Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen. We sought to determine the frequency of the different types of SCCmec in MRSA isolates by performing a cross-sectional study. A total of 72 S. aureus isolates were collected from Imam Khomeini and Golestan hospitals and analysed for MRSA and SCCmec typing by multiplex PCR. The pattern of antibiotic resistance among S. aureus isolates was determined by disc diffusion analysis. Of the 72 S. aureus isolates, 29 (40.27%) were recognized as MRSA. SCCmec type III was the most common type, with 55.17% (16/29), followed by type II with 27.58% (8/29); type IV with 10.34% (3/29); and type I with 6.89% (2/29). All 29 MRSA isolates were resistant to chloramphenicol and erythromycin. In addition, resistance to cephalothin, gentamicin, clindamycin, ciprofloxacin, tetracycline and rifampicin was seen in 24 (75%), 26 (63.4%), 17 (94.4%), 27 (71.05%), 10 (71.42%) and 13 (68.42%) MRSA isolates, respectively. A decreased sensitivity of MRSA to the antibiotics used was observed, with type III SCCmec being the predominant isolate.
The emergence of heterogeneous populations of methicillin-resistant Staphylococcus aureus (MRSA) causes major problems in routine screening for MRSA. Cefoxitin is a potent inducer of the mecA regulatory system and can be use for detection of heterogeneous populations of MRSA. Detection of the mecA gene by PCR was considered to be the "gold standard". In this study we determined the sensitivity and specificity of the oxacillin disk diffusion test, cefoxitin disk diffusion test and oxacillin agar screening for detection of MRSA. A total of 124 non-duplicate isolates of S. aureus were included in the study. Methicillin resistance was measured using oxacillin (1μg) and cefoxitin(30μg) disc diffusion method and oxacillin agar screening test (6 mg/ml oxacillin) according to CLSI guideline and PCR for the mecA gene. Compared with the molecular detection of methicillin resistance the overall sensitivities and specificities of the phenotypic tests for cefoxitin disc diffusion were 100%, for oxacillin disc diffusion were 91.7 and 92.8% and for oxacillin agar screening were 95 and 95.5%, respectively. We concluded that in the absence of availability of molecular biology techniques, the cefoxitin disc was the best detector of methicillin resistance in S. aureus related to the other phenotypic tests.
Objective
Moraxella catarrhalis is a non-motile Gram-negative diplococcus bacterium that contributed to several human infections including conjunctivitis. This study aimed to reveal the prevalence of M. catarrhalis in patients who suffered from conjunctivitis in Ahvaz city, southwest of Iran.
Results
Out of 100 conjunctiva swab specimens, M. catarrhalis was isolated only from one (1%) conjunctivitis cases using the culture method. This strain was isolated from a 34 years old female patient. Also, the results of the polymerase chain reaction (PCR) were in agreement with the culture method, and the specimen that showed positive culture was also positive for specific gene of M. catarrhalis. The remaining 99 specimens did not show positive results with any of the culture and PCR methods.
reference strains. Results: EPI test showed 4-64 fold MIC reduction in 23/40(58%) isolates for carbenicillin and erythromycin and in 32/40(80%) isolates for norfloxacin. No MIC reduction was observed in 32 (80%) isolates for gentamicin whereas one isolate showed 64-fold reduction. Quantitative analysis revealed that on comparison with PAO1 strain, expression of mexA and mexE increased by 3-10 and 2-3 fold respectively in all isolates. mexC expression ranged from 5-24 fold increase in 14(67%) isolates, 73-294 fold and 630-fold in 4 and 1 isolate respectively. One isolate each showed 2 and 17 fold difference in mexX expression whereas no expression was observed for the remaining isolates.
Conclusion:The present study documents the prevalence of efflux pump mediated resistance among MDR isolates of P. aeruginosa. All MDR isolates over-expressed at least one of the efflux pumps. Among the RND family genes studied, mexC showed a wide range as well as high levels of expression indicating its role in multidrug resistance in P. aeruginosa.
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