Infectious Diseases in Critical Care Medicine

Epidemiology of CA-MRSA
Adult ICUs.Outbreaks of CA-MRSA infections have been described in hospitals in Australia,
and CA-MRSA has spread to hospitals around the world (16,18,19,52–54). However, there have
been no reports of outbreaks in ICUs due to CA-MRSA.

Neonatal ICUs.There have been several published reports of transmission of CA-MRSA in
NICUs (21,57,58,80). In one report six patients had severe disease due to CA-MRSA and three
(50%) died (80). One study identified infections due to CA-MRSA, HA-MRSA and methicillin-
sensitiveS. aureus(MSSA) in neonates but was unable to identify risk factors for colonization
with CA-MRSA (57). There was no difference in mortality between the three groups. In an
investigation of the emergence of CA-MRSA PFGE type USA300 in an NICU the epidemiology
was unique in that it involved transmission between patients, HCWs, and family members
(58). Three HCWs acquired soft tissue infections from the colonized/infected infants and four
members of two of the HCW families developed soft tissue infections (58). Eight of nine
isolates typed by PFGE were USA300. Only one study has provided data on risk factors for
colonization by CA-MRSA in NICU patients (21). In this article it was noted that vaginal
delivery and maternal tobacco or marijuana use were significant predictors for CA-MRSA
colonization among infants whose mothers had received systemic antibacterial therapy
immediately before delivery. Although there are few published epidemiologic data on the
spread of CA-MRSA in NICUs, it is clear that CA-MRSA may enter NICUs and cause outbreaks
with resultant colonization and infection of neonates. It is likely that CA-MRSA will continue to
enter many areas of hospitals, and more definitive studies will be needed to better understand
how to prevent entry of CA-MRSA and to control it once present in health care facilities.

Table 2 Risk Factors for Acquisition of Nosocomial MRSA in Adults

Publications Type of ICU Risk Factors

Adjusted Odds

Ratio (95% CI) pValue

Marshall et al. (43) Medical-surgical Previous admission to the
ICU

3.3 (1.7–6.6).

Previous admission to trauma/

orthopedics ward

2.9 (1.2–7.2)

Previous admission to the

neurology/endocrinology/

rheumatology/renal ward

2.6 (1.0–6.9)

LOS more than three days

prior to admission to the

ICU

8.6 (4.4–16.9)

Being a trauma patient 3.9 (1.8–8.7)

LOS two to seven days in the

ICU

11.1 (1.4–86)

LOS more than seven days in

the ICU

109.8 (14.5–833)

Merrer et al. (60) Medical Weekly colonization pressure

40%

5.8 (1.7–20.1) <0.0001

Grundmann et al. (62) Interdisciplinary Clustered cases
Days of staff deficit 1.05 (1.020–1.084) 0.001
Sporadic cases
Urgent/emergency admission 3.50 (1.328–9.209) 0.011
APACHE II score at 24 hours 1.07 (1.002–1.147) 0.044
Bronchoscopy 3.68 (1.38–9.84) 0.009
Marshall et al. (79) Trauma Laparotomy 6.3 (1.4–28.9)
Motor vehicle accident 10.4 (1.2–93.7)
Ticarcillin–clavulanic acid 4.5 (1.3–15.0)
Glycopeptide 5.9 (1.7–21.0)

Abbreviations:MRSA, methicillin-resistantStaphylococcus aureus; ICU, intensive care unit; LOS, length of stay;
APACHE, acute physiology and chronic health evaluation.

MRSA/VRE Colonization and Infection in the Critical Care Unit 107