The emergence of hypervirulent and carbapenem-resistant hypermucoviscous Klebsiella pneumoniae strains presents a significant public health challenge due to their increased virulence and resistance to multiple antibiotics. This study evaluates the antibiotic susceptibility patterns and virulence profiles of classical and hypervirulent K. pneumoniae strains isolated from various clinical samples. A total of 500 clinical samples were collected from patients at the Mardan Medical Complex and Ayub Medical Complex in KPK between July 2022 and June 2024. Among these, 64 K. pneumoniae strains were isolated and subsequently subjected to antimicrobial susceptibility testing (AST) and phenotypic virulence detection. Among the 64 isolates, 21 (32.8%) exhibited hypermucoviscosity, a characteristic associated with increased pathogenicity. Hemagglutination was observed in 35 (54.1%) of the isolates, indicating the presence of surface adhesins that facilitate bacterial adherence to host tissues. A high prevalence of biofilm formation was noted, with 54 (84%) isolates capable of forming biofilms, which are known to protect bacteria from antibiotics and the host immune response. Most isolates (59/64, 92.1%) were resistant against ampicillin, highlighting its limited efficacy against these strains. Conversely, the lowest resistance was observed for tigecycline, with only 15% (10/64) of the isolates showing resistance, indicating its potential utility as a treatment option. The study also found that 38 (59.3%) of the isolates were extended-spectrum beta-lactamase (ESBL) producers, 42 (65.6%) were multidrug-resistant (MDR), 32 (50%) were extensively drug-resistant (XDR), and 13 (20.3%) were resistant to carbapenems. The genetic study revealed biofilm producer and enhancer genes (mrkD, pgaABCD, fimH, treC, wzc, pilQ, and luxS) mainly in the hypervirulent strains. These hypervirulent strains also show a high number of resistance genes. The findings of this study underscore the critical need for the active surveillance of antimicrobial resistance and virulence determinants in K. pneumoniae. The coexistence of high levels of antibiotic resistance and virulence factors in these isolates poses a severe threat to public health, as it can lead to difficult-to-treat infections and increased morbidity and mortality.

Antibiotic use has risen sharply in recent decades, fueling resistance. Since China reported colistin resistance in 2015, global concern has grown. While few cases of colistin resistance have been reported in Enterobacteriaceae from Pakistan, molecular factors remain unclear. This study aimed to determine the prevalence of colistin-resistant Enterobacteriaceae (ColRE) in a tertiary care hospital in Abbottabad, Pakistan. Altogether 89 Enterobacteriaceae isolates were collected from in-patients or out-patients at Ayub Teaching Hospital Abbottabad. The isolates were identified using API 20E kit and antibiotic susceptibility testing was performed following CLSI guidelines. Molecular screening of antibiotic resistance genes was conducted by PCR. The results showed E. coli (40.4%) as the most common pathogen, followed by K. pneumoniae (21.3%), S. typhi (19%), Enterobacter (9%), Raoultella ornithinolytica (4.4%), K. aerogenes (2.2%), Citrobacter (2.2%) and K. oxytoca (1%). Antibiotic testing showed highest resistance to aztreonam and cefepime (65.1%), and lowest to colistin (29.2%) and meropenem (22.4%). Overall, 48.3% of the isolates were multidrug resistant (MDR), with K. pneumoniae showing the highest MDR rate (68.4%). Molecular screening of colistin resistance genes found 15.3% of isolates positive for mcr-1 or mcr-2 genes. Simultaneous presence of mcr-1 and mcr-2 was identified in 3.8% of isolates. The study also found the first case of K. aerogenes with mcr-1 positivity. In conclusion, the study reveals a high rate of colistin resistance Enterobacteriaceae with notable presence of plasmid mediated genes. The study recommends nationwide surveillance of ColRE, with emphasis on the screening of plasmid-mediated determinants.