Search

Background: Pseudomonas aeruginosa commonly causes nosocomial bloodstream infections and the emergence of a variety of β-lactamases (BLs) is worrying. In 5 hospitals in Belo Horizonte, Brazil, the presence of phenotypes encoding BL genes was established and the genetic diversity of the P. aeruginosa strains recovered from bloodstream infections was analyzed., Materials and Methods: The isolates were investigated using a disk diffusion (DD) method and the Etest, for encoding metallo-β-lactamases (MBLs), oxacillinases and cephalosporinases. Genes and genetic diversity were evaluated by random amplified polymorphic DNA (RAPD) genotyping and enterobacterial repetitive intergenic consensus (ERIC)-PCR., Results: Twelve strains (30%) were positive for MBLs by Etest and DD, 15 were cephalosporinase-positive and 87.5% were positive for blaSPM-1 and blaVIM-1. Twenty-three strains (57.5%) were grouped into profile A, 32.5% into profile B and 10% into profile C by RAPD genotyping. ERIC-PCR revealed a varying degree of similarity between strains, ranging from 45 to 100%., Conclusions: The results suggest distinct clonal populations in the 5 hospitals studied, indicating a potentially problematic epidemiological situation in Belo Horizonte, Brazil.

Background: The aim of this study was to compare the bactericidal activity of cefepime plus amikacin against experimental pneumonia induced by a stably derepressed cephalosporinase-producing Enterobacter cloacae strain in immunocompetent and leucopenic rats., Methods: Sixty Wistar rats were used. Leucopenia was induced in half of them by a single intravenous administration of 30 mg/kg cyclophosphamide, while the remaining rats received the same volume of saline. All rats were infected 96 h later by tracheal instillation of 8 log(10) colony-forming units of E. cloacae. Twelve rats (6 immunocompetent and 6 leucopenic) were sacrificed 6 h later to assess the initial bacterial burden to the lungs. Then, the remaining 48 rats received a combination of 60 mg/kg cefepime twice a day and 25 mg/kg amikacin once a day given intraperitoneally or the same volume of saline. Six rats per group (leucopenic or not, treated or not) were sacrificed 12 and 30 h after therapy started., Results: Spontaneous bacterial clearance with time was observed only in immunocompetent rats. Compared to untreated animals, antibiotic administration induced a decrease in lung bacterial titres in immunocompetent and leucopenic rats. The difference was statistically significant only in leucopenic rats., Conclusions: The use of leucopenic rats reduced spontaneous bacterial clearance in the lungs and increased the bactericidal effect of the antibiotic combination and ultimately the confidence in the reliability of the results., (Copyright © 2012 S. Karger AG, Basel.)

Background: Recently, new 'fourth-generation' cephalosporins, such as cefepime and cefpirome, were introduced into antibacterial chemotherapy., Methods: In order to explore whether these new cephalosporins offer real advantages against Pseudomonas aeruginosa, we matched the in vitro activity of cefepime with that of ceftazidime and imipenem as reference compounds., Results: Among the 1,005 clinical isolates tested, 86.6% were susceptible to ceftazidime, whereas 80.7 and 76.9% were susceptible to imipenem and cefepime, respectively. Furthermore, the activity of the three compounds against a significant number of clinical isolates of P. aeruginosa expressing different resistance mechanisms to beta-lactam antibiotics was investigated. Among these isolates, 62.5% were still susceptible to ceftazidime, and 52.1 and 38.7% were inhibited by imipenem and cefepime, respectively., Conclusion: Ceftazidime and imipenem retained their activity against the majority of clinical P. aeruginosa isolates collected in Italy. Cefepime did not offer competitive advantages in terms of in vitro activity., (Copyright 2000 S. Karger AG, Basel)

Two multiple drug resistant Enterobacter cloacae isolates (Nos. 460 and 493) varied phenotypically in bacteriocin susceptibility in the absence of significant O antigen variation. Both isolates were susceptible to chloramphenicol, nitrofurantoin, polymyxin B, nalidixic acid, norfloxacin, and enoxacin only. One isolate carried a non-conjugative resistance (R) plasmid, whereas the other isolate contained a conjugative, 'curable' R plasmid and a cryptic plasmid. Both wild-type isolates constitutively produced a chromosomal cephalosporinase (nitrocefin hydrolysis); 'cured' variants of E. cloacae isolate No. 493, which had become susceptible for lamoxactam, produced a cefazolin-inducible beta-lactamase. The two E. cloacae isolates, including their 'cured' variants, were of low-grade virulence for outbred NMRI mice. Both isolates differed somewhat in susceptibility to defibrinated human blood. Inhibitory (0.25 microgram/ml), but not subinhibitory (0.125 microgram/ml) concentrations of norfloxacin and enoxacin combined with human blood yielded additive effects against both E. cloacae isolates.