Assay for integrons and pattern of antibiotic resistance in clinical Escherichia coli strains by PCR-RFLP in Southern Iran.

The purpose of this study was to determine the prevalence of multidrug-resistant Escherichia coli in clinical specimens. In addition, the existence of integrons in resistant isolates was assessed by amplification of intergase genes. Susceptibility of 200 isolates from five Shiraz hospitals and health centers to 13 antibiotics was determined by the Kirby-Bauer disk diffusion method. The majority of the bacteria were isolated from urine (70.5%) and stool (25.5%) specimens. Antibiotic resistance patterns were observed as follows: amoxicillin 63%, tetracycline 57.5%, co-trimoxazole 48%, cephalotin 40%, nalidixic acid 36%, ciprofloxacin 21%, nitrofurantoin 25%, norfloxacin 20.5%, gentamicin 18%, chloramphenicol 18%, ceftazidime 14%, amikacin 8.5% and imipenem 2%. Of 200 isolates tested, 165 (82.5%) were multidrug resistant. The frequency of multidrug resistance to more than 5 antibiotics was 24.2%. The existence of integrons was confirmed in 44.8% of isolates. Significant association between resistance to gentamicin, amikacin, cephalotin, nalidixic acid, ciprofloxacin, norfloxacin and co-trimoxazole with the existence of integrons was obtained by the PCR-RFLP method. These results showed that integrons may be partly responsible for multidrug resistance. Imipenem, amikacin and ceftazidime were the most effective antibiotics in vitro; however, the clinical efficacy of these antibiotics remains to be assessed.

Characterization of Shigella strains in Iran by plasmid profile analysis and PCR amplification of ipa genes.

To characterize Shigella clinical strains, we studied 82 Shigella strains recovered from 719 stool samples of patients with bloody diarrhea in Shiraz, Iran, over the period from April to October 2003. Serological assay classified the Shigella isolates as follows: 61 (74.39%) Shigella sonnei isolates, 16 (19.51%) Shigella flexneri isolates, 3 (3.65%) Shigella boydii isolates, and 2 (2.43%) Shigella dysenteriae isolates. In an antibiogram test, all Shigella strains were susceptible to ceftazidime, ciprofloxacin, and ceftriaxone. They showed high degrees of sensitivity to nalidixic acid, gentamicin, cephalothin, and amikacin. Approximately 90.24% of the Shigella isolates were resistant to co-trimoxazole. The plasmid profile patterns of all strains were determined by a modified alkaline lysis method. The average number of plasmid bands for each strain was 9.5. By plasmid profile analysis we identified 56 genotypes among all isolates and 42, 14, 3, and 2 genotypes among the S. sonnei, S. flexneri, S. boydii, and S. dysenteriae strains, respectively. PCR assays showed that all isolates were positive for two virulence genes, ipaBCD and ipaH. In conclusion, these data mandate local monitoring of drug resistance and its consideration in the empirical therapy of Shigella infections. These results also demonstrate that plasmid profile analysis is more reliable than antibiotic susceptibility pattern analysis for the identification of Shigella epidemic strains isolated in Iran.