Evaluation of mechanisms of colistin resistance in Klebsiella pneumoniae strains isolated from patients with urinary tract infection in ICU.

Background and Objectives: One of the major causes of urinary tract infections is Klebsiella pneumoniae. Currently, few studies investigated the mechanisms of resistance to colistin in Iran. The current study aimed to determine the prevalence of plasmid and chromosome-mediated resistance to colistin in K. pneumoniae isolates. Materials and Methods: 177 urine samples were collected from patients with urinary tract infections hospitalized in the intensive care unit (ICU) of hospitals in the city of Qazvin. K. pneumoniae isolates were identified by standard biochemical methods, resistance to colistin among K. pneumoniae isolates were tested by disk diffusion and microbroth dilution methods. The chromosomal mutation and presence of the mcr genes in colistin-resistant K. pneumoniae were evaluated by PCR. Results: Out of 177 samples, 65 K. pneumoniae were obtained from patients in the ICU. Six colistin-resistant isolates were isolated with MIC values ≥4 µg/mL, none of them was positive for mcr1-5. In 4 isolates, missense mutation in mgrB gene resulted in amino acid substitutions and in one isolate of mgrB gene was found intact mgrB gene. Conclusion: The results suggest that mgrB mutation was the main mutation among colistin-resistant isolates and plasmid-borne colistin resistance was not expanded among strains.

Phenotypic Identification and Genotypic Characterization of Plasmid-Mediated AmpC ß-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae Isolates in Iran.

One of the mechanisms of Klebsiella pneumoniae and Escherichia coli resistance to ß-lactam antibiotics is the production of ß-lactamase enzymes. Among these are the AmpC ß-lactamases, which confer resistance to a class of antibiotics. However, little is known about the AmpC ß-lactamases of K. pneumoniae and E. coli clinical isolates in Qazvin, Iran. This study was designed to assess the AmpC ß­lactamases-producing strains and also identify the prevalence of AmpC ß­lactamases genes. Antimicrobial susceptibility tests were performed on 435 K. pneumoniae and E. coli isolates using disk diffusion technique. Plasmid-mediated AmpC genes were studied using a multiplex PCR assay. The AmpC ß-lactamase-producer isolates were studied by employing cefoxitin disk diffusion test, AmpC induction test, AmpC cefoxitin-EDTA test, and boronic acid disk test. Our results showed that of 46 (18.4%) cefoxitin-insensitive E. coli isolates, 10 (21.7%) were positive for AmpC ß-lactamase genes, among them 4 (8.69%) isolates were positive for blaDHA genes and 6 (13%) for blaCIT genes. Of 57 (30.4%) cefoxitin-insensitive K. pneumoniae isolates, 10 (17.5%) were positive for AmpC gene with 4 (6.34%) and 6 (9.5%) isolates positive for blaDHA and blaCIT genes, respectively. However, no MOX, ACC, FOX, or EBC genes were detected in the isolates. Considering the results of different confirmatory phenotypic tests, the AmpC cefoxitin-EDTA test showed a higher discriminatory power for detecting AmpC ß-lactamase-producing strains. The specificity and sensitivity of AmpC cefoxitin-EDTA were 77%, 100% for K. pneumonia and 70%, 90% for E. coli higher than the other two tests, respectively. Also, the authors demonstrated high prevalence rate for resistance to certain antibiotics, such as cefuroxime, trimethoprim-sulfamethoxazole, ampicillin, and cefotaxime. In conclusion, our study provided valuable information regarding the plasmid-mediated AmpC ß-lactamase gene content, antibiotic resistance, and confirmatory phenotypic tests for AmpC ß-lactamases in E. coli and K. pneumoniae isolates from clinical sources.

Molecular mechanisms and prevalence of colistin resistance of Klebsiella pneumoniae in the Middle East region: A review over the last 5 years.

The increasing prevalence of multidrug-resistant (MDR) Klebsiella pneumoniae is a serious clinical and public health problem, and colistin is the last-resort treatment option for MDR infections. However, resistance to colistin has been increasingly reported in the world, such as the Middle East region, where antibiotics are used more in the human and agriculture industry. In this paper, we review the available data on the molecular mechanisms and prevalence of colistin resistance of K. pneumoniae in the Middle East over the last 5 years. To the best of our knowledge, 590 colistin-resistant K. pneumoniae isolates were reported from six countries, including Turkey (438), Iran (86), Saudi Arabia (24), United Arab Emirates (31), Kuwait (5), Israel (3) and Lebanon (3), between 2013 and 2018. However, there has been no reports about colistin resistance among K. pneumoniae isolates in Iraq, Yemen, Syria, Jordan, Palestine, Oman, Qatar, Bahrain and Cyprus. Moreover, it seems that mutations and insertion sequence transpositions in the mgrB gene were the most common colistin resistance mechanisms among K. pneumoniae in the Middle East region, which is similar to other parts of the world.