470. Characteristics of Methicillin-Resistant Staphylococcus aureus (MRSA) Bacteremia (SAB) in Hemodialysis (HD): Trends Over 13 Years
Session: Poster Session: Hospital-acquired and Transplant Infections
Friday, October 30, 2009: 12:00 AM
Room: Poster Hall A
Background: MRSA is a leading cause of morbidity in HD. Whether its epidemiology is changing is unclear.
Methods: We reviewed adult HD inpatients with MRSA SAB (1996-2009), determined their clinical and microbiologic characteristics including SCCmec typing, and assessed the trends over time.
Results: Among 1122 patients with SAB, 253 (21.6%) were HD; MRSA accounted for 141 (55.7%) cases; adequate records were available in 123. The frequency of MRSA was stable between 2000 and 2006 (50.0-54.5%); it decreased in 2008-9 (47.2%; p=0.01 compared to 2006 cases). Patients' age, sex and comorbidities, duration of bacteremia (2.3±2.3-6.3±13.1 d) and persistence (≥7 d) frequency were similar throughout the study period. Intravenous catheters accounted for 49.2% of the cases. SCCmec typing (1996-2006 isolates) revealed that SCCmec II accounted for 69.2-77.8% of 1996-2003 cases and 51.2% of 2006 cases (p=0.001). For the same periods, SCCmec IV accounted for 8.8-23.1% and 19.5% (p=0.44). Rep-PCR of isolates with hVISA ± vancomycin MIC (V-MIC) ≥ 2 μg/ml (n=21) revealed a cluster of 13 with 97.5% similarity (rep-PCR-1); it was present throughout 1996-2006. V-MIC remained unchanged. No VISA was detected but hVISA was noted in 15/106 (14.2%) cases (table). Most isolates (88.5%) were susceptible to trimethoprim/sulfa (T/S) and resistant to clindamycin (74.5%) and erythromycin (87.3%). All 2008-09 isolates were susceptible to rifampin (R). Mortality rate fluctuated without significant differences.
Conclusion: MRSA frequency in HD associated SAB is trending down with apparent decrease in SCCmec II, probably reflecting increasing prevalence of other SCCmec types such as the community acquired. V-MIC did not change over the study period. Most isolates remain susceptible to T/S. Rep-PCR revealed possible strain-persistence over 11 years.
MRSA Bacteremia in Hemodialysis-Dependents: Trends Over 13 Years
Year of the Study (Number of MRSA isolates)1996-07
(13)
2000-03
(18)
2002-03
(34)
2005-06
(41)
2008-09
(17)
Total
(123)
MRSA frequency%53.8Not Available52.953.747.251.2
V-MIC (g/ml;Mean+SD)1.8 + 0.52.0 + 0.51.9 + 0.51.9 + 0.61.8 + 0.31.9 + 0.5
hVISA (%)05.629.49.8Not Done14.2
T/S susceptible (%)81.868.875.094.910088.5
SCCmec II (%)69.277.876.551.2Not Done56.9
Rep-PCR-1/tested isolates (%)2/2 (100)2/3 (66.7)6/10 (60)3/6 (50)Not Done13/21 (61.9)
Mortality (%)30.844.426.512.223.524.4
Persistence (≥7days) (%)15.341.25.928.935.323.5
Leonard Johnson, MD, Riad Khatib, MD, Karam Obeid, MD, Kathleen Riederer, BS, MT, St John Hospital and Medical Center, Grosse Pointe Woods, MI, Stephen Shemes, BS, St. John Hospital and Medical Center, Grosse Pointe Woods, MI, Anilrudh Venugopal, MD, Medicine, St. John Hospital and Medical Center, Grosse Pointe Woods, MI and  K. Obeid, None..
K. Riederer, None..
S. Shemes, None..
A. A. Venugopal, None. 
L. B. Johnson,
pfizer Role(s): Speaker's Bureau.
R. Khatib, None.