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D Sirot

Publications and source records attributed to D Sirot.

At least 73 records · Page 4Linked to original sources
PubMed1992

Nucleotide sequences of CAZ-2, CAZ-6, and CAZ-7 beta-lactamase genes.

CAZ-2, CAZ-6, and CAZ-7 are plasmid-mediated beta-lactamases that are markedly active against ceftazidime. The corresponding structural genes were amplified by the polymerase chain reaction. Nucleotide sequences were determined by direct sequencing of the amplified products. Analysis of the nucleotide and the deduced amino acid sequences showed that CAZ-2, CAZ-6, and CAZ-7 are derived from TEM-2 by three, four, and two amino acid substitutions, respectively. All these substitutions are located at positions 102, 162, 235, 236, and 237 (Sutcliffe numbering), which are known to extend the substrate range of beta-lactamases. These substitutions are Lys-102, Ser-162, and Ser-236 in CAZ-2; Lys-102, Ser-162, Thr-235, and Lys-237 in CAZ-6; and Lys-102 and His-162 in CAZ-7. These results indicate that the nucleotide sequence of CAZ-2 is identical to that of TEM-8. The nucleotide sequence of CAZ-7 possesses the two mutations described in TEM-16 by the oligotyping method. In contrast, the combination of mutations encountered in CAZ-6 has not yet been described, and this enzyme was designated TEM-24.

Base Sequence↗
PubMed1992

R-plasmid-encoded adhesive factor in Klebsiella pneumoniae strains responsible for human nosocomial infections.

Klebsiella pneumoniae strains involved in hospital outbreaks of nosocomial infections, such as suppurative lesions, bacteremia, and septicemia, were resistant to multiple antibiotics including broad-spectrum cephalosporins. Epidemiologic investigations revealed that the reservoir for these K. pneumoniae strains was the gastrointestinal tracts of the patients. The study of the adherence ability of the strains reported here showed that these bacteria adhered to the microvilli of the Caco-2 cell line. This adhesion was mediated by a nonfimbrial protein with a molecular mass of 29,000 Da designated CF29K. Pretreatment of bacteria with antibodies raised against CF29K or Caco-2 cells with purified CF29K prevented the adhesion of K. pneumoniae strains to Caco-2 cells. CF29K immunologically cross-reacted with the CS31A surface protein of Escherichia coli strains involved in septicemia in calves. Genes encoding CF29K were located on a high-molecular-weight conjugative R plasmid, which transferred to E. coli K-12. Transconjugants expressed a large amount of CF29K protein and adhered to the brush border of Caco-2 cells. These findings show that K. pneumoniae strains were able to colonize the human intestinal tract through a plasmid-encoded 29,000-Da surface protein. Hybridization experiments indicated that the gene encoding resistance to broad-spectrum cephalosporins by the production of CAZ-1 enzyme and the gene encoding the adhesive property to intestinal cells were both located on a 20- to 22-kb EcoRI restriction DNA fragment. Genes encoding aerobactin and the ferric aerobactin receptor were also found on this R plasmid.

Bacterial Adhesion↗
PubMed1992

[Detection of extended-spectrum beta-lactamases by the rapid ATB E technique. Value of the API V2.1.1 expert system].

Twenty-two extended-spectrum betalactamase-producing strains of enterobacteriaceae recovered in the authors' hospital were tested using the Rapid ATB E coupled with the API V2.1.1. expert system. The expert system detected 90.9% of ESBL-producing strains. Two strains producing a SHV2 and a CTX1, respectively, escaped detection by the expert system despite concomitant resistance to aminoglycosides.

4-Quinolones↗
PubMed1991

A case-control study of an outbreak of infections caused by Klebsiella pneumoniae strains producing CTX-1 (TEM-3) beta-lactamase.

In July 1984 Klebsiella pneumoniae producing beta-lactamase CTX-1(TEM-3) (K. pneumoniae-CTX-1) spread from an Intensive Care Unit (ICU) throughout the hospitals of Clermont-Ferrand, France, and were isolated in four other hospitals of the region. A retrospective case control study was conducted in the ICU to characterize the risk factors for nosocomial infection with this organism. The cases were the 74 patients who had had K. pneumoniae-CTX-1 isolated from one or more clinical samples between July 1984 and December 1987. They were compared with 74 controls for host risk factors, underlying disease, procedures and antibiotic treatment. The monthly incidence of infection/colonization varied from 0% to 14.6%. The mortality rate attributable to this organism was 0.26% during the study period. The duration of stay of cases was longer than that of controls. More cases than controls had ventilatory assistance. However, the predominant risk factor was emergency abdominal surgery. Before K. pneumoniae-CTX-1 was isolated, cases received quinolones and trimethoprim sulphamethoxazole more often than controls. However, only 15% of cases had received third generation cephalosporins while at the onset of K. pneumoniae-CTX-1 infection colonization, 32 patients were no longer being given antibiotics. The use of antibiotic prophylaxis by, for example, selective digestive tract decontamination should be considered in patients at high risk of infection.

Adult↗
PubMed1991

Chromosomally-mediated beta-lactamases produced by Levinea amalonatica with activity against methoxyimino-cephalosporins.

Levinea amalonatica strain A2370 was isolated from the blood culture of a patient hospitalized in Charles Nicolle hospital (Tunis) during July 1986 and had decreased susceptibility to cefotaxime. Isoelectric focusing of crude extracts from this strain demonstrated three bands of beta-lactamase activity which focused at pH 5.4, 5.5 and 6.05. The three bands were separated and analysed for their kinetic properties. One enzyme (pI 5.4) had the properties of a TEM-1 beta-lactamase and did not confer resistance to third-generation cephalosporins. The two other bands, named B1 and B2, had pIs of 6.05 and 5.5 respectively, hydrolysed cefotaxime and similar cephalosporins, and were produced constitutively. After prolonged storage (six months at -20 degrees C) of the highly purified B1 enzyme, a mixture of B1/B2, with the B2 band predominating, was obtained. This observation suggested that the B2 enzyme was derived from B1. These enzymes appeared to differ from the MJ-2 beta-lactamase described previously in L. amalonatica.

Anti-Bacterial Agents↗
PubMed1991

Concomitant dissemination of three extended-spectrum beta-lactamases among different Enterobacteriaceae isolated in a French hospital.

From January 1988 to August 1989, 267 non-repetitive strains of Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBla) derived from TEM (CTX-1/TEM-3, CAZ-6) or SHV (CAZ-5) were isolated from 219 colonized or infected patients. ESBlas were characterized by analytical isoelectric focusing. Biotypes, resistance phenotypes and plasmid patterns were determined in order to differentiate the isolates in each species. Among the 116 CTX-1-producing Enterobacteriaceae, 48 strains were differentiated: 27 from 74 Klebsiella pneumoniae isolates, seven from 22 Enterobacter aerogenes isolates, and 14 from a combined total of seven K. oxytoca, five Serratia marcescens, six Escherichia coli, 1 Enterobacter cloacae and 1 Citrobacter freundii. CAZ-5 has been isolated since January 1988 in 16 different strains among 101 K. pneumoniae isolates. CAZ-6 was first identified in K. pneumoniae (January 1988). Among the 48 Enterobacteriaceae producing CAZ-6, 12 strains were differentiated: four from 39 E. aerogenes isolates, three from four K. pneumoniae, and five from a combined total of two S. marcescens, two E. coli and one E. cloacae. During this outbreak, CTX-1 was found to be encoded by 85 kb (Inc 7/M) or greater than or equal to 150 kb (Inc 6/C) plasmids. CAZ-6 was always encoded by an 85 kb (Inc 7/M) plasmid and CAZ-5 by a greater than 150 kb plasmid. These results show that strain epidemics and plasmid dissemination occurred mainly in K. pneumoniae and E. aerogenes for CTX-1, in E. aerogenes for CAZ-6, and in K. pneumoniae for CAZ-5. They also suggest that the bla(tem) gene (CTX-1) has spread between different plasmids present in the same ecosystem.

Cross Infection↗
PubMed1991

Identification of CTX-2, a novel cefotaximase from a Salmonella mbandaka isolate.

A strain of Salmonella mbandaka isolated from the feces of an Algerian infant showed a reduced susceptibility to cefotaxime (MIC, 8 mg/liter). This strain produced two transferable beta-lactamases of pIs 5.3 and 5.6. The novel beta-lactamase with a pI of 5.3 inhibited by clavulanic acid showed cefotaxime hydrolysis and was therefore designated CTX-2.

Anti-Bacterial Agents↗
PubMed1991

Translocation of antibiotic resistance determinants including an extended-spectrum beta-lactamase between conjugative plasmids of Klebsiella pneumoniae and Escherichia coli.

The extended-spectrum beta-lactamase CAZ-7, derived from TEMs, was produced by two different strains of the family Enterobacteriaceae, Klebsiella pneumoniae and Escherichia coli, isolated from the same patient. Both isolates were resistant to amikacin. In addition, the K. pneumoniae strain was TEM-1 producing and resistant to gentamicin. An E. coli HB101 transconjugant obtained from K. pneumoniae, selected on ceftazidime, showed that CAZ-7 and amikacin resistance were encoded by an 85-kb Inc7 or M plasmid, while an E. coli HB101 transconjugant obtained from E. coli under the same conditions showed that CAZ-7 and amikacin resistance were encoded by a greater than 150-kb Inc6 or C plasmid. Two other E. coli HB101 transconjugants obtained from K. pneumoniae, selected on gentamicin or chloramphenicol, showed that TEM-1 and gentamicin resistance could be encoded either by a greater than 150-kb Inc6 or C plasmid or by an 85-kb Inc7 or M plasmid. It was hypothesized that the genes for beta-lactam and aminoglycoside resistances were located on translocatable sequences. EcoRI digestion and hybridizations obtained with blatem, aacA4, and IS15 probes demonstrated that the CAZ-7 gene, amikacin resistance gene, and IS15 element were clustered on an approximately 20-kb fragment common to 85- and greater than 150-kb plasmids. E. coli HB101 transconjugants from K. pneumoniae and E. coli isolates were used to obtain translocations of CAZ-7 and amikacin resistance and of TEM-1 and gentamicin resistance between the 85- and greater than 150-kb plasmids. This study shows a typical example of in vivo gene dissemination involving transposable elements which translocate multiresistance genes, including an extended-spectrum beta-lactamase.

Ampicillin Resistance↗
PubMed1990

Molecular epidemiology of TEM-3 (CTX-1) beta-lactamase.

A total of 33 clinical isolates encoding TEM-3 (CTX-1) from four French hospitals were studied. The strains belonged to seven species, Klebsiella pneumoniae (n = 24), Escherichia coli (n = 3), Serratia marcescens (n = 2), Citrobacter freundii (n = 1), Enterobacter aerogenes (n = 1), Enterobacter cloacae (n = 1), and Klebsiella oxytoca (n = 1). All the strains harbored an Inc7 or M self-transferable plasmid with a size of approximately 85 kilobases. The plasmids had closely related EcoRI, HincII, HindIII, and PvuII restriction endonuclease-generated patterns and conferred resistance to all beta-lactams, except cephamycins and imipenem; to tetracycline, because of the presence of the genes blatem-3 and tetC, respectively, as determined by hybridization with specific probes; and to sulfonamide. Depending on the presence or absence and level of expression of the genes aacA4, aadA, and dfrI and of insertion element IS15, four types of plasmids could be distinguished. Plasmid pCFF04, the prototype plasmid encoding TEM-3, was widespread and appeared, by Southern hybridization, as the progenitor of the other types of replicons. The plasmid epidemic responsible for dissemination of TEM-3 in clinical isolates of members of the family Enterobacteriaceae may have originated in S. marcescens since pCFF04 was first detected in this species.

Aminoglycosides↗
PubMed1990

[Piperacillin-amikacin combinations: killing curves].

Bactericidal activity as a function of time of piperacillin (PIP) and amikacin (AKN) alone and in combination was evaluated by killing curves technique on 23 clinical isolates: E. coli (6), K. pneumoniae (5), E. cloacae (6) and P. aeruginosa (6), for which the minimal inhibitory concentrations ranges of piperacillin were 0.25 to 64 mg/l and of amikacin 1 to 8 mg/l. For each species, the strains were chosen according to the most frequent phenotypes: beta-lactams susceptible, penicillinase (Pase), cephalosporinase (Case) and Pase + Case producers. Killing curves were carried out with the following concentrations (mg/l): piperacillin (2, 16, 64); amikacin (4, 8, 16); piperacillin (2) + amikacin (4); piperacillin (16) + amikacin (8); piperacillin (64) + amikacin (16). Antibiotic concentrations corresponded to pharmacokinetics and/or to critical values of piperacillin and amikacin. Bactericidal activity was defined as a 4 log 10 decrease in CFU/ml between 2 and 24 hours. When piperacillin (64) was combined with amikacin (16), the bactericidal effects were nearly the same as those with amikacin alone. But piperacillin (16) + amikacin (8) combination had bactericidal effect for the majority of strains (21/23) and it prevented for some of them the bacterial regrowth observed with amikacin alone at the same concentration. A bactericidal activity without regrowth (until the 24th hour) was obtained for 9 strains; 2 susceptible E. coli, 3 K. pneumoniae (chromosomal Pase producer) and 4 cefotaxime susceptible E. cloacae, with low dose combination piperacillin (2) + amikacin (4). Finally, only combinations piperacillin (64) + amikacin (16) or piperacillin (16) + amikacin (8) had bactericidal activity on 2 Ticarcillin-resistant P. aeruginosa, the two antibiotics being separatedly bacteriostatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Amikacin↗
PubMed1989

Characterization of the plasmid genes blaT-4 and blaT-5 which encode the broad-spectrum beta-lactamases TEM-4 and TEM-5 in enterobacteriaceae.

We have determined the nucleotide sequence of the plasmid genes blaT-4 and blaT-5 which encode the broad-substrate-range beta-lactamases TEM-4 and TEM-5, respectively. The TEM-4 enzyme, which confers high-level resistance to cefotaxime (Ctx) and ceftazidime (Caz), differed from the TEM-1 penicillinase by four amino acid substitutions. Two of the mutations are identical to those responsible for the wide substrate range of the TEM-3 beta-lactamase which hydrolyses Ctx and Caz. The amino acid sequence of TEM-5, which confers higher levels of resistance to Caz than to other recently developed cephalosporins, differed from that of TEM-1 by three mutations distinct from those of TEM-4. Analysis of the location of the mutations in the primary and tertiary structures of class A beta-lactamases suggests that interactions between the substituted residues and beta-lactam antibiotics non-hydrolysable by TEM-1 and TEM-2 allow TEM-4 and TEM-5 to hydrolyse efficiently novel broad-spectrum cephalosporins such as Ctx and Caz.

Amino Acid Sequence↗
PubMed1989

Comparative study of five plasmid-mediated ceftazidimases isolated in Klebsiella pneumoniae.

Five plasmid-mediated beta-lactamases conferring a high level of resistance to ceftazidime were isolated from Klebsiella pneumoniae strains. These ceftazidimases (CAZ) differed in their isoelectric point (from 5.3 to 8.2) and were encoded by large self-transferable plasmids of 85 kb (CAZ-2, CAZ-3) or greater than or equal to 150 kb (CAZ-1, CAZ-4, CAZ-5). The 85 kb plasmids seemed closely related to pCFF04 encoding CTX-1 enzyme and belonged to the same incompatibility group 7 or M. These beta-lactamases hydrolysed all beta-lactams with the exception of cephamycins and carbapenems. For CAZ-1, CAZ-2 and CAZ-3 producers, MICs of ceftazidime (32-256 mg/l) were higher than MICs of cefotaxime (0.12-2 mg/l) and aztreonam (1-16 mg/l). For the strains producing the beta-lactamases CAZ-4 and CAZ-5, MICs of aztreonam were the highest (greater than or equal to 256 mg/l). The impaired activities of cephalosporins and monobactams were restored equally well by 2 mg/l of clavulanate, sulbactam and CL-298741 for CAZ-2 producing strains (wild type and transconjugant). Sulbactam (2 mg/l) had a lower protective effect than other inhibitors on ceftazidime for CAZ-1 and CAZ-3 producing K. pneumoniae. The protective effect of sulbactam (2 mg/l) was lower than that of the other inhibitors on all beta-lactams for CAZ-4 and CAZ-5 producers. The enzymes CAZ-1, CAZ-2 and CAZ-3 derived from TEM beta-lactamase whereas CAZ-4 and CAZ-5 derived from SHV-1 enzyme.

Autoradiography↗
PubMed1989

Comparative in-vitro activity of meropenem against clinical isolates including Enterobacteriaceae with expanded-spectrum beta-lactamases.

Meropenem, a new parenteral carbapenem, was tested in vitro by an agar-dilution method against 373 standard strains (aerobes and anaerobes) and against nine expanded-spectrum beta-lactamase-producing strains and their transconjugants (5 CTX-1, 2 CAZ-1, 2 CAZ-2). Meropenem was compared with methicillin, imipenem, piperacillin, cefoxitin, cefotaxime, ceftazidime, gentamicin, chloramphenicol, clindamycin, ciprofloxacin, vancomycin and metronidazole. Meropenem and imipenem exhibited an extended spectrum of activity, with low MICs. Only methicillin-resistant staphylococci, and Pseudomonas (Xanthomonas) maltophilia were resistant. Of the carbapenems, imipenem was more active against methicillin-susceptible staphylococci, streptococci and Enterococcus faecalis, but meropenem was markedly more active against all the Enterobacteriaceae and some pseudomonads. Both had similar activity against Ps. aeruginosa, Acinetobacter spp. and anaerobes. The carbapenem MICs were very low for Enterol acteriaceae producing the expanded-spectrum beta-lactamases. Against CTX-1-producing strains resistant to cefotaxime and ceftazidime and against CAZ-1 or CAZ-2-producers highly resistant to ceftazidime meropenem was the most active, with MICs lower (0.03-0.12 mg/l) than those of imipenem (0.06-0.5 mg/l), for wild type producers and their transconjugants.

Bacteria↗
PubMed1989

Interactions of meropenem, with beta-lactamases, including enzymes with extended-spectrum activity against third-generation cephalosporins.

The interactions of a meropenem were studied with a set of beta-lactamases including the new TEM- and SHV-related plasmid-mediated enzymes that have extended-spectrum activity against third-generation cephalosporins ('cefotaximases' and 'ceftazidimases'). Meropenem and imipenem were highly resistant to the hydrolytic activity of all the TEM and SHV related beta-lactamases, and to the OXA enzymes, as were the cephamycins: cefoxitin and cefotetan. The two carbapenems were also highly stable to Class C beta-lactamases (chromosomal cephalosporinases) whereas third-generation cephalosporins and cephamycins were slowly hydrolyzed. Both carbapenems demonstrated quite similar affinities for all the enzymes studied. In some instances, and particularly with Class A (TEM- and SHV-derived) enzymes, meropenem inactivated the beta-lactamase activity. Imipenem appeared less reactive in this respect.

Acylation↗
PubMed1989

Prospective survey of colonization and infection caused by expanded-spectrum-beta-lactamase-producing members of the family Enterobacteriaceae in an intensive care unit.

The occurrence of expanded-spectrum-beta-lactamase-producing strains was prospectively studied in 56 patients in an intensive care unit. Ten patients were infected or colonized; some of these patients had asymptomatic intestinal colonization. Four different expanded-spectrum beta-lactamases were identified and used as epidemiological markers to survey nosocomial infections.

Acute Kidney Injury↗
PubMed1989

The kinetics of CAZ-5, a novel SHV-related plasmid-mediated beta-lactamase with enhanced hydrolytic activity against ceftazidime.

The kinetic constants for "CAZ-5", a novel plasmid-mediated beta-lactamase with noticeable activity against third-generation cephalosporins and particularly ceftazidime have been determined. Two closely-related plasmid-mediated beta-lactamases have also been studied: SHV-2 and PIT-2 (also known as SHV-1). These enzymes were synthesized constitutively; they were highly sensitive to the action of the inhibitors clavulanic acid and sulbactam and they lacked activity against the cephamycins and imipenem. PIT-2/SHV-1 had poor hydrolytic activity against the third-generation cephalosporins, SHV-2 was markedly active against cefotaxime and related compounds, whereas the new enzyme, which was also active against these cephalosporins, had a noticeably greater activity against ceftazidime. Aztreonam was slowly hydrolysed by CAZ-5 beta-lactamase, but demonstrated an unusually high affinity for this enzyme.

Ceftazidime↗
PubMed1988

Kinetic properties of two plasmid-mediated beta-lactamases from Klebsiella pneumoniae with strong activity against third-generation cephalosporins.

We determined the kinetic constants for two plasmid-mediated beta-lactamases with strong activity against third-generation cephalosporins: CTX-1 and SHV-2. The enzymes had many similar properties: their synthesis was constitutive and they were significantly active against penicillins as well as cephalosporins. The two enzymes thus differed considerably from the chromosomal cephalosporinases, but bore some resemblance to the commonly-encountered plasmid-coded penicillinases, such as TEM beta-lactamases. Moreover, like the TEM enzymes, the plasmid-mediated CTX-1 and SHV-2 enzymes were highly sensitive to the action of the inhibitors clavulanic acid and sulbactam. These inhibitors protected cefotaxime from hydrolysis by these enzymes. Both CTX-1 and SHV-2 lacked activity against the cephamycins, cefoxitin, latamoxef (moxalactam) and cefotetan. The CTX-1 and SHV-2 enzymes had a low activity against oxacillin and were not sensitive to chloride ions. Thus, they were not related to the OXA type beta-lactamases. For the third-generation cephalosporins the rates of hydrolysis were high and thus bore no relation with those observed for the other presently-known beta-lactamases, with perhaps the exceptions of those produced by K. oxytoca. Imipenem was very resistant to the action of these CTX-1 and SHV-2 beta-lactamases.

Cephalosporins↗