The complex genetic region conferring transferable antibiotic resistance in multidrug-resistant and extremely drug-resistant Klebsiella pneumoniae clinical isolates

Abstract

Antibiotic resistance due to transferable resistance genes is one of the most important concerns in Klebsiella pneumoniae isolated from nosocomial infections. Eighty-eight K. pneumoniae isolates were confirmed through biochemical methods. In addition, antimicrobial susceptibility testing was performed using a disc-diffusion method. Extended-spectrum β-lactamase production among the isolates was screened using a double-disc synergism test, and the resistance genes were identified using PCR. The eight loci for multiple-locus variable number tandem repeat analysis (MLVA) genotyping were selected along with the primers. According to our findings, neomycin (5; 5.6%) and carbapenems (10; 11.3%) showed the most remarkable inhibitory effect but co-trimoxazole (46; 52.2%) was the least effective antibiotic against K. pneumoniae isolates. bla _CTX-M-1 , qnrA, qnrB, qnrS, intI, intII, aac3 and aac6 were detected in 30 (34%), 5 (5.6%), 29 (32.9%), 23 (26.1%), 88 (100%), 72 (81.8%), 26 (29.5%) and 28 (31.8%) of the 88 isolates, respectively. But none of the K. pneumoniae isolates expressed the intIII gene. Using MLVA, 23 MLVA types and eight clusters were identified. Extended-spectrum β-lactamase-producing K. pneumoniae isolates were classified into two clonal complexes. Effective strategies for infection control should be applied to monitor and control the spread of multidrug-resistant isolates by the resistance genes located on the mobile genetic elements.

Keywords: Antibiotics resistance; ESBLs; K. pnemoniae; MLVA; carbapenem; multidrug-resistant; nosocomial infections.

Fig. 1

Dendrogram showing the cluster analysis of 30 extended-spectrum β-lactamase (ESBL) -positive Klebsiella pneumoniae isolates based on the multiple-locus variable number tandem repeat analysis (MLVA) profile. I = HAI (hospital-acquired infections) and OPD (community-acquired infections), II = numbers of different hospitals, III = M (multidrug resistance), IV = X (extreme drug resistance), V to XII = different alleles of variable number of tandem repeat markers.

Fig. 2

Minimum spanning tree representation of the multiple-locus variable number tandem repeat analysis (MLVA) clustering of the 30 ESBL-positive Klebsiella pneumoniae clinical isolates isolated from patients in five hospitals of Tehran. Each circle represents a unique genotype, numbers under the circles represent the number of hospitals. The colour halo around the circles corresponds to CCs. Circles without a colour halo represent singletons. Numbers on the lines show the number of loci that are different between two MLVA profiles.