Topical oropharyngeal vancomycin to control methicillin resistant Staphylococcus aureus lower airway infection in ventilated patients

L. Silvestry et al. 2010. Minerva Anestesiol 76:193–202

Mark LopezYessenia Velazco

Micr 454L04/07/10

Objectives

To evaluate the effectiveness of two different policies for topical vancomycin administration on oropharyngeal carriage and lower airway infection due to MRSA.

To monitor the emergence of vancomycin-resistant enterococci (VRE) and vancomycin-intermediate Staphylococcus aureus (VISA).

Experimental Approach Subject population: July 2002 – June 2005

Patients over 18 years old Required mechanical ventilation for >72 hours.

Study intervention: Period one (07/2002 – 12/2003) Vancomycin to all

MRSA carriers Period two (01/2004 – 06/2005) Vancomycin to all patients

Antibiotic and non antibiotic policies of the unit: SDD (enteral and parental antimicrobials, hygiene, and surveillance culture of throat and rectum)

Microbiology: Columbia plus 5% sheep blood, mannitol salt agar, McConkey,

Chocolate Haemophilus, Columbia colistin-nalidixic acid plus 5% sheep blood, and yeast agar

Statistical analysis: Fisher’s exact test, Chi-square (X2), Student’s t-test

Significance was set at 0.05

Results

Figure 1. Oropharyngeal carriage indices of MRSA. CI: carriage index

Main Findings

The immediate administration of topical oropharyngeal vancomycin on ICU admission significantly reduced the levels of MRSA carriage and lower airway infection compared with patients whom topical oropharyngeal vancomycin was only given after MRSA carriage was detected.

Neither VRE nor VISA were isolated from surveillance and diagnostic samples during the study period.

Discussion The effectiveness of MRSA carriage prophylaxis over MRSA

carriage treatment may be explained by: 1. MRSA carriage treatment caused delay and promoted overgrowth, colonization, and subsequent infection of the lower airways 2. MRSA carriage prophylaxis protected patients against MRSA acquisition, and MRSA found during admission was cleared promptly by vancomycin administration. Treatment of populations without MRSA may lead to the

development of more resistant strains of MRSA No evidence of vancomycin-resistant strains found in

test subjects.

Critiques

1. Two different consecutive time periods of data acquisition

-Epidemiological changes in frequency of MRSA in general population

-Contamination2. No control group given placebo

-Cannot say with certainty that changes in MRSA frequency are due to vancomycin

treatment3. Variations in sample populations

-Differing underlying medical issues may increase or decrease vulnerability to MRSA

Take Home Message

1. Prophylactic treatment of populations with vancomycin is more effective at controlling MRSA outbreaks than treatment of individual MRSA infections.

2. Treatment with vancomycin may reduce or eliminate MRSA infections in the short term, but may cause problems in the future by encouraging more resistant forms of MRSA to develop.

Questions?