Isolation and characterization of Staphylococcus aureus in rats trapped at restaurants in buildings in downtown Tokyo.

165 (18.1%) out of 910 rats captured at restaurants in 14 buildings in downtown Tokyo were positive for Staphylococcus aureus. The 165 S. aureus strains isolated were biotyped into A, B, C, D, G, and untypable groups (UT1 and UT2). The UT1 was the most frequent (72 strains, 43.6%), followed by biotype G (33 strains, 20.0%). The strains were classified into coagulase types I, II, III, IV, V, VI, VII, VIII, and an untypable group. Coagulase type V was the most frequent (92 strains, 55.8%), followed by coagulase type VII (25 strains, 15.2%). Enterotoxins A, B, C, or D were produced by 35 strains. Enterotoxins A and B were the most frequent (13 strains each). Toxic shock syndrome toxin-1 was produced by 3 strains. 65 strains were resistant to ampicillin, 2 to oxytetracycline, and 1 to erythromycin.

[Relationship between coagulase toxin-type and drug susceptibility in Staphylococcus aureus strains isolated in all the Japanese National University Hospitals].

Drug susceptibility of 430 Staphylococcus aureus strains isolated in 1991 from clinical specimens at all of the Japanese national university hospitals was evaluated in relationship with the epidemiological markers, namely, coagulase typing, and staphylococcal enterotoxins (SE) and toxic shock syndrome toxin 1 (TSST-1) production. There were five major methicillin-resistant Staphylococcus aureus (MRSA) groups in all the 252 MRSA strains: coagulase-type II-SEC + TSST-1- producing strains (II-SEC + TSST-1): 34.5%; coagulase-type II-no toxin-producing strains (II-): 15.4%; coagulase-type IV-SEA-producing strains (IV-SEA): 10.3%; coagulase-type II-SEA + SEC + TSST-1- producing strains (II-SEA + SEC + TSST-1): 8.7%; and coagulase-type III-no toxin-producing strains (III-): 7.1%. II-SEA + SEC + TSST-1 group was highly resistant to OFLX, whereas half of the other strain groups were sensitive to OFLX. Seventy-eight percent of the IV-SEA group was sensitive to FMOX, but there was no sensitive strain to FMOX in the II-SEA + SEC + TSST-1 group. More than 50% of the IV-SEA, III- and II-groups were sensitive to IPM, while the II-SEC + TSST-1 and II-SEA + SEC + TSST-1 groups were highly resistant to IPM. The III- and II-groups showed very good sensitivity to MINO, but the sensitivity to it of the II-SEA + SEC + TSST-1 group was very low. All of the strain groups were sensitive to ST except for the IV-SEA group. These results may provide useful information in the choice of antibacterial agents for MRSA infection.

[Epidemiological study of Staphylococcus aureus isolated from the Japanese National University and Medical College Hospitals with coagulase typing, and production of enterotoxins and toxic shock syndrome toxin-1].

Coagulase typing, staphylococcus enterotoxins (SE) A to E or toxic shock syndrome toxin-1 (TSST = 1) production, and susceptibility to Oxacillin (MPIPC) were examined in 430 strains of S. aureus, which were isolated from clinical specimen of 43 Japanese National University or Medical College Hospitals during the one month period of August in 1990. Methicillin-resistant Staphylococcus aureus (MRSA): more than 4 mmg/ml of minimum inhibitory concentration for MPIPC in Mueller-Hinton broth containing 2% NaCl, occupied 58.6% of all the S. aureus, and more than 60% of the strains from admitted patients in all the areas of Japan except Hokkaidoh. Coagulase type II, SEC and TSST-1 producing strains were most frequently detected, 34.5% of all the MRSA. This kind of strain was distributed mainly in the eastern part of the Honshyu island, and showed high percentage especially in the Tohhoku and the Chyubu area. The second most frequent kind of MRSA was coagulase type II, no SE nor TSST-1 producing one, 15.4%, which was distributed mainly in the western part of Japan. Coagulase type IV, SEA producing MRSA strains and Coagulase type II, SEA, SEC and TSST-1 producing strains were detected in relatively high incidence, 10.3% and 8.7% respectively. Coagulase type III, no SE nor TSST-1 producing MRSAs demonstrated characteristic distribution, and were detected only in the western part of Japan, presenting the highest incidence in the Shikoku Island.

Kinetics of Escherichia coli destruction by microwave irradiation.

The kinetics of destruction of Escherichia coli cells suspended in a solution by microwave irradiation with a microwave oven were studied. During radiation at several powers, the temperature of 0.01 M phosphate buffer (PB), pH 7.0, in a glass beaker increased linearly at a rate of A (degrees Centigrade per second) according to the exposure time. When E. coli cells suspended in PB were exposed in the same beaker, the number of viable cells decreased according to the exposure time and the power used. The survival curve was approximated to a set of three linear parts. For each part, a rate constant of destruction (k) and an extrapolated starting temperature (T0) at several powers were estimated. Thereafter, the relationships between A and k and between A and T0 were studied. When a flat petri dish was used, the A value of exposed PB was lower and bacterial destruction was inhibited; the survival curve was similar to a curve predicted from the A value by using the relationships between the parameters. As the concentration of salt in the solution increased (from 0 to 1.35 M), the A value decreased and bacterial destruction was more suppressed. No remarkable difference between the destruction profiles for microwave exposure and conventional heating, which had the potential to generate an equal A value, was detected. These results showed that the parameter A of an irradiated solution is essential when kinetics of bacterial destruction by microwave exposure are studied and that the destruction profile can be interpreted mostly by means of thermal effects.

Staphylococcal food poisonings in Tokyo, with special reference to the coagulase types of the isolates.

Staphylococcus aureus strains isolated from the 391 confirmed cases of staphylococcal food poisonings in Tokyo, in the period 1967-1986, were studied for their coagulase types. Consequently, it was found that all the isolates could be classified into the coagulase types II, III, VI and VII. Namely, the isolates from 54 (13.8%) of 391 outbreaks were typed as type II, 72 (18.4%) as type III, 38 (9.7%) as type VI, and 227 (58.1%) as type VII, respectively. Throughout the investigation, it was found that the outbreaks of staphylococcal food poisonings due to coagulase type VII organisms were remarkably increased since 1975.