, from an area with low prevalence trachoma, indicates the potential importance of nonchlamydial bacterial pathogens in the production of a follicular phenotype. The possibility of reverse causality in the association between bacterial pathogens and follicular conjunctivitis (namely, that eyes with TF are more susceptible to being infected with bacteria) cannot be ruled out in a cross-sectional study. However, even if this is part of the explanation for the observed association, it remains probable that these other bacteria contribute to the inflammatory response. It has long been recognized that various viral and bacterial pathogens can cause a follicular conjunctivitis. It is conceivable that these effects are amplified in a trachoma-endemic population: individuals who have previously developed a follicular conjunctivitis in response to C. trachomatis may more readily reform conjunctival follicles when challenged with certain other bacterial species. This may provide part of the explanation why the community prevalence of TF declines more slowly than chlamydial infection after the successful introduction of MDA. 8,9 A rapid, inexpensive point of care (POC) test would potentially be very useful to control programs, by providing an indication of whether C. trachomatis is no longer endemic in the face of persisting TF, allowing MDA to be stopped at an earlier stage. 26 Unfortunately, because there is not currently a POC test available, control programs have to base the decision of whether to continue treating on the community prevalence of TF. There is probably some potential to refine the treatment algorithm further as more empiric data on the relationship between infection and disease at different prevalence levels becomes available. 
Footnotes
 Supported by The Wellcome Trust Grant 080741/Z/06/Z.
Footnotes
 Disclosure: M.J. Burton, None; V.H. Hu, None; P. Massae, None; S.E. Burr, None; C. Chevallier, None; I.A. Afwamba, None; P. Courtright, None; H.A. Weiss, None; D.C.W. Mabey, None; R.L. Bailey, None
References
Mariotti SP Pascolini D Rose-Nussbaumer J . Trachoma: global magnitude of a preventable cause of blindness. Br J Ophthalmol. 2009;93:563–568. [CrossRef] [PubMed]
World Health Organizaion. Report of the 2nd global scientific meeting on trachoma. Geneva: World Health Organization; 2004.
Thylefors B Dawson CR Jones BR West SK Taylor HR . A simple system for the assessment of trachoma and its complications. Bull World Health Organ. 1987;65:477–483. [PubMed]
Schachter J West SK Mabey D . Azithromycin in control of trachoma. Lancet. 1999;354:630–635. [CrossRef] [PubMed]
Burton MJ Holland MJ Faal N . Which members of a community need antibiotics to control trachoma? Conjunctival Chlamydia trachomatis infection load in Gambian villages. Invest Ophthalmol Vis Sci. 2003;44:4215–4222. [CrossRef] [PubMed]
Wright HR Taylor HR . Clinical examination and laboratory tests for estimation of trachoma prevalence in a remote setting: what are they really telling us? Lancet Infect Dis. 2005;5:313–320. [CrossRef] [PubMed]
Harding-Esch EM Edwards T Sillah A . Active trachoma and ocular Chlamydia trachomatis infection in two Gambian regions: on course for elimination by 2020? PLoS Negl Trop Dis. 2009;3:e573. [CrossRef] [PubMed]
Solomon AW Harding-Esch E Alexander ND . Two doses of azithromycin to eliminate trachoma in a Tanzanian community. N Engl J Med. 2008;358:1870–1871. [CrossRef] [PubMed]
Burton MJ Holland MJ Makalo P . Profound and sustained reduction in Chlamydia trachomatis in the Gambia: a five-year longitudinal study of trachoma endemic communities. PLoS Negl Trop Dis. 2010;4:e835. [CrossRef] [PubMed]
Keenan JD Lakew T Alemayehu W . Clinical activity and polymerase chain reaction evidence of chlamydial infection after repeated mass antibiotic treatments for trachoma. Am J Trop Med Hyg. 2010;82:482–487. [CrossRef] [PubMed]
Bailey R Duong T Carpenter R Whittle H Mabey D . The duration of human ocular Chlamydia trachomatis infection is age dependent. Epidemiol Infect. 1999;123:479–486. [CrossRef] [PubMed]
Dawson CR Jones BR Tarizzo ML . Guide to trachoma control. Geneva: World Health Organization; 1981.
Holland MJ Jeffries D Pattison M . Conjunctival gene expression profiling using pathway focused arrays reveals increased matrix metalloproteinase-7 (matrilysin) transcription in trachomatous trichiasis. Invest Ophthalmol Vis Sci. 2010;51:3893–3902. [CrossRef] [PubMed]
Grassly NC Ward ME Ferris S Mabey DC Bailey RL . The natural history of trachoma infection and disease in a gambian cohort with frequent follow-up. PLoS Negl Trop Dis. 2008;2:e341. [CrossRef] [PubMed]
Capriotti JA Pelletier JS Shah M Caivano DM Ritterband DC . Normal ocular flora in healthy eyes from a rural population in Sierra Leone. Int Ophthalmol. 2009;29:81–84. [CrossRef] [PubMed]
Woolridge RL Gillmore JD . Bacteriological studies on trachomatous and normal persons from three areas on Taiwan. Bull World Health Organ. 1962;26:789–795. [PubMed]
Wood TR Dawson CR . Bacteriologic studies of a trachomatous population. Am J Ophthalmol. 1967;63(suppl):1298–1301. [CrossRef] [PubMed]
Reinhards J Weber A Nizetic B Kupka K Maxwell-Lyons F . Studies in the epidemiology and control of seasonal conjunctivitis and trachoma in southern Morocco. Bull World Health Organ. 1968;39:497–545. [PubMed]
Vastine DW Dawson CR Daghfous T . Severe endemic trachoma in Tunisia. I. Effect of topical chemotherapy on conjunctivitis and ocular bacteria. Br J Ophthalmol. 1974;58:833–842. [CrossRef] [PubMed]
Yoneda C Dawson CR Daghfous T . Cytology as a guide to the presence of chlamydial inclusions in Giemsa-stained conjunctival smears in severe endemic trachoma. Br J Ophthalmol. 1975;59:116–124. [CrossRef] [PubMed]
Chern KC Shrestha SK Cevallos V . Alterations in the conjunctival bacterial flora following a single dose of azithromycin in a trachoma endemic area. Br J Ophthalmol. 1999;83:1332–1335. [CrossRef] [PubMed]
Burton MJ Kinteh F Jallow O . A randomised controlled trial of azithromycin following surgery for trachomatous trichiasis in the Gambia. Br J Ophthalmol. 2005;89:1282–1288. [CrossRef] [PubMed]
Burton MJ Adegbola RA Kinteh F . Bacterial infection and trachoma in the gambia: a case control study. Invest Ophthalmol Vis Sci. 2007;48:4440–4444. [CrossRef] [PubMed]
Hu VH Massae P Weiss HA . Bacterial infection in scarring trachoma. Invest Ophthalmol Vis Sci. 2011;52:2181–2186. [CrossRef] [PubMed]
Burton MJ Bailey RL Jeffries D . Conjunctival expression of matrix metalloproteinase and proinflammatory cytokine genes after trichiasis surgery. Invest Ophthalmol Vis Sci. 2010;51:3583–3590. [CrossRef] [PubMed]
Michel CE Solomon AW Magbanua JP . Field evaluation of a rapid point-of-care assay for targeting antibiotic treatment for trachoma control: a comparative study. Lancet. 2006;367:1585–1590. [CrossRef] [PubMed]
Table 1.
 
Clinical Disease and C. trachomatis Infection
Table 1.
 
Clinical Disease and C. trachomatis Infection
Follicular Inflammation Papillary Inflammation
n (%) Infected (%)* n (%) Infected (%)*
FPC score FPC score
    F0 323 (68.3) 13 (4.0)     P0 372 (78.6) 16 (4.3)
    F1 85 (18.0) 8 (9.4)     P1 69 (14.6) 5 (7.3)
    F2 35 (7.4) 2 (5.7)     P2 26 (5.5) 4 (15.4)
    F3 30 (6.3) 2 (6.7)     P3 6 (1.3) 0 (0.0)
TF TI
    No 408 (86.3) 21 (5.1)     No 467 (98.7) 25 (5.4)
    Yes 65 (13.7) 4 (6.1)     Yes 6 (1.3) 0 (0.0)
Table 2.
 
Bacteria Cultured from Conjunctival Swabs
Table 2.
 
Bacteria Cultured from Conjunctival Swabs
Name All Eyes (n = 473) No TF (n = 408) TF (n = 65) P *
n (%) n (%) n (%)
Commensal organisms
    Viridans group streptococcus 153 (32.4) 131 (32.1) 22 (33.9) 0.78
    Staphylococcus epidermidis 70 (14.8) 61 (14.9) 9 (13.8) 0.82
    Corynebacterium spp. 45 (9.5) 40 (9.8) 5 (7.7) 0.59
    Bacillus spp. 8 (1.7) 8 (2.0) 0 (0.0) 0.26
Pathogenic organisms
    Streptococcus pneumoniae 48 (10.2) 34 (8.3) 14 (21.5) 0.001
    Haemophilus influenzae, type B 66 (14.0) 50 (12.6) 16 (24.6) 0.008
    Haemophilus influenzae, non–type B 43 (9.1) 28 (6.9) 15 (23.1) <0.001
    Micrococcus spp. 8 (1.7) 8 (2.0) 0 (0.0) 0.30
    Moraxella catarrhalis 3 (0.6) 3 (0.7) 0 (0.0) 1.00
    Haemophilus parainfluenza 2 (0.4) 2 (0.5) 0 (0.0) 1.00
    Branhamella catarrhalis 2 (0.4) 2 (0.5) 0 (0.0) 1.00
    Neisseria spp. 1 (0.2) 1 (0.3) 0 (0.0) 1.00
    Enterobacter spp. 1 (0.2) 1 (0.3) 0 (0.0) 1.00
    Klebsiella spp. 1 (0.2) 1 (0.3) 0 (0.0) 1.00
Table 3.
 
Clinical Signs of Trachoma and Type of Conjunctival Bacterial Isolates
Table 3.
 
Clinical Signs of Trachoma and Type of Conjunctival Bacterial Isolates
Follicular Inflammation Papillary Inflammation
No Growth Commensal Pathogen No Growth Commensal Pathogen
n (%) n (%) n (%) n (%) n (%) n (%)
FPC score FPC score
    F0 130 (40.3) 99 (30.7) 94 (29.1)     P0 145 (39.0) 114 (30.7) 113 (30.4)
    F1 27 (31.8) 30 (35.3) 28 (32.9)     P1 16 (23.2) 21 (30.4) 32 (46.4)
    F2 6 (17.1) 7 (20.0) 22 (62.9)     P2 6 (23.1) 6 (23.1) 14 (53.9)
    F3 5 (16.7) 7 (23.3) 18 (60.0)     P3 1 (16.7) 2 (33.3) 3 (50.0)
TF TI
    No 157 (38.5) 129 (31.6) 122 (29.9)     No 167 (35.8) 141 (30.2) 159 (34.0)
    Yes 11 (17.0) 14 (21.5) 40 (61.5)     Yes 1 (16.7) 2 (33.3) 3 (50.0)
Table 4.
 
Univariate Associations with Trachomatous Inflammation-Follicular
Table 4.
 
Univariate Associations with Trachomatous Inflammation-Follicular
Variable OR 95% CI P *
Sex, female 1.33 0.79–2.26 0.28
Age group, y
    0–3 1 0.06
    4–6 0.68 0.37–1.25
    7–10 0.46 0.23–0.90
Chlamydia trachomatis 1.21 0.40–3.64 0.74
Bacterial infection
    None 1.00 <0.001
    Commensal only 1.54 0.68–3.53
    Pathogen 4.68 2.31–9.50
Bacterial species
    Viridans group streptococcus 1.08 0.62–1.88 0.78
    Staphylococcus epidermidis 0.91 0.43–1.94 0.81
    Corynebacterium spp. 0.77 0.29–2.02 0.58
    Streptococcus pneumoniae 3.02 1.52–6.01 0.003
    Haemophilus influenzae, type B 2.34 1.24–4.42 0.01
    Haemophilus influenzae, non–type B 4.07 2.04–8.14 <0.001
Table 5.
 
Multivariable Logistic Regression Model for Trachomatous Inflammation-Follicular
Table 5.
 
Multivariable Logistic Regression Model for Trachomatous Inflammation-Follicular
Variable OR 95% CI P *
Age group, y
    0–3 1 0.25
    4–6 0.80 0.42–1.52
    7–10 0.66 0.33–1.35
Bacterial species
    Streptococcus pneumoniae 3.22 1.56–6.66 0.003
    Haemophilus influenzae, type B 2.92 1.47–5.81 0.003
    Haemophilus influenzae, non-type B 5.34 2.57–11.3 <0.001
Table 6.
 
Studies of Conjunctival Bacterial Infection in Children in Trachoma Endemic Communities
Table 6.
 
Studies of Conjunctival Bacterial Infection in Children in Trachoma Endemic Communities
Country (Year) Study Population and Design Findings Comments
Taiwan (1962) 16 Three separate trachoma endemic areas; conjunctival swab samples from preschool and first-grade children; about half had active trachoma; cultured (blood and chocolate agar) Culture positive; normal, 42/144 (29%); active trachoma, 74/201 (37%); organisms: Staphylococcus pneumoniae, 15.6%; α-streptococci, 11.6%; Haemophilus, 6.4%; Staphylococcus spp., 5.0% Sampling frame not specified, drawn from a number of different settings; variation of MacCallan's trachoma grading system used, making it difficult to relate to current clinical grades (to derive an approximation to active trachoma, Tr-D, Tr-I Tr-II, Tr-III, and CFC have been combined here); no Chlamydia trachomatis test data presented; reanalysis of the data suggests a significant association between active trachoma and bacterial infection (OR, 2.58; 95% CI, 1.6–4.0; P < 0.0010)
USA (1967) 17 School children (140) enrolled in a treatment trial for active trachoma; cultured (blood agar); microbiology results from before and after treatment combined Culture positive; normal/Tr-4, 41%, and Tr-I, Tr-II, and Tr-III, 43% Sampling frame not specified; MacCallan's trachoma grading system used; microbiology results from before and after treatment combined; no C. trachomatis test data presented.
Morocco (1968) 18 Sample from 16 communities enrolled in a trachoma control study; in each community, 160–180 children 0–8 years of age were randomly selected; conjunctival scrapings were Gram stained; no culture Positive slide: Haemophilus, 81%; Moraxella, 20%; S. pneumoniae, 19% MacCallan's trachoma grading system used; denominator not stated; no C. trachomatis test data presented; no analysis of bacterial infection in relation to active trachoma
Tunisia (1974) 19 Two villages—(A) 151 children 6–9 years with active trachoma; (B) 44 children <15 years, randomly selected; conjunctival swab (cultured blood agar); conjunctival smear, Giemsa stain for chlamydial inclusions Culture positive: S. viridans, 65%; Diphtheroids, 52%; Haemophilus spp., 40%; S. epidermidis, 13% The number of children contributing data to the reported culture results was 277, and this is higher than the 195 children described in the subject description; the age and clinical status of the additional 82 children is not presented; Haemophilus was found to be the major cause of mucopurulent conjunctivitis; no analysis of bacterial infection in relation to active trachoma
Tunisia (1975) 20 Single village—151 children initially having active trachoma were enrolled into a treatment trial; conjunctival scraping with Giemsa staining; no culture; each child had both eyes sampled on three occasions Results of 927 slides presented; slides positive for bacteria: 48% (Haemophilus, 25% and Moraxella, 16%) Difficult to interpret, because multiple data from both eyes are presented together; no analysis of bacterial infection in relation to active trachoma
Nepal (1999) 21 Single village—122 children 1–10 years of age; conjunctival swab (cultured blood agar) Active trachoma in 38%; S. pneumoniae, 22%; Haemophilus spp., 7%; Moraxella, 16% The focus of this study was the change in bacterial antibiotic sensitivity patterns after azithromycin treatment; no C. trachomatis test data presented; no analysis of bacterial infection in relation to active trachoma
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