Bases of variation in resistance to beta-lactams in Klebsiella oxytoca isolates hyperproducing K1 beta-lactamase

Nineteen isolates of Klebsiella oxytoca were examined, representing 18 distinct strains. All were from a 1994 survey of resistance amongst klebsiellae in intensive care units in Europe, and all had reduced susceptibility, or were resistant, to cefuroxime, ceftriaxone and aztreonam, suggesting hyperproduction of the chromosomal K1 beta-lactamase. We sought to confirm this mechanism and to identify why the levels of resistance varied between isolates. Possible reasons for variation were differences in the quantity or subtype of the K1 enzyme or differences in this enzyme's interplay with permeability. Spectrophotometric assays showed that all 19 isolates had K1-like beta-lactamases and that these were present at > or = 15-fold higher levels than in beta-lactam-sensitive K. oxytoca isolates. Fourteen of the 19 isolates had the OXY-2 form of K1 enzyme, while the remaining five had the OXY-1 form, as determined by isoelectric focusing and PCR amplification. Most isolates with the OXY-2 enzyme were more resistant than those with the OXY-1 subtype, but this difference partly reflected enzyme quantity rather than subtype. More generally, and irrespective of enzyme subtype, levels of resistance were broadly related to beta-lactamase specific activity, and the degree of hyperproduction was a major determinant of the level of resistance. Nevertheless, other factors had a role too: several isolates had reduced susceptibility or were resistant to cefoxitin, which is not a substrate for K1 enzyme, and examination of outer membrane protein profiles revealed considerable strain-to-strain diversity in the molecular weight range typical of the major enterobacterial porins (40-48 kDa).

[Enterobacteriaceae isolated in eastern Romania: the evolution of ampicillin sensitivity in the 1970-1995 period]

The activity of ampicillin against 3383 Enterobacteriaceae (community and clinical isolates), collected in Eastern Romania, during 25 years was tested. Data were prelucrated by the box-plot method proposed by Simpson and Donnelly. The resistance degree for all species tested has progressively increased. In the studied region Enterobacteriaceae strains maintain their natural sensitivity only exceptionally: e.g., S. typhi and S. java, with limited circulation. Enterobacteriaceae which have contact with the resistance genic reservoir of the colon microbiota during the justified or nonjustified antibiotic treatment development resistance to usual antibiotics in the same ratio as most existent commensals present in this habitat.

Reduced susceptibility to co-amoxiclav in Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae isolated in Romania between 1985 and 1993

By determining the beta-lactam susceptibility of Enterobacteriaceae isolated in Eastern Romania from 1985 to 1993, three Escherichia coli, three Salmonella typhimurium and one Klebsiella pneumoniae isolates with reduced susceptibility to co-amoxiclav were found. The antibiotic susceptibility of the isolates and their E. coli derivatives, and kinetic values suggested the following resistance mechanisms: hyperproduction of TEM in S. typhimurium, limited antibiotic uptake in K. pneumoniae and OXA production in one strain of E. coli. Despite a normal beta-lactamase activity, the two remaining E. coli strains and their derivatives were less susceptible to co-amoxiclav.

Detection of beta-lactamase production and enzyme profiles in Enterobacteriaceae isolated in Moldova

In our study, out of 449 Enterobacteriaceae strains isolated between 1985 and 1990, 16 strains (3 Proteus, 6 nontyphoidal Salmonella, 7 Escherichia coli) were resistant both to Ampicillin- Sulbactam and Amoxycillin-Clavulanic acid associations. The activity profiles of the beta-lactamases produced by these resistant strains are described. Sarcina lutea ATCC 9341 was used as test strain. The effect of the enzymatic filtrate against beta-lactam antibiotics: Ampicillin, Cloxacillin, Cefadroxil, Cefuroxime, Cefotaxime, Ceftriaxone, was followed up. The enzyme types were established according to the ability of inactivating the tested antibiotics. Penicillins and cephalosporins were inactivated by these enzymes, except for Carbenicillin and Oxacillin. These beta-lactamases were resistant to Sulbactam and Clavulanic acid. In the studied Salmonella strains they are plasmidic codified, demonstrating that they belong to a new beta-lactamase class.

[Seroepidemiological data on the circulation of influenza virus in Moldova in 1991-1992]

OBJECTIVES

1. To establish the predominant circulating antigenic subtypes of influenza viruses in the epidemic season (19911992). 2. To evaluate the efficiency of seroepidemiological method in determining the circulating antigenic subtypes and its practical consequences.

METHODS

Our study consist of 1082 patients with acute respiratory disease or their contacts. Antigens prepared at "Cantacuzino Institute", C.D.C. Atlanta and from viral strains isolated in our laboratory were used. Hemagglutination-inhibiting Test was preceded by the elimination of the unspecific inhibitors with IO4K M/90. Significant titers were considered those > 1/10.

RESULTS

Were assessed by determining the number of antibody carriers, their ratio and geometrical mean of the reciprocal value of H.I. antibody titers.

CONCLUSIONS

1. In the winter of 1991 and 1992 A/H3N2 infections and in the spring 1991 and 1992 A/H1N1 virus prevailed, while B virus circulated by the end of spring 1992 epidemic season. 2. The decrease in 1992 of A/Iaşi/1/69 (H3N2) activity at the same time with high titers against A/Iaşi/1/76 (H3N2) and A/Iaşi/1/80 (H3N2) suggests a marked antigenic drift occurring in this interval 3. Serological method for determining the presence of hemagglutination inhibiting antibodies seemed enough and compulsory for detecting the etiological agent of acute respiratory disease, and an epidemic outbreak. 4. The circulation of three distinct antigenic subtypes determines the options for composition of anti-influenza vaccine.