English abstract
Background: Integrons are semi-mobile elements that have a significant role in the
dissemination of antibiotic-resistance-conferring genes between bacteria. This study
aims to describe the prevalence and characterize the molecular features of integrons
in clinical isolates of Klebsiella pneumoniae.
Methods: A total of 50 multidrug-resistant representatives K. pneumoniae isolates
from Sultan Qaboos University Hospital (SQUH) were investigated for the presence
of integrons class 1, 2, and 3 by Polymerase Chain Reaction (PCR). Antimicrobial
susceptibility test was performed by disc diffusion method according to the Clinical
and Laboratory Standards Institute (CLSI) guidelines. The variable regions of the
integrons were PCR-amplified and sequenced to detect the gene cassettes. To assess
the horizontal transferability for the gene cassettes, filter- mating conjugation
experiments were conducted. Whole genome sequencing (WGS) was performed in
representative (n=23) isolates and analyzed using various bioinformatics tools, to
determine the sequence type (ST), acquired antimicrobial resistance genes, and
perform plasmid-typing of integron-carrying strains. Highly virulent serotypes of K.
pneumoniae were identified through amplifying 5 capsule serotype genes from the
integron-positive isolates.
Results: Class 1 integron was detected in 96% (48/50) of isolates, whereas, class 2
and class 3 integrons were not detected. Among integron-positive isolates, 18 stains
contained variable regions. All the representative samples that were tested for the
horizontal transferability, confirmed the successful transfer of integrons between cells
and WGS confirmed their presence in conjugative plasmids. Ten different gene
cassette arrays were detected with dihydrofolate reductase (dfrA14) as the most
prevalent (34.8%) gene cassettes in class 1 integrons. Furthermore, MLST analysis
detected 9 sequence types (ST), with ST-231 and ST-395 as the predominant STs.
BlaOXA-232 and blaCTX-M-15 were the most frequently detected carbapenems and betalactamases in sequenced isolates. Three isolates were classified as highly virulent
serotypes (k1 and k2).
Conclusions: This study highlighted the widespread of class 1 integrons among MDR
isolates of K. pneumoniae and confirmed the spread of antimicrobial resistance genes
by horizontal transfer. Therefore, the wise use of antibiotics and the adherence to
effective infection control measures are necessary to limit further dissemination of
multidrug-resistant organisms.
