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Biomedical subjects

G A Hébert

Publications and source records attributed to G A Hébert.

At least 19 recordsLinked to original sources
PubMed1994

Comparison of traditional and molecular methods of typing isolates of Staphylococcus aureus.

Fifty-nine Staphylococcus aureus isolates and 1 isolate of Staphylococcus intermedius were typed by investigators at eight institutions by using either antibiograms, bacteriophage typing, biotyping, immunoblotting, insertion sequence typing with IS257/431, multilocus enzyme electrophoresis, restriction analysis of plasmid DNA, pulsed-field or field inversion gel electrophoresis, restriction analysis of PCR-amplified coagulase gene sequences, restriction fragment length polymorphism typing by using four staphylococcal genes as probes, or ribotyping. Isolates from four well-characterized outbreaks (n = 29) and a collection of organisms from two nursing homes were mixed with epidemiologically unrelated stock strains from the Centers for Disease Control and Prevention. Several isolates were included multiple times either within or between the sets of isolates to analyze the reproducibilities of the typing systems. Overall, the DNA-based techniques and immunoblotting were most effective in grouping outbreak-related strains, recognizing 27 to 29 of the 29 outbreak-related strains; however, they also tended to include 3 to 8 epidemiologically unrelated isolates in the same strain type. Restriction fragment length polymorphism methods with mec gene-associated loci were less useful than other techniques for typing oxacillin-susceptible isolates. Phage typing, plasmid DNA restriction analysis, and antibiogram analysis, the techniques most readily available to clinical laboratories, identified 23 to 26 of 29 outbreak-related isolates and assigned 0 to 6 unrelated isolates to outbreak strain types. No single technique was clearly superior to the others; however, biotyping, because it produced so many subtypes, did not effectively group outbreak-related strains of S. aureus.

Bacterial Typing Techniques↗
PubMed1990

Hemolysins and other characteristics that help differentiate and biotype Staphylococcus lugdunensis and Staphylococcus schleiferi.

Reference strains and clinical isolates representing the newly defined species Staphylococcus lugdunensis and Staphylococcus schleiferi were examined with the battery of tests previously recommended (G.A. Hébert, C.G. Crowder, G.A. Hancock, W.R. Jarvis, and C. Thornsberry, J. Clin. Microbiol. 26:1939-1949, 1988) for other species of coagulase-negative staphylococci (CNS). The Staph-Ident system (Analytab Products, Plainview, N.Y.) supplemented with tests for synergistic hemolysis, adherence to glass, pyroglutamyl-beta-naphthylamide hydrolysis, and susceptibility to a set of five antimicrobial disks differentiated each of these species from other species of CNS and separated strains within each species into several biotypes. Most strains (95%) of S. lugdunensis produced a delta hemolysin like that seen with nine other species of CNS. Most strains (91%) of S. schleiferi produced a beta hemolysin, which is a unique characteristic among CNS. Most (95%) of the S. schleiferi but very few (12%) of the S. lugdunensis were adherence positive. Both hemolysins and adherins are potential virulence factors among CNS. Some (29%) of the S. lugdunensis were beta-lactamase positive. The S. lugdunensis were resistant to polymyxin B and bacitracin (10 U), but the S. schleiferi were susceptible to both disks. Clinical isolates of S. lugdunensis were aligned in 18 biotypes because of eight biochemical profiles and eight physiologic subtypes; isolates of S. schleiferi were in 8 biotypes because of three biochemical profiles and subtypes. These tools for correctly identifying and then biotyping two more clinical species of CNS should enhance both epidemiologic and ecologic investigations.

Bacterial Adhesion↗
PubMed1988

Characteristics of coagulase-negative staphylococci that help differentiate these species and other members of the family Micrococcaceae.

One hundred reference strains and 1,240 clinical isolates representing 26 species of the family Micrococcaceae were used to evaluate the potential of tests for synergistic hemolysis, adherence to glass, pyroglutamyl-beta-naphthylamide hydrolysis, and susceptibility to a set of five antimicrobial agents for differentiating these species and strains within the species. Sixty-eight percent of the clinical isolates exhibited synergistic hemolysis; 69% of the clinical staphylococci but none of the micrococci or stomatococci were adherence positive, and 92% of the strong positive adherence reactions were produced by strains of Staphylococcus epidermidis. Strains from 15 of the species were pyroglutamyl-beta-naphthylamide positive, but this test separated Staphylococcus xylosus from other novobiocin-resistant staphylococci and Staphylococcus intermedius from other coagulase-positive species. A polymyxin B disk helped differentiate S. epidermidis from most other coagulase-negative staphylococci, and a bacitracin disk (10 U) helped differentiate Staphylococcus haemolyticus from most other novobiocin-susceptible staphylococci. All strains that were susceptible to furazolidone and resistant to Taxo A disks (bacitracin, 0.04 U; BBL Microbiology Systems, Cockeysville, Md.) were staphylococci. We observed a 91% correlation between species identification obtained with the Staph-Ident system (Analytab Products, Plainview, N.Y.) and conventional methods; but the micrococci and stomatococci were incorrectly identified as staphylococci with Staph-Ident, and several isolates of S. epidermidis were misidentified as Staphylococcus hominis because they were alkaline phosphatase negative. Both these problems can be prevented by adding the simple tests we describe to those already recommended when the Staph-Ident system is used to identify isolates of gram-positive, catalase-positive cocci.

Bacitracin↗
PubMed1988

Biotyping coagulase-negative staphylococci.

The biochemical profiles obtained with Staph-Ident (Analytab Products, Plainview, N.Y.) panels were combined with the results of adherence and synergistic hemolysis tests to define biotypes among 1,064 clinical isolates representing eight species of coagulase-negative staphylococci. The 672 isolates of Staphylococcus epidermidis were aligned in 69 of 144 potential biotypes in our scheme because of 18 different biochemical profiles and the eight physiologic subtypes. Isolates of most other species were in fewer biotypes because of more uniform adherence and synergistic hemolysis data, as well as fewer biochemical profiles. Since adherence and synergistic hemolysis may prove to be related to virulence and pathogenicity, biotyping with these test results would help evaluate the reliability of adherence and synergistic hemolysis as possible indices of the clinical significance of some of these organisms. When the antimicrobial susceptibility and plasmid profiles obtained on two clusters of S. epidermidis isolates were compared with the biotyping results, one cluster was not further differentiated by plasmid profiles, but was by antimicrobial profiles; the other cluster with only two biotypes was further divided into five distinct types by plasmid profiles but was not separated at all by antimicrobial profiles.

Bacterial Adhesion↗
PubMed1985

Synergistic hemolysis exhibited by species of staphylococci.

The synergistic hemolysis reactions of 61 reference strains and 189 clinical isolates representing 17 species of staphylococci were examined on plates of Trypticase soy blood agar (BBL Microbiology Systems, Cockeysville, Md.). Some or all of the strains of Staphylococcus aureus, S. epidermidis, S. capitis, S. cohnii, S. haemolyticus, S. hyicus, S. simulans, S. warneri, and S. xylosus produced a delta-hemolysin that gave synergistic, complete hemolysis of washed human, sheep, and ox blood cells in an area of beta-lysin activity from strains of S. aureus and S. intermedius. Strains of the same nine species were positive with a commercial beta-lysin paper disk designed for presumptive identification of group B streptococci; most of these strains also gave synergistic, complete hemolysis with exotoxin from a strain of Corynebacterium pseudotuberculosis. None of the strains of S. auricularis, S. carnosus, S. caseolyticus, S. hominis, S. intermedius, S. saprophyticus, S. sciuri, or S. lentus were positive by any of these tests for synergistic hemolysis. These results indicate that a synergistic hemolysis test could prove very useful for differentiating these species; they also suggest that one role of some of these organisms in human infections could be that of a synergist. Further studies of synergism may clarify the clinical significance of these results.

Antimicrobial Cationic Peptides↗
PubMed1984

Comparison of Legionella pneumophila, L. micdadei, L. bozemanii, and L. dumoffii by transmission electron microscopy.

Clinical isolates of Legionella pneumophila, L. micdadei, L. bozemanii, and L. dumoffii were grown on charcoal-yeast extract agar from a living-medium inoculum and prepared for transmission electron microscopy by three different methods. Cells of all four Legionella species possessed cytoplasmic vacuoles, a gram-negative type of cell envelope with a dense peptidoglycan-like layer, a ruthenium red-positive polysaccharide capsule, and a single subpolar flagellum. The dense polysaccharide capsule seen on cells of L. micdadei was separated from the outer membrane by an extra layer of electron-lucent material that was not present on cells of the other species examined.

Cell Membrane↗
PubMed1984

DNA relatedness among strains of Campylobacter jejuni and Campylobacter coli with divergent serogroup and hippurate reactions.

Eleven strains of Campylobacter from earlier fluorescent-antibody studies were examined by DNA hybridization to determine their species. Three of the strains hydrolyzed sodium hippurate, and eight did not. Four of the hippurate-negative strains were in Campylobacter jejuni serogroups, and the remaining strains were in both C. jejuni and Campylobacter coli serogroups. DNA relatedness to type strains of C. jejuni and C. coli indicated that all three of the hippurate-positive strains and two of the hippurate-negative strains were C. jejuni. The six remaining hippurate-negative strains were C. coli. Two of the hippurate-negative strains in C. jejuni serogroups were C. jejuni, and two were C. coli. Three of the strains in serogroups of both species were C. jejuni, and four were C. coli. These studies confirm that a few strains of C. jejuni are hippurate negative and show that identical or highly related antigens are found in C. coli and C. jejuni.

Campylobacter↗
PubMed1983

Serogroups of Campylobacter jejuni, Campylobacter coli, and Campylobacter fetus defined by direct immunofluorescence.

Rabbits were inoculated with whole, formalinized Campylobacter jejuni, C. coli, and C. fetus cells; the C. jejuni and C. coli immunogens were identified by their DNA relatedness at the species level to the type strains of C. jejuni or C. coli. The designation C. coli was not used among the other C. jejuni strains; they were classified as hippurate-positive or hippurate-negative C. jejuni. Immunoglobulin G was isolated from the antisera and labeled with fluorescein isothiocyanate. These conjugates defined 10 serogroups of C. jejuni, 2 serogroups of C. coli, and 2 serogroups of C. fetus. Of the 316 strains of C. jejuni tested, 258 (82%) were groupable; 173 were single-serogroup strains, and 85 were multiple-serogroup strains. Of the 226 strains in C. jejuni serogroups, 223 (98.7%) were hippurate positive; of the 27 strains in C. coli serogroups, 26 (96.3%) were hippurate negative. Five strains were equally reactive in immunofluorescent staining with a conjugate for a C. jejuni serogroup and a conjugate for a C. coli serogroup. A total of 58 strains of C. jejuni were ungroupable: 33 (13%) of the 259 hippurate-positive strains and 25 (44%) of the 57 hippurate-negative strains. All 121 strains of C. fetus tested were groupable as A, B, or A:B. The 14 conjugates used to define serogroups of C. jejuni, C. coli, and C. fetus reacted with the flagella but not the cells of other Campylobacter species and were negative on 256 other bacteria from 21 genera.

Animals↗
PubMed1983

Correlation of an expanded direct fluorescent-antibody system with an established passive hemagglutination system for serogrouping strains of Campylobacter jejuni and Campylobacter coli.

Rabbits were inoculated with whole, formalinized cells from eight passive hemagglutination reference strains of Campylobacter. Fluorescein isothiocyanate-labeled immunoglobulin G from these antisera defined seven new direct fluorescent-antibody serogroups of C. jejuni and one new serogroup of C. coli. This expanded the Campylobacter direct fluorescent antibody system to include 17 serogroups of C. jejuni, 3 serogroups of C. coli, and 2 serogroups of C. fetus. We then compared the passive hemagglutination method (57 serotypes) and the direct fluorescent-antibody method (20 serogroups) for typing strains of C. jejuni and C. coli. The data obtained by testing 101 strains by both methods revealed that the two test systems were measuring completely different sets of antigen complexes. The two serogrouping methods were complementary, and their combined use discriminated among strains more effectively than did either method individually.

Campylobacter↗
PubMed1982

30 years of campylobacters: biochemical characteristics and a biotyping proposal for Campylobacter jejuni.

Several biochemical test systems were studied for their potential usefulness for the examination of strains of Campylobacter species. Most (81%) of the C. jejuni strains hydrolyzed sodium hippurate, but strains of C. fetus, C. sputorum, and C. fecalis did not. Some (46%) of the C. jejuni strains and all of the C. sputorum subsp. sputorum, C. sputorum subsp. bubulus, and C. fecalis strains hydrolyzed DNA, but the C. fetus and C. sputorum subsp. mucosalis strains did not. Strains of all species of Campylobacter grew on charcoal-yeast extract agar, but 47% of the C. jejuni strains did not. Alkaline phosphatase activity was recorded for some strains of C. jejuni, but all other species were negative for this activity. Aryl sulfatase activity was detected in 7% of the C. jejuni, 15% of the C. fetus subsp. fetus, and all of the C. sputorum subsp. sputorum, C. sputorum subsp. bubulus, and C. fecalis strains, but it was not detected in the C. fetus subsp. venerealis and C. sputorum subsp. mucosalis strains. Most (93%) of the C. jejuni but none of the other Campylobacter strains contained lactobacillic acid when examined for cellular fatty acids. On the basis of results from three of these tests (hippurate hydrolysis, DNA hydrolysis, and growth on charcoal-yeast extract agar), clinical strains of C. jejuni were placed in eight biotypes.

Alkaline Phosphatase↗
PubMed1981

Hippurate hydrolysis by Legionella pneumophila.

Strains of Legionella pneumophila were shown to hydrolyze sodium hippurate in an overnight test system, but strains of L. bozemanii, L. micdadei, L. dumoffii, and some other organisms similar to the legionellae did not. Although only a small number of strains of legionellae other than L. pneumophila have been classified and tested, the results indicate that the hippurate hydrolysis test may prove useful for differentiating among Legionella species.

Hippurates↗
PubMed1981

Optimal fluorescein-to-protein ratios of bacterial direct fluorescent-antibody reagents.

A number of bacterial systems were studied with specific direct fluorescent-antibody reagents prepared from rabbit antiserum fractions and having a wide range of fluorescein-to-protein ratios. These systems included Bacteroides, Bordetella, Clostridium, Escherichia, Legionella, Listeria, Salmonella, Shigella, and Streptococcus. For all systems studied, a fluorescein-to-protein ratio of 30 was optimal for conjugates prepared from ammonium sulfate fractions (greater than 75% gamma globulin) and pure immunoglobulin G desorbed from the Sepharose-bound protein A of Staphylococcus aureus. A pepsin digestion procedure is described that yielded the F(ab')2 piece of pure immunoglobulin G; this was labeled and studied at two fluorescein-to-protein ratios.

Antibodies, Bacterial↗
PubMed1980

Development and characterization of high-titered, group-specific fluorescent-antibody reagents for direct identification of rickettsiae in clinical specimens.

Rabbits were inoculated with purified antigen preparations of Coxiella burnetii and representative species of the spotted fever and typhus groups of rickettsiae. Their antibody responses were monitored by complement fixation tests; high-titered antisera were fractionated with ammonium sulfate and then labeled with fluorescein isothiocyanate by the dialysis method. The conjugates had homologous 3+ staining titers of 1:256 to 1:2,048 and did not exhibit nonspecific staining. The Rickettsia rickettsii, R. conorii, and R. akari conjugates reacted only with rickettsiae of the spotted fever group; the R. canada, R. prowazekii, and R. typhi conjugates were specific for the typhus group rickettsiae; and the C. burnetii conjugate stained only homologous organisms. One of these conjugates (R. rickettsii) is currently being used to identify rickettsiae in clinical specimens and has already proven its value as a diagnostic tool.

Animals↗
PubMed1980

Room temperature storage of Legionella cultures.

Charcoal-yeast extract agar slant cultures of Legionella representing all four named species were stored at room temperature in the dark. Some L. pneumophila strains survived 2 months, L. bozemanii and L. dumoffii strains were viable at 4 months, and L. micdadei strains remained viable after 1 year in storage.

Agar↗
PubMed1980

The rickettsia-like organisms TATLOCK (1943) and HEBA (1959): bacteria phenotypically similar to but genetically distinct from Legionella pneumophila and the WIGA bacterium.

Two "rickettsia-like organisms," TATLOCK and HEBA, isolated from human blood via guinea pigs and embryonated eggs in 1943 and 1959, respectively, have been cultured on artificial media (charcoal yeast extract agar) for the first time and characterized. TATLOCK and HEBA have identical cultural, biochemical, and antigenic characteristics, as well as identical cellular fatty-acid composition and antimicrobial susceptibilities. These two bacteria have most of the cultural and biochemical characteristics of Legionella pneumophilia, and their gas-liquid chromatography cellular fatty-acid profile is similar to that of WIGA, another bacterium similar to L. pneumophila. Direct fluorescent-antibody reagents prepared for HEBA and TATLOCK gave equal high-titered reciprocal staining and were negative on 220 other bacteria, including L. pneumophila. Deoxyribonucleic acid relatedness studies, however, showed that these bacteria are not genetically related to either L. pneumophila or the WIGA bacterium.

Anti-Bacterial Agents↗
PubMed1980

"Pittsburgh pneumonia agent": a bacterium phenotypically similar to Legionella pneumophila and identical to the TATLOCK bacterium.

The "Pittsburgh pneumonia agent," isolated by Pasculle and co-workers from human lung tissue, has been cultured on artificial media and characterized. The "Pittsburgh" bacterium and the TATLOCK and HEBA bacteria have identical cultural, biochemical, and antigenic characteristics. They also have the same cellular fatty-acid composition, and DNA relatedness indicates that they belong to the same species.

Antigens, Bacterial↗