Anti-anaerobic therapy over-prescribed for patients with aspiration community-acquired pneumonia

1. Nearly all patients hospitalized for community-acquired pneumonia have at least one risk factor for aspiration, though few present with clinical aspiration pneumonia.

2. Bacterial isolates from patients hospitalized with aspiration community-acquired pneumonia do not support the use of anti-anaerobic coverage, despite widespread use among such patients.

Evidence Rating Level: 2 (Good)

Study Rundown: Community-acquired pneumonia (CAP) is one of the most common outpatient infections, and it contributes significantly to the global burden of disease. Aspiration community-acquired pneumonia (ACAP) accounts for approximately 10-20% of all CAP cases and is associated with a dramatically higher risk of in-hospital and 30-day mortality compared with non-ACAP patients. In this secondary analysis of the observational, point-prevalence GLIMP (Global Initiative for Methicillin-resistant Staphylococcus aureus Pneumonia) study, researchers sought to delineate aspiration risk factors, patterns of microbiology, and empiric anti-anaerobic use among patients hospitalized for CAP. The analysis revealed that nearly all hospitalized patients with CAP had one risk factor for aspiration, and most had at least two; among them, male sex, dementia, mental illness, being underweight, enteral tube feedings, being bedridden, and admission from a nursing home were independently associated with ACAP. It was found that the prevalence of anaerobes isolated from sputum cultures was similar for patients with ACAP compared with those with non-ACAP, regardless of their risk for aspiration or culture status, though patients with ACAP had a higher proportion of total gram-negative bacteria. Interestingly however, a larger proportion of ACAP patients received anti-anaerobic coverage when compared to non-ACAP patients, regardless of their risk for aspiration.

As ACAP is a clinical diagnosis and lacks a uniform definition, individual cases may have been overlooked or patients may have been misdiagnosed. Similarly, acquiring sputum samples is technically challenging and may have affected the data. Overall, this secondary analysis revealed that most hospitalized patients with CAP have risk for aspiration, though only a small percentage present with ACAP. Additionally, without a difference in prevalence of anaerobic infection between ACAP and non-ACAP patients, study findings suggest that empiric anti-anaerobic bacterial coverage may be largely inappropriate, and cautions for its over-prescription. These findings are in keeping with recent ATS/IDSA guidelines that caution against the use of anti-anaerobic coverage in patients presenting with ACAP unless an abscess or empyema is suspected.

Click here to read the study in Chest

Relevant reading: Aspiration Pneumonia

In-depth [secondary analysis]: Drawing from the GLIMP study, 2,606 hospitalized patients (mean [IQR] age = 69 [54-80] years, 58% male) with CAP were included for analysis, 193 of whom had ACAP (mean [IQR] age = 76 [61-85] years, 67.4% male). Among all hospitalized patients with CAP, more than 90% had least one risk factor for aspiration, with male sex and age ≥65 being the most common. However, the prevalence of anaerobes across all patients with ACAP, non-ACAP with aspiration risk factors, and non-ACAP without aspiration risk factors was not significantly different (0.5% vs. 0.3% vs. 0.0%, p = 0.27), with a similar pattern seen when comparing only culture-positive patients (1.6% vs. 1.0% vs. 0.0%, p = 0.33). Patients with ACAP when compared with non-ACAP patients with and without aspiration risk factors did, however, differ with regards to an increased prevalence of gram-negative bacteria (p = 0.04), mostly in the form of Pseudomonas aeruginosa, and a decreased prevalence of Streptococcus pneumoniae (p = 0.032), a gram-positive organism that is implicated in many cases of CAP. With regards to antibiotic therapy, more than half of hospitalized patients with CAP received anti-anaerobic coverage, the largest proportion being those with ACAP (72.5%), compared to 53.4% of patients with non-ACAP with aspiration risk factors and 49.8% of those without received anti-anaerobic coverage. Without a significant difference in prevalence of anaerobic infection, this suggests that anti-anerobic antibiotic therapy may be over-prescribed in the former population.

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