Epidemiological Surveys of Methicillin-Resistant Staphylococcus aureus in Tottori Prefecture, Japan

To study the isolation frequency of methicillin-resistant Staphylococcus aureus (MRSA) and susceptibility of MRSA to antibiotics, a questionnaire survey was performed every half year from 1993 until 1997. The questionnaire was sent to medical doctors, and it asked retroactively about the isolation of S. aureus from clinical specimens. The isolation rate of MRSA from patients over 65 years of age was higher, and that from patients under 16 years of age was lower, than the rates in other age groups (P< 0.01). Ratios of isolation of MRSA among S. aureus strains were from 12 to 38% in the clinics, from 39 to 71% in the small-scale hospitals and from 47 to 62% in large-sized hospitals. These isolation rates increased gradually from 1993 to 1997 (P< 0.001). The isolation rate of MRSA from the sputum was higher, and those from pus, pharyngeal secretion and urine were lower, than those from feces and other specimens and from total specimens. The isolation rate of antibiotic-resistant strains of MRSA was highest for penicillins and cepharosporins. MRSA was highly susceptible to arbekacin (isolation rate of resistant strains: 3.0%) and vancomycin (3.0%), and was slightly susceptible to minocycline (21%), doxycycline (24%), amikacin (39%) and dibekacin (37%). These results indicate that more careful surveillance of MRSA and more stringent precautions against nosocomial infection with antibiotic-resistant MRSA are needed in hospitals even in relatively isolated parts of Japan.