Molecular typing of Staphylococcus epidermidis and other CNS with repetitive element sequence-based PCR

PCR-based identification of Staphylococcus epidermidis targeting gseA encoding the glutamic-acid-specific protease

The frequency of the gseA gene encoding a glutamic acid-specific serine protease, GluSE, of Staphylococcus epidermidis was investigated. DNA hybridization analysis demonstrated that gseA existed exclusively in S. epidermidis but not in other bacteria examined. A single step PCR assay with a set of designed primers yielded amplification of gseA from all 69 clinical isolates of S. epidermidis taken from patients and healthy adults, whereas production of GluSE was observed in 74% (51/69) of the isolates. Furthermore, none of the 46 clinical isolates of other species of coagulase-negative staphylococci and 45 clinical isolates of Staphylococcus aureus showed amplification, except a Staphylococcus capitis strain. However, this strain was positive for a S. epidermidis-specific DNA region and the DNA sequence of the 16S rRNA gene showed 99% identity with that of S. epidermidis. Therefore, these results indicated that the present PCR assay for gseA was ubiquitous and highly specific for detection of S. epidermidis.

Prevalence of Staphylococcus aureus carriage by young Malaysian footballers during indoor training

BACKGROUND

Research has shown that athletes are carriers of Staphylococcus aureus during physical activity.

OBJECTIVE

To estimate the mean total plate count of S aureus carried by footballers before and after training at an indoor venue.

METHODS

Forty Malay and 20 Indian students volunteered to participate. There was also a control group consisting of 40 Malay and 20 Indian students who were not active. The experimental group were active footballers who had played at school or club level. The subjects were healthy and free of skin infection. The experiment was divided into three sessions, with 20 subjects present at each. At each session, the subjects trained for one hour. Swabs were taken from the skin, nose, and ear before and after training. For the control group, swabs were taken only once from the skin, nose, and ear. The swabs were subjected to biochemical tests and then streaked and cultured aerobically in Baird Parker agar plates for 24 hours at 37 degrees C. Black colonies with a clear zone were presumed to be S aureus, and the mean total plate count of the colonies was estimated. Gram staining, catalase, coagulase slide, coagulase tube, acetoin production, o-nitrophenyl beta-D-galactopyranoside (ONPG), and mannitol fermentation tests were used to confirm the colonies as S aureus. A haemolysin test was conducted with human blood to confirm haemolytic activity.

RESULTS

All subjects in the experimental group were carrying S aureus both before and after training. The estimated mean total counts of colonies from the skin, ear, and nose for the Malays before training were 33, 71, and 312 respectively. Counts after training were 21, 44, and 452 respectively. The results for the Indians were 72, 80, and 309 respectively before training and 55, 200, and 466 respectively after training. The positive results for Gram staining, catalase, coagulase slide, coagulase tube, acetoin production, ONPG, and mannitol fermentation tests were 100%, 96%, 95%, 95%, 93%, 93%, and 90% respectively. All subjects in the control group were also carrying S aureus.

CONCLUSIONS

All of the players were carriers of S aureus during training. The decrease in total count from the skin for both races may be due to lysozyme activity lysing the bacterial cells. Contamination of the environment with these bacteria may have increased the estimated total plate count in the nose. The experimental group face a higher risk of infection because of lower immunity during training and higher rate of injuries compared with the control group.

Evaluation of a multilocus sequence typing system for Staphylococcus epidermidis

Staphylococcus epidermidis is a significant cause of nosocomial disease. However, the taxonomy of this pathogen, particularly at subspecies level, is unclear. A multilocus sequence typing (MLST) scheme has therefore been investigated as a tool to elucidate taxonomic relationships within this group, based on genetic relatedness. DNA sequences for internal fragments of seven housekeeping genes were compared in 47 geographically and temporally diverse S. epidermidis isolates that were obtained from clinical infections. Twenty-three different allelic profiles were detected; 17 of these were represented by single strains and the largest profile group contained 17 isolates. Diversity of the same collection of isolates was investigated by using PFGE of SmaI-digested genomic DNA to test the discrimination and validity of the MLST approach. Isolates within the largest profile group were resolved into four distinct PFGE clusters on the basis of their SmaI digest patterns. Isolates within other profile groups that contained multiple isolates had matching PFGE SmaI patterns within each group. It appears that MLST is an effective method for grouping S. epidermidis strains at the subspecies level; however, it is not as discriminatory as it has been for other species for which MLST schemes have been established and, used alone, would not be a useful method for epidemiological studies. In addition, it was demonstrated that this method was effective for confirming the identity of S. epidermidis CoNS (coagulase-negative) isolates.