Abstract INTRODUCTION The relationships between phagocytosis, and mucoid phenotype, plasmid profile and virulence, and resistance genetic characteristics of Klebsiella pneumoniae clinical isolates were evaluated. METHODS Thirty isolates were used to determine the mucoid aspect. Four were selected for analysis of phagocytosis by alveolar macrophages. RESULTS Thirty percent of the samples presented the mucoid phenotype. The phagocytosis rate ranged from 21.5% to 43.43%. Phagocytosis was not correlated with the plasmid profile, but was apparently correlated with mucoid phenotype and antibiotic susceptibility. CONCLUSIONS: Several virulence factors act in parallel in K. pneumoniae to impair host defense.

PCR analysis of 16S-23S internal transcribed spacer (PCR ribotyping) and tRNA intergenic spacer (tDNA-PCR) were evaluated for their effectiveness in identification of clinical strains of Klebsiella pneumoniae and differentiation with related species. For this purpose both methods were applied to forty-three clinical isolates biochemically identified as K. pneumoniae subsp. pneumoniae isolated from patients clinical specimens attended at five hospitals in three Brazilian cities. References strains of K. pneumoniae subsp. pneumoniae, K. pneumoniae subsp. ozaenae, K. oxytoca, K. planticola and Enterobacter aerogenes were also analyzed. Both PCR methods showed specific patterns for each species. A conserved PCR ribotype pattern was observed for all clinical K. pneumoniae isolates, while differing from other related analyzed species. tDNA-PCR revealed five distinct patterns among the K. pneumoniae clinical isolates studied, demonstrating a predominant group with 90,6% of isolates presenting the same pattern of K. pneumoniae type strain. Both PCR-based methods were not able to differentiate K. pneumoniae subspecies. On the basis of the results obtained, both methods were efficient to differentiate the Klebsiella species analyzed, as well as E. aerogenes. Meanwhile tDNA-PCR revealed different tRNA arrangements in K. pneumoniae, suggesting intra-species heterogeneity of their genome organization, the polymorphism of the intergenic spacers between 16S and 23S rRNA genes appears to be highly conserved whithin K. pneumoniae clinical isolates, showing that PCR ribotyping can be an useful tool for identification of K. pneumoniae isolates.

The Gram-negative bacterium Pseudomonas aeruginosa has a wide environmental and ecological distribution. It is an opportunistic pathogen that acquires resistance to multiple antimicrobial agents and can infect plants, animals and humans. We used rDNA and tDNA PCR markers to characterize the bacterial diversity of P. aeruginosa strains isolated at a Brazilian teaching hospital (Oswaldo Cruz University Hospital, Recife, Brazil) between March 2003 and February 2004. Clonal groups of P. aeruginosa clinical isolates were identified from different patients in different hospital units using either rDNA or tDNA markers, or a combination of both in a duplex PCR. These PCR-typing methods together with drug-resistance profiles were used to trace the distribution of antibiotic resistant P. aeruginosa clones and to identify cross-infection of the same patient with a different bacterial clone after being moved to a different hospital unit. The data presented here demonstrates a rapid, reliable and useful method for epidemiological surveillance that can contribute to the control of P aeruginosa infections in hospital environments.