Hospital-Acquired Pneumonia Guidelines May Lead to Overtreatment of MRSA

Recent hospital-acquired pneumonia guidelines for antibiogram threshold and characteristics did not improve the prediction of MRSA or resistant gram-negative rods infection.

The recent hospital-acquired pneumonia (HAP) guidelines from the Infectious Disease Society of America and American Thoracic Society for antibiogram threshold and characteristics did not improve the prediction of methicillin-resistant Staphylococcus aureus (MRSA) or resistant gram-negative rods (R-GNR) infection, and would lead to increased MRSA treatment, according to study results published in the Annals of the American Thoracic Society.

This retrospective analysis of patients with HAP at Veterans Affairs Medical Centers between October 2012 and September 2015 was designed to describe antibiotic use and microbiology patterns in this patient population, measure the antibiogram threshold and risk factors predictive of performance, and estimate how practice would have changed with the implementation of new HAP guidelines. The presence of MRSA and R-GNR in cultures, the administration of anti-MRSA and antipseudomonal antimicrobials, and the prevalence of MRSA and R-GNR at the facility level were extracted for each hospitalization. Additionally, researchers calculated the predictive performance of patient characteristics and prevalence thresholds for MRSA, the percentage of hospitalizations with resistant organisms, and broad spectrum antibiotics.

Among the total 1.8 million hospitalizations during the time period, 76,227 (4.23%) had a secondary pneumonia diagnosis and after excluding patients admitted for sepsis or respiratory distress, the remaining 3562 (0.20%) met the criteria for HAP. Of these cases, 5.17% (n=184) were positive for MRSA and 2.30% (n=82) were positive for R-GNR. The recommended prevalence threshold for MRSA was 100% sensitive (95% CI, 98.02-100.00%) and 0.03% specific (95% CI, 0.00-0.16%) for MRSA-positive culture, which would have led to an overtreatment of 94.81% of patients (95% CI, 94.02-95.50%). Intravenous antibiotic administration within the past 90 days (odds ratio [OR], 1.98; 95% CI, 1.03-3.81; P =.04) and vasopressor orders were associated with MRSA (OR, 3.89; 95% CI, 1.17-12.91; P =.03), and mechanical ventilation was associated with R-GNR (OR, 4.37; 95% CI, 1.52-12.57; P =.01).

Study limitations included using administrative data that relied on principal diagnostic codes meaning that inconsistencies in coding or altogether missed diagnoses may have led to the exclusion of HAP cases. In addition, the researchers were limited by provider culturing practices to determine detection rates as well as a lack of generalizability due to differing antimicrobial practices, and the inclusion of secondary diagnoses of pneumonia.

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“At present, the evidence behind using a single antibiogram-based threshold to guide broad spectrum antibiotic use is limited, making universal recommendations difficult,” the investigators wrote. “[C]linicians and stewardship programs will be wise to heed the guideline’s admonition to use local data to anticipate potential impact and inform local adaptation of guideline implementation.”

They recommended that future studies should compare the benefits and harms of initial broad spectrum antibiotic treatment in this patient population.


Bostwick AD, Jones BE, Paine R, Goetz MB, Samore M, Jones M. Potential impact of HAP guidelines on empiric antibiotics: an evaluation of 113 VA medical centers [published online August 6, 2019]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201902-162OC