Comparison of Virulence Factors among Clinical Isolates of Pseudomonas aeruginosa Producing and Non-producing Extended Spectrum -lactamases

Multidrug Resistance (MDR) Pseudomonas aeruginosa is an emerging nosocomial pathogen worldwide. In severe infections, Extended Spectrum -lactamases (ESBLs) and expression of various virulence factors may work in harmony, resulting in the treatment failure. An association between ESBL production and two virulence factors: cell surface hydrophobicity and biofilm formation in P. aeruginosa has been demonstrated previously. This study was designed to compare the antimicrobial resistance pattern and production of some virulence factors in ESBL producers ( ESBL+) and ESBL non-producers (ESBL-) clinical isolates of P. aeruginosa. ESBL production was detected by the double disk method and antimicrobial activity was tested by agar dilution methods. Antibacterial resistance pattern showed 48 different antibiotypes with 25 and 23 different types in ESBL+ and ESBL- isolates, respectively. The Minimum Inhibitory Concentrations (MICs) and percentage of isolates resistant to nearly all antibacterial agents tested, was significantly higher in ESBL+ isolates compared to ESBL-isolates ( p=0.001). The activity of LasA in ESBL+ isolates was higher than the negative isolates and statistically significant (p=0.05). Expression of mannose sensitive haemagglutination and production of pyoverdin in the ESBL+ isolates was significantly lower than the ESBL-isolates (p=0.04). No significant difference in the expression of mannose resistant haemagglutination and production of LasB was found between the ESBL+ positive or negative isolates. The result of present study suggests a correlation between ESBL phenotype and production of some factors that are reported to be involved in the virulence in P. aeruginosa.