Carriage of methicillin-resistant Staphylococcus aureus (MRSA) among

nursing home residentsEisenring MC1, Schüttel C1, Metral M1, Obi D1, Constantin D2, Praz G2, Troillet N1

1Center of Infectious Diseases and Epidemiology, 2 Microbiology; Central Institute of the Valais Hospitals, Sion, Switzerland

BACKGROUND: During the last decade, the incidence of MRSA has increased in many acute care hospitals in Switzerland. Due to frequent transfers between hospitals and nursing home (NH), the latter have become a significant reservoir of MRSA.

OBJECTIVE: To investigate the prevalence of MRSA in nursing home (N=43) residents (N=2440) from the canton Valais during the period from September 2006 to March 2007.

METHODS:

RESULTS:

Screening and data collection of demographic and clinical features in every 2nd resident of small NH (<50 resident) and every 4th resident in larger NH.

Overnight broth enrichment. Culture on mannitol-salt agar and Mueller-Hinton with oxacillin. Identification of MRSA by Vitek 2 (BioMérieux), coagulase and PBP2 agglutination tests.

43/43 NH were included and 759/2440 (31.1%) of the nursing home resident (NHR) were screened. Only 24/783 NHR refused to participate (3%). Proportion of screening was well distributed in the 3 areas, respectively 30% in area 1, 29% in area 2 and 34 % in area 3.

MRSA was found in 13/759 NHR (1.7%) from 12/43 NH (27.9%). 4 MRSA cases were known previously but included by chance. The MRSA prevalence among NH ranged from 3.2 to 11.8% in area 1 and 2. No cases were identified in area 3 (High Valais). The carriage of MRSA was much higher in the center area as 10/15 of NH (66.7%) had cases, comparing to area 1 where MRSA was found in only 2/12 NH (16.7%). Among the 13 cases, 12/13 pool and 3/4 wounds were positives.

CONCLUSION: - Although found in 28% nursing homes, the global prevalence of MRSA among residents was less than 2%.

5.03.2

6.77.7

4.53.4 3.4

5.9 5.3

11.8

7.1

3.3

0.02.0

4.06.08.0

10.0

12.014.0

1/20(44)

1/31(42)

1/15(31)

1/13(54)

1/22(46)

1/29(118)

1/29(129)

1/17(70)

1/19(73)

2/17(65)

1/14(52)

1/30(120)

E1 E10 E12 E14 E17 E2 E26 E29 E3 E34 E4 E6

Central Valais 10/15 (66.7%) Low Valais2/12 (16.7%)

Nursing homes

Pre

vale

nce

(%

)

- Observation of a difference between the 3 areas, prevalence of MRSA carriage in area 2 higher.

- Only the presence of wounds was associated with MRSA carriage (4/13 vs. 36/746, P=0.003)

Residents characteristics Risk factors for MRSA carriage

Variable Total MRSA + MRSA- OR [95% CI] or P Value

Mean age, years (sd) 83.8 (8.3) 81.8 (8.5) 83.8 (8.3) P=0.37

Median LOS in NH, days (IQR) 841 (331-1655) 1211 (349-1616) 840 (311-1655) P=0.64

Male Gender, N (%) 202 (26.6) 5 (38.5) 197 (26.4) 1.74 [0.56-5.39]

Antibiotics ≤ 1 month, N (%) 65 (8.6) 0 (0) 65 (8.7) P=0.61

Hospitalization ≤ 2 years, N (%) 155 (20.5) 3 (23.1) 152 (20.4) 1.17 [0.32-4.31]

BESA nursing score, N (%)

0 2 (0.3) 0(0) 2 (0.3)

P=0.06

1 68 (9.0) 1 (7.7) 67 (9.0)

2 160 (21.2) 1 (7.7) 159 (21.4)

3 204 (27.0) 1 (7.7) 203 (27.4)

4 321 (42.5) 10 (76.9) 311 (41.9

Open wound, N (%) 40 (5.3) 4 (30.8) 36 (4.8) 8.77 [2.58-29.8]

Urinary catheter, N (%) 31 (4.1) 1 (7.7) 30 (4.0) 1.99 [0.25-15.8]

Area 2Central Valais

P=66.7% (10/15)

Area 1 Low Valais

P=16.7% (2/15)

Area 3High ValaisP=0% (0/16)

EMS with resident MRSAEMS without resident MRSA