Staphylococcus aureus , 2016
Invasive Staphylococcus aureus (SA) infections are classified into one of three categories: hospital-onset (HO-SA), healthcare-associated, community-onset (HACO-SA), and community-associated (CA-SA). SA must be isolated from a normally sterile body site >3 days after the date of hospital admission for a case to be considered HO-SA. HACO-SA cases have at least one HA risk factor identified in the year prior to infection; examples of risk factors include residence in a long term care facility, recent hospitalization(s), dialysis, presence of an indwelling central venous catheter, and surgery. CA-SA cases do not have any identifiable HA risk factors present in the year prior to infection.
In 2005, as part of EIP, population-based surveillance of invasive methicillin-resistant SA (MRSA) was initiated in Ramsey County; surveillance was expanded to include Hennepin County in 2008. The incidence rate was 11.6 per 100,000 in 2016 (Ramsey: 12.0/100,000 and Hennepin: 11.4/100,000) compared to 11.2 per 100,000 population in 2015. In 2016, MRSA was most frequently isolated from blood (75%, 155/206), and 10% (21/206) of the cases died in the hospital. HACO-MRSA cases comprised the majority (65%, 133/206) of invasive MRSA infections in 2016; CA-MRSA cases accounted for 25% (52/206) and 10% (21/206) cases were HO-MRSA. The median age for all cases was 61 years (range, <1 to 93); the median age was 59 (range, 20 to 82), 64 (range, 20 to 93), and 54 years (range, <1 to 86) for HO-, HACO-, and CA-MRSA cases, respectively.
In August 2014, as part of EIP, population-based surveillance of invasive methicillin-sensitive SA (MSSA) was initiated in Hennepin and Ramsey Counties. The incidence rate was 26.5 per 100,000 in 2016 (Ramsey: 27.4/100,000 and Hennepin: 26.1/100,000) compared to 28.7 per 100,000 population in 2015. In 2016, MSSA was most frequently isolated from blood (74%, 346/470), and 10% (45/470) of the cases died in the hospital. HACO-MSSA cases comprised the majority (55%, 261/470) of invasive MSSA infections in 2016; CA-MSSA cases accounted for 36% (168/470) and 9% (41/470) cases were HO-MSSA. The median age for all cases was 58 years (range, <1 to 103); the median age was 52 (range, <1 to 94), 61 (range, 2 to 103), and 53 years (range, <1 to 95) for HO-, HACO-, and CA- MSSA cases, respectively.
Vancomycin-intermediate (VISA) and vancomycin-resistant S. aureus (VRSA) are reportable, as detected and defined by Clinical and Laboratory Standards Institute approved standards and recommendations: a minimum inhibitory concentration (MIC)=4- 8 μg/ml for VISA and MIC ≥16 μg/ ml for VRSA. Patients at risk for VISA and VRSA generally have comorbidities such as diabetes and end stage renal disease requiring dialysis, previous MRSA infections, recent hospitalizations, and recent exposure to vancomycin. There have been no VRSA cases in Minnesota. Prior to 2008, the PHL had confirmed 1 VISA case. Between 2008 and 2015, the PHL confirmed 16 VISA cases; 2008 (3), 2009 (3), 2010 (2), 2011 (5), and 2013 (3). MDH confirmed 2 VISA cases in 2016: 1 isolated from a tissue biopsy from a psoas abscess, and the other from a blood specimen. Both patients were hospitalized at time of specimen collection, had been prescribed vancomycin during the year before collection, and had a history of MRSA. Among all 18 cases of VISA, 10 (53%) were male and the median age was 64 years (range, 27 to 86). Of those cases with known history (17), 89% reported recent exposure to vancomycin.
- For up to date information see: Staphylococcus aureus
- Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2016