Staphylococcus aureus , 2015

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 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 decreased to 11.2 per 100,000 in 2015 (Ramsey: 10.3/100,000, Hennepin: 11.6/100,000) compared to 15.2/100,000 population in 2014. In 2015, MRSA was most frequently isolated from blood (77%), and 13% (25/196) of the cases died in the hospital. HACO-MRSA cases comprised the majority (72%, 141/196) of invasive MRSA infections in 2015; CA-MRSA cases accounted for 18% (35/196) and 10% (20/196) cases were HO-MRSA. The median age for all cases was 62 years (range, <1 to 96 years); the median age was 58 (range, 41 to 79), 63 (range, 5 to 96 years), and 53 years (range, <1 to 91) for HO-, HACO-, and CA-MRSA cases, respectively. Please refer to the MDH Antibiogram (pp. 28-29) for details regarding antibiotic susceptibility testing results.

In August 2014, population-based surveillance of invasive methicillin-sensitive (MSSA) was initiated in Hennepin and Ramsey Counties. The incidence rate was 28.7 per 100,000 in 2015 (Ramsey: 28.5/100,000, Hennepin: 28.8/100,000). In 2015, MSSA was most frequently isolated from blood (72%), and 10% (51/501) of the cases died in the hospital. HACOMSSA cases comprised the majority (58%, 289/501) of invasive MSSA infections in 2015; CA-MSSA cases accounted for 32% (159/501) and 11% (53/501) cases were HO- MSSA. The median age for all cases was 60 years (range, <1 to 102 years); the median age was 60 (range, <1 to 94), 62 (range, <1 to 102), and 57 years (range, <1 to 90) for HO-, HACO-, and CAMSSA cases, respectively.

Vancomycin-intermediate (VISA) and vancomycin-resistant S. aureus (VRSA) are reportable in Minnesota, as detected and defined according to 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 underlying health conditions such as diabetes and endstage 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 2013, we confirmed 16 VISA cases; 2008 (3), 2009 (3), 2010 (2), 2011 (5), and 2013 (3). No VISA cases were confirmed in 2014 or 2015. Among all cases, 8 (47%) were male and the median age was 62 years (range, 27 to 86). Of those cases with known history (15), 80% 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, 2015