Moraxella species are primarily responsible for generating malodor in laundry

Abstract

Many people in Japan often detect an unpleasant odor generated from laundry that is hung to dry indoors or when using their already-dried laundry. Such an odor is often described as a "wet-and-dirty-dustcloth-like malodor" or an "acidic or sweaty odor." In this study, we isolated the major microorganisms associated with such a malodor, the major component of which has been identified as 4-methyl-3-hexenoic acid (4M3H). The isolates were identified as Moraxella osloensis by morphological observation and biochemical and phylogenetic tree analyses. M. osloensis has the potential to generate 4M3H in laundry. The bacterium is known to cause opportunistic infections but has never been known to generate a malodor in clothes. We found that M. osloensis exists at a high frequency in various living environments, particularly in laundry in Japan. The bacterium showed a high tolerance to desiccation and UV light irradiation, providing one of the possible reasons why they survive in laundry during and even after drying.

Fig 1

Survival levels of Moraxella osloensis ATCC 19976^T, M. osloensis NCIMB10693, M. osloensis KMC41, M. osloensis KMC43, M. osloensis KMC44, M. osloensis KMCB7a, Micrococcus luteus KMC2i, Pseudomonas aeruginosa KMCy1, Roseomonas mucosa KMC7546-04, Bacillus cereus KMC7546-05, Acinetobacter radioresistens KMC7546-06, Escherichia coli NBRC3972, and Staphylococcus aureus NBRC13276 under dry (A) and wet (B) environmental conditions and during desiccation (C). The bacterial cells in test clothes were incubated at 30°C for 35 days under dry conditions (A), which were controlled using saturated LiCl solution, and wet conditions (B), which were controlled using SDW. The 1-h air-dried bacterial cells on the filters were incubated with silica gel at 30°C for 24 h (C). The error bars indicate the standard deviations of three independent samples. a, below the detection limit.

Fig 2

Tolerance of M. osloensis ATCC 19976^T, M. osloensis NCIMB10693, M. osloensis KMC41, M. osloensis KMC43, M. osloensis KMC44, M. osloensis KMCB7a, E. coli NBRC3972, and S. aureus NBRC13276 to ABS (A) and SDS (B). Bacterial cells were suspended in ABS (A) and SDS (B) solution at the concentrations indicated and incubated for 10 min. The error bars indicate the standard deviations of three independent samples. a, below the detection limit.