Acinetobacter spp. are opportunistic nosocomial pathogens notorious for their multidrug resistance, complicating the treatment of infections such as bacteremia and pneumonia. The dissemination of aminoglycoside resistance genes, particularly via integrons, is a major therapeutic concern. This study aimed to characterize gentamicin resistance in clinical Acinetobacter isolates using phenotypic and molecular methods. Thirty Acinetobacter isolates were collected from medical centers in Lahijan and Amlash, Iran. Gentamicin resistance was phenotypically assessed by disk diffusion and macrodilution MIC methods per CLSI guidelines. Genotypically, the presence of the *aac(3)-IV* aminoglycoside resistance gene was detected by PCR following DNA extraction. Disk diffusion identified 40% of isolates as gentamicin-resistant. The macrodilution method confirmed resistance in 33.33% of isolates, with MIC values ranging from 7.81 μg/mL to 125 μg/mL. The *aac(3)-IV* gene was detected in 30% of all isolates. The high prevalence of the *aac(3)-IV* gene underscores its significant contribution to gentamicin resistance in these clinical isolates. Integrating molecular detection with phenotypic screening is crucial for surveillance and informs effective empirical therapy to combat multidrug-resistant Acinetobacter infections in the Guilan region.

Backgrounds: Enterococci are Gram-positive bacteria that colonize the intestine of warmblooded animals and humans as normal flora. Enterococci cause a variety of communityacquired and nosocomial infections. The emergence of vancomycin and gentamicin resistant enterococci has made a major challenge in the treatment of enterococcal infections worldwide. Therefore, the present study was conducted to evaluate the prevalence of vancomycin and gentamycin resistance among Enterococcus spp in Iran during 2007-2019. Materials & Methods: In this study, 26 studies were reviewed to collect data on the frequency of vancomycin and gentamicin resistant enterococci in Iran. To find studies published during January 2007 to January 2019, a search strategy was performed by searching different Iranian and international databases, including SID, Google Scholar, Scopus, Medline, Pub Med, and Web of Science. Findings: The prevalence of vancomycin-and gentamicin-resistant enterococci was very high in Iran (41 and 44%, respectively). Accordingly, Enterococcus faecalis was more prevalent in clinical samples compared to E. faecium (75. 49% vs. 24. 05%). However, resistance to vancomycin was higher in E. faecium strains compared to E. faecalis. Conclusion: Due to the increasing vancomycin and gentamicin resistance among Enterococcus species in Iran, it is necessary to design strategies that lead to the rational prescription of antibiotics and limit the spread of resistant enterococci.

Background: Enterococci are members of the normal gut flora and released into the environment via sewage outlets, where they can survive for long times. Infections with high-level gentamicin resistant (HLGR) enterococci are emerging worldwide. HLGR enterococci have developed a resistance to most antibiotics commonly used for enterococcal infections therefore; treatment of infections caused by HLGR enterococci is difficult. The present study investigated the distribution and antibiotic resistance of HLGR Enterococcus faecium and E. faecalis isolates from raw wastewater samples in Tehran.Methods: Raw wastewater samples were collected during the period from November 2006 to May 2007 at 3 sewage treatment plants located in different parts of Tehran. All 90 HLGR enterococcal isolates were identified to the species level by biochemical and PCR assays and subjected to antibiotic susceptibility testing.Results: Sixty four percent (58 of 90) of isolates were E. faecium and 29% (26 of 90) of them were E. faecalis. The highest level of antibiotic resistance was observed with erythromycin (63%), co-trimoxazole (69%) and tetracycline (92%) for E.faecalis and with erythromycin (97%), ciprofloxacin (47%), co-trimoxazole (45.5%) and tetracycline (47%) for E. faecium.Multiresistance against 3 to 4 antimicrobial was present in 27.5% and 15.5% of the isolates, respectively.Conclusion: HLGR E. faecium were more commonly found than E. faecalis. Species identification of HLGR enterococci enables us to assess species-specific antibiotic susceptibility patterns in our area. The present study reviled that HLGR E. faecalis remained more susceptible than E. faecium against the usual first-line and alternative treatments.

Background: Enterococci form a part of the normal flora of the intestinal tract, the oral cavity, and the vagina; also, they can cause UTI, septicemia, intraabdominal abscesses, and nosocomial infections. High-level gentamicin resistance (HLGR) in enterococci is mediated by aminoglycoside modifying enzymes, which is mainly encoded by aac (6’ )-Ie-aph (2” )-Ia gene. Objectives: The present study aimed at investigating high-level gentamicin resistance in enterococci isolated from a pediatric hospital in Tabriz and detecting aac (6’ ) Ie-aph (2” ) Ia gene. Methods: In a descriptive and prospective study, a total of 100 enterococcal isolates were collected during September 2014 and June 2015 from a pediatric hospital in Tabriz, northwest of Iran. Bacterial identification and species determination were performed by standard biochemical tests. Antimicrobial susceptibility tests were performed by Kirby Bauer disc diffusion method. The frequency of aac (6’ )-Ie-aph (2” )-Ia gene in the isolates was determined by polymerase chain reaction. Results: Antibiotic susceptibility tests revealed that the highest resistance was against erythromycin (79%) and tetracycline (74%), whereas the highest susceptibility was observed against chloramphenicol (86%). Resistance to ampicillin, ciprofloxacin, and vancomycin were detected in 47%, 53%, and 42% of the isolates, respectively. In this study, 31 isolates (31%) were identified as HLGR from which 21 (67. 74%) had resistance gene of aac (6’ )-Ie-aph (2” )-Ia in their genome. The prevalence of resistance to other antibiotics and multi-drug resistance (MDR) was higher among the HLGR isolates compared to the non-HLGR isolates. Conclusions: High prevalence rates of MDR and HLGR enterococci are important problems associated with medical settings. The results of this study indicated that aac (6’ )-Ie-aph (2” )-Ia resistance gene is highly prevalent among gentamicin resistant isolates.