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Staphylococcus aureus isolates in 2001 from the nose and the throat of an adult population were characterized for their incidence and type. The incidence was 51%, present in 80 out of 157 individuals examined, consisting of 34 nasal carriers, 24 throat carriers, and 22 who carried the isolates in both the nose and throat. Among these isolates, 2 and 5 from the nose and the throat, respectively, were identified as methicillin-resistant S. aureus. S. aureus from the nose and throat of the same individuals were characterized for identification. Examination of their phenotypes revealed that in 11 individuals the clone of S. aureus in the throat was different from the nasal clone. These results suggested that staphylococcal flora in the nose and the throat were independently formed, and that attention should also be directed to the carriers of S. aureus in the throat for the control of nosocomial infection.

Staphylococcus aureus isolated from hospital staff (nurses and doctors) in Laos were characterized for future reference and for comparison with organisms found in Okinawa, Japan. No methicillin-resistant S. aureus (MRSA), among 38 isolates examined, was found in Laos, but 16 of 36 Japanese isolates (44%) were identified as MRSA. The minimum inhibitory concentrations (MICs) of ampicillin and tetracycline against Lao isolates were definitely higher than those against Japanese isolates. The MIC(80) of tetracycline was 50 microg/ml and 0.4 microg/ml in Lao and Japanese isolates, respectively. There was no marked difference in the production of enterotoxin by S. aureus strains in the two countries. Toxic shock syndrome toxin-1 was produced by only 1 of 38 Lao isolates but by 5 of 36 Japanese isolates. Coagulase types varied greatly, but about 50% of the isolates in both countries produced untypable coagulase. Since the interaction of Laotians with foreigners has increased rapidly in recent years, the careful monitoring of drug-resistant pathogens is required.

The usefulness of the clump-formation test described by Albert et al. for identifying enteroaggregative Escherichia coli (EAggEC) and the incidence of EAggEC in Japan were studied. One hundred and seventy strains of E. coli agglutinated with enteropathogenic E. coli diagnostic antisera were collected from a variety of districts in Japan. All isolates were from diarrheal stools. EAggEC was identified on the basis of the presence of the aggR gene accompanied by aggregative adhesion to HEp-2 cells. After 24 strains carrying eaeA, elt, est, stx-1, stx-2, or ipaH genes were eliminated, the remaining 145 strains were examined for adhesion to Hep-2 cells, the presence of the aggRgene, and clump formation on the surface of Muller-Hinton broth. aggR was detected in 10 strains, and 9 of them displayed aggregative adhesion to HEp-2 cells. Seven strains produced marked clumps and 22 showed moderate clump formation. The sensitivity and specificity of the clump-formation test for detecting EAggEC were each about 90%, and they varied slightly depending on the stringency of evaluation for the degree of clump formation. From these results, we conclude that the incidence of EAggEC cannot be ignored as a possible cause of diarrheal disease in Japan, and we strongly recommend the clump-formation test for detecting EAggEC.

The changes of drug susceptibilities of Vibrio cholerae O1 isolated during the past 7 years (1993-1999) in Lao PDR were investigated. The most noteworthy finding was the appearance of polymyxin B sensitive El Tor vibrios. Until 1996, the susceptibilities were almost as expected and cholera disappeared in 1997. When a cholera outbreak resurfaced in 1998, the susceptibilities of isolated V. cholerae O1 against tetracycline, sulfamethoxazol-trimethoprim, chloramphenicol and polymyxin B were quite different from those of previously isolated organisms. Minimum inhibitory concentrations (MICs) of tetracycline and chloramphenicol against the isolates in 1998 were about 16 times higher than those against the previous isolates, and the MICs of sulfamethoxazol-trimethoprim were about 256 times higher than those against the previous isolates, (trimethoprim 32 microg/ml: sulfamethoxazol 608 microg/ml). Eleven percent of the isolates (11/99) were as sensitive to polymyxin B as the classic cholera vibrios (MIC < 2 microg/ml). In 1999, the susceptibility pattern was almost the same as that in 1998 except for polymyxin B to which 58% of the isolates (21/36) became sensitive.

The isolation frequency of pathogenic bacteria for acute respiratory infection (ARI) in the pharynx and nasal vestivulum was investigated. Age group-matched children with or without ARI including 109 individuals in each group were examined. Any of the organisms, which are widely regarded as the pathogens causing ARI such as Haemophilus influenzae, Streptococcus pneumoniae, beta-haemolytic Streptococcus, Staphylococcus aureus, and Moraxella catarrhalis, were isolated from 91% of the patient group and from 77% of the healthy group. The isolation frequency of S. pneumoniae in the nasal vestivulum of the patient group was outstanding. The healthy carrier rates of S. pneumoniae in the pharynx and nasal vestivulum were 9% and 8%, respectively. Whereas the isolation frequencies from the patient group were 7% and 28%, respectively. alpha-haemolytic Streptococci except S. pneumoniae revealed different tendency from S. pneumoniae. These organisms were almost always isolated from their pharynx but rarely isolated from the nasal vestivulum. The isolation frequency of H. influenzae from the pharynx of the patient group was 41%, which was slightly higher than 34% in the healthy group, but the difference was statistically not significant. H. influenzae was not isolated from the nasal vestivulum of the healthy group, nevertheless it was isolated from 25% of the patient group. The isolation of H. influenzae from the nasal vestivulum may have some important information about ARI. S. aureus was isolated from the pharynx with higher rate than the nasal vestivulum in both groups, and moreover, the isolation frequency of S. aureus in the healthy group was higher than the patient group. It means that the diagnosis of staphylococcal infection should be made very carefully. Considering the results of this study, it could be said that bacteriologic examination of the specimens from nasal vestivulum is valuable to determine S. pneumoniae and H. influenzae as the etiologic agents of ARI.

Verotoxin-producing Escherichia coli (VTEC) were examined for production of type I pili. None of 34 strains of VTEC serogroup O157 examined expressed any pili, whereas 26 strains of 27 VTEC serogroup O26 and seven strains of nine non-VTEC O157 produced type I pili. These VTEC strains were collected from sporadic human cases and cattle in Okinawa in 1997. The genes encoding the major structural component (FimA) and the adhesin (FimH) of type I pili were detected in all 70 strains examined. The inability to express type I pili could be a unique character of VTEC O157 and this trait could be a new candidate to identify the organisms.