568. Prevalence of Staphylococcus aureus Bacteremia (SAB):  Declining Trends Over Nine years
Session: Poster Abstract Session: MRSA Surveillance and Infection Prevention
Friday, October 21, 2011
Room: Poster Hall B1
Background: Decreasing incidence of hospital acquired (HA) Methicillin-resistant S. aureus (MRSA) infections has been noted. Whether this impacted the epidemiology of SAB is unknown. We assessed the trends of HA, healthcare-associated (HCA), and community associated (CA) SAB among adult inpatients in a single medical center.

Methods: 

Retrospective review of adult (≥ 18y) inpatients with SAB during 1/1/2002-6/30/03, 11/1/2005-12/31/06, 7/15/2008-12/31/09 and 1/1-12/31/2010. SAB incidence was calculated using the number of discharges during each study period.  Cases were stratified according to methicillin-susceptibility and acquisition mode: HA, HCA and CA based on CDC definitions.

Results: 

SAB was noted in 1128 cases over the study periods with a steadily declining incidence:  6.9, 6.7, 5.4, 4.9 /103 during 2002-3, 2005-6, 2008-9 and 2010 (p<0.0001). MRSA and MSSA accounted for 671 (59.5%) and 457(40.5%) cases, respectively, both with decreasing incidence (table). MRSA/MSSA ratio did not significantly change.  Stratifying cases according to acquisition mode  showed decreasing rates of CA and HA SAB and stable rate of HCA. The topmost decrease was in CA-MSSA cases.

Table: S. aureus bacteremia trends over nine years: n (rate/103 discharges)

Study period

2002-3

2005-6

2008-9

2010

p

SAB

371 (6.9)

287 (6.7)

296 (5.4)

174 (4.9)

<0.0001

MRSA

197 (3.7)

189 (4.4)

172 (3.1)

113 (3.2)

0.045

MSSA

174 (3.2)

98 (2.3)

124 (2.3)

61 (1.7)

<0.0001

Hospital-acquired

148 (2.8)

74 (1.7)

80 (1.5)

34 (1.0)

<0.0001

Healthcare-Associated

167 (3.1)

180 (4.2)

184 (3.4)

126 (3.6)

0.55

Community-associated

56 (1.0)

33 (0.8)

32 (0.6)

10 (0.4)

<0.0001

Conclusion:  These observations reveal changing SAB epidemiology with decreasing incidence in HA and CA cases. The decline in overall SAB rate and CA cases has not been reported. HA-SAB decrease could be attributed to improved compliance with infection control measures. Factors leading to CA cases decrease are uncertain; they may be the result of the changing role of MRSA and MSSA in community and healthcare settings or the circulation of strains with different virulence characteristics. Whether this observation is unique to Detroit Metropolitan population or represents a national trend needs to be substantiated by other investigators.


Subject Category: C. Clinical studies of bacterial infections and antibacterials including sexually transmitted diseases and mycobacterial infections (surveys, epidemiology, and clinical trials)

Sugantha Iyer, MD, Mamta Sharma, MD, Mohamad Fakih, MD and Riad Khatib, MD, St. John Hospital and Medical Center, Grosse Pointe Woods, MI

Disclosures:

S. Iyer, None

M. Sharma, None

M. Fakih, None

R. Khatib, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.