Abstract
Purpose:
To document the molecular characteristics and mupirocin profiles of Staphylococcus aureus isolates recovered from chronic and or recalcitrant ocular disease.
Methods:
We used three separate multiplex PCR reactions to characterize molecular profiles for SCCmec, Panton Valentine leukocidin (PVL) toxin and the global accessory gene regulator (ARG) for 135 isolates recovered (2011-2014) from 52 patients with chronic staphylococcal disease (persistent colonization/recovery of S. aureus after a treatment course of at least 14 days). Mupirocin MIC profiles (N=60) were documented using E tests. Resistance was categorized as high level (HL), >512 ug/ml, low level (LL), 8-256 ug/ml and susceptible (SL), less than 8 ug/ml.
Results:
.The average number of repeat isolates per patient averaged 2.9 with an average time interval of 174 days (range 10-810 days). Reservoirs for repeat infections included conjunctiva (38.5%), cornea (16.3%), lacrimal system (11.1%), lids (10.4%), socket (9.6%) and ocular other (14.1%). Methicillin susceptible isolates were recovered from 25.9% (n=35) of patients.. The majority of the MRSA isolates were healthcare associated (n=66/75, 88%). SCCmec profiles included SCCmec I (4.5%), SCCmec II-95.5% (N= 66/75, 88%,) . Community associated MRSA profiles (n=28) were all SCCmec IV, (IVa-39.3%, IVd-60.7%). 4,4% of isolates were untypable. The PVL toxin was present in 94.8% of isolates. ARG type 2(51.8%, n=70) was the most common ARG genotype followed by ARG 1 (29.6%), ARG 3 (14.8%), ARG 4 (0.07%) and nontyable (3%). Isolates with genotype: SSCmec II, ARG2 and PVL + (50.3%, n=68) served as markers for chronic ocular disease. High level mupirocin resistance was found in 6.7% (4/60) of isolates (conjunctiva-2, cornea-2). Low level resistance was document in 2 (3.3%-conjunctiva, lids). Resistance occurred more frequently in MRSA isolates (5/6, 83.3%). General in vitro susceptibility for mupirocin was 90% (n=54/60).
Conclusions:
Unique molecular profiles may serve as markers for chronic ocular staphylococcal disease and high level resistance to mupirocin. Mupirocin could be useful in decolonizing and reducing ocular surface reservoirs.