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Background: Antibiotic resistance in Klebsiella pneumoniae isolates, particularly resistance to colistin, has become a growing concern. This study seeks to investigate the upregulation of specific genes (pmrA, pmrB, pmrC, phoQ, phoP, and arnT) that contribute to colistin resistance in K. pneumoniae isolates collected from human clinical samples in Tehran, Iran. Methods: Thirty eight K. pneumoniae isolates were obtained and subjected to antibiotic susceptibility testing, as well as evaluation for phenotypic AmpC and ESBL production according to CLSI guidelines. The investigation of antibiotic resistance genes was conducted using polymerase chain reaction (PCR), whereas the quantification of colistin resistance related genes expressions was performed via Real-Time PCR. Results: The highest and lowest antibiotics resistance were observed for cefotaxime 33 (86.8%) and minocycline 8 (21.1%), respectively. Twenty-four (63.2%) and 31 (81.6%) isolates carried AmpC and ESBLs, respectively. Also, antibiotic resistance genes containing blaNDM, blaIMP, blaVIM, blaSHV, blaTEM, blaCTXM, qnrA, qnrB, qnrS, and aac(6')-Ib were detected in K. pneumoniae isolates. Only 5 (13.1%) isolates were resistant to colistin and the MIC range of these isolates was between 4 and 64 µg ml-1. Upregulation of the pmrA, pmrB, pmrC, phoQ, phoP, and arnT genes was observed in colistin-resistant isolates. The colistin-resistant isolates were found to possess a simultaneous presence of ESBLs, AmpC, fluoroquinolone, aminoglycoside, and carbapenem resistant genes. Conclusions: This study reveals escalating antibiotic resistance in K. pneumoniae, with notable coexistence of various resistance traits, emphasizing the need for vigilant surveillance and innovative interventions.
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OBJECTIVES: Chronic infections and treatment failure are concerning issues in patients with Pseudomonas aeruginosa infections. Persister cell formation in biofilm is considered a key reason for antibiotic resistance and treatment failure. In this study, expression of type II toxin/antitoxin (TA) system genes (relBE, Xre-COG5654, vapBC and Xre-GNAT) in persister cells of biofilm was evaluated in the presence of the antibiotics ciprofloxacin and colistin during exponential and stationary phases. METHODS: The impact of antibiotics on biofilm persister cell formation during exponential and stationary phases of P. aeruginosa strains was examined by colony count at different time intervals in the presence of 5-fold minimum inhibitory concentration (MIC) of ciprofloxacin and colistin. Furthermore, expression of relBE, Xre-COG5654, vapBC and Xre-GNAT genes in P. aeruginosa strains undergoing antibiotic treatment for 3.5 h during exponential and stationary phases was examined by RT-qPCR. RESULTS: Formation of persister cells was observed in biofilms formed by P. aeruginosa strains in the presence of 5 × MIC of ciprofloxacin and colistin compared with the control group after 3.5 h of incubation both during exponential and stationary phases. The number of biofilm persister cells was higher in stationary phase than in exponential phase. According to the findings of RT-qPCR, ciprofloxacin and colistin may induce persister cell formation by enhancing the expression of type II TA systems during stationary and exponential phases. CONCLUSION: The result of this study indicate that ciprofloxacin and colistin have the potential to increase persister cells formation in biofilms by influencing the expression of type II TA systems.