EPIDEMIOLOGY OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS BLOODSTREAM INFECTION AT MAHARAJ NAKORN CHIANG MAI HOSPITAL, CHIANG MAI UNIVERSITY, CHIANG MAI, THAILAND (2013-2017)

Bloodstream infection (BSI) caused by methicillin-resistant Staphylococcus aureus (MRSA) is associated with significant high prevalence of morbidity and mortality. In order to determine mortality risk factors, clinical characteristics of nosocomial MRSA BSI at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai University, Thailand from January 2013 to December 2017 were gathered including minimal inhibitory concentration (MIC) of vancomycin against MRSA isolates. Of 84 patients, 63% were male, median age (interquartile range) was 68.5 years (56, 79 years) and 69% had MRSA bloodstream infection together with other co-morbidities, namely (in decreasing order of frequency), pneumonia (43%), skin and soft tissue infections (25%), osteomyelitis (11%), arterial graft infection (6%), infective endocarditis (6%), septic arthritis (6%), and urinary tract infection (3%). Percent patients with vancomycin MIC >= 1.5 mg/l were 68, 62, 47, 27, and 75% in 2013, 2014, 2015, 2016, and 2017, respectively. Overall mortality rate was 64%, with significant associated factors being >= 40 years of age (odds ratio (OR) = 11.35, 95% confidence interval (CI): 1.35-95.78), alteration of consciousness (OR = 11.19, 95% CI: 2.83-44.18) and concurrent pneumonia (OR = 4.44, 95% CI: 1.09-18.14), but there is no significant difference in mortality between those infected with MRSA with vancomycin MIC <1.5 and >= 1.5mg/l. In conclusion, pneumonia was the most common concurrent infection and increased mortality. As half of the patients had clinical isolates with vancomycin MIC >= 1.5 mg/l, careful monitoring of vancomycin MIC creep is crucial for appropriate antibiotic and dose selection.