Stewardship / Resistance Scan for Oct 01, 2019

MRSA nasal screening
MDR Acinetobacter baumannii pneumonia

VA study finds negative MRSA nasal swabs effective at ruling out infection

A study today in Clinical Infectious Diseases indicates that nasal screening of patients for methicillin-resistant Staphylococcus aureus (MRSA) colonization has a high negative predictive value (NPV) for ruling out MRSA infection and could be a powerful antibiotic stewardship tool.

In a retrospective study conducted across Veterans Affairs (VA) medical centers nationwide, researchers from the VA Western New York Healthcare System looked at data from all VA patients who were screened for MRSA colonization via the nares (nostrils) from 2007 (when the screening policy was initiated in VA medical centers) to 2018. They then evaluated the subsequent clinical cultures collected within 7 days of the nares swab for the presence of MRSA. The aim was to determine whether the absence or presence of MRSA nasal carriage predicts the presence of MRSA in clinical cultures.

Nasal screening on admission was done in 96.5% of patients. The cohort yielded 561,325 clinical cultures from a variety of anatomical sites, mainly urine (40%), wound (24.7%), respiratory (16.2%), and blood (12.5%). A positive screen for MRSA nares occurred in 22.9% of patients, and MRSA was identified in 8.3% of subsequent clinical cultures. The sensitivity and specificity of MRSA nasal screening for positive MRSA clinical culture were 67.4% and 81.2%, respectively, and the NPV of a negative MRSA nares swab for ruling out MRSA infection was 96.5%. The positive predictive value was only 24.6%.

The NPV was highest for ruling out MRSA in urinary cultures (99.2%), followed by intra-abdominal cultures (98.5%), blood cultures (96.5%), respiratory cultures (96.1%), and wound cultures (93.1%).

The authors of the study conclude, "This study suggests that a negative MRSA nares swab, taken within 7 days of culture, is useful to predict the absence of MRSA in a subsequent clinical culture. This information may be used as a stewardship tool to avoid the use of or de-escalate anti-MRSA therapy. It is not, however, appropriate to use MRSA nares as a tool to predict current infection."
Oct 1 Clin Infect Dis abstract


High global MDR prevalence, death noted in A baumannii pneumonia

A systematic review and meta-analysis of data from 29 countries highlights the global burden and severity of Acinetobacter baumannii causing nosocomial pneumonia, researchers from Australia and Malaysia reported yesterday in The Journal of Infection.

Among the 6,445 studies and reports screened from four databases, the researchers identified 126 relevant studies on A baumannii in patients with hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). The review aimed to provide a global picture of the  prevalence of multidrug-resistant A baumannii (MDRAB) in HAP and VAP, and the associated mortality rate. While A baumannii is known to be intrinsically highly resistant to many antibiotics, and numerous studies have reported on the prevalence of MDRAB in HAP and VAP, those studies have been geographically limited.

A meta-analysis of the 126 studies found that the overall prevalence of multidrug resistance among A baumannii causing HAP and VAP was 79.9%, with the highest reported prevalence in Central America (100%), Latin America and the Caribbean (100%), and Western Europe (100%). The regions with the lowest prevalence were Eastern Europe (70.6%), North America (69.8%), and Eastern Asia (64.6%). Among countries, the prevalence ranged from 56% (Argentina) to 100% (Mexico, Cuba, Uruguay, Nepal, Pakistan, Lebanon, Qatar, and Croatia).

The overall mortality estimate pooled from 27 studies was 42.6%, with the highest reported rates in Western Asia (56.2%), Southern Europe (55.7%), and Northern Africa (53.3%). The lowest reported mortality rates were in Western Europe (33.3%), Southeast Asia (31.9%), and North America (28.6%). The mortality rate among countries ranged from 28% (Iran) to 68% (Greece).

The authors of the study say the differences in MDRAB prevalence likely reflect the level of urbanization, sanitation, poverty, and variation in medical resources.

"It is clear that the burden of MDRAB in HAP and VAP and the mortality rate is high," they write. "Continuous monitoring of drug resistance and strict infection control are recommended for the prevention and control of MDRAB in HAP and VAP."
Sep 30 J Infect abstract

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