Hospital-Associated Flies as Potential Reservoirs of Antimicrobial-Resistant Bacteria: An Entomological and Molecular Investigation in Iraq

Abstract

Background: In Iraq, it has not been characterized how the synanthropic flies in the hospital ward and the waste disposal and the surrounding community can transmit an ARB. This study used a combination of entomological, microbiological and molecular approaches to investigate the carriage of clinically important ARB by flies in hospitals in Baghdad.

Methods: Adult flies (n=432) were collected between March and October 2024 from ICUs, surgical wards, hospital kitchens and waste disposal locations of three tertiary hospitals, and from community control sites located at least 1 km away.  The cultures of external body surfaces and gut homogenates were maintained separately.  The susceptibility testing of isolates was done by CLSI M100 (34th edition) as per conventional and automated methods and these were screened for ESBL, carbapenemase, colistin and other resistant genes by PCR.

Results: Most of the flies captured were Musca domestica (70.6%).  In total, 384 isolates were recovered as a result of 91.2% of flies having at least one bacteria with a clinical background. More than fifty percent of Escherichia coli and Klebsiella pneumoniae were resistant to third-generation cephalosporins; Acinetobacter baumannii had carbapenem resistance of 67.7%. Two-thirds of resistance were observed in Escherichia coli with most of them constitutively AmpC strain with the methylation of the tetM gene only occurring in 1 strain.  The gene blaCTX-M-1 was identified in 52.4% of Enterobacterales and blaNDM-1 in 15.3% of K. 44.7% Staphylococcus aureus has a mecA.

Conclusions: Flies from hospitals in Baghdad carry a substantial burden of multi-drug resistant organisms which include WHO critical-priority pathogens. In addition, they constitute mobile reservoirs which are capable of linking clinical, environmental and community resistomes. In Iraq infection prevention and antimicrobial stewardship programmes must integrate fly surveillance and control.