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C Chanal

Publications and source records attributed to C Chanal.

At least 19 recordsLinked to original sources
PubMed2003

Effect of D240G substitution in a novel ESBL CTX-M-27.

Escherichia coli clinical strain Gre-1 collected in 2000 from a French hospital harboured a novel CTX-M-encoding gene, designated blaCTX-M-27. CTX-M-27 differed from CTX-M-14 only by the substitution D240G and was the third CTX-M enzyme harbouring this mutation after CTX-M-15 and CTX-M-16. The Gly-240-harbouring enzyme CTX-M-27 conferred to E. coli higher MICs of ceftazidime (MIC, 8 versus 1 mg/L) than did the Asp-240-harbouring CTX-M-14 enzyme. Comparison of CTX-M-14 and CTX-M-27 showed that residue Gly-240 decreased Km for ceftazidime (205 versus 940 microM), but decreased hydrolytic activity against good substrates, such as cefotaxime (kcat, 113 versus 415 s-1), probably owing to the alteration of beta3 strand positioning during the catalytic process.

Amino Acid Substitution↗
PubMed2003

Effects of Ser130Gly and Asp240Lys substitutions in extended-spectrum beta-lactamase CTX-M-9.

In CTX-M-9 extended-spectrum beta-lactamases (ESBLs), an S130G mutation induced a 40- to 650-fold increase in 50% inhibitory concentrations but decreased hydrolytic activity against cefotaxime. A D240K mutation did not modify enzymatic efficiency against ceftazidime. Residue K240 could interact with Q270 and therefore not with ceftazidime, in contrast with what was observed with certain TEM/SHV-type ESBLs.

Amino Acid Substitution↗
PubMed2002

CTX-M-1, CTX-M-3, and CTX-M-14 beta-lactamases from Enterobacteriaceae isolated in France.

Six clinical CTX-M-producing isolates of the family Enterobacteriaceae were detected between 1999 and 2000 in different French hospitals. Two strains produced CTX-M-1 and CTX-M-3 and four strains produced CTX-M-14, a mutant Ala-231-->Val of CTX-M-9. A putative transposable element, ISEcp-1, was located 43 bp upstream of all the bla(CTX-M) genes. Two CTX-M-14-encoding plasmids exhibited similar restriction patterns. The CTX-M-1- and CTX-M-3-encoding plasmids were related to the CTX-M-1- and CTX-M-3-encoding plasmids previously reported in 1990 in France and in 1998 in Poland, respectively.

DNA Transposable Elements↗
PubMed2002

TEM derivative-producing Enterobacter aerogenes strains: dissemination of a prevalent clone.

TEM-24 (CAZ-6) extended-spectrum beta-lactamase (ESBL) was detected in 1988 in Clermont-Ferrand, France, in Klebsiella pneumoniae (bla(TEM-24)) and Enterobacter aerogenes (bla(TEM-24b)), and since 1994, a TEM-24-producing E. aerogenes clonal strain has been observed elsewhere in the country. To determine if the spread of this clonal strain was restricted to TEM-24-producing E. aerogenes strains, 84 E. aerogenes strains (non-TEM/SHV-producing strains, TEM-1- or -2-producing strains, and different ESBL-producing strains), isolated from 1988 to 1999 in Clermont-Ferrand (n = 59) and in 11 other French hospitals in 1998 (n = 25), were studied. A clonal strain was found for TEM-24- but also for TEM-3- and TEM-1- or 2-producing isolates. This study shows that there is a clonal strain dependent on acquisition of the TEM-type enzyme (TEM-24 and other TEM types).

Bacterial Proteins↗
PubMed2002

Chromosome-encoded class D beta-lactamase OXA-23 in Proteus mirabilis.

Ten nonrepetitive Proteus mirabilis isolates, which were collected over 4 years (1996 to 1999) at the teaching hospital of Clermont-Ferrand, France, produced class D carbapenemase OXA-23. MICs of imipenem were 0.25 to 0.5 microg/ml for these clinical isolates. Molecular typing revealed that the 10 P. mirabilis isolates originated from the same clonal strain. Hybridization of I-CeuI-generated chromosome fragments with a bla(OXA-23) probe showed that the gene was chromosome encoded in the P. mirabilis strain.

Anti-Bacterial Agents↗
PubMed2001

New TEM variant (TEM-92) produced by Proteus mirabilis and Providencia stuartii isolates.

The sequences of the bla(TEM) genes encoding TEM-92 in Proteus mirabilis and Providencia stuartii isolates were determined and were found to be identical. Except for positions 218 (Lys-6) and 512 (Lys-104), the nucleotide sequence of bla(TEM-92) was identical to that of bla(TEM-20), including the sequence of the promoter region harboring a 135-bp deletion combined with a G-162-->T substitution. The deduced amino acid sequence of TEM-92 differed from that of TEM-52 by the presence of a substitution (Gln-6-->Lys) in the peptide signal.

Amino Acid Substitution↗
PubMed2001

Novel cefotaximase (CTX-M-16) with increased catalytic efficiency due to substitution Asp-240-->Gly.

Three clinical strains (Escherichia coli Rio-6, E. coli Rio-7, and Enterobacter cloacae Rio-9) collected in 1996 and 1999 from hospitals in Rio de Janeiro (Brazil) were resistant to broad-spectrum cephalosporins and gave a positive double-disk synergy test. Two bla(CTX-M) genes encoding beta-lactamases of pl 7.9 and 8.2 were implicated in this resistance: the bla(CTX-M-9) gene observed in E. coli Rio-7 and E. cloacae Rio-9 and a novel CTX-M-encoding gene, designated bla(CTX-M-16), observed in E. coli strain Rio-6. The deduced amino acid sequence of CTX-M-16 differed from CTX-M-9 only by the substitution Asp-240-->Gly. The CTX-M-16-producing E. coli transformant exhibited the same level of resistance to cefotaxime (MIC, 16 microg/ml) but had a higher MIC of ceftazidime (MIC, 8 versus 1 microg/ml) than the CTX-M-9-producing transformant. Enzymatic studies revealed that CTX-M-16 had a 13-fold higher affinity for aztreonam and a 7.5-fold higher k(cat) for ceftazidime than CTX-M-9, thereby showing that the residue in position 240 can modulate the enzymatic properties of CTX-M enzymes. The two bla(CTX-M-9) genes and the bla(CTX-M-16) gene were located on different plasmids, suggesting the presence of mobile elements associated with CTX-M-encoding genes. CTX-M-2 and CTX-M-8 enzymes were found in Brazil in 1996, and two other CTX-M beta-lactamases, CTX-M-9 and CTX-M-16, were subsequently observed. These reports are evidence of the diversity of CTX-M-type extended-spectrum beta-lactamases in Brazil.

Amino Acid Sequence↗
PubMed2000

Clinical relevance of Proteus mirabilis in hospital patients: a two year survey.

A retrospective study was performed on 1072 non-duplicate isolates of Proteus mirabilis, taken in the period April 1996 to March 1998, and on 100 patient charts randomly selected during the same period. P. mirabilis isolates accounted for 7.7% of Enterobacteriaceae. The isolates were predominantly from urine (70.2%); of the total, 38.0% were penicillinase-producing isolates, 6.9% were extended-spectrum beta-lactamase (ESBL)-producing isolates and 3.6% produced inhibitor-resistant beta-lactamase (IRB). ESBL-producing isolates were observed in long-stay and intensive care and IRB-producing isolates in paediatric units. Of the 95 patients whose charts were examined, 69 had a confirmed infection, which in 42 cases was nosocomial.

Anti-Bacterial Agents↗
PubMed2000

A novel class A extended-spectrum beta-lactamase (BES-1) in Serratia marcescens isolated in Brazil.

Serratia marcescens Rio-5, one of 18 extended-spectrum beta-lactamase (ESBL)-producing strains isolated in several hospitals in Rio de Janeiro (Brazil) in 1996 and 1997, exhibited a high level of resistance to aztreonam (MIC, 512 microgram/ml) and a distinctly higher level of resistance to cefotaxime (MIC, 64 microgram/ml) than to ceftazidime (MIC, 8 microgram/ml). The strain produced a plasmid-encoded ESBL with a pI of 7.5 whose bla gene was not related to those of other plasmid-mediated Ambler class A ESBLs. Cloning and sequencing revealed a bla gene encoding a novel class A beta-lactamase in functional group 2be, designated BES-1 (Brazil extended-spectrum beta-lactamase). This enzyme had 51% identity with chromosomal class A penicillinase of Yersinia enterocolitica Y56, which was the most closely related enzyme and 47 to 48% identity with CTX-M-type beta-lactamases, which were the most closely related ESBLs. In common with CTX-M enzymes, BES-1 exhibited high cefotaxime-hydrolyzing activity (k(cat), 425 s(-1)). However, BES-1 differed from CTX-M enzymes by its significant ceftazidime-hydrolyzing activity (k(cat), 25 s(-1)), high affinity for aztreonam (K(i), 1 microM), and lower susceptibility to tazobactam (50% inhibitory concentration [IC(50)], 0.820 microM) than to clavulanate (IC(50), 0.045 microM). Likewise, certain characteristic structural features of CTX-M enzymes, such as Phe-160, Ser-237, and Arg-276, were observed for BES-1, which, in addition, harbored different residues (Ala-104, Ser-171, Arg-220, Gly-240) and six additional residues at the end of the sequence. BES-1, therefore, may be an interesting model for further investigations of the structure-function relationships of class A ESBLs.

Amino Acid Sequence↗
PubMed2000

A 1998 survey of extended-spectrum beta-lactamases in Enterobacteriaceae in France. The French Study Group.

In a 3-month period in 1998, 79 consecutive isolates of Enterobacteriaceae producing an extended-spectrum beta-lactamase (ESBL) were collected. ESBLs were predominantly TEM derivatives (74 of 79): TEM-24-like (40 isolates), TEM-3-like (29 isolates), TEM-21 (3 isolates), and TEM-4 and TEM-52 (1 isolate each). Four isolates produced SHV derivatives SHV-4 (three isolates) and SHV-5 (one isolate), and one strain produced a CTX-M-3 enzyme. The high proportion of TEM-24-like-producing Enterobacter aerogenes isolates (36 of 79) suggests the occurrence of an epidemic strain in France.

Data Collection↗
PubMed2000

Prevalence of beta-lactamases among 1,072 clinical strains of Proteus mirabilis: a 2-year survey in a French hospital.

beta-Lactam resistance was studied in 1,072 consecutive P. mirabilis clinical strains isolated at the Clermont-Ferrand teaching hospital between April 1996 and March 1998. The frequency of amoxicillin resistance was 48.5%. Among the 520 amoxicillin-resistant isolates, three resistance phenotypes were detected: penicillinase (407 strains [78.3%]), extended-spectrum beta-lactamase (74 strains [14. 2%]), and inhibitor resistance (39 strains [7.5%]). The penicillinase phenotype isolates were divided into three groups according to the level of resistance to beta-lactams, which was shown to be related to the strength of the promoter. The characterization of the different beta-lactamases showed that amoxicillin resistance in P. mirabilis was almost always (97%) associated with TEM or TEM-derived beta-lactamases, most of which evolved via TEM-2.

Amoxicillin↗
PubMed2000

A novel CTX-M beta-lactamase (CTX-M-8) in cefotaxime-resistant Enterobacteriaceae isolated in Brazil.

To estimate the diversity of extended-spectrum beta-lactamases in Brazil, 18 strains from different species of the family Enterobacteriaceae exhibiting a positive double-disk synergy test were collected by a clinical laboratory from several hospitals in Rio de Janeiro, Brazil, in 1996 and 1997. Four strains (Proteus mirabilis, Enterobacter cloacae, Enterobacter aerogenes, and Citrobacter amalonaticus) hybridized with a 550-bp CTX-M probe. The P. mirabilis strain produced a CTX-M-2 enzyme. The E. cloacae, E. aerogenes, and C. amalonaticus isolates harbored a bla gene which was identified by cloning and sequencing as a bla(CTX-M) gene. E. coli HB101 transconjugants and the E. coli DH5alpha transformant harboring a recombinant plasmid produced a CTX-M beta-lactamase with an isoelectric point of 7.6 conferring a resistance phenotype characterized by a higher level of resistance to cefotaxime than to ceftazidime, as observed with the other CTX-M enzymes. The deduced protein sequence showed a novel Ambler class A CTX-M enzyme, named CTX-M-8, which had 83 to 88% identity with the previously described CTX-M enzymes. The phylogenic study of the CTX-M family including CTX-M-8 revealed four CTX-M types, CTX-M-8 being the first member of a new phylum of CTX-M enzymes. The evolutionary distances between the four types of CTX-M were large, suggesting that the four clusters branched off early from a distant unknown enzyme and that intermediate enzymes probably existed.

Amino Acid Sequence↗
PubMed1999

Diversity of TEM mutants in Proteus mirabilis.

In a survey of resistance to amoxicillin among clinical isolates of Proteus mirabilis, 10 TEM-type beta-lactamases were characterized: (i) the well-known penicillinases TEM-1 and TEM-2, the extended-spectrum beta-lactamases (ESBLs) TEM-3 and TEM-24, and the inhibitor-resistant TEM (IRT) TEM-44 and (ii) five novel enzymes, a penicillinase TEM-57 similar to TEM-1, an ESBL TEM-66 similar to TEM-3, and three IRTs, TEM-65, TEM-73, and TEM-74. The penicillinase TEM-57 and the ESBL TEM-66 differed from TEM-1 and TEM-3, respectively, by the amino acid substitution Gly-92-->Asp (nucleotide mutation G-477-->A). This substitution could have accounted for the decrease in pIs (5.2 for TEM-57 and 6.0 for TEM-66) but did not necessarily affect the intrinsic activities of these enzymes. The IRT TEM-65 was an IRT-1-like IRT (Cys-244) related to TEM-2 (Lys-39). The two other IRTs, TEM-73 and TEM-74, were related to IRT-1 (Cys-244) and IRT-2 (Ser-244), respectively, and harbored the amino acid substitutions Leu-21-->Phe and Thr-265-->Met. In this study, the ESBLs TEM-66, TEM-24, and TEM-3 were encoded by large (170- to 180-kb) conjugative plasmids that exhibited similar patterns after digestion and hybridization with the TEM and AAC(6')I probes. The three IRTs TEM-65, TEM-73, and TEM-74 were encoded by plasmids that ranged in size from 42 to 70 kb but for which no transfer was obtained. The characterization of five new plasmid-mediated TEM-type beta-lactamases and the first report of TEM-24 in P. mirabilis are evidence of the wide diversity of beta-lactamases produced in this species and of its possible role as a beta-lactamase-encoding plasmid reservoir.

Alleles↗
PubMed1996

Survey of prevalence of extended spectrum beta-lactamases among enterobacteriaceae.

During the first six months of 1990 and 1994 respectively, 3179 and 2721 non-repetitive strains of Enterobacteriaceae were isolated at the teaching hospital of Clermont-Ferrand. Extended-spectrum beta-lactamases were found in 147 isolates, mainly in Klebsiella pneumoniae (n = 73), Enterobacter aerogenes (n = 37) and Proteus mirabilis (n = 15). TEM-3/CTX-1, SHV-4/CAZ-5 and TEM-24/CAZ-6 were the prevalent enzymes. However, the most frequently involved enzyme in 1990 was TEM-3 (48.6%) whereas in 1994 it was SHV-4 (56.0%). Two salient features emerged from this study: the high frequency of TEM-3 production in P. mirabilis and the production of SHV-4 enzyme, heretofore observed solely in K. pneumoniae, in two other species, E. aerogenes and Escherichia coli.

Anti-Bacterial Agents↗
PubMed1996

Characterization of an inhibitor-resistant enzyme IRT-2 derived from TEM-2 beta-lactamase produced by Proteus mirabilis strains.

Ten clinical isolates of Proteus mirabilis were found to produce an inhibitor-resistant TEM beta-lactamase (IRT) in association with a TEM-1 enzyme. The IRT enzyme was derived from TEM-2. The blaIRT gene differs from blaTEM-2 gene by one point mutation which leads to the amino-acid substitution Arg-->Ser at position 244, as observed for the original IRT-2 enzyme derived from TEM-1 reported in Escherichia coli. This is the first report of an IRT beta-lactamase derived from TEM-2.

Microbial Sensitivity Tests↗
PubMed1996

[Detection of pneumococci with reduced susceptibility to penicillin G using the ATB++STREP strip].

Antibiotic susceptibility of 104 clinical isolates of Streptococcus pneumoniae was routinely tested using ATB STREP strips (Bio-Mérieux), and interpreted with ATB PLUS Expert V 2.3.1 software. In parallel, CMI of penicillin G was determined by Etest, strains with MIC < or = 0.06 mg/l were classified as penicillin susceptible. ATB system proved to be both sensitive and specific for the detection of strains of reduced susceptibility to penicillin G, accurately detecting 70 out of the 71 susceptible strains, and all of the 33 resistant strains. However the level of resistance cannot be deduced from ATB results.

Anti-Bacterial Agents↗