Microbiological Etiology and Detection of Drug-Resistant Bacteria in Pneumonia in Patients with Organophosphate Poisoning in the Intensive Care Unit.

Purpose: Organophosphate (OP) poisoning, a frequent method of suicide in the Asia-Pacific region and rural areas, inhibits cholinesterase (ChE), causing an acute cholinergic crisis. Pneumonia occurs in 20-50% of these cases, contributing to disease severity and mortality. However, data on the causative pathogens and the risk of drug-resistant bacteria in this patient population are limited. Thus, our study aimed to address these gaps. Patients and Methods: This retrospective cohort study (April 2011-March 2023) investigated patients admitted to the intensive care unit (ICU) or emergency medical center at Niigata University Medical & Dental Hospital with acute OP poisoning. Data on patient demographics, pneumonia diagnosis, sputum culture results, prior antibiotic use, and risk factors for drug-resistant bacteria were collected. We also analyzed the detection rates of methicillin-resistant Staphylococcus aureus and SPICE (Serratia, Pseudomonas, indole-positive Proteus, Citrobacter, and Enterobacter) organisms. Results: Among the 21 patients with OP poisoning, 13 (62%) developed pneumonia and received antibiotic treatment. They had a longer ICU stay, higher Sequential Organ Failure Assessment scores on admission, and lower serum ChE activity (<100 IU/L). Gram-negative bacilli (GNB) were observed in five sputum cultures from 12 patients with pneumonia, with Pseudomonas aeruginosa isolated from three cases. None of the patients had known risk factors for drug-resistant bacteria. Conclusion: Pneumonia in patients with OP poisoning was predominantly caused by GNB, particularly P. aeruginosa. Thus, despite the absence of known risk factors for drug-resistant bacteria, clinicians should consider the possibility of resistant pathogens when selecting empirical antibiotic therapy for pneumonia in these patients.