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P. G. Agarwal, Y. R. Sharma, N. Nayak, G. Satpathy; Invitro Susceptibility of Bacterial Isolates in Endophthalmitis, Emerging Resistance to Cephalosporins and Efficacy of Newer Fluoroquinolones. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5120.
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To determine the bacterial spectrum causing endophthalmitis and their susceptibility against commonly used antibiotics.
A retrospective review of microbiological records from January 2008 to November 2008 yielded 217 cases of post traumatic and post surgical endophthalmitis for which vitreous aspirate was collected and intravitreal antibiotics were given. Antibiotic susceptibility of the culture proven bacterial isolates was determined using the Kirby-Bauer disk-diffusion test.
Among 217 samples, 120 samples were sterile, 82 samples had bacterial growth, whereas 12 samples were commensals. Out of the 82 culture proven bacterial endophthalmitis cases, 53 were attributable to gram-positive bacteria while 29 to gram- negative bacteria. 3 cases had fungal growth. Gram-negative bacteria included Pseudomonas aeruginosa (24; 29%), Acinetobacter (3;4%), Klebshiella (1;1.2%) and Enterobacter (1;1.2%). Gram-positive bacteria included S. epidermidis (40;49%), S. aureus (4;5%), Streptococcus viridans (3;4%) and S. pnemoniae (6;7%). Among these, 76/82(93%) were sensitive to ciprofloxacin, 72/82(89%) were sensitive to amikacin, 72/82(89%) were sensitive to chloramphenicol, 68/82(83%) were sensitive to tobramycin, 65/82(79%) were sensitive to gentamicin, 63/82(77%) were sensitive to tetracycline, 52/82(63%) were sensitive to cefazolin. Out of the 53 gram positive samples tested for vancomycin, 45/53(85%) were sensitive and among the gram negative samples, 27/29(93%) were sensitive to polymyxin B. All tested 16 vitreous aspirate samples were sensitive to Gatifloxacin and Moxifloxacin.
In this large series of endophthalmitis, Staphylococcus epidermidis bacteria were the most common pathogen causing endophthalmitis followed by P. aeruginosa. High degree of resistance of cefazolin (37%) was seen in the study, followed by resistance to tetracycline, gentamicin and tobramycin. Such high resistance to cephalosporins has not been reported earlier. Gatifloxacin and moxifloxacin showed 100% efficacy against all organisms.
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