Characterization of the chromosomal cephalosporinases produced by Acinetobacter lwoffii and Acinetobacter baumannii clinical isolates

Abstract

The beta-lactamases produced by Acinetobacter lwoffii ULA-501, Acinetobacter baumannii ULA-187, and A. baumannii AC-14 strains were purified and characterized, and their kinetic interactions with several beta-lactam molecules, including substrates and inhibitors, were studied in detail. The three enzymes appeared to be cephalosporinases with different acylation efficiencies (kcat/Km ratio values), and their hydrolytic activities were inhibited by benzylpenicillin, piperacillin, and cefotaxime, which did not behave as substrates. Carbenicillin was a substrate for the beta-lactamase from A. lwoffii ULA-501, whereas it acted as a transient inactivator of the enzymes produced by the two A. baumannii strains. Clavulanic acid was unable to inactivate the three beta-lactamases, whereas sulbactam behaved as an inactivator only at a high concentration (1 mM) which is difficult to achieve during antibiotic therapy. Analysis of the interaction with 6-beta-iodopenicillanic acid also allowed us to better discriminate the three beta-lactamases analyzed in the present study, which can be included in the group 1 functional class (5).

Molecular Epidemiology and Mechanisms of Carbapenem Resistance in Acinetobacter baumannii Endemic in New York City

“…All of our ribotype A and B isolates possessed a b-lactamase consistent with the chromosomal AmpC enzyme found in A. baumannii [27]. AmpC enzymes may possess weak hydrolytic activity of carbapenems and contribute to resistance in porin-deficient isolates of P. aeruginosa [28].…”

Multidrug resistant Acinetobacter baumannii isolates from a teaching hospital

“…Intrinsic -lactamase production has been reported in A. baumannii, 10,13 but the present study is the first to report such a high incidence of resistance in A. baumannii.…”

“…4 Antibiotic susceptibility disks used for the studies were purchased from HiMedia Laboratory (Bombay, India), except for those for aztreonam, imipenem, and moxalactam, which were obtained from Difco (Detroit, MI, USA). The antimicrobial disks used with the concentrations in micrograms in parentheses, were: amikacin (30), ampicillin (30), ampicillin ϩ sulbactam (30), aztreonam (30), carbenicillin (100), cefazoline (30), cefoperazone (75), ceftazidime (30), ceftizoxime (30), ceftriaxone (30), cefuroxime (30), cephaloridine (30), cephotaxime (30), ciprofloxacin (5), cotrimoxazole (25), doxycycline (30), enrofloxacin (10), gentamicin (10), imipenem (10), moxalactam (30), netilmicin (30), ofloxacin (5), piperacillin (100), sparfloxacin (5), sulfasomadine (300), tetracycline (30), triple sulfas (300), ticarcillin (75), and tobramycin (10). Antibiotic susceptibility testing was carried out, as per the directives of the manufacturer and National Committee for Clinical Laboratory Standards (NCCLS) guidelines, 5 on Mueller-Hinton Agar (Difco), using Escherichia coli ATCC 25922 as a quality control strain.…”

Interaction of Acinetobacter baumannii 19606 and 1656-2 with Acanthamoeba castellanii

“…Among them, Acinetobacter genomic species 2 (Acinetobacter baumannii or A. baumannii) is the most prevalent species among the clinical specimens (Bouvet and Grimont, 1987;Bergogne-Bérézin and Towner, 1996). Recently, A. baumannii has emerged as an important pathogen causing infections in severely ill patients in intensive care units or immuno-compromised individuals (Bergogne-Bérézin and Towner, 1996;Villegas and Hartstein, 2003) due to its remarkable ability to acquire resistance determinants to various kinds of antimicrobial agents (Perilli et al, 1996). In addition to multi-drug resistance (MDR), it has been found that most of the MDR A. baumannii strains have the ability to form considerable amounts of biofilms (Lee et al, 2008).…”