Objectives Genetic determinants conferring resistance to macrolide, lincosamide, and streptogramin B (MLS B ) via ribosomal modification such as, erm , msrA/B and ereA/B genes are distributed in bacteria. The main goals of this work were to evaluate the dissemination of MLS B resistance phenotypes and genotypes in methicillin-resistant Staphylococcus aureus (MRSA) isolates collected from clinical samples. Methods A total of 106 MRSA isolates were studied. Isolates were recovered from 3 hospitals in Tehran between May 2016 to July 2017. The prevalence of MLS B -resistant strains were determined by D-test, and then M-PCR was performed to identify genes encoding resistance to macrolides, lincosamides, and streptogramins in the tested isolates. Results The frequency of constitutive resistance MLS B , inducible resistance MLS B and MS B resistance were 56.2%, 22.9%, and 16.6%, respectively. Of 11 isolates with the inducible resistance MLS B phenotype, ermC , ermB , ermA and ereA were positive in 81.8%, 63.6%, 54.5% and 18.2% of these isolates, respectively. In isolates with the constitutive resistance MLS B phenotype, the prevalence of ermA , ermB , ermC , msrA , msrB , ereA and ereB were 25.9%, 18.5%, 44.4%, 0.0%, 0.0%, 11.1% and 0.0%, respectively. Conclusion Clindamycin is commonly administered in severe MRSA infections depending upon the antimicrobial susceptibility findings. This study showed that the D-test should be used as an obligatory method in routine disk diffusion assay to detect inducible clindamycin resistance in MRSA so that effective antibiotic treatment can be provided.
Aims and Objectives: The present work aimed to evaluate the frequency of aminoglycoside- modifying enzymes encoding genes in the E. faecalis and E. faecium and their antibiotic resistance profile. Methods: A total of 305 different clinical samples were subjected for identification and antibiotic susceptibility test. The high-level aminoglycoside resistance was identified by MIC and Kirby Bauer disc diffusion method. The prevalence of aac (6')-Ie-aph (2'')-Ia, aph (3')-IIIa and ant (4')- Ia genes was determined by multiplex- PCR. In total, 100 enterococci strains were isolated. The prevalence of E. faecalis and E. faecium isolates was 78% and 22%, respectively. Results: All isolates were susceptible to linezolid. So, all E. faecalis were susceptible to vancomycin but, 36.4% of E. faecium were resistant to it. The prevalence of multiple drug resistance strains was 100% and 67.9% of E. faecium and E. faecalis, respectively. High-level-gentamicin and streptomycin resistant rates were as follows; 26.9% and 73.1% of E. faecalis and 77.3% and 90.1% of E. faecium. Conclusion: The results of the current study showed a high frequency of aac (6')-Ie-aph (2'')-Ia genes among enterococcal isolates. A high rate of resistance to antimicrobials in Enterococcus is obviously problematic, and a novel policy is needed to decrease resistance in these microorganisms.
Objective: The present study aimed to investigate the frequency and antibiotic susceptibility pattern of Gram-negative bacteria (GNB) isolated from surgical site infections (SSIs) in the North of Iran. Results: This cross-sectional study conducted over a two-year period during 2018-2020 on all cases of SSIs who had a positive culture for a GNB. Standard microbiological tests were followed for the bacterial isolation and identification. Antimicrobial susceptibility profiles were determined using disk diffusion method. During the study period, a total of 78 nonduplicated GNB isolated from SSIs. The most prevalent surgical procedures were fracture fixation (37.2%), and tissue debridement (23.1%). Klebsiella isolates showed the highest isolation rate (29.5%) followed by Enterobacter (28.2%), and Acinetobacter (16.7%). Antibiotic susceptibility results showed that Acinetobacter isolates were almost resistant to all of the tested antibiotics, except gentamicin, co-trimoxazole, and meropenem. Enterobacteriaceae isolates showed the lowest resistance against amikacin, co-trimoxazole, and imipenem. Overall, 49 (62.8%) of isolates were multiple drug-resistant (MDR). In summary, a remarkable rate of MDR isolates which showed an increasing trend during recent years is a serious alarm for the management of SSIs caused by GNB. Moreover, the results of regional assessments, provide good epidemiological background for comparing our situation with other regions.
Objectives: The purpose of this study was to determine the antimicrobial resistance-related genes in Staphylococcus aureus isolated from patients referred to 14 teaching hospitals, Tehran, Iran. Methods: A total of 225 S. aureus were obtained from clinical samples in a period of 12 months. Antimicrobial resistance, minimum inhibitory concentration minimal inhibitory concentration and Inducible resistance phenotypes were determined based on the Clinical laboratory standard institute (CLSI) guidelines. PCR was performed for amplification of mecA/B/C, iles-2, ermA/B/C and ereA/B genes. Results: 39.5 and 40.8% of isolates were resistant to oxacillin and cefoxitin (FOX), respectively. The frequency of constitutive macrolide-lincosamide-streptograminB, inducible macrolide-lincosamide-streptograminB and MS phenotypes were 55.3, 28.6 and 16.1%, respectively. 40.8, 4, 7.5, 6.2, 16 and 3.1% of strains harbored the mecA, ileS-2, ermA, ermB, ermC and ereA genes, respectively. Conclusion: The frequency of methicillin-resistant S. aureus isolates in our hospitals was high and disk diffusion testing using FOX or oxacillin and/or FOX minimal inhibitory concentration E test as an alternative to PCR for identification of methicillin-resistant S. aureus is suggested. This study highlights the hypothesis that rapid testing plays an important role in antibiotic stewardship by getting patients on targeted therapy faster.
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