Objectives: This study was undertaken to evaluate AmpC β-lactamase-producing Escherichia coli urine isolates and to characterize the frequency of plasmid-mediated AmpC (pAmpC)-encoding genes. Methods: Antimicrobial susceptibility tests were performed using the disk diffusion technique. AmpC β-lactamase production was assessed with a phenotypic inhibitor-based method. The presence of 6 pAmpC-encoding cluster genes was detected by multiplex polymerase chain reaction (PCR). Results: The proportion of antibiotic resistance of E. coli isolates ranged from 7.4% to 90.5%, and more than half (51.6%) of the total isolates were multidrug-resistant (MDR). Among the 95 E. coli isolates, 60 (63.2%) were found to be cefoxitin-resistant, but only 14 (14.7%) isolates were confirmed as AmpC β-lactamase-producers. In the PCR assay, pAmpC-encoding genes were found in 15 (15.8%) isolates, and blaDHA was the most prevalent type. However, blaFOX, blaMOX, and blaACC genes were not detected in the isolates. Conclusion Our findings contributed valuable information concerning antibiotic resistance, confirmatory phenotypic testing for AmpC production, and pAmpC β-lactamase gene content in E. coli isolates in southwestern Iran. The level of MDR recorded in AmpC-producing strains of this study was worrying; therefore, implementing strong infection control approaches to reduce the MDR burden is recommended.

Objective: To investigate the antimicrobial resistance patterns and prevalence of integrons in Shigella species isolated from children with diarrhea in southwest Iran. Methods: In this study, 1 530 stool samples were collected from children under 15 years with diarrhea referred to teaching hospitals in Ahvaz and Abadan, southwest Iran. Shigella spp. were identified by standard biochemical tests and PCR. The antibiotic resistance pattern of all Shigella isolates was determined by the disk diffusion method and minimum inhibitory concentration (MIC) by E-test. Results: Of 1 530 stool samples, 91 (5.9%, 91/1 530) were positive for Shigella spp. the most common Shigella isolates were Shigella flexneri 47 (51.6%, 47/1 530). Antibiotic susceptibility tests showed that the highest antibiotic resistance was related to trimethoprim-sulfamethoxazole (87.9%, 80/91) and ampicillin (86.8%, 79/91). Multiplex PCR results revealed that 56% and 86.9% of Shigella isolates carried integron class I and integron class II genes, respectively. None of the isolates included the integron class III gene. Conclusions: The high prevalence of multi-drug resistance in Shigella isolates in our area increases the concerns about dissemination of the antibiotic-resistant isolates in this bacterium.