OBJECTIVES: To determine the prevalence of class A extended spectrum β-lactamases (ESBL)-producing Escherichia coli and Klebsiella spp., and to investigate clonality among ESBL-producing isolates of nosocomial and community infections. METHODS: The study involved 354 nosocomial infections samples and 992 community infections samples, obtained between 2003 and 2006 at Caxias do Sul, RS. The detection of ESBL was performed by the disk-diffusion test. Presence of blaCTX-M, blaSHV and blaTEM β-lactamase genes was evaluated by PCR, and genomic typing was determined by pulsed-field gel electrophoresis analysis. RESULTS: Higher frequency of ESBL-producing isolates were detected among nosocomial samples of E. coli (6.7%) and Klebsiella (43.7%), than those obtained from community infections (0.4% and 2.6%). blaTEM and blaCTX were the most prevalent ESBL gene families in both E. coli and Klebsiella isolates. Different pulsotypes were obtained among ESBL-producing E. coli and 11 clones for Klebsiella spp., which occurred over the years and in different hospital wards. Among ESBL-producing K. pneumoniae, 74.3% transferred ESBL genes by conjugation and exhibited concomitant decreased aminoglycosides susceptibility. CONCLUSION: ESBL-producing E. coli, and especially K. pneumoniae are essentially a nosocomial problem, and their dissemination to the community is relatively limited. The great genetic variability observed among ESBL-producing bacteria indicates polyclonal spread and high transference of ESBL genes between bacteria in the hospital environment. This information is of paramount importance for nosocomial infection control.

Aeromonas foram isoladas de 27 (6.6%) dos 408 pacientes admitidos com gastroenterite aguda em dois hospitais do Rio Grande do Sul, Brasil. Os isolados foram classificados com A. hydrophila (51.8%), A. caviae (40.8%), e A. veronii biotype sobria (7.4%). A maior prevalência de Aeromonas ocorreu em lactantes e crianças. Genes (aerA -aerolisina/hemolisina, ahpA -serina-protease, satA - glicerofosfolipidio-colesterol aciltransferase, lipA -lipase, e ahyB -elastase) e factores (atividade hemolítica, proteolítica, lipolítica, e formação de biofilme) de virulência foram identificados na maioria dos isolados de A. hydrophila e A. veronii biotype sobria, com freqüências menores em A. caviae. Todos os isolados de Aeromonas apresentaram resistência a ampicilina, ticarcilina/ácido clavulânico, cefalotina e cefazolina, e a maior parte (>70%) exibiram resistência a imipenem, carbenicilina, amoxacilina/sulbactam e piperacilina. Resistência múltipla foi evidenciada em 29,6% dos isolados. Os antibióticos mais eficientes foram as quinolonas (ciprofloxacina e norfloxacina) e os aminoglicosídicos (amicacina e netilmicina).

Aeromonas were isolated from 27 (6.6%) of 408 patients admitted with acute gastroenteritis in two hospitals at Rio Grande do Sul, Brazil. Isolates were classified as A. hydrophila (51.8%), A. caviae (40.8%), and A. veronii biotype sobria (7.4%). The highest prevalence of Aeromonas associated infections occurred in lactants and children. Virulence genes (aerA -aerolysin/hemolysin, ahpA -serine-protease, satA - glycerophospholipid-cholesterol acyltransferase, lipA -lipase, and ahyB -elastase) and virulence factors (hemolytic, proteolitic, lipolitic activities, and biofilm formation) were identified in most A. hydrophila and A. veronii biotype sobria isolates, with lower frequencies on A. caviae. All Aeromonas isolates were resistant to ampicillin, ticarcillin/clavulanic acid, cephalotin, and cephazolin, and most of them (>70%) exhibited resistance to imipenem, carbenicillin, amoxillin/sulbactan, and piperacillin. Multiple-resistance, more than four antibiotics, was evidenced in 29.6% of the isolates. The most efficient antibiotics were the quinolones (ciprofloxacin and norfloxacin), and the aminoglycosides (amikacin and netilmicin).

O efeito de solutos orgânicos no crescimento de Aeromonas trota e A. hydrophila foi avaliado. A prolina e o ácido glutâmico não apresentaram efeito osmoprotetor, mas a betaina exerceu osmoproteção permitindo o crescimento de ambas bactérias em concentrações inibitórias de NaCl. A cinética do crescimento sugere que a diferença em halotolerância entre as linhagens está associada à síntese de osmolitos, mais do que à capacidade de acúmulo de betaina.

The effect of organic solutes on the growth of Aeromonas trota and A. hydrophila was evaluated. Proline and glutamic acid were not effective as osmoprotectors, but betaine exerts osmoprotection allowing the growth of both strains in inhibitory concentrations of NaCl. Growth kinetics suggests that the halotolerance difference between the strains is associated with the synthesis of osmolytes rather than betaine uptake.