Klebsiella pneumoniae is a leading cause of healthcare acquired infections. The severity of the infections is multifactorial including virulence and antimicrobial resistance properties. The objective of the study was to investigate the virulence determinants of K. pneumoniae strains colonizing patients hospitalized in the intensive care units (ICU) of a tertiary hospital in Uganda. A hospital based cross-sectional study involving 103 patients admitted in the ICU of Mulago National Referral hospital was conducted from January 2022 to April 2022. A total of 31 identified clinical strains of K. pneumoniae isolated from rectal swabs of the same number of patients were characterized. Susceptibility testing of colistin was performed by broth microdilution method, thereafter, 5 colistin resistant K. pneumoniae were purposefully selected for whole genome sequencing. Bioinformatics analysis was performed using established web-based tools to detect virulence genes, sequence type and other genomic features. Numerous virulence factor genes related to pathogenicity of K. pneumoniae were identified. They ranged from those related to colonization to those of persistence and dissemination including capsule genes (wzi), siderophore systems; yersiniabactin (ybt15), aerobactin (iutA), enterobactin (entC, entD, entF, entS, fepB, fepD, fepG, fes), and salmochelin (iroN), secretion systems; type II (T2SS) and type VI (T6SS-1). Furthermore, the isolates harbored outer membrane protein (ompA) gene, biofilm synthesis gene (fimH) and several adhesion genes. The results demonstrate the dual-risk of K. pneumoniae strains combining high level of virulence and colistin resistance which is a great concern as it leads to unmanageable infection outbreaks with high morbidity and mortality.

Multidrug resistance (MDR) among gram-negative bacteria is a global public health threat because it has exhausted all standard therapeutic options. This has necessitated clinicians to reconsider colistin, an “old sort” antibiotic which was deemed toxic for clinical use. Unfortunately, swift resistance towards colistin by K. pneumoniae has been reported in different parts of the world. The study aimed at investigating the genetic determinants of colistin resistance in K. pneumoniae isolated from patients admitted in a tertiary care hospital in Kampala, Uganda. 31 archived multidrug resistant K. pneumoniae isolates obtained from rectal swabs of patients admitted to the Mulago Hospital ICU were retrieved. From this collection, we selected 7 colistin resistant K. pneumoniae isolates for whole genome sequencing and molecular profile analysis. In silico sequence data analyses were performed using established web-based bioinformatics tools. The sequence analysis of the genes involved in colistin resistance revealed several non-synonymous mutations in nucleotide sequences of pmrA, pmrB, phoP, phoQ and mgrB genes. Insertion transposase genes for the insertion sequences IS1 and IS5 which are highly implicated in colistin resistance via modification or inactivation of mgrB gene were identified in all isolates and were located in the chromosomal DNA at different genomic positions. No plasmid-borne mcr genes were detected. More so, the strains harbored numerous multidrug resistant genes. This study underscores the need of genomic surveillance of K. pneumoniae strains to limit further spread of colistin resistance genes to avert the potential risk of pandrug resistance. And high throughput sequencing is imperative.