Comparative evaluation of a commercial test for rapid identification of methicillin-resistant Staphylococcus aureus.

The performance and ease of use of the recently introduced MRSA screen test (Denka Seiken Co. Ltd., Japan) for the identification of methicillin-resistant Staphylococcus aureus was evaluated in comparison with the BBL Crystal MRSA ID System (Becton Dickinson Europe, France). A total of 109 strains of S. aureus, consisting of 57 strains of MecA-negative S. aureus and 52 strains of MecA-positive S. aureus, were tested. With MecA PCR as the gold standard, the MRSA screen test had 98% sensitivity and 98% specificity, whereas the BBL Crystal MRSA ID System had 98% sensitivity and 95% specificity. The simplicity of use and rapid result make the MRSA screen test a valuable tool in the clinical microbiology laboratory pending demonstration of the MecA gene that should still always be done.

Temafloxacin: in vitro comparison with five other antibacterial agents.

The in vitro activity of the new fluorinated quinolone temafloxacin was compared with the activities of ciprofloxacin, fleroxacin, ofloxacin, ceftazidime and tobramycin. A total of 662 recent clinical isolates were included in the study, representing a variety of gram-negative and gram-positive bacteria. An agar dilution method was employed for the determination of minimal inhibitory concentrations (MICs). Ciprofloxacin showed the highest potency against the Enterobacteriaceae, 90% of the isolates being inhibited by 0.06 mg/l or less. The other quinolones were also highly active (MIC90 = 0.25-0.5 mg/l). Ciprofloxacin and tobramycin were the most active agents against the Pseudomonas isolates (MIC90 = 0.25 and 0.5 mg/l, respectively), whereas the activities of temafloxacin, fleroxacin and ofloxacin were more variable. All the quinolones had relatively high and similar activity against Staphylococcus aureus and S. epidermidis, but S. saprophyticus was markedly less susceptible to fleroxacin than to the other quinolones. The activity of temafloxacin against Streptococcus pneumoniae was somewhat higher than those of the other quinolones tested. Temafloxacin showed variable activity against Bacteroides fragilis isolates but was generally more potent against these isolates than were the other quinolones. The MICs of temafloxacin were slightly lower at pH 7.3 compared with those obtained at pHs 5.8 or 8.8.

Effects of carbon dioxide upon the in vitro activity of erythromycin.

The in vitro activity of erythromycin against clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae was examined by agar dilution and agar diffusion methods. The plates were incubated in air alone or in 8% CO2 and air. The minimal inhibitory concentrations (MICs) measured in air alone were lower for most of the isolates, compared to those found in 8% CO2. The greatest differences in MIC values were found for H. influenzae; the MIC 50% was 0.5 mg/l in air and 4 mg/l in 8% CO2. Sensitivity testing by the agar diffusion method (ICS) showed considerable differences between results obtained in air and in 8% CO2; the inhibition zones were generally smaller in CO2. The most marked reduction in zone sizes after incubation in 8% CO2 was seen with the H. influenzae isolates; 15 out of 43 isolates moved from the "sensitive" to "moderately sensitive" group. Sensitivity determination of aerobic bacteria for erythromycin should be performed in air alone in the routine laboratory.

Evaluation of Rosco diagnostic beta-glucuronidase tablets in the identification of urinary isolates of Escherichia coli.

Rosco diagnostic beta-glucuronidase tablets have been evaluated as a method for the identification of urinary isolates of Escherichia coli. Results were compared with those from traditional biochemical testing. A total of 539 isolates were employed, representing a variety of Gram-negative species. Reproducibility testing was also performed. After 4h incubation, 86% of E. coli isolates (both lactose-positive and lactose-negative) gave a positive reaction. Some Salmonella, many Shigella and one Citrobacter freundii isolate also gave positive reactions. All other organisms gave negative reactions. Results were highly reproducible and not influenced by choice of primary medium. The tablets are suitable for routine use in the diagnostic laboratory for the identification of lactose-positive E. coli. A suitable diagnostic table has been suggested.