Biomedical subjects

J P Gayral

Publications and source records attributed to J P Gayral.

14 recordsLinked to original sources

PubMed2000

16S ribosomal DNA sequence analysis of a large collection of environmental and clinical unidentifiable bacterial isolates.

Some bacteria are difficult to identify with phenotypic identification schemes commonly used outside reference laboratories. 16S ribosomal DNA (rDNA)-based identification of bacteria potentially offers a useful alternative when phenotypic characterization methods fail. However, as yet, the usefulness of 16S rDNA sequence analysis in the identification of conventionally unidentifiable isolates has not been evaluated with a large collection of isolates. In this study, we evaluated the utility of 16S rDNA sequencing as a means to identify a collection of 177 such isolates obtained from environmental, veterinary, and clinical sources. For 159 isolates (89.8%) there was at least one sequence in GenBank that yielded a similarity score of > or =97%, and for 139 isolates (78.5%) there was at least one sequence in GenBank that yielded a similarity score of > or =99%. These similarity score values were used to defined identification at the genus and species levels, respectively. For isolates identified to the species level, conventional identification failed to produce accurate results because of inappropriate biochemical profile determination in 76 isolates (58.7%), Gram staining in 16 isolates (11.6%), oxidase and catalase activity determination in 5 isolates (3.6%) and growth requirement determination in 2 isolates (1.5%). Eighteen isolates (10.2%) remained unidentifiable by 16S rDNA sequence analysis but were probably prototype isolates of new species. These isolates originated mainly from environmental sources (P = 0.07). The 16S rDNA approach failed to identify Enterobacter and Pantoea isolates to the species level (P = 0.04; odds ratio = 0.32 [95% confidence interval, 0.10 to 1.14]). Elsewhere, the usefulness of 16S rDNA sequencing was compromised by the presence of 16S rDNA sequences with >1% undetermined positions in the databases. Unlike phenotypic identification, which can be modified by the variability of expression of characters, 16S rDNA sequencing provides unambiguous data even for rare isolates, which are reproducible in and between laboratories. The increase in accurate new 16S rDNA sequences and the development of alternative genes for molecular identification of certain taxa should further improve the usefulness of molecular identification of bacteria.

Animals↗

PubMed1996

Evaluation of an expert system linked to a rapid antibiotic susceptibility testing system for the detection of beta-lactam resistance phenotypes.

Interpretive reading of antibiotic disc agar diffusion tests indicates the resistance mechanisms, if any, expressed by a bacterium. An expert system for determining resistance mechanisms using rapid automated antibiotic susceptibility tests has been developed. The beta-lactam susceptibility of each of 300 strains of clinically significant species of enterobacteria, displaying natural and acquired resistance mechanisms, was determined by disc agar diffusion and by a rapid automated method of susceptibility testing associated with an expert system. For every strain, the conclusion of the expert analysis of the automated test was compared with the commonly accepted interpretation of disc agar diffusion tests. Of the 300 strains studied, 275 were similarly interpreted (91.7% agreement). The susceptible and naturally beta-lactam-resistant phenotypes (wild phenotypes) were equally recognized by both methods. Similarly, the results of the two methods concurred for most of the acquired resistance phenotypes. However, for 25 strains (8.3%) the results diverged. The expert system proposed an erroneous phenotype (5 strains), several phenotypes including the correct one (17 strains), or no phenotype (1 strain). For 2 strains the natural resistance mechanism was not detected at first by the automated method but was subsequently deduced by the expert analysis according to bacterial identification. These results demonstrate that satisfactory interpretive reading of automated antibiotic susceptibility tests is possible in 4 to 5 hours but requires careful selection of the antibiotics tested as phenotypic markers.

Anti-Bacterial Agents↗

PubMed1987

[Evaluation of the ATB system and the 32 GN tests for the identification and determination of the antibiotic sensitivity of Acinetobacter calcoaceticus var. anitratum. Comparison with the reference dilution method in a gel medium].

The authors determined the susceptibility to 24 antibiotics of 95 strains of Acinetobacter calcoaceticus variety anitratum with the automated API ATB System in comparison with the agar dilution method for MIC measurement. The strains have been identified with API 32 GN (automated system) and API NE. There was a good agreement between the two sets of identification results. In susceptibility tests the discrepancies ranged from 0.86% to 3% with a mean value of 1.8%. The overall agreement was 95% between the two methods. This study allowed the authors to define susceptibility phenotypes to the three major antibiotic classes: beta-lactams, aminoglycosides and quinolones. The use of 32 GN tests and ATB in the automated system seems very useful, especially in epidemiologic studies in order to analyse numerous data in a short time.

Acinetobacter↗

PubMed1986

[Rapid ATB staph: 4-hour antibiotic sensitivity test of staphylococci. Description and performance].

Rapid ATB Staph is a method for four-hour antimicrobial susceptibility testing of staphylococci. The equipment and theoretical basis are identical to those already described for rapid testing of enterobacteriaceae. A standardized procedure is required to perform the test. The inoculum should be prepared from a culture no older than 24 hours and accurately standardized at 10(8). Temperature of incubation should be 35 degrees C to 37 degrees C; otherwise growth is delayed by approximately one hour. Time of incubation should not exceed 5 hours. Using these standardized conditions, rapid ATB Staph was compared with the reference agar dilution method for 22 antibiotics. Overall agreement was 96.3%. The rapid system is more sensitive than the reference method fort the detection of netilmicin and amikacin resistance; it is reliable for detecting penicillin resistance, oxacillin resistance and inducible resistance to erythromycin (agreement 96.7%, 94.8% and 98.4% respectively). A Rapid ATB Staph strip containing 15 antibiotics has been designed for routine susceptibility testing.

Anti-Bacterial Agents↗

PubMed1986

[Sensitivity of 858 strains of staphylococci to 27 antibiotics].

Susceptibility to 27 antimicrobial agents of 858 strains of staphylococci was determined. Tested strains belonged to the following species: S. epidermidis, S. saprophyticus, S. haemolyticus, S. hominis, S. simulans, S. warneri, S. cohnii, S. xylosus and S. intermedius. The antibiotics were: penicillin G, amoxycillin, augmentin, oxacillin, streptomycin, kanamycin, tobramycin, dibekacin, amikacin, gentamicin, sisomycin, netilmicin, doxycycline, minocycline, chloramphenicol, erythromycin, josamycin, clindamycin, pristinamycin, rifampin, fusidic acid, fosfomycin, trimethoprim, sulfamethoxazole, cotrimoxazole, and vancomycin. The ATB system was used, with the criteria for categorization recommended by the Antibiotic Sensitivity Testing Committee. Penicillin-resistance, that was found in all species, was high for hospital-acquired strains (67 to 75%) but also for some other strains (32% for S. simulans). Oxacillin-resistance varied across species (0% for the least prevalent hospital strains, 6% for S. epidermidis and 28% for S. haemolyticus). All strains were susceptible to vancomycin. For some drugs, resistance was a characteristic of the species: resistance to fosfomycin was often found for S. saprophyticus, S. haemolyticus, S. warneri, S. cohnii, and S. capitis; resistance to trimethoprim was common for S. simulans, and S. haemolyticus. S. haemolyticus was the most resistant species, a fact that justifies routine identification of this pathogen in clinical specimens.

Anti-Bacterial Agents↗

PubMed1986

[Evaluation of the antibiotic sensitivity of Pseudomonas sp. using the API-ATB-PSE system. Comparison with diffusion and the reference agar dilution method].

In vitro activity of twelve antibiotics (ticarcillin, mezlocillin, azlocillin, piperacillin, cefoperazone, cefsulodin, ceftazidime, gentamicin, netilmicin, pefloxacin and ciprofloxacin) was determined by measuring minimum inhibitory concentrations (MICs) using agar dilution according to WHO recommendations, agar diffusion and the API-ATB-PSE system. One-hundred and forty-two Pseudomonas strains were studied. Five species of Pseudomonas were represented, i.e. aeruginosa, maltophilia, cepacia, stutzeri and paucimobilis. Isolates came from two Paris hospitals. Percentages of total agreement, minor discrepancies and major discrepancies between the results obtained with the API-ATB-PSE method and those recorded with the reference methods were determined. After checking the discordant strains, the results are discussed in order to evaluate the reliability of the ATB method for antibiotic susceptibility testing with Pseudomonas sp.

Agar↗

PubMed1986

[Evaluation of the Rapid-ATB system for testing the sensitivity of staphylococci to antibiotics. Comparison with the agar dilution reference method].

Rapid ATB Staph is a new, automated, four-hour procedure for testing the susceptibility to antibiotics of staphylococci. Results obtained with this method were compared to those recorded using agar dilution. For all tested antibiotics as a group (5 on 201 strains, 8 on 100 strains), overall agreement between the two sets of results was 96%. 1,809 susceptibility tests were performed, with only 24 minor discrepancies (1.3%) mainly involving cotrimoxazole, and 50 major discrepancies (2.7%) mainly involving doxycycline and chloramphenicol. Rapid ATB Staph clearly demonstrates the heterogeneous oxacillin-resistance of staphylococci as well as their inducible resistance to erythromycin. Our results show that this new system is a very accurate means for testing the susceptibility to antibiotics of staphylococci.

Anti-Bacterial Agents↗

PubMed1985

[Rapid ATB. A new system of antibiotic testing in 4 hours. Description and parameters of variation].

Rapid ATB is a new automated system which performs antibiotic sensitivity testing of Enterobacteriaceae in four hours. It is composed of strips containing dehydrated antibiotics and a medium which ensures rapid bacterial growth, and of the equipment required for standardization of the inoculum, reading of results and interpretation. Strains are classified as susceptible or resistant according to the value of the growth index (IC) which is the ratio of growth in the presence of the antibiotic to growth of a control inoculum. Use of this system requires standardization. The main factors to control are state of the culture used to prepare the inoculum, standardization of the inoculum, incubation temperature (35 to 37 degrees C), and duration of incubation (4 to 5 hours). Variations of these factors usually induce significantly delayed growth. Under well standardized conditions, results are highly reproducible, as proved by testing ten strains ten times each by three investigators.

Culture Media↗

PubMed1985

[Evaluation of a new rapid antibiogram method, the Rapid-ATB system. Comparison with the agar dilution reference method and the standard antibiogram].

Results given by Rapid-ATB, a new automated system for the four hour susceptibility testing of bacteria were compared in this study to results given by agar dilution test and disc agar diffusion test. For 100 Enterobacteriaceae strains tested against ten antibiotics, overall agreement between agar dilution test and Rapid-ATB was 99.4%. 6 major discordances concerning especially chloramphenicol were only detected in 1 000 realized susceptibility tests. Overall agreement between agar dilution test and disc agar diffusion test was 96.7%. Eighteen major discordances concerning alike chloramphenicol, but also doxycycline and nalidixic acid, and fifteen minor discordances were detected in this comparison. These results prove the high reliability of this new system which give results more precise than these of disc agar diffusion test.

Anti-Bacterial Agents↗

PubMed1984

Differentiation of Enterobacteriaceae and Vibrionaceae by a micromethod for determination of carbon substrate assimilation.

The assimilation techniques described for taxonomic study are unsuitable for routine diagnosis because of the need for purification and standardization of substrates, the great quantity of medium consumed and difficulties in interpreting the results. A standardized micromethod (API strip) for the study of carbon substrate assimilation by bacteria has recently been described (Zbl. Bakt. Hyg., I. Abt. Orig. A 255 (1983) 479-488). The prototype gallery used consisted of two strips of 32 microtubes each containing dehydrated carbon substrate. Each strip contained 30 tests plus positive and negative controls. The suspension medium was a synthetic semi-gel. A total of 914 strains of Gram negative rods representing 44 species of Enterobacteriaceae and Vibrionaceae were tested (Table 1). Automatic reading was performed after incubation at 32 degrees C for one day, or two days for slow growing bacteria using an ATB - 1500 reader (API System) linked to a HP 85 microcomputer (Hewlett-Packard). Most species showed typical carbon substrate assimilation patterns allowing their differentiation from other species within each genus (Table 2). The results obtained with the micromethod agreed in large measure with the nutritional patterns reported by other workers. It should be possible to use these results to construct a coherent framework of tests suitable for identifying species of Enterobacteriaceae and Vibrionaceae of clinical significance.

Bacteriological Techniques↗

PubMed1984

Differentiation of gram negative rods other than Enterobacteriaceae and Vibrionaceae by a micromethod for determination of carbon substrate assimilation.

The assimilation techniques described for taxonomic study are unsuitable for routine diagnosis because of the need for purification and standardization of substrates, the great quantity of medium consumed and difficulties in interpreting the results. A standardized micromethod (API Strip) for the study of carbon substrate assimilation by bacteria has recently been described (Zbl. Bakt. Hyg., I. Abt. Orig. A 255 (1983) 479-488). The prototype gallery used consisted of two strips of 32 microtubes each containing dehydrated carbon substrate. Each strip contained 30 tests plus positive and negative controls. The suspension medium was a synthetic semi-gel. A total of 1046 strains of Gram-negative rods representing 41 species belonging to the genera Pseudomonas, Alcaligenes, Moraxella, Acinetobacter, Flavobacterium and to the EF4 group were tested (Tables 1 to 6). Automatic reading was performed after incubation at 32 degrees C for one day, or two days for slow growing bacteria, using an ATB 1500 reader (API System) linked to a HP 85 microcomputer (Hewlett-Packard). Most species showed typical carbon substrate assimilation patterns allowing their differentiation from other species within each genus. The results obtained with the micromethod agreed in large measure with the nutritional patterns reported by other workers. It should be possible to use these results to construct a set of tests suitable for identifying species of Gram-negative rods other than Enterobacteriaceae and Vibrionaceae.

Acinetobacter↗

PubMed1984

[Bioenzymatic and lysotypic study of 200 strains of Acinetobacter calcoaceticus].

Two hundred strains of Acinetobacter calcoaceticus isolated between 1971 and 1978 at the Bichat Hospital were studied by means of a biochemical and enzymatic technique thanks to 150 tests per strain. Most strains (about 60%) were Acinetobacter calcoaceticus variety anitratus which is more frequently isolated than var. lwoffi . Three bioenzymatic groups have been statistically defined. This classification corresponds to the main lines of previous descriptions by Henriksen (1960) and those indicated in the Bergey's Manual (1974). The results of the study do not show any correlation between the clinical origin of the strains, their bioenzymatic profile and their phage-type which was determined for 60 strains. Otherwise, it was to be noted that glucose is not a basic character of this classification which is based on an average profile of strains; some tests are particularly important for the differentiation of species (amino-acids); some characteristics have been observed and have to be related to the enzymatic properties of the strains and their role in the catabolism of some carbohydrates. The results of the study might constitute a new approach of epidemiological criteria to be determined for Acinetobacter strains ( Bergogne -Bér ezin and al., 1970, 1980, Gardner and al., 1970; Glew and al., 1977).

Acinetobacter↗

PubMed1984

[Antibiotic sensitivity test. Comparative multicenter study of the gel diffusion and ATB methods].

The ATB method is a new method for antibiotic susceptibility testing. In a collaborative study, it was compared to a standard disc diffusion method. 23 strains were tested to determine reproducibility and 969 strains were used in the comparative study. Reproducibility of both methods is equivalent; differences due to strains were observed. Agreement between both methods is 87,9%, minor discrepancies are 8,7% and major discrepancies are 3,3%. Significant differences were found for carbenicillin and cefalotin and confirmed by MIC determination using the agar dilution method. Overall results show that the ATB method is reliable and comparable to disc diffusion for routine susceptibility testing.

Automation↗

PubMed1979

Micrococcaceae isolated from meat and dairy products (taxonomic study).

149 Micrococcaceae strains (35 reference strains and 114 strains isolated from meat and dairy products) have been studied using 61 biochemical microtests. Numerical taxonomy has distinguished two main biochemical groups which may be characterized by their varying ability to use heteroside compounds. -- A small number of biochemical tests in each group enable the differentiation of 17 taxa corresponding to diverse origins. The wild strains of Micrococcaceae found in foods are very different from reference strains in collections. -- With regard to the present study, it seems that a central biotype exists which may be represented by the taxa 13, 14, 15 and 16 in Fig. 1. -- Given this central biotype, various biochemical differences may be considered as ecological adaptability. Group I corresponds to meat orgin -- Taxa No. 1, 2, correspond to collection strains -- Taxon No. 12 corresponds to cheese origin -- Taxa No. 8, 9 and 10 correspond to milk origin.

Bacteriological Techniques↗