# Bioaerosol assessment of indoor air in hospital wards for isolation of Nocardia species from a tertiary care hospital in Iranshahr, Iran

## TL;DR

This study found several Nocardia species in hospital air, highlighting a potential infection risk for immunocompromised patients.

## Contribution

This is one of the first studies to document Nocardia species in hospital indoor air, identifying multiple clinically relevant strains.

## Key findings

- The orthopedic ward had the highest particle concentration among hospital wards.
- Fourteen Nocardia isolates were identified, including species like N. cyriacigeorgica and N. asteroides.
- Nocardia species were detected in patient-care areas, suggesting a potential risk for immunocompromised individuals.

## Abstract

Bioaerosols can be a critical role in the transmission of hospital-acquired infections. Nocardia species are opportunistic pathogens that primarily affect immunocompromised patients, accounting for approximately 1–2% of all hospital-acquired bacterial infections in this population. To date, there are no comprehensive studies examining the presence of Nocardia in hospital indoor air. This study aimed to assess the species diversity of the Nocardia genus in different hospital indoor environments at Khatam Hospital, Iranshahr, Iran.

Particle concentration in various hospital wards was measured using the direct reading method. Bioaerosol sampling followed NIOSH methods 0800 and 0801, using Sauton's medium plates. Each Petri dish was incubated in an inverted position for three weeks at both 25 °C and 37 °C in parallel. Nocardia isolates were identified through phenotypic tests, including growth in lysozyme broth and substrate degradation assays (tyrosine, xanthine, and hypoxanthine), followed by molecular confirmation.

The orthopedic ward exhibited the highest particle concentration among all wards. Fourteen Nocardia isolates were recovered: four from the emergency department, four from infectious diseases, and three from surgery, two from hemodialysis, and one from orthopedics. The identified species included N. cyriacigeorgica, N. asteroides, N. otitidiscaviarum, N. wallacei, N. kroppenstedtii, N. farcinica, and N. nova.

This study represents one of the earliest documented investigations, detecting clinically relevant Nocardia species in hospital indoor air. Although the direct link between airborne Nocardia and hospital-acquired infections remains to be proven, the detection of pathogenic species in patient-care environments underscores a potential risk to vulnerable individuals.