Literature Update - October, 2006
Compiled by Dr Emma McBryde, VICNISS ID Physician
Prevention of MRSA has been a big topic in the infection control literature in the last two months:
Mupiricin Clears Staphylococcus aureus Colonisation but does not Prevent Infection
There have been many studies on the role of mupiricin in preventing S. aureus infection,
with mixed conclusions as to the efficacy and concern regarding the emergence of resistance. Konvalinka et al in
JHospInfect 2006; 64:162-8 revisited this topic looking at 263 patients with nasal S. aureus carriage who were
undergoing cardiac surgery (note: the study included all staph not just MRSA). The randomised double blinded study
found that the mupiricin group were more likely to clear S. aureus, but there was no
difference in surgical site infection rates. This study was not sufficiently powered to detect a small difference
in infection rates.
Isolation and Cohorting of Colonised Patients are Associated with Reduced MRSA Prevalence
To date there has been little evidence of efficacy of isolation or cohorting of MRSA colonised patients.
A randomised trial suggested that there was no effect (Cepeda et al, Lancet 2005; 365(9456):295-304). Two studies
have appeared recently that give support to the efficacy of isolation or cohorting. Curran et al
(in J Hosp Infect 2006;63:374-9) conducted a planned interrupted time series intervention conducting
weekly surveillance cultures and using a cohort ward for MRSA colonised patients on a vascular surgery
ward. The study found that the number of colonised patients was significantly reduced during and after
the cohort period unlike control wards that did not have the intervention.
A study published in Clin Infec Dis 2006;43:971-8 examined the impact of surveillance cultures and
patient isolation on MRSA bacteraemia. The study found a significant decrease in MRSA bacteraemia
following surveillance and isolation of patients, but not following other infection control measures
introduced prior to isolation. These measures included: conducting maximally sterile CVC placement;
introducing hand gels and hand hygiene education. This study had some flaws in that it was retrospective
without control groups, thus potentially influenced by confounders such as changes in case mix. This study
is important because it is one of few that have examined changes in infection rather than just colonisation.
Risk Factors for Sternal Surgical Site Infection
A risk factor study of 991 patients undergoing cardiothoracic surgery (Infect Control Hosp Epidemiol
2006;27:958-63) found diabetes, female sex, duration of surgery greater than 5 hours and use of older operating
theatres to be significantly associated with sternal surgical site infections. The study was in a specialised
cardiothoracic surgical hospital. The old hospital theatres was constructed in 1968 and had plenum flow which
is a positive pressure flow system leading to flow from clean to less clean areas with 27 air exchanges per hour.
The new hospital wards were built at the beginning of the study period and used laminar flow.