We determined the entire nucleotide sequence of Sa2958-carrying Panton-Valentine leukocidin (PVL) gene, which was lysogenized in a sequence type 5 staphylococcal cassette chromosome mec (SCCmec) type II strain of methicillin-resistant Staphylococcus aureus (MRSA). Based on the nucleotide sequences of PVL phages, we developed PCRs to discriminate among five PVL phages, with a preliminary classification into two morphological groups (elongated-head type and icosahedral-head type) with four PCRs, including two PCRs for identifying the gene lineage between lukS-PV and the tail gene. The phages were then classified into five types by four PCRs identifying each phage-specific structure. With these PCRs, we examined the PVL phage types of 67 MRSA strains isolated in Japan from 1979 through 1985 and since 2000 and found that two morphologically distinct phages were predominant in Japan. The icosahedral-head-type phage, represented by the 108PVL type, was identified for 39 of 53 strains isolated from 1979 through 1985. Of 26 other Japanese isolates, 25 belonged either definitively or presumably to elongated-head types as follows: 3 belonged to the Sa2958 type; 8 were determined to belong to an elongated-head type, but a determination of greater specificity was not made; and 14 belonged to a Sa2958-like phage of unknown type. We induced prophages by treatment with mitomycin C from six strains of the Sa2958 type or of Sa2958-like unknown-type phages; five of six strains carried intact PVL-carrying phages, which can infect other S. aureus strains and might generate novel PVL-positive strains of S. aureus. That various SCCmec elements were carried by different strains of the same phage type suggests that S. aureus strains might independently acquire PVL phages before they acquire various SCCmec elements.

MRSA isolates can be genotyped rapidly by detecting phage-derived ORFs. As particular pandemic clones can be found in a specific region, a typing method localized to a pandemic clone may be effective for the rapid genotyping of MRSA during outbreaks.

These findings suggest that more than one antigenically different strain of H. pylori may exist in same infected individuals.

A total of 103 methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients and 78 MRSA from hospital workers during the years 1990 to 1994, and 52 MRSA from patients in year 2000, in one hospital at Wakayama Prefecture, were typed by pulsed-field gel electrophoresis (PFGE) profiles. MRSA isolates were grouped into 20 genomic types. These types were further divided into 57 subtypes. The type 1 was dominant among patients, and closely related type 1 strains were spread during 1990-1993. In contrast, the type 2 was dominant among medical workers in the same period. In 2000, the type 2 and 4 strains increased, and the diversity and complication of types appeared. The common types between the patients and medical workers were only type 1 to 3. Some strains isolated from both during the same period were shown to have the same types. Others were shown to be patient-specific types. These results suggest that there are complicated transmissions of MRSA in the hospital, i.e., the endogenous infection, patient-patient cross infection and medical worker-patient cross infection.

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