Investigation of Virulence Genes and Carbapenem Resistance Genes in Hypervirulent and Classical Isolates of Klebsiella pneumoniae Isolated from Various Clinical Specimens

Abstract

Klebsiella pneumoniae is a global pathogen that can cause hospital-acquired and community-acquired infections and is known for its resistance to antibiotics. The pathotype, which is defined as hypervirulent K.pneumoniae (hvKp) is more lethal than classical K.pneumoniae (cKp) isolates and causes many community-acquired infections such as liver abscess, endophthalmitis, pneumonia in healthy young adults. There are no clear clinical or microbiological criteria to define hvKp. String test showing hypermucoviscosity and the iucA gene encoding aerobactin, a siderophore, were used to demonstrate hypervirulence. In this study, it was aimed to investigate the presence of various virulence genes and carbapenem resistance genes in the isolates of K.pneumoniae isolated from various clinical samples in our laboratory and classified as classical and hypervirulent by string test and also to detect the presence of various virulence and carbapenem resistance genes in hvKp isolates. Presence of four virulence genes (fimH-1, rmpA, magA, iucA), K1-K2 serotypes in all isolates and five carbapenem resistance genes (blaOXA-48, blaKPC, blaIMP, blaVIM, blaNDM-1) in carbapenem resistant isolates were investigated with polymerase chain reaction (PCR) method. Forty-five percent of the isolates were defined as hvKp and 55% as cKp. The fimH-1 gene was found to be positive in 94% of the isolates, the iucA gene in 37%, the magA gene (K1) in 34%, the rmpA gene in 5%, and the K2 serotype in 3% of the isolates. iucA gene was positive in 68.9% of hvKp isolates and 10.9% of cKp isolates, and the presence of iucA gene in hvKp isolates was statistically significant compared to cKp isolates (p<0.05). magA gene and K1 serotype were detected in 28.9% of hvKp isolates and 38.2% of cKp isolates. Although the magA gene ratio was high in cKp isolates, this difference was not statistically significant (p> 0.05). fimH-1 gene was found positive in 93.3% of hvKp isolates and 94.5% of cKp isolates. The rmpA gene was positive in 8.9% of hvKp isolates and 1.8% of cKp isolates. The K2 serotype was positive in 4.4% of hvKp isolates and 1.8% of cKp isolates. Although there was no statistical difference in antibiotic susceptibility between hvKp and cKp isolates; ceftriaxone, cefuroxime, ceftazidime, amikacin, cefoxitin, ertapenem, cefuroxime axetil were found to be more sensitive in hvKp isolates. Ciprofloxacin and trimethoprim sulfamethoxazole were found to be more sensitive in hvKp isolates than cKp isolates, and the difference was statistically significant (p<0.05). Although gentamicin, amoxicillin, piperacillintazobactam were not statistically significant in the cKp group, they were more sensitive than the hvKp group (p> 0.05). Carbapenem resistance were found to be 65.7% in cKp and 34.3% in hvKp isolates. Although not statistically significant, hvKp isolates were found to be more sensitive to carbapenems. The most common gene among 35 carbapenem resistant isolates was blaOXA-48 detected in 29 isolates. While the blaKPC gene was detected in five isolates, blaIMP, blaVIM and blaNDM-1 were not detected in any isolates. Sixty nine percent of blaOXA-48 positive samples were found to be in cKp isolates and 31% in hvKp isolates. It was determined that all of the blaKPC positive isolates were hvKp isolates. It was concluded that the string test and virulence factors alone would not be sufficient to show hypervirulence, and that more than one virulence factor combination should be shown in the presence of clinical features of hypervirulent infections to show hypervirulence.