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, satAglycerophospholipid-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).

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.