Summary auto-generated
This article investigated virulence factors and antimicrobial resistance in clinical isolates of Gram-negative bacteria, including Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, and Hafnia alvei. Researchers analyzed 385 bacterial strains collected from clinical specimens, examining the presence of virulence factors such as adhesins and toxins using molecular methods. The study evaluated resistance to various antimicrobial agents, including extended-spectrum beta-lactams and fluoroquinolones. K. pneumoniae was the most frequently isolated species (n=207), followed by E. cloacae (n=72) and H. alvei (n=70). The bacteria displayed varying degrees of virulence factor expression, with some strains carrying multiple virulence determinants. Resistance patterns varied significantly among species, with certain strains showing multidrug resistance. The authors found correlations between virulence factor profiles and antimicrobial resistance phenotypes. Results suggest that highly resistant strains often possessed multiple virulence factors, potentially enhancing their pathogenic potential. The findings highlight the clinical significance of monitoring virulence and resistance traits in these opportunistic pathogens, which are associated with nosocomial infections and complicate treatment options.
Key findings
- K. pneumoniae was the predominant species among 385 clinical isolates tested, followed by E. cloacae and H. alvei
- Strains carrying multiple virulence factors (5-6 factors) were frequently observed, with varying prevalence among different species
- Significant correlations existed between virulence factor profiles and multidrug resistance phenotypes
- Extended-spectrum beta-lactam and fluoroquinolone resistance were common, with 50% or more of some species showing resistance
- High virulence and antimicrobial resistance co-occurrence in clinical isolates poses increased clinical challenges for treatment
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Abstract
Extra-intestinal Hafnia alvei isolates are rarely considered to be pathogenic. To investigate whether such strains are able to produce virulence factors, a total of 70 clinical H. alvei isolates was compared with clinical extra-intestinal isolates of other members of the enterobacterial tribe Klebsiellae (Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens). Whereas mannose-sensitive haemagglutination (MSHA) was less common in H. alvei (59%) than in K. pneumoniae (86%) and E. cloacae (89%) isolates, the incidences of mannose-resistant haemagglutination indicative of type 3 pili (MR/K-HA) and of serum resistance properties were not lower. All H. alvei strains secreted siderophores but, unlike the other enterobacterial species examined, the siderophore type was neither enterobactin nor aerobactin. Although the low pathogenicity of H. alvei isolates could not be attributed to any of the factors investigated, the mean number of factors expressed by each H. alvei isolate was significantly lower than that expressed by K. pneumoniae and E. cloacae isolates but did not differ significantly from that of S. marcescens. Based on these findings, the low pathogenicity of H. alvei appears to be due to its low frequency of expression of virulence factors as compared with clinically significant species such as K. pneumoniae and E. cloacae.