Objective To characterize the differences in virulence genes, antimicrobial resistance profiles, and integron-resistance gene cassette systems between hypervirulent Klebsiella pneumoniae (hvKP) and classical Klebsiella pneumoniae (cKP) isolates from food-producing animals in Sichuan Province, elucidate the unique pathogenicity and antimicrobial resistance mechanism of hvKP, and provide a foundation for new strategies for the prevention and treatment of hvKP infection in veterinary clinical practice.
Method A total of 139 K. pneumoniae (KP) isolates were classified as hvKP or cKP using the string test and PCR detection of virulence genes. The broth microdilution method and PCR sequencing were used to detect the antimicrobial susceptibility and integron-cassette distribution patterns in these isolates, respectively. Multilocus sequence typing (MLST) was conducted for hvKP isolates.
Result Among the 139 KP isolates, 16 were identified as hvKP, which were high viscosity and carried rmpA-iucA-iutA, the other 123 were cKP. Compared to cKP, the hvKP isolates demonstrated a significantly higher prevalence of rmpA, iucA, aero, iroB, and ybtA (P≤0.01) and possessed more complex virulence profiles. All KP isolates exhibited varying levels of antimicrobial resistance and widespread multidrug resistance profile. hvKP demonstrated significantly lower resistance rates to kanamycin, gentamicin, doxycycline, and enrofloxacin compared to cKP (P≤0.05 or P≤0.01). The IntI 1 was detected in nearly all isolates (100.00% in hvKP and 99.19% in cKP). Among these, only one hvKP isolate carried cassette, which was arr3-dfrA27. In contrast, 31 cKP isolates harbored cassettes, including nine distinct arrays, with dhfrI-aadA2 and dfrA12-orf-aadA2 being the main ones. The IntI 2 gene was rare, found in only three cKP isolates, all of which contained empty cassettes. MLST analysis identified the predominant sequence types (STs) among hvKP were ST25 (43.75%) and ST60 (31.25%). Notably, both of these STs isolates displayed concurrent multidrug resistance and complex virulence profiles.
Conclusion Antimicrobial resistance in KP isolates from food animals in Sichuan Province is significant. The integron-mediated resistance mechanisms heightens the risk of antimicrobial resistance dissemination. Of particular concern is hvKP, which combines complex virulence factors with serious antimicrobial resistance, complicating veterinary clinical treatment. Therefore, the rapid and accurate identification of hypervirulent strains, continuous monitoring of antimicrobial resistance, and the development of optimal treatments are urgent priorities in veterinary practice.
DownLoad: