Role of MRSA Swabs for
De-escalation of
Antibiotics in HCAP
Colleen Linsenmayer, Pharm.D.
PGY2 Internal Medicine Pharmacy Resident
Richard L. Roudebush VA Medical Center
This speaker has no actual or potential conflicts of interest to
disclose in relation to this presentation
Methicillin-resistant
Staphylococcus aureus (MRSA)
• Increasingly important pathogen in pulmonary infections
• Incidence of MRSA healthcare-associated pneumonia
(HCAP) is predicted to be 2-26.5%.
• Associated with significant morbidity and mortality
Niederman MS et al. Am J Respir Crit Care Med. 2005;171:388-416.
Dangerfield B et al. Antimicrobial Agents Chemother. 2014;58(2):859-62.
IDSA HAP Guidelines
HAP, VAP or HCAP suspected
Late onset (≥5 Days) or risk factors for
multi-drug resistant (MDR) pathogens
Broad spectrum antibiotic therapy for
MDR pathogens (Including MRSA)
Niederman MS et al. Am J Respir Crit Care Med. 2005;171:388-416.
IDSA HAP Guidelines
Consider de-escalation of antibiotic based on:
1) Results of lower respiratory tract cultures are available
2) Patient’s clinical response
How do you de-escalate in
absence of adequate
lower-respiratory cultures?
Niederman MS et al. Am J Respir Crit Care Med. 2005;171:388-416.
MRSA Colonization
• Identifying patients with
MRSA colonization may
guide initial antibiotic
treatment and isolation
measures
• MRSA swabbing is a
standard method for
screening in many facilities
for MRSA screening
Dangerfield B et al. Antimicrobial Agents Chemother. 2014;58(2):859-62.
MRSA Nasal Colonization
• MRSA nasal colonization can be reliably detected
using nasal swab PCR test
• Presence of MRSA nasal colonization has been
correlated with the development of subsequent
MRSA infections
Dangerfield B et al. Antimicrobial Agents Chemother. 2014;58(2):859-62.
Boyce JM et al. Antimicrobial Agents Chemother. 2013;57(3):1163-8.
Predictive Value of MRSA Nasal
Swabs for MRSA Pneumonia
Result
95% Confidence
Interval
Sensitivity (%)
88.0
67.6 – 96.9
Specificity (%)
90.1
86.6 – 92.8
Positive predictive value (%)
35.4
24.0 – 48.7
Negative predictive value (%)
99.2
97.4 – 99.8
Test Characteristic
Dangerfield B et al. Antimicrobial Agents Chemother. 2014;58(2):859-62
MRSA Nasal Swabs Negative Predictive Value (NPV)
Clinical Trial
Population
Culture Site
NPV
Non-ICU
Any Body Site
98%
Robicsek et al.
All admissions/
ICU transfers
Any Body Site
98%
Robissek et al
(Subgroup)
All admissions/
ICU transfers
Respiratory
98%
Sarikonda et al
ICU
Respiratory
84.4%
Harris et al.
Harris AD et al. Antimicrobial Agents Chemother. 2010;54(8):3143-8.
Robicsek A, et al. J Clin Microbiol. 2008 ;46(2):588-92.
Sarikonda KV, et al. Crit Care Med. 2010;38(10):1991-5.
Discontinuation of Empiric Vancomycin
Population: patient receiving empiric vancomycin for suspected or
proven HCAP with no adequate lower-respiratory cultures
If nasal + throat MRSA cultures were negative then de-escalation of
vancomycin was recommended
Results: no difference in mortality compared to previous study of
pneumonia patients who underwent de-escalation of antibiotics when
respiratory cultures were not obtained
Boyce JM et al. Antimicrobial Agents Chemother. 2013;57(3):1163-8.
Debunking Myths
“The patient’s nasal swab may be negative
because they received empiric vancomycin
therapy prior to the admission nasal swab”
Vancomycin has been shown to have little
effect on staphylococcus aureus nasal
colonization and seldom would eradicate
MRSA in the first several days of therapy
Boyce JM et al. Antimicrobial Agents Chemother. 2013;57(3):1163-8.
Clinical Pearl
Empiric HCAP Treatment
Patient meets the following criteria:
1) Blood cultures negative x 48 hours
2) Negative MRSA nasal swab
Consider discontinuation of
MRSA-directed antibiotic
Summary
• MRSA pneumonia is unlikely in patients who
are not colonized and have no evidence of
MRSA bacteremia
• Data suggests that MRSA PCR nasal swabs
have negative predictive value of up to 99% for
MRSA pneumonia
• A negative MRSA swab can be reasonably used
to guide antibiotic de-escalation for HCAP
Role of MRSA Swabs for
De-escalation of
Antibiotics in HCAP
Colleen Linsenmayer, Pharm.D.
PGY2 Internal Medicine Pharmacy Resident
Richard L. Roudebush VA Medical Center