Transition of drug susceptibilities of Vibrio cholerae O1 in Lao People's Democratic Republic.

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.

[Pathogenic bacteria in the nasal vestivulum of children with acute respiratory tract infection].

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.

Expression of type I pili is abolished in verotoxin-producing Escherichia coli O157.

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.

Nucleoside-nucleotide mixture increases bone marrow cell number and small intestinal RNA content in protein-deficient mice after an acute bacterial infection.

The aim of this study was to determine if intraperitoneal administration of a nucleoside-nucleotide mixture would affect small intestinal morphology, bone marrow cell number, and DNA content in protein-deficient mice subjected to acute bacterial infection. Mice were randomized into two groups and orally fed protein-free diet or nucleotide-free 20% casein diet for 10 d. The mice in each group were divided into two subgroups and intraperitoneally administered 0.35 mL saline or nucleoside-nucleotide mixture (17.5 mL/kg body weight) for 10 d. On day 10, one subgroup from each major dietary group was either inoculated intravenously with methicillin-resistant Staphylococcus aureus or saline. Three days later, small intestinal morphology, bone marrow cell number, and DNA content were evaluated in infected and noninfected mice. Protein-deficiency in association with infection significantly (P < 0.05) reduced body weight, small intestinal weight, crypt depth, villous height, and wall thickness. All dietary groups exhibited similar small intestinal DNA and protein contents (protein:DNA ratio, RNA:DNA ratio) at 3 d postinfection. However, small intestinal RNA content in the infected protein-free dietary group administered nucleoside-nucleotide mixture was higher (P < 0.05) and tended to be higher relative to the infected nucleotide-free 20% casein group administered nucleoside-nucleotide mixture compared with the rest of the groups. In the infected protein-free dietary group administered nucleoside-nucleotide mixture, bone marrow cell number and bone marrow DNA content were higher (P < 0.05) relative to the infected protein-free dietary group, nucleotide-free 20% casein diet administered saline, or nucleoside-nucleotide mixture, respectively. We conclude that intraperitoneal administration of nucleoside-nucleotide mixture may stimulate bone marrow cell proliferation, DNA content, and small intestinal RNA content during periods of relative deficiency such as protein-deficiency in combination with infection.