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Herminia Mino de Kaspar, Norma Farina, Margarita Samudio, Letizia Carpinelli, Martin M. Nentwich, Rosa Guillen; Methicillin Resistance and Biofilm Production in Staphylococcus epidermidis Isolated from Pathological Specimen and Normal Conjunctival Flora. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1933.
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To determine biofilm-production capability and presence of methicillin resistance genes (mec A) in S. epidermidis isolated from pathological clinical infections and from normal conjunctival flora
We used 20 S. epidermidis isolates (study group) from different infected specimen (urin tract, abscess, sepsis, etc.) and 22 S. epidermidis isolates (control group) from normal conjunctival flora infection. All isolates were tested for their ability to produce biofilm using the conventional Christensen's method. Presence of mec A, the structural gene of a low-affinity penicillin-binding protein (PBP 2'), was determined with PCR and agarose gel electrophoresis from bacterial lysates, using 22-mer primers which covered the 533-bp region.
Biofilm production was detected in 15 (75%) and mec A gene in 14 (70%) of the 20 isolates of the study group. In the 22 isolates from the control group, 8 (36,3%) showed biofilm production and in 4 (18.2%) the mec A gene was identified. Both, biofilm production and mec A genes together, were detected in 13 isolates (65.0%) in the study group, and 4 isolates (18.2%) in the control group. Regardless of the group, biofilm production was detected in 94% of the strains with mec A. The resistance rate for the study group and control group was, respectively, as follows: penicillin G (100% vs 91%), oxacillin (70% vs 18%), cephalotin (65% vs 18%), erythromycin (55% vs 59%), clindamycin (30% vs 14%), ciprofloxacin (75% vs 14%), trimethoprim-sulfamethoxazole (25% vs 14%), gentamicin (25% vs 18%). Multiresistance was observed in 55% in the study group and 9% in the control group. Fifty seven percent of the biofilm producing strains were multiresistant in contrast to none of the non-producing strains. All multiresistant strains showed biofilm production.
S. epidermidis isolated of a variety infections, displayed a higher degree of antibiotic resistance compared to the control group. In mecA positive strains, also biofilm formation capability was present to a great extent. Because S. epidermidis is a major saprophyte of the eye and often associated with ocular infections, the high frequency of mecA positve, multiresistance strains in pathological samples, together with their strong association with biofilm production highlights the potential of a pathogenic role of this otherwise saprohytic bacterium.
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