Methicillin-Resistant Staphylococcus saprophyticus Isolates Carrying Staphylococcal Cassette Chromosome mec Have Emerged in Urogenital Tract Infections

Abstract

Staphylococcus saprophyticus is a uropathogenic bacterium that causes acute uncomplicated urinary tract infections, particularly in female outpatients. We investigated the dissemination and antimicrobial susceptibilities of 101 S. saprophyticus isolates from the genitourinary tracts of patients in Japan. Eight of these isolates were mecA positive and showed β-lactam resistance. Pulsed-field gel electrophoresis showed that only some isolates were isogenic, indicating that the mecA gene was apparently acquired independently by mecA -positive isolates through staphylococcal cassette chromosome mec (SCC mec ). Type determination of SCC mec by multiplex PCR showed a nontypeable element in the eight mecA -positive isolates. Sequence analysis of the entire SCC mec element from a prototype S. saprophyticus strain revealed that it was nontypeable with the current SCC mec classification due to the novel composition of the class A mec gene complex (IS 431 - mecA - mecR1 - mecI genes) and the ccrA1/ccrB3 gene complex. Intriguingly, the attachment sites of SCC mec are similar to those of type I SCC mec in S. aureus NCTC 10442. Furthermore, the genes around the mec gene complex are similar to those of type II/III SCC mec in S. aureus , while those around the ccr gene complex are similar to those of SCC 15305RM found in S. saprophyticus ATCC 15305. In comparison with known SCC mec elements, this S. saprophyticus SCC mec is a novel type.