Isolation and Antimicrobial Resistance of <i>Staphylococcus aureus</i> Associated with Respiratory Devices

Abstract

Respiratory care devices used in oxygen therapy are essential in hospital settings, but may serve as reservoirs for pathogenic microorganisms if not properly maintained. <i>Staphylococcus aureus</i> is a major cause of healthcare-associated respiratory infections, on the other hand the emergence of antimicrobial resistance including multidrug resistance (MDR), presents significant treatment challenges. This study aimed at isolating <i>S. aureus</i> from respiratory care devices in regional referral hospitals and determining their antimicrobial susceptibility profile. A cross-sectional study was conducted from January to March 2024 in 29 regional referral hospitals across mainland Tanzania. A total of 231 samples were collected from humidifier water, device connectors, and reusable oxygen masks in Emergency departments, Intensive care units and Medical wards. Samples were enriched in Tryptic Soy Broth and cultured on Mannitol Salt Agar. Identification of <i>S. aureus</i> was performed using Gram staining, catalase tests and confirmation by PCR targeting the <i>nuc</i><i> gene</i>. Antimicrobial susceptibility testing was conducted using the Kirby–Bauer disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) guidelines, 33<sup>rd</sup> edition. MDR was defined as resistance to at least three classes of antibiotic. Among the total isolates collected (N=231), 6.5% (n=15) were confirmed as <i>S. aureus</i>. There was no statistically significant difference in isolate distribution across hospital units or sample types (p > 0.05). High susceptibility was observed for ciprofloxacin and meropenem, while azithromycin showed the highest resistance among antibiotics tested while intermediate resistance was noted for erythromycin and trimethoprim. MDR was detected at 46.7% (n=7) of isolates, with variability observed across hospitals. Although the prevalence of <i>S. aureus</i> on respiratory care devices was low, the high proportion of MDR isolates highlights the need for continuous antimicrobial resistance surveillance, strict infection control practices, and strengthened antimicrobial stewardship programs in Tanzanian hospitals.