OBJECTIVETo investigate drug-resistance and carriage of virulence factors of Pseudomonas aeruginosa (Pa) isolated from children.

METHODThirty-eight strains of Pa were collected and isolated in pediatric clinic during 2006-2009, and tests were undertaken to identify bacteria and susceptibility test was performed using VITEK-2 COMPACT GNI and AST-GN13 cards. The virulence factors were confirmed by using polymerase chain reaction (PCR) and sequencing.

RESULTAll the 38 strains of Pa were resistant to ampicillin, ampicillin/sulbactam, cefazolin, nitrofurantoin, trimethoprim/sulfamethoxazole, resistance rates were 100%. Except for ceftriaxone (60.53%), the resistance rates to other antibiotics were all below 16%. PCR test showed that all the 38 strains of Pa carried exotoxin A(toxA) and nitric oxide reductase A (norA), however, detective ratio of the other virulence factors, exoenzyme Y (exoY) was 84.21% (32/38), exoenzyme S (exoS) 57.89% (22/38), pyocyanin (pyp) 42.11% (16/38), exoenzyme U (exoU) 34.21% (13/38), and 38 strains of Pa did not carry exoenzyme T (exoT) and elastase B (lasB) without exception. By analyzing tests, we discovered that 3 pan-drug resistant strains of Pa were all combination of exo U+/pyp+, there were 4 strains of Pa which were moderately-resistant to imipenem, including exoU+/pyp+/exoY+ (2 isolates), exo U+/pyp+ (1 isolate), and exoY+/exoS+ (1 isolates). It indicated that the drug-resistance rate of exoU+/pyp+ is much higher, compared with exoS+ and exoY+. Molecular epidemiological detection revealed that 2 of 3 extensive-resistance strains of Pa were the same clone, but another one had 96.3% of homology with them.

CONCLUSIONThe above mentioned 34.21% of Pa isolated from children carried virulence factors toxA, norA, exoS, exoY, pyp and exoU. The strains with exoU/pyp had rather high resistance. The strains with pyp had strong toxicity, they easily cause generalized infection, the patients with them had very high mortality.