Mutant Prevention Concentration of Ciprofloxacin against Klebsiella pneumoniae Clinical Isolates: An Ideal Prognosticator in Treating Multidrug-Resistant Strains

Molecular identification of plasmid-mediated quinolone resistance genes among klebsiella pneumoniae clinical isolates from southwest Iran

In recent years, the resistance rate to quinolone antibiotics has been increasing in Klebsiella pneumoniae. Plasmid-mediated quinolone resistance (PMQR) genes are one of the factors causing resistance to quinolones. Hence, this study aimed to determine the incidence of PMQR genes in clinical K. pneumoniae isolates from southwest Iran. In total, 96 K. pneumoniae isolates were identified during the study period. Sixty-seven (69.8%) isolates were resistant to at least one quinolone antibiotic. Resistance rates to levofloxacin, norfloxacin, nalidixic acid, ofloxacin, and ciprofloxacin were 50% (48/96), 56.3% (54/96), 60.4% (58/96), 62.5% (60/96), and 68.8% (66/96), respectively. The highest frequencies of PMQR genes were related to qnrS, aac (6')-Ib-cr, and qnrB genes with 85.1% (57/67), 83.6% (56/67) and 65.7% (44/67), respectively. The qnrD, qnrC, qepA, and qnrA were detected in 23.9% (16/67), 19.4% (13/67), 13.4% (9/67), and 6.0% (4/67) of isolates, respectively. This study was the first to report a high-frequency rate of PMQR genes in K. pneumoniae isolates from the clinical setting of Ahvaz, southwest Iran. As a result, antibiotic prescribing policies should be amended to hinder the further spread of PMQR genes in the studied region.

Investigation of gyrA and parC mutations and the prevalence of plasmid-mediated quinolone resistance genes in Klebsiella pneumoniae clinical isolates

BACKGROUND

The emergence of fluoroquinolone resistance in clinical isolates of Klebsiella pneumoniae is a growing concern. To investigate the mechanisms behind this resistance, we studied a total of 215 K. pneumoniae isolates from hospitals in Bushehr province, Iran, collected between 2017 and 2019. Antimicrobial susceptibility test for fluoroquinolones was determined. The presence of plasmid mediated quinolone resistance (PMQR) and mutations in quinolone resistance-determining region (QRDR) of gyrA and parC genes in ciprofloxacin-resistant K. pneumoniae isolates were identified by PCR and sequencing.

RESULTS

Out of 215 K. pneumoniae isolates, 40 were resistant to ciprofloxacin as determined by E-test method. PCR analysis revealed that among these ciprofloxacin-resistant isolates, 13 (32.5%), 7 (17.5%), 40 (100%), and 25 (62.5%) isolates harbored qnrB, qnrS, oqxA and aac(6')-Ib-cr genes, respectively. Mutation analysis of gyrA and parC genes showed that 35 (87.5%) and 34 (85%) of the ciprofloxacin-resistant isolates had mutations in these genes, respectively. The most frequent mutations were observed in codon 83 of gyrA and codon 80 of parC gene. Single gyrA substitution, Ser83→ Ile and Asp87→Gly, and double substitutions, Ser83→Phe plus Asp87→Ala, Ser83→Tyr plus Asp87→Ala, Ser83→Ile plus Asp87→Tyr, Ser83→Phe plus Asp87→Asn and Ser83→Ile plus Asp87→Gly were detected. In addition, Ser80→Ile and Glu84→Lys single substitution were found in parC gene.

CONCLUSIONS

Our results indicated that 90% of isolates have at least one mutation in QRDR of gyrA orparC genes, thus the frequency of mutations was very significant and alarming in our region.

Association of qnr Genes and OqxAB Efflux Pump in Fluoroquinolone-Resistant Klebsiella pneumoniae Strains

Background

The aim of this study was to investigate the frequency and relationship between plasmid-mediated quinolone resistance genes and OqxAB pump genes, as well as the genetic linkage in K. pneumoniae strains isolated from Hamadan hospitals in the west of Iran.

Materials and Methods

In this study, 100 K. pneumoniae clinical strains were isolated from clinical samples of inpatients at Hamadan Hospital in 2021. The antimicrobial susceptibility testing was performed using the disk diffusion method. The frequencies of genes encoding OqxAB efflux pumps and qnr were investigated by PCR. Molecular typing of qnr-positive K. pneumoniae isolates was assessed by ERIC-PCR.

Results

Antibiotic susceptibility testing showed high resistance (>80%) to fluoroquinolones. The gene encoding the OqxAB efflux pump was detected in more than 90% of K. pneumomiae strains. All K. pneumoniae isolates were negative for qnrA, and 20% and 9% of the isolates were positive for qnrB and qnrS, respectively. The genes encoding oqxA and oqxB were detected in 96% of qnr-positive strains. A qnrB + /qnrS + profile was observed in 16% of qnr-positive K. pneumoniae strains. Ciprofloxacin MIC ≥ 256 μg/ml was detected in 20% of qnr-positive strains. Genetic association analysis by ERIC-PCR revealed genetic diversity among 25 different qnr-positive strains of K. pneumonia.

Conclusion

However, no significant correlation was found between the qnr and the OqxAB efflux pump genes in this study. The high rate of fluoroquinolone resistance and determinants of antibiotic resistance among diverse K. pneumoniae strains increase the risk of fluoroquinolone-resistance transmission by K. pneumoniae strains in hospitals.

Relationship of OqxAB efflux pump to antibiotic resistance, mainly fluoroquinolones in Klebsiella pneumoniae, isolated from hospitalized patients

Objectives

This research was designed to study the prevalence of OqxAB efflux pump genes and also to investigate the relationship between efflux pump and resistance to antibiotics, especially to fluoroquinolones, evaluate the expression levels of OqxAB genes, and molecular typing of Klebsiella pneumoniae isolated from hospitalized patients in Hamadan hospitals, west of Iran.

Materials and Methods

In a cross-sectional study, 100 clinical strains of K. pneumoniae were isolated from hospitalized patients in three major teaching hospitals from January to June 2021. The antibiotic susceptibility of isolates was evaluated by the disk-diffusion agar method. The frequency of genes encoding oqxA and oqxB of efflux pump genes was investigated by PCR, and the expression of the oqxA efflux pump gene was investigated by the Real-time PCR method. The genetic relationship of K. pneumoniae isolates was analyzed by the Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR technique.

Results

According to our results, the multi-drug resistance phenotype (MDR) in 65% and high prevalence resistance to ciprofloxacin in 89% of K. pneumoniae isolates was detected. The higher prevalence of oqxA (95%) and oqxB (98%) was also detected. There was a significant relationship between ciprofloxacin resistance and the oqxB gene as well as between ceftriaxone and chloramphenicol resistance and the oqxA gene. The expression of the oqxA gene was higher in ciprofloxacin-resistant isolates.

Conclusion

The results of this study suggest a potential reservoir for the spread of OqxAB genes among hospital-acquired bacteria. Infection control strategies should be used prudently to reduce the spread of resistant strains of K. pneumoniae in hospitals.

Investigation of plasmid-mediated quinolone resistance genes among clinical isolates of Klebsiella pneumoniae in southwest Iran

Background

Extensive and inappropriate use of quinolones has led to growing resistance rates to these broad‐spectrum antibiotics. The present study purposed to investigate the prevalence of plasmid‐mediated quinolone resistance (PMQR) genes in Klebsiella pneumoniae clinical isolates.

Method

Ninety‐two non‐repetitive K. pneumoniae clinical isolates were confirmed by standard microbiological methods. Antibacterial susceptibility of isolates toward seven agents from the quinolone family was evaluated by the disc diffusion method. Ciprofloxacin minimum inhibitory concentrations (MICs) were determined using the standard agar dilution method. PCR amplification was used to detect the existence of PMQR genes in the studied isolates.

Results

In the present study, significant quinolones' resistance (40%) was observed in K. pneumoniae isolates, and most of the strains were resistant to nalidixic acid (94.6%) and ofloxacin (45.6%). MIC analysis showed 15 strains were resistant to 6–128 μg/ml of ciprofloxacin, and five were intermediately‐resistant. PMQR genes were detected in 88% of all isolates. Acc(6’)‐Ib‐cr was constituted half of the total PMQR genes detected among ciprofloxacin non‐susceptible isolates. Of 20 ciprofloxacin non‐susceptible isolates, 65% (n = 13) harbored multiple PMQR determinants, and 15 strains were determined as integron carriage.

Conclusion

The findings of this study indicated considerable resistance against quinolones, which could be correlated with the extensive and inappropriate use of this class of antibiotics as empirical treatment.