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A Philippon

Publications and source records attributed to A Philippon.

At least 19 recordsLinked to original sources
PubMed1997

A plasmid-mediated CMY-2 beta-lactamase from an Algerian clinical isolate of Salmonella senftenberg.

Multiresistance to antibiotics including beta-lactams, e.g. cefoxitin, was transferred by conjugation to Escherichia coli strain C1a from a clinical isolate of Salmonella senftenberg recovered from stools of an Algerian child. The susceptibility pattern to beta-lactams was similar to the profile mediated by an AmpC-type beta-lactamase. By biochemical analysis, typical AmpC-type enzyme substrate and inhibition profiles were obtained. Finally, an ampC plasmid-encoded beta-lactamase gene was cloned and sequenced. Its deduced amino acid sequence confirmed its identity as a class C beta-lactamase. It showed 99.5% sequence identity with the plasmid-mediated beta-lactamase CMY-2. The differences in the amino acid sequences of the two enzymes were located in the signal peptide.

Algeria↗
PubMed1997

Substitution of alanine for aspartate at position 179 in the SHV-6 extended-spectrum beta-lactamase.

SHV-6 was previously identified by its susceptibility pattern and biochemical criteria in a clinical isolate of Klebsiella pneumoniae which was resistant to ceftazidime. It contains only a single point difference with the beta laSHV-1 gene as determined by PCR amplification and nucleotide sequencing. This is the result of a single amino acid substitution, Ala for Asp, at position 179. Directed mutagenesis experiments have shown this substitution to confer selective resistance to ceftazidime in the TEM family.

Amino Acid Sequence↗
PubMed1997

[New gram-positive opportunistic bacteria: pathogenic role and treatment].

NOVEL BACTERIA: The appearance of novel bacterial species among Gram positive microorganisms is mainly related to progress in bacterial taxonomy justifying such nomen species, i.e. C. jeikeium, C. urealyticum or R. equi. Another feature of such emergence of "Novel" bacteria is related to the rise in the number of clinical observations mediated by some well-known species described elsewhere such as in food bacteriology. PREDISPOSING FACTORS: Among Gram positive microorganisms, emergence for some species and renaissance or rebirth for others is mainly explained by natural resistance to widely used antibiotics including beta-lactams such as third generation cephalosporins, aminoglycosides, or more recently glycopeptides and the combined effect of several predisposing factors (hospitalized patients, underlying disease or prematurity, interruption of the normal integumentary defense via intravascular catheters). Clinical features depend on the bacterial species. Bacteriological diagnosis is easily obtained in terms of isolation and identification. Nevertheless, as for any opportunistic pathogen, a distinction must be made between colonization and infection. Finally successful treatment regimens depend on the bacterial species and may include surgery.

Drug Resistance, Microbial↗
PubMed1997

Cloning and sequencing of the gene encoding the AmpC beta-lactamase of Morganella morganii.

The chromosomal beta-lactamase gene of a clinical isolate of Morganella morganii was cloned in Escherichia coli and sequenced. The beta-lactamase had a pI of 7.4 and conferred a typical AmpC susceptibility pattern. The insert obtained was found to encode a protein of 379 amino acids. Its deduced amino acid sequence revealed it to be a class C beta-lactamase: 39-56% identity with chromosomal AmpC beta-lactamases of Serratia marcescens, Yersinia enterocolitica, Citrobacter freundii, Enterobacter cloacae and Escherichia coli; and 37-56% identity with plasmid-mediated beta-lactamases (MOX-1, CMY-1, FOX-1, ACT-1, LAT-1, BIL-1 and CMY-2). The ampC gene was linked to a gene only part of which (450 bp) was cloned homologous to the regulatory ampR genes of chromosomal class C beta-lactamases.

Bacterial Proteins↗
PubMed1997

Novel transferable beta-lactam resistance with cephalosporinase characteristics in Salmonella enteritidis.

An isolate of Salmonella enteritidis was found to produce a plasmid-encoded beta-lactamase (DHA-1) that conferred resistance to extended-spectrum cephalosporins and cephamycins. The substrate and inhibition profiles of this enzyme resemble a class C beta-lactamase. This is the first report of a plasmid-mediated cephalosporinase of this class in the Salmonella genus.

Anti-Bacterial Agents↗
PubMed1996

Detection of SHV-5 extended-spectrum beta-lactamase in Klebsiella pneumoniae strains isolated in Italy.

Thirty-five Klebsiella pneumoniae strains isolated during 1993-1994 in intensive care units of a large Italian hospital were examined for the presence of extended-spectrum beta-lactamases. Five strains showed a high level of simultaneous resistance to beta-lactam agents, including ceftazidime and aztreonam, conferred by a large (130 kb) self-transferable plasmid (in 4 of 5 strains). Isoelectrofocusing and hybridisation studies suggest that these enzymes can be identified as SHV-5 extended-spectrum beta-lactamases. Pulsed-field get electrophoresis analysis showed three different genomic fingerprinting profiles, while plasmid restriction enzyme digestion revealed three different patterns, demonstrating that the diffusion of SHV-5 beta-lactamase is not the result of a single strain or plasmid dissemination.

Conjugation, Genetic↗
PubMed1996

Antibiotic susceptibility in aerobic gram-negative bacilli isolated in intensive care units in 39 French teaching hospitals (ICU study).

OBJECTIVE: Evaluation of the distribution and antibiotic susceptibility of the aerobic gram-negative bacilli (AGNB) isolated from patients in intensive care units (ICU study). DESIGN AND SETTING: Microbiological study carried out in 1991 in 39 teaching hospitals. A standardized method was used to determine the minimum inhibitory concentrations of 12 antibiotics against 3366 strains of AGNB (close to 100 strains per hospital) during a period of 3 months. RESULTS: The 2773 initial strains (i.e., the first AGNB isolate for a given species and a given patient) were mainly isolated from the respiratory tract (34.4%), urinary tract (23%), or blood (9.6%) and were mainly Pseudomonas aeruginosa (22.9%), Escherichia coli (22%), Acinetobacter (9.7%), and Klebsiella pneumoniae (8.3%). E. coli was prominent in urine and blood and P. aeruginosa in the respiratory tract. Overall, the rate of susceptibility of AGNB was 58 to 65% to piperacillin, cefotaxime, and gentamicin; 69 to 75% to aztreonam, tobramycin, and ciprofloxacin; 83% to ceftazidime; and 91% to imipenem. The overall rates of susceptibility were higher for the initial strains isolated from blood than for those from the urinary or respiratory tracts, mostly reflecting differences in species distribution. Susceptibility rates were lower for the 593 repeat strains (i.e., all the subsequent isolates for a given species and a given patient) than for the initial strains, mostly due to the higher proportion of resistant species (P. aeruginosa 45.9%) but also due to the difference in susceptibility rates for some species-antibiotic combinations. Concomitant resistance (i.e., resistance to several antibiotics due to independent mechanisms of resistance) was marked between beta-lactams and aminoglycosides or quinolones, particularly in P. aeruginosa and K. pneumoniae. CONCLUSIONS: Rates of resistance in AGNB as a whole and in particular species (P. aeruginosa, Klebsiella), as well as frequency of concomitant resistance found in the French ICU study, were higher than those found in ICU studies conducted with the same methodology in Belgium, The Netherlands, and Germany, which may reflect differences in case mix.

Bacteria, Aerobic↗
PubMed1996

In-vitro susceptibility of Klebsiella oxytoca strains to 13 beta-lactams in the presence and absence of beta-lactamase inhibitors.

The susceptibility of Klebsiella oxytoca isolates was tested by an agar diffusion method (167 strains collected in six countries) and an agar dilution method (38 strains). Multivariate analysis of inhibition zone diameters by principal component analysis clearly individualised four susceptibility patterns, including the phenotype of strains overproducing beta-lactamase and resistant to penicillins, first-generation cephalosporins, cefuroxime and aztreonam, but susceptible to ceftazidime. This phenotype was different from that conferred by plasmid-mediated extended-spectrum beta-lactamases; strains expressing these enzymes were also resistant to ceftazidime and cefotaxime. The bla(oxy) gene from K. oxytoca was introduced into Escherichia coli and K. oxytoca recipients and conferred increased resistance to beta-lactams in the recipient cells. Clavulanic acid was effective in association with piperacillin (MIC decreased 36-fold), ceftriaxone (35-fold) and aztreonam (19-fold) against overproducing strains, in spite of a relatively high IC50 (0.3 microM). Sulbactam (IC50, 400 microM) was ineffective in this context when combined with piperacillin (MIC decreased 1.5-fold), ceftriaxone (1.6-fold) and aztreonam (1.6-fold). The inhibitory activity of tazobactam (IC50, 8.2 microM) was heterogeneous depending on the strain and the beta-lactam with which it was combined. When combined with piperacillin or ceftriaxone little potentiation in antibiotic activity occurred (MIC decreased 3.9-fold and 4.5-fold, respectively); however, tazobactam plus aztreonam resulted in a 50-fold decrease in MIC of antibiotic.

Enzyme Inhibitors↗
PubMed1996

Chromosomal beta-lactamase genes of Klebsiella oxytoca are divided into two main groups, blaOXY-1 and blaOXY-2.

The chromosomally encoded beta-lactamase gene (blaOXY-2) of the wild-type Klebsiella oxytoca SL911 was cloned and sequenced. Its nucleotide sequence similarity with the previously sequenced K. oxytoca beta-lactamase gene (blaOXY-1) (Y. Arakawa, M. Ohta, N. Kido, M. Mori, H. Ito, T. Komatsu, Y. Fujii, and N. Kato, Antimicrob. Agents Chemother. 33:63-70, 1989) is 87.3%, and its amino acid similarity is 89.7%. This group of K. oxytoca beta-lactamases is related to chromosomal beta-lactamases of Citrobacter diversus, Proteus vulgaris, and Yersinia enterocolitica and to the plasmid-mediated extended-spectrum beta-lactamases MEN-1 and Toho-1. By colony hybridization with 86 strains susceptible and resistant to aztreonam, isolated in six countries, K. oxytoca beta-lactamase genes hybridized with either a specific blaOXY-1 DNA probe (668 bp) or a blaOXY-2 DNA probe (723 bp). Thus, beta-lactamase genes could be divided into two groups: blaOXY-1 (47% of the strains) and blaOXY-2 (53% of the strains). A study of isoelectric points confirmed the great variability reported in the literature. However, the two beta-lactamase groups were each represented by four different pIs: for OXY-2, 5.2, 5.7, 6.4, and 6.8, with the 5.2 form representing 59% of all OXY-2 enzymes, and for OXY-1, 7.1, 7.5, 8.2, and 8.8, with the 7.5 form representing 88% of all OXY-1 enzymes.

Amino Acid Sequence↗
PubMed1996

beta-lactamase gene promoters of 71 clinical strains of Klebsiella oxytoca.

beta-Lactamase gene promoters of 45 clinical Klebsiella oxytoca isolates resistant to beta-lactams and exhibiting beta-lactamase hyperproduction differed from those in 26 susceptible strains. Direct sequencing revealed one mutation in either the -10 or -35 conserved sequences: a G-to-A transition of the fifth base (67%) or a G-to-T transversion of the first base of the -10 sequence (27%) or a T-to-A transversion in the fourth base in the -35 sequence (4%). One strain carried both the -10 transition and the -35 transversion.

Base Sequence↗
PubMed1995

Molecular characterisation by PCR-restriction fragment length polymorphism of TEM beta-lactamases.

To rapidly characterise TEM-derived extended-spectrum beta-lactamases a fast and easy method using polymerase chain reaction-restriction fragment length polymorphism was developed. This method was validated with ten reference TEM-type extended-spectrum beta-lactamases. The mutations involved in TEM-20 and TEM-21, which were previously reported only with biochemical analysis, were then characterised. TEM-20 differed from TEM-19 by a silent mutation at position 925 (A for G), and TEM-21 differed from TEM-3 and TEM-14 by a single mutation (G for A) in an unreported position 660. beta-lactamase conferring low resistance to ceftazidime (TEM-29), was described. TEM-29 derived from TEM-1, with an amino acid substitution, his-164. Finally, the combination of polymerase chain reaction-restriction fragment length polymorphism and plasmid analysis allowed us to investigate nosocomial outbreaks due to clinical isolates of multi-resistant Klebsiella pneumoniae in three hospitals.

Cross Infection↗
PubMed1995

Virulence factors (aerobactin and mucoid phenotype) in Klebsiella pneumoniae and Escherichia coli blood culture isolates.

We examined the presence of two virulence factors in 241 blood isolates of Klebsiella pneumoniae from patients hospitalized during 1989 and 1990 in 7 French hospitals, and 125 blood isolates of Escherichia coli from one hospital. Aerobactin was scored phenotypically and genotypically with an intragenic DNA probe of 2 kb. The mucoid phenotype was assessed by culture on trypticase soy agar and by genotypic analysis (intragenic DNA probe of 235 bp). Only 6% K. pneumoniae isolates were aerobactin-positive with no significant variation according to geographical location while 20% of K. pneumoniae isolates displayed the mucoid phenotype, with a significant variation according to hospital. Aerobactin was always associated with the mucoid phenotype. The frequency of aerobactin production but not mucoid phenotype (14%) was higher among E. coli isolates (48%). They harbored two types of large plasmids. Intraperitoneal injection into mice of 10(3) cfu of K. pneumoniae producing both virulence factors demonstrated that capsular serotype K2 was the more virulent K23 and K28.

Animals↗
PubMed1995

Escherichia hermannii: susceptibility pattern to beta-lactams and production of beta-lactamase.

The susceptibility pattern of Escherichia hermannii, although closely related to Escherichia coli according to its biochemical patterns, was clearly distinguishable by its susceptibility to beta-lactams by both diffusion and dilution methods from E. coli penicillinase producing or non-producing strains, Citrobacter diversus, Klebsiella pneumoniae, and Klebsiella oxytoca. Beta-lactamase clavulanate-sensitive activity was localized with various isoelectric points from 7.0 to 8.5. No cross hybridization with DNA intragenic probes (blaTEM, blaSHV, blaCARB and blaOXY) was observed by dot blot procedure.

Anti-Bacterial Agents↗
PubMed1995

Identification of a carbenicillin-hydrolyzing beta-lactamase in Alcaligenes denitrificans subsp. xylosoxydans.

Eleven strains of Alcaligenes denitrificans subsp. xylosoxydans produced a beta-lactamase with a pI of 5.7 with kinetic data characteristic of a PSE-1-type enzyme. A CARB-type enzyme was identified by using an intragenic DNA probe of blaCARB. Hybridization of genomic DNA after XbaI restriction and pulsed-field electrophoresis suggested a chromosomal location for the gene.

Alcaligenes↗
PubMed1995

Point mutation in the pribnow box, the molecular basis of beta-lactamase overproduction in Klebsiella oxytoca.

Klebsiella oxytoca mutants resistant to a variety of beta-lactams were obtained in vitro on aztreonam. Constitutive beta-lactamase production was much higher in the mutants than in the susceptible strains (75-fold). The only difference observed in these mutants compared with the susceptible strains were point mutations in the Pribnow box: a transversion (G-->T) in the first base for one mutant or a transition (G-->A) in the fifth base of the -10 consensus sequence for the other three mutants. The transcriptional output of the beta-lactamase gene (blaOXY) from the mutants was significantly higher than that of the blaOXY gene from the susceptible strains.

Anti-Bacterial Agents↗
PubMed1995

[Azithromycin: critical points].

The determination of the French breakpoints (< or = c, > C) were selected by the use of different criteria including bacteriological, pharmacokinetic and obviously clinical criteria. Concerning the bacteriological results, azithromycin, being an acid stable orally administered antimicrobial drug, is in vitro marginally less active than erythromycin against Gram-positive organisms including beta-haemolytic streptococci and Staphylococcus aureus. But in contrast, this azalide is more active than erytromycin against many Gram-negative pathogens, notably Neisseria gonorrhoeae, H. influenzae, Branhamella (Moraxella) catarrhalis, Ureaplasma urealyticum, and Borrelia burgdorferi. The activity of azithromycin is unaffected by the inoculum, unlike of pH, serum, and presence of CO2 for anaerobes. However, erythromycin-resistant micro-organisms are also resistant to azithromycin. Considering the pharmacokinetic criteria and the clinical results such as infections of the lower and upper respiratory tracts, skin and soft tissues, uncomplicated urethritis/cervicitis associated with N. gonorrhoeae, Chlamydia trachomatis or U. urealyticum, the preliminary breakpoints of azithromycin are defined by the following concentrations (< or = 0.12 and > 4 mg/l). Additional experimental and clinical results are required to confirm the in vitro activity against some other bacterial species (E. faecalis, L. monocytogenes, Brucella, P. multocida, or even Salmonella and Shigella).

Anti-Bacterial Agents↗