Chikako Mochida

Analysis of Genetic Relationships and Antimicrobial Susceptibility of Verotoxin-Producing Escherichia coli Strains Isolated in Nagasaki Prefecture, Japan in 1996

A total of 19 Escherichia coli O157 isolates were obtained in Nagasaki Prefecture, in the southwestern part of Japan, between 1990 and 1996. Pulsed‐field gel electrophoresis (PFGE) and computer‐assisted analysis were applied to determine genetic relationships among these strains. Fragment patterns of the isolates in Nagasaki, as determined by PFGE, were compared with those of isolates in other areas where large outbreaks and sporadic cases of E. coli O157 infection occurred. Similarity values of all the strains isolated in Nagasaki Prefecture were over 0.65 except for E. coli O26. Some strains were identical to the strains isolated from the areas where large outbreaks occurred. All strains were susceptible to ampicillin, fosfomycin, minocycline, amikacin, ofloxacin and sulfamethoxazole‐trimethoprim.

Infections caused by multiple strains of methicillin-resistant Staphylococcus aureus —a pressing epidemiological issue

The genotype of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from several foci in the same patient was studied to identify the rate of infections caused by multiple MRSA strains during hospitalization. Twenty-one patients with MRSA bacteraemia and other specimens diagnosed between 1990-1994 were studied. Clinical data were retrospectively collected from the medical records. Genotyping of 113 MRSA isolates was performed by pulsed-field gel electrophoresis (PFGE), using the Gene Navigator System. More than one type of MRSA was detected from different foci in eight of 21 (38%) patients, and three types were identified in a single patient. Our results indicate that epidemiological investigations must be conducted carefully, especially in immunocompromised hosts with MRSA bacteraemia, as the probability of infection with multiple strains among these patients is relatively high.