# P-1117. In-hospital cluster of Mycobacterium lentiflavum colonization/infection at a Japanese tertiary care center: outbreak investigation

## TL;DR

A hospital in Tokyo identified a cluster of Mycobacterium lentiflavum infections linked to contaminated water aerators, leading to infection control measures.

## Contribution

Identified a hospital-based outbreak of M. lentiflavum and traced it to contaminated water aerators, providing insights into nosocomial transmission.

## Key findings

- 27 cases of M. lentiflavum colonization or infection were identified between February 2023 and May 2024.
- MLST analysis showed 100% genetic identity among isolates, suggesting a single source of contamination.
- Hospital water aerators were identified as the likely source after cleaning and chlorination stopped new cases.

## Abstract

Mycobacterium lentiflavum is a ubiquitous yet rare nontuberculous mycobacterium (NTM) found in drinking water and public water systems, posing a potential contamination risk. NTMs have been increasingly reported in healthcare settings, causing pulmonary diseases. In April 2024, we identified a cluster of hospitalized patients with sputum cultures positive for M. lentiflavum, suggesting nosocomial transmission. An outbreak investigation was undertaken to determine the source of infection or colonization, and infection control measures were implemented.Multi-locus Sequence Typing analysis for the classification of 6 isolates of Mycobacterium lentiflavum with a comparison to previously reported M. lentiflavumEpidemiology curve for the cluster of Mycobacterium lentiflavum infection and colonization at the study hospital

Multi-locus Sequence Typing analysis for the classification of 6 isolates of Mycobacterium lentiflavum with a comparison to previously reported M. lentiflavum

Epidemiology curve for the cluster of Mycobacterium lentiflavum infection and colonization at the study hospital

The cluster occurred at Tachikawa Sogo Hospital, a 287-bed acute care hospital in Tokyo, Japan. Following the identification of an M. lentiflavum cluster in April 2024, patients with NTM-positive cultures from February 2023 to May 2024 were retrospectively assessed to determine if a long-standing outbreak had occurred. Environmental sampling included 113 water samples (200 mL each) collected from four-bed rooms (n=34), private rooms (n=35), nursing stations, nurse break rooms at the six hospital wards, the nutritional department, and water reservoirs. Air-conditioner outlets were also examined. Multi-locus sequence typing (MLST) was performed on selected clinical isolates to determine clonality.

In April 2024, a hospital infection control nurse reported M. lentiflavum in four hospitalized patients. A retrospective investigation (February 2023–May 2024) subsequently identified 27 cases (Figure 1), with two meeting the NTM disease criteria outlined by the ATS/IDSA guidelines. MLST of six selected isolates showed no allelic variants and 100% identity. Compared with deposited data, 16S rDNA and hsp65 genes exhibited 100% identity with M. lentiflavum ATCC51985, while 16S-23S rRNA and rpoB genes matched M. lentiflavum KKC-1, previously isolated in Japan (Table 1). In May 2024, hospital faucets were thoroughly cleaned, and aerators were sterilized with sodium hypochlorite. Additional chlorination was performed in June 2024. As of September 2024, no new cases have been detected.

The likely source of the M. lentiflavum cluster was contaminated hospital tap water aerators. Given that some patients were clinically infected, aggressive measures are needed to control nosocomial outbreaks.

Yusuke Minato, Ph.D., Shionogi & Co., Ltd.: Grant/Research Support