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CAP patients often receive unnecessary MRSA antibiotics
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Despite a low prevalence of MRSA and methicillin-susceptible Staphylococcus aureus, nearly 30% of patients hospitalized with community-acquired pneumonia received treatment regimens containing either vancomycin or linezolid, according to a recent multicenter study.
“During the past decade, several reports described the emergence of community-acquired pneumonia (CAP) caused by [S. aureus], and specifically [MRSA], as a cause of severe pneumonia leading to critical illness and death,” Wesley H. Self, MD, associate professor at Vanderbilt University School of Medicine, and colleagues wrote. “Although the prevalence of MRSA among acute cases of CAP has not been fully elucidated, recent studies suggest MRSA is an uncommon cause of CAP in the United States.”
Although the Infectious Diseases Society of America and the American Thoracic Society currently do not recommend routine empirical anti-MRSA antibiotics for CAP, recently published data suggest clinicians often use vancomycin or linezolid due to concerns of potential MRSA pneumonia, the researchers said.
MRSA CAP patients’ clinical characteristics similar to non-S. aureus cases
To identify the incidence of unnecessary treatment, the researchers parsed adult patient data from the CDC’s Etiology of Pneumonia in the Community multicenter study. Collected between Jan. 1, 2010 and June 30, 2012, the researchers examined these data — which included treatment courses, testing results from patient specimens and clinical diagnoses — to gauge the receipt of MRSA antibiotics in relation to the pathogen’s prevalence. The researchers also reviewed the clinical characteristics of patients with S. aureus-related CAP to identify potential predictors of the condition and guide future decision-making.
Self and colleagues included 2,259 CAP patients in their analysis. Of these, 0.7% were diagnosed with MRSA, 1% with methicillin-susceptible S. aureus (MSSA) and 5.1% with S. pneumoniae. Empirical use of MRSA antibiotics exceeded incidence of the infection, the researchers wrote, with 29.8% of all patients given vancomycin or linezolid within their first 3 days of admission. Nearly all patients with MRSA CAP received these antibiotics, compared with just less than half of those with pneumococcal CAP.
The researchers more frequently observed chronic hemodialysis and diabetes among patients with MRSA CAP than pneumococcal and all-cause non-S. aureus CAP, but all other clinical features at admission were similar. Those with S. aureus CAP more frequently experienced higher severity scores and death than pneumococcal and non-S. aureus patients.
Although these prescription and incidence rates represent an area of care in need of improvement, the researchers said the several similarities between MRSA CAP and other forms of the illness complicate the development of an accurate clinical prediction model.
“Low prevalence of MRSA combined with a lack of highly distinctive clinical features make accurate targeting of empirical anti-MRSA antibiotics very difficult,” they wrote. “Development of diagnostic tests capable of rapidly and accurately identifying S. aureus could greatly improve the current approach to CAP management and reduce overutilization of anti-MRSA antibiotics.”
Molecular testing improves CAP diagnoses
One such diagnostic was recently described by Naomi J. Gadsby, PhD, from the department of laboratory medicine at the Royal Infirmary of Edinburgh, and colleagues, who wrote that their CAP-focused multiplex molecular assay could improve patient diagnoses and reduce the use of broad-spectrum antibiotics.
They evaluated the device — which is capable of measuring bacterial loads from a single lower respiratory tract (LRT) specimen — against routine culturing using single sputum (96%) or endotracheal aspirate (4%) specimen collected from 323 adults (median age, 67 years) who presented with suspected CAP at one of two tertiary care hospitals in Edinburgh, United Kingdom, from September 2012 to February 2014. The comprehensive molecular testing method identified a bacterial pathogen in 86.7% of patients with CAP vs. 39.3% of patients with routine culture alone, the researchers wrote. In addition, nearly 85% of patients with available information received antimicrobials during the 72 hours before a LRT specimen was collected.
After reviewing their collected efficacy, treatment and antimicrobial resistance data, Gadsby and colleagues estimated that physicians using their molecular testing platform could de-escalate treatment among 77.2% of patients.
“Our study illustrates the feasibility of providing the physician with significantly more information on which to base treatment decisions than is currently available and suggest that comprehensive PCR testing including bacterial load quantification should be one of the inputs to future prospective studies in this area,” they wrote. – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures.
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