Biomedical subjects

C Chanal

Publications and source records attributed to C Chanal.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1995

First characterization of inhibitor-resistant TEM (IRT) beta-lactamases in Klebsiella pneumoniae strains.

Two clinical strains of Klebsiella pneumoniae, TP 01 and TP 02, presented resistance to amoxicillin-clavulanate and were fully susceptible to cephalothin. These strains produced two beta-lactamases, SHV-1 and a TEM enzyme with a pI of 5.2. The previously described changes Arg-244-->Cys and Arg-244-->Ser in IRT-1 and IRT-2 (A. Belaaouaj, C. Lapoumeroulie, M. M. Caniça, G. Vedel, P. Nevot, R. Krishnamoorthy, and G. Paul, FEMS Microbiol. Lett. 120:75-80, 1994) were found in TEM enzymes from the TP 01 and TP 02 strains, respectively. This is the first report of inhibitor-resistant TEM (IRT) in species other than Escherichia coli from the family Enterobacteriaceae.

Amoxicillin↗

PubMed1995

Molecular characterization of nine different types of mutants among 107 inhibitor-resistant TEM beta-lactamases from clinical isolates of Escherichia coli.

DNA-DNA hybridization and sequencing were performed to determine the molecular basis of resistance to clavulanic acid in 107 inhibitor-resistant TEM (IRT) enzymes produced by Escherichia coli clinical isolates. These beta-lactamases derived from TEM-1 enzyme focused at pI 5.2 (n = 68) or 5.4 (n = 39) and were very poorly inhibited by clavulanic acid compared with TEM-1 enzyme. Results showed that the amino acid sequences of 84 of the 107 enzymes differ from TEM-1 by one or two substitutions previously described: Arg-244-->Ser (IRT-2) in 22 strains, Met-69-->Leu (TEM-33) in 17 strains, Met-69-->Val (TEM-34) in 14 strains, Met-69-->Ile (IRT-3) in 6 strains, Met-69-->Leu associated with Asn-276-->Asp (IRT-4) in 13 strains, and Met-69-->Val associated with Asn-276-->Asp (TEM-36) in 12 strains. A new combination, Met-69-->Ile with Asn-276-->Asp, was found in 20 strains and was called IRT-8. Two IRT enzymes not previously described were characterized. The substitution Met-69-->Val associated with a novel substitution Arg-275-->Leu occurred in one strain. The combination Met-69-->Leu and Asn-276-->Asp was associated with the novel substitution Trp-165-->Arg in two strains. These two novel enzymes were called IRT-9 and IRT-10, respectively. The implication of these novel mutated positions, 165 and 275, in resistance to inactivation by clavulanate was supported by crystallographic data on the TEM-1 enzyme and results of site-directed mutagenesis. Molecular characterization of these mutants showed great diversity among the genes coding for inhibitor-resistant TEM enzymes produced by clinical E. coli isolates.

Base Sequence↗

PubMed1995

[Detection of beta-lactamases resistant to inhibitors (IRT) by the disk diffusion method].

UNLABELLED: 85 E. coli strains producing various beta-lactamase were studied: TEM low level: n = 11, TEM high level: n = 4, oxacillinase (OXA): n = 5, céphalosporinase (CASE) +/- TEM: n = 5, inhibitor resistant TEM (IRT) n = 50, IRT+TEM: n = 3, IRT+ CASE: n = 7. Their susceptibility to amoxicillin (AMX), amoxicillin+clavulanate (AMC), ticarcillin (TIC), ticarcillin+clavulanate (TCC), piperacillin (PIP), piperacillin+tazobactam (TAZ), mecillinam (MEC), cephalotin (CF), cefoxitin (FOX) et ceftazidime (CAZ) were evaluated by a disk diffusion method, in order to determine the resistance pattern which allows a reliable detection of IRT-producing strains. The phenotype AMX R, TIC R, AMCI/R, TCCI/R et CFS was observed in 46 out of 53 IRT +/- TEM strains, 4/5 of OXA strains and 1/11 of TEM low level strains. A better sensitivity could be obtained by a modification of breakpoints for AMC, TCC and CF, however OXA-producing strains remain indistinguishable from IRT-strains.

Anti-Bacterial Agents↗

PubMed1994

Clinical isolates of Escherichia coli producing multiple TEM mutants resistant to beta-lactamase inhibitors.

Twenty clinical isolates of Escherichia coli resistant to amoxycillin and ticarcillin, both in combination with clavulanic acid, were studied. The ranges of MICs for these strains as determined by the agar dilution method were as follows: amoxycillin, 2048- > 4096 mg/L; ticarcillin, 512- > 4096 mg/L; piperacillin, 32-256 mg/L; mecillinam, 0.5-8 mg/L; and cephalothin 4-16 mg/L. Combining amoxycillin with beta-lactamase inhibitors, each at a fixed concentration of 4 mg/L, had only modest potentiating effects on the activities of this agent, the ranges of MICs falling to 256- > 2048 mg/L in the presence of clavulanic acid or sulbactam and to 64-1024 mg/L and 128-2048 mg/L in the presence of tazobactam and brobactam respectively. The pI values for the beta-lactamases produced by the 20 isolates were 5.2 for 15 strains, 5.4 for four strains and 7.4 for a single strain. Colony hybridization with oligonucleotides was performed in order to detect substitutions of arginine at position 241 (Arg-241) and methionine at position 67 (Met-67). Based on this technique, the four beta-lactamases with pI values of 5.4 were grouped into two oligotypes (+ = hybridization, - = non-hybridization)-Arg-241+, Met-67- (n = 3) and Arg-241+, Met-67+ (n = 1); in one of the three mutants which did not hybridize with the Met-67 probe, leucine had been substituted for methionine at position 67. The beta-lactamases with pI values of 5.2 which were identified in 15 strains were grouped into the following three oligotypes: Arg-241-, Met-67+ (n = 7); Arg-241-, Met-67- (n = 6); and Arg-241+, Met-67- (n = 2). In three of the 13 mutants which failed to hybridize with the Arg-241 probe, serine residues had replaced arginine residues at position 241. Substitutions of Arg-241 or Met-67 led to reduced affinities of the mutant enzymes for the beta-lactams tested. The results of the hybridization studies demonstrate that, amongst E. coli clinical isolates, there is a diversity of mutant TEM enzymes mediating resistance to beta-lactamase inhibitors.

Amoxicillin↗

PubMed1994

Frequency of inhibitor-resistant TEM beta-lactamases in Escherichia coli isolates from urinary tract infections in France.

Over a six-month period in 1993, 2972 non-duplicated isolates of Escherichia coli causing urinary tract infections were collected in a French teaching hospital (n = 785) and in three private laboratories (n = 2187). The resistance rate to amoxycillin-clavulanate combination (MIC > 16 mg/l) was 25.0% in the hospital isolates and 10.0% in the community isolates. Respectively, 27.5% and 45.0% of hospital and community isolates resistant to amoxycillin-clavulanate exhibited an unusual beta-lactam resistance pattern, suggesting inhibitor-resistant TEM (IRT) beta-lactamase production. These isolates were highly resistant to amoxycillin-clavulanate (MIC90 > 1024 mg/L), but were susceptible to cephalosporins (MIC < 32 mg/L). Enzyme extracts of these IRT-producing strains focused at pI 5.2 (n = 100) or 5.4 (n = 53). DNA-DNA hybridization confirmed that the beta-lactamases involved in this resistance mechanism were TEM-1 derived and contained variations in the altered positions described in IRT enzymes. This study shows a total frequency of 4.9% of IRT-producing isolates among E. coli isolated from urine specimens.

Amoxicillin↗

PubMed1994

Sequences of CAZ-3 and CTX-2 extended-spectrum beta-lactamase genes.

The nucleotide sequences of blaTEM genes coding for the extended-spectrum beta-lactamases CAZ-3 and CTX-2 were determined. The gene for CAZ-3 is identical to blaTEM-12b. The gene for CTX-2 differs from characterized blaTEM genes for extended-spectrum beta-lactamases by a new combination of already known mutations. We propose for CTX-2 the designation TEM-25.

Amino Acid Sequence↗

PubMed1993

[Haemophilus parainfluenzae meningitis in an 8-year-old boy].

Invasive infections caused by Haemophilus parainfluenzae, a saprophyte of the respiratory tract, are exceptional and should arise suspicion of abnormalities in immunocompetence. So far, about thirty cases of H. parainfluenzae meningitis affecting neonates, infants or adults have been published. A case of such meningitis in an 8-year old boy without any risk factor is reported here.

Child↗

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↗

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↗

PubMed1991

[In vitro antibacterial activity of piperacillin-tazobactam combination on hospital isolates and regression curve].

Minimal inhibitory concentrations (MICs) of piperacillin (P) in combination with 4 micrograms/ml of tazobactam (T) were evaluated by agar dilution for 1,245 strains isolated in 4 hospitals. In addition antibiograms by agar diffusion were performed with disks loaded of 75 micrograms of P + 10 micrograms of T. For naturally non beta-lactamase producing Enterobacteriaceae (E), MIC 50 and 90% of P + T were (microgram/ml): E. coli 1-2; P. mirabilis: 0.5-1; activity was practically identical on plasmid mediated penicillinase (Pase) producing strains. Strains of K. pneumoniae only resistant (R) to amino- and carboxypenicillins (C) had MICs less than or equal to 4 (mode MIC 2); MICs of strains R to cephalothin and/or cefotaxime were 2 to 16 (mode MIC 4). For chromosomal cephalosporinase (Case) producing species, MICs of P + T were less than or equal to 8, including for acquired Pase producing strains, but were greater than or equal to 16 for Case hyperproducing strains. Strains of P. aeruginosa susceptible (S) to C were inhibited by 1 to 16 (with MIC 4) and strains R to C by 8 to greater than 128. MICs were generally 2 to 32 for A. baumannii S to C at 0.12 to greater than 128 for strains R to C. Haemophilus, S or R to ampicillin, were inhibited by 0.008 to 2 (MIC 50 and 90: 0.016-0.12). S. aureus S to methicillin (M), Pase producing on not, were inhibited by 0.5 to 2 (mode MIC 1) and strains R to M by 8 to greater than 128. Activity of P + T for coagulase-Staphylococci was similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Acinetobacter↗