Phenotypic and Genotypic Characterization of ESBL-, AmpC-, and Carbapenemase-Producing Klebsiella pneumoniae and Escherichia coli Isolates.

OBJECTIVES: Drug resistance among gram-negative bacteria is a worldwide challenge. Due to the importance of drug-resistant Klebsiella pneumoniae and Escherichia coli strains in hospital-acquired infections, we aimed to determine the phenotypic and genotypic characteristics of ESBL-, AmpC-, and carbapenemase-producing isolates obtained from hospitalized patients in Tehran and Ilam (Iran). MATERIALS AND METHODS: In total, 90 K. pneumoniae isolates and 65 E. coli isolates were collected from various infections. Phenotypic identification of bacterial isolates was performed using standard methods. Phenotypic screening of ESBL, AmpC, and carbapenemase enzymes was carried out. Detection of ESBL, AmpC, and carbapenemase genes was also performed by the PCR method. RESULTS: Phenotypic detection tests showed that 36 (40%) K. pneumoniae and 23 (35.4%) E. coli isolates were ESBL producers. Moreover, 18 (20%) and 6 (9.2%) K. pneumoniae and E. coli isolates were AmpC producers, respectively. Modified Hodge test results indicated that 39 (43.3%) K. pneumoniae and 18 (27.7%) E. coli isolates produced carbapenemase. Molecular tests showed that 40% of K. pneumoniae and 36.9% of E. coli isolates were ESBL positive. AmpC was detected in 24.4 and 13.8% of K. pneumoniae and E. coli isolates. Carbapenemase was detected in 34 (37.8%) K. pneumoniae and 13 (20%) E. coli isolates. -Conclusion: In this study, 3 K. pneumoniae isolates simultaneously carried ESBL, AmpC, and carbapenemase genes. Up-to-date strategies such as combination therapy or utilization of new antimicrobial agents might help to combat such drug-resistant organisms.

Genomic diversity and virulence genes among clinical isolates of Pseudomonas aeruginosa.

BACKGROUND: Typing of nosocomial pathogens is necessary to determine the source of an outbreak. The aim was to determine the genomic variability among Pseudomonas aeruginosa (P. aeruginosa) by random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC) methods. METHODS: Fifty P. aeruginosa isolates were obtained from the hospitals. The source of these isolates were burn wound and urinary tract infections. After detection of P. aeruginosa by biochemical methods, chromosomal deoxyribonucleic acid (DNA) was extracted by a DNA extraction kit. ERIC-PCR and RAPD- PCR was done by standard methods. The polymerase chain reaction (PCR) products were run and visualized in 1.5% agarose gels stained with ethidium bromide. RESULTS: Fifty P. aeruginosa isolates were analyzed by ERIC-PCR and RAPD-PCR methods. Multiple PCR fragment sizes generated by two PCR methods and PCR product size were between 200-3500 bp, and 10 and 7 different PCR patterns were detected by ERIC-PCR and RAPD-PCR, respectively. Eleven isolates were not detected by ERIC-PCR method. Fifteen isolates were typed to a single genotype by the RAPD-PCR method. CONCLUSIONS: We suggested that ERIC and RAPD PCR are equally suitable, inexpensive, fast, reproducible, and discriminatory as rapid DNA typing tools for effective epidemiological surveillance of P. aeruginosa isolates. Our results suggest that these DNA typing tools could be used in routine epidemiological surveillance, outbreak surveillance, and in the identification of the source of transmission of P. aeruginosa.

Comparison of toxin-antitoxin expression among drug-susceptible and drug-resistant clinical isolates of Mycobacterium tuberculosis.

INTRODUCTION: Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB), is a significant global public health threat. Besides extensive multidrug resistance, MTB possesses several properties for long-term viability in the host as well as stress adaptation and resistance in harsh conditions. The role of toxin-antitoxin (TA) systems in disseminating and maintaining antimicrobial resistance in bacterial populations has also been demonstrated. This study aimed to evaluate differences in expression of MazEF (a well-known TA system) related genes (mazE3, mazF3, mazE6, and mazF6) amongst drug-susceptible and resistant MTB isolates in Iran. MATERIAL AND METHODS: A total of 20 confirmed clinical isolates of MTB including 10 drug-susceptible and 10 drug-resistant (nine MDR, and one XDR) species were included in this study. M. tuberculosis H37Rv was used as the standard strain. RNA extraction, cDNA synthesis, and relative quantitative real-time PCR were performed according to the standard procedures. RESULTS: Our analysis indicated significant enhanced expression of the mazE6 antitoxin gene in drug-susceptible isolates compared to drug-resistant isolates and the standard strain. The expression of the mazF6 toxin gene was also increased in drug-susceptible isolates compared with the standard strain. In drug-resistant isolates, the expression levels of mazF3 and mazF6 genes were significantly higher than that in the susceptible isolates and the standard strain. CONCLUSIONS: In this study, there was significant overexpression of mazE6 in drug-susceptible isolates. As well, mazF3 and F6 were overexpressed in drug-resistant isolates when compared with the standard strain. The changes in expression levels of MazEF6 associated genes were greater than that of MazEF3 in both groups of isolates.

What about Urinary Tract Infections and its Antibiotic Resistance Bacteria in Ilam, Iran?

BACKGROUND: Because of the unknown situation of antibiotic resistance pattern in the main hospital in Ilam, Iran, we aimed to evaluate the antibiotic resistance pattern of uropathogenic bacteria obtained from referred patients to Imam Khomaini Hospital, Ilam, Iran. So, 114 bacteria were collected during 9-month period and evaluated for their antibiotic resistance patterns. RESULTS: Our results demonstrated that Escherichia coli as the dominant responsible for urinary tract infection. Our results demonstrated that 61.4 % (n = 70) of isolates were positive for E.coli, while lowest prevalence was observed for Staphylococcus aureus and Acinetobacter baumannii. The results also showed that 6.4% (n = 7) were metallo beta lactamase (MBL) producers. Our findings showed only 4 gram positive bacteria were obtained from patients with urinary tract infections including one methicillin resistant S. aureus (MRSA) and 2 vancomycin resistant Enterococcus faecalis (VRE). CONCLUSION: In conclusion, we strongly recommended to perform a perfect study among all hospitals in Iran to evaluate the situation of antibiotic resistance and make a real panel to control this issue.