Clinically significant Klebsiella pneumoniae persistence in wastewater: co-occurrence of virulence and multidrug resistance genes.

BACKGROUND

Wastewater monitoring is an effective approach for assessing public health, providing insight into circulating pathogens and their associated antimicrobial resistance genes. Klebsiella pneumoniae, a clinically and environmentally significant opportunistic pathogen, was investigated in this study.

METHODS

120 wastewater samples were collected from various sources, and the isolates were analyzed for antimicrobial susceptibility using the Kirby-Bauer disk diffusion method against 11 antibiotics, in addition to PCR-based detection of β-lactamase and virulence genes.

RESULTS

Among 81 K. pneumoniae isolates from different wastewater sources, 51% were resistant to at least one antibiotic, with hospital wastewater being the main source of resistant strains (74.2%), followed by community wastewater (50%), WWTP influent (35%), and effluent (21.4%). Resistance was most frequent to ampicillin/sulbactam (35.8%), whereas gentamicin showed the highest efficacy (4.9%). Multidrug resistance was observed in 53.7% of resistant isolates, primarily in samples from hospitals (69.6%) and WWTP influents (57.1%). ESBL producers accounted for 67.5% of isolates, while 32.5% co-produced ESBLs and carbapenemases. The blaSHV gene was detected in all isolates (100%), while blaOXA-48 (22.5%) was the most common carbapenemase gene. Almost all isolates (98.8%) possessed at least one virulence gene, with mrkD (96.3%) and entB (79.0%) being the most detected. Additionally, 86.5% of the isolates carried two or more virulence genes. Notably, no hypervirulent strains were observed.

CONCLUSION

Overall, wastewater from diverse sources constitutes a significant reservoir of multidrug-resistant and virulent K. pneumoniae strains. Their environmental release poses a considerable public health risk, highlighting the urgent need for improved wastewater management and continuous microbial surveillance.