Biomedical subjects

M Bes

Publications and source records attributed to M Bes.

49 records · Page 3Linked to original sources

PubMed1993

rRNA gene restriction patterns as an epidemiological marker in nosocomial outbreaks of Staphylococcus aureus infections.

rRNA gene restriction patterns (ribotyping) were compared with phage typing, serotyping, enterotoxins and exfoliatin production in the analysis of 26 Staphylococcus aureus strains isolated from two different nosocomial outbreaks. Total DNA was cleaved by EcoRI restriction endonuclease. After agarose gel electrophoresis and Southern transfer, the hybridization of the membranes was done with radiolabelled 16S rRNA gene from Bacillus subtilis inserted into a plasmid vector. Six to 13 fragments were visualized. A core of common fragments was discerned for all strains tested. A full correlation between ribotyping and conventional markers was observed in only one of the outbreaks studied. In both outbreaks, ribotyping proved helpful in characterizing otherwise untypable strains.

Bacterial Typing Techniques↗

PubMed1993

Identification of Staphylococcus aureus using a DNA probe: Accuprobe.

A non-isotopic nucleic probe (Accuprobe) has been presented recently by Gen-Probe for the direct specific 1-h identification of Staphylococcus aureus isolated from culture. 50 S aureus strains previously characterized by conventional methods as well as 26 atypical strains (absence of coagulase, thermonuclease and fibrinogen affinity factor) were tested. Moreover, the Accuprobe system was evaluated using 29 other staphylococcal type strains representing all the species described to date. Only the strains that belonged to the S aureus species, including the 26 atypical strains, were detected by Accuprobe, which proved to be a rapid specific mean of identifying S aureus strains, particularly those that are not readily identified by conventional methods.

DNA Probes↗

PubMed1993

[Evolution of resistance to antibiotics and antiseptics of hospital Staphylococcus aureus strains isolated from 1980 to 1991].

From 1980 to 1991, 925 non epidemic hospital isolates of S. aureus were selected and phage typed. MIC of 20 antibiotics and 4 antiseptics were determined by agar dilution method. The proportion of isolates susceptible to all antibiotics remains constant; however the trend to the resistance is strong during the study period (oxacillin 10-->20%, erythromycin 17-->28%, pefloxacin 4-->19%...). Strains resistant to oxacillin become more and more multiple resistant; some of recent isolates are resistant to 7 antibiotic families. There are very few products active against these strains i.e, glycopeptides (100%), pristinamycin (96%), fusidic acid (94%). This finding implies the need for continuous surveillance at the local and national level.

Aminoglycosides↗

PubMed1992

Identification of coagulase negative staphylococci isolated from lambs as Staphylococcus caseolyticus.

A group of 17 strains of coagulase negative staphylococci isolated from slaughtered lambs, and which could not be identified with the conventional methods, exhibited high levels of DNA homology (92%) with the S. caseolyticus reference strain. The isolates described in this study provide a more extensive comprehension of S. caseolyticus. The original description of this species was based on only two strains isolated from milk. To our knowledge, S. caseolyticus had never been previously associated with animal microflora.

Abscess↗

PubMed1992

Synthetic DNA probes for detection of genes for enterotoxins A, B, C, D, E and for TSST-1 in staphylococcal strains.

A dot blot hybridization technique with oligonucleotide probes was developed for the specific detection of the TSST-1 gene and the staphylococcal enterotoxin (SE) genes A, B, C, D and E. For each toxin gene a probe sequence was chosen from the previously determined sequence. A total of 145 staphylococcal strains (133 Staphylococcus aureus and 12 coagulase-negative staphylococci (CNS) were studied by this genotypic method and by two phenotypic assays (gel immunodiffusion and ELISA). An excellent correlation (96%) was observed between the genotypic and phenotypic assays. DNA from two CNS strains hybridized with a probe without detection of the corresponding toxin (SEB for one strain and SEC for the other strain). One Staph. aureus strain was shown to be an SEC producer, but was not detected by the corresponding probe. Gene probe and immunological assays seem to be complementary methods for studies of staphylococcal strains producing (or potentially producing) TSST-1 or enterotoxins.

Bacterial Toxins↗

PubMed1991

Characterization of clinically significant isolates of Staphylococcus epidermidis from patients with cerebrospinal fluid shunt infections.

Biotyping, slime production, antibiograms, extrachromosomal DNA banding and total DNA restriction analysis were used to characterize Staphylococcus epidermidis strains causing cerebrospinal fluid shunt infections in 11 patients. Infections considered to be community acquired and those acquired in the first 2 weeks of hospital admission were due to oxacillin-susceptible isolates. Multiply resistant strains were isolated from patients who were in hospital for more than 1 month before tube implantation. Slime was detected in staphylococci for 54% of cases, but its expression varied. Strains from different patients could be differentiated from one another by the extrachromosomal DNA bandings and total DNA restriction patterns, but isolates from the same patient were usually similar. During the period of external drainage, epidemiological markers were useful in differentiating persistence of infection from contamination or re-infection by a new strain.

Adult↗

PubMed1990

International collaborative evaluation of the ATB 32 staph gallery for identification of the Staphylococcus species.

This international collaborative study evaluates a new system (ATB 32 Staph) for the identification of staphylococci taking into account the new novobiocin-sensitive and -resistant species reported. This study involved eight laboratories and 792 strains were tested. The reproducibility obtained for the cumulative results of the inter- and intra-laboratory tests was more than 90%. For 713 strains relevant of a species 95.5% were correctly identified by the system. Eight strains (1.2%) were misidentified and 24 strains (3.3%) were not identified. For 79 strains initially considered as not-classified, 62% were identified at the species level by the new system. The newer ATB 32 Staph gallery is a performant and useful method for routine identification of the currently described staphylococci species from clinical and animal origin.

Animals↗

PubMed1990

Instability of characteristics amongst coagulase-negative staphylococci causing endocarditis.

Variation in typing of clinically significant isolates of coagulase-negative staphylococci (CNS) was determined by five typing methods with 143 isolates obtained from 19 patients over periods from 2 days to 1 year. In only one case did all isolates give exactly the same typing pattern by all five tests. No single method, or simple combination, provided a ready means of confirming the relatedness of separate isolates. The most frequently useful tests were antibiotic susceptibility and extrachromosomal DNA banding patterns. However, the results of biotyping, serotyping and phage typing were also helpful in showing the relationship between different isolates from a given patient. In most cases a core pattern varying by the gain or loss of a small number of features, characterised a given patient's isolates. In two causes, apparently radical changes in the infecting organism were observed, and confirmed by restriction endonuclease analysis. Care should be taken when successive isolates of CNS show distinct typing differences in deciding their clinical relevance.

Anti-Bacterial Agents↗

PubMed1988

Characterization of clinically significant isolates of Staphylococcus epidermidis from patients with endocarditis.

Biotyping, slime production, bacteriophage typing, serotyping, antibiograms, and plasmid profiles were used to characterize 19 Staphylococcus epidermidis strains isolated from 12 patients with prosthetic valve endocarditis and from 7 patients with native valve endocarditis. With the API Staph battery, 12 different biocodes with, at the most, three differences were obtained. Slime production was found for 10 strains (53%). Agglutinogens investigated by agglutination with two specific sera were found for 12 strains (63.1%). Three strains were phage typable (15.2%). Against a panel of nine antimicrobial agents, 15 different profiles were found. Multiply antibiotic-resistant strains were isolated from patients with prosthetic valve endocarditis when disease onset occurred less than 18 months after heart surgery and from patients with native valve endocarditis who received antibiotics immediately prior to their illness. All of the strains were available for plasmid analysis, and all the DNA profiles were distinct. On gels run in Tris-borate buffer, 73.7% of the strains had large plasmids of more than 30 megadaltons. A small plasmid of 2.8 megadaltons was found in multiply resistant strains and in strains resistant only to tetracyclines. None of the isolates appeared to be the same strain, and the bacteriological differences between the strains were confirmed mainly by the antibiotic susceptibility profile and the plasmid pattern analysis. These bacteriological results were in agreement with the clinical data.

Bacteriophage Typing↗

PubMed1988

Restriction endonuclease analysis of Staphylococcus epidermidis DNA may be a useful epidemiological marker.

We compared the epidemiological markers of 13 Staphylococcus epidermidis strains isolated from an adult inpatient during a febrile episode and 23 S. epidermidis strains isolated during a presumptive outbreak of nosocomial infection in a neonatal ward. The total DNA restriction endonuclease analysis (REA) was processed along with the following conventional markers: biotyping, serotyping, phage typing, antibiotic susceptibility profiles, and plasmid profiles. The REA method was reproducible, giving stable results both in vitro and in vivo. For the hospitalized adult patient, the conventional markers of the 13 strains were concordant and the restriction profiles were identical. Five restriction groups were demonstrated during the course of the outbreak. Within two of the groups, the identities of all of the markers were used to verify whether all of the isolates belonged to the same cell clone. In a third group, combined analysis of the conventional markers and REA had to be used to demonstrate isolate similarity. On the other hand, in another group, none of the markers were similar; interpretation was not easy. An epidemiological study of S. epidermidis infections in hospitals must take into account all of the epidemiological markers: biotypes, serotypes, phage types, antibiograms, plasmid profiles, and REA.

Bacterial Typing Techniques↗

PubMedDate not supplied

Morphology of Staphylococcus saprophyticus bacteriophages.

The morphology of 6 bacteriophages isolated from Staphylococcus saprophyticus was studied by electron microscopy. Phages had isometric heads and non-contractile tails, thus belonging to the Siphoviridae family. They were subdivided into two morphological groups based on head diameter and tail length. Type I, represented by phages 1154A and 1405, and characterized by an unusually small capsid, may be a new species.

Capsid↗

PubMedDate not supplied

Characterization of thirteen Staphylococcus epidermidis and S. saprophyticus bacteriophages.

Thirteen bacteriophages of coagulase-negative staphylococci belonging to the Siphoviridae family (morphotype B1) were compared by seroneutralization kinetics, protein profiles, G + C content, DNA size and DNA/DNA hybridization. A previous classification into three morphological groups was confirmed. The Staphylococcus epidermidis phage group, although morphologically homogeneous, was heterogeneous by DNA/DNA hybridization (27 to 100% homology) and seroneutralization kinetics. Two new phage "species", STA1139 (STA for Staphylococcus) and STA1154A, corresponding to two morphological types of S. saprophyticus phages, were identified. Species STA1154A was particularly interesting because the size of its capsid, only 46 nm in diameter, and of its DNA, evaluated as 13 kbp, were smaller than those of other staphylococcal phages.

Base Composition↗

PubMedDate not supplied

[New bacteriophages of Staphylococcus epidermidis: evaluation of their epidemiological value].

Coagulase-negative staphylococci, and in particular Staphylococcus epidermidis, are now being recognized as causing human infections with increasing frequency; the absence of an internationally accepted system of phage-typing for coagulase-negative staphylococci led us to isolate new phages. Fifty strains of S. epidermidis isolated from human infections were induced with mitomycin C: eight phages (41, 63, 118-II, 138, 245, 336, 392 and 550) were isolated. These phages were propagated on five different strains of S. epidermidis. Their phages were propagated on five different strains of S. epidermidis. Their lytic activity as studied on 561 strains. Phages 336, 392 and 550 had a different host-range and different propagative strains; they typed 93% of the strains susceptible to the 8 phages. The other phages had an activity similar to that of phage 336. Twenty-one per cent of non-epidemic strains were susceptible to at least one of the three phages. The reproducibility, specificity and discriminatory power of these phages suggest they may be a useful addition to previously recognized phages.

Bacteriophage Typing↗