Background: New syndromic rapid diagnostic tests seem to be promising for antimicrobial stewardship purposes. We have tested one of them, the BIOFIRE® FILMARRAY® Pneumonia Panel (PNplus Panel) as Investigational Use Only (IUO), in patients diagnosed with hospital-acquired pneumonia (HAP), including ventilator-associated pneumonia (VAP) episodes, with the aim to describe its potential impact on the management of anti-methicillin resistant Staphylococcus aureus (MRSA) therapy.
Materials/methods: Single-center observational study of consecutive adult patients diagnosed with HAP, hospitalized from June 2018 to October 2018. We performed PNplus Panel on residual samples of endotracheal aspirate (ETA) or bronchoalveolar lavage (BAL) obtained for the etiological diagnosis of pneumonia. The gold standard was culture method. The cut-off of bacterial growth considered as positive was ≥10^4 and ≥10^3 colony forming unit (CFU)/ml for ETA and BAL, respectively. The performance of the test did not interfere in the decision making process, so that patients were managed according to the standard of care (SoC).
Results: 58 patients were diagnosed with late-onset (≥5 days after admission) HAP, 74% was on mechanical ventilation at diagnosis. Collected samples included 43 ETA and 15 BAL.PNplus Panel resulted positive for MRSA in 7 cases, but in only one of them standard culture showed the growth of MRSA. On the contrary, none of the 51 samples with a negative PNplus Panel result showed bacterial growth on standard culture (Table 1). According to the observed prevalence of MRSA (1.7%), PNplus Panel sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for MRSA detection were 100%, 89%, 14% and 100%, respectively. According to the data of our Microbiology laboratory showing a pre-test probability (overall prevalence of MRSA among isolates from lower respiratory tract samples) of 5%, positive and negative likelihood ratio were 9.5 and <0.1 respectively.
Conclusions: Our findings suggest that PNplus Panel could be useful in reducing exposure to anti-MRSA drugs in patients with late HAP/VAP. However, further studies assessing the impact of such test on therapeutic management and patient outcome are needed.
Table 1: BIOFIRE® FILMARRAY® Pneumonia Panel (PNplus Panel) Operating Characteristics for methicillin-resistant Staphylococcus aureus (MRSA)