Mycobacteria in nail salon whirlpool footbaths, California

Emerging Infectious Diseases, April, 2005 by Duc J. Vugia, Yvonne Jang, Candi Zizek, Janet Ely, Kevin L. Winthrop, Edward Desmond

In 2000, an outbreak of Mycobacterium fortuitum furunculosis affected customers using whirlpool footbaths at a nail salon. We swabbed 30 footbaths in 18 nail salons from 5 California counties and found mycobacteria in 29 (97%); M. fortuitum was the most common. Mycobacteria may pose an infectious risk for pedicure customers.

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In October 2000, we investigated the first known outbreak of Mycobacterium fortuitum cutaneous infections acquired from whirlpool footbaths, also called footspas, at a nail salon in northern California (1). Over 100 pedicure customers had prolonged boils on the lower legs that left scars when healed (1,2). In the investigation, we swabbed the area behind the screen of the recirculation inlet in each of 10 footspas at the nail salon and recovered strains of M. fortuitum from all 10. Isolates from 3 footbaths and 14 patients were indistinguishable by pulsed-field gel electrophoresis and by multilocus enzyme electrophoresis (1).

Before this outbreak, M. fortuitum and other rapidly growing mycobacteria (RGM) caused localized cutaneous infections but usually in a healthcare-associated setting with surgical or clinical devices contaminated with water from the hospital or from the municipal water system (3). In the nail salon outbreak, we suspected that the mycobacteria entered the footspas through the municipal tap water and thrived in the large amount of organic debris accumulated behind the footspa recirculation screens. However, cultures of tap water at that nail salon later in the investigation yielded RGM in the M. chelonae-abscessus group but not M. fortuitum (1).

Since RGM are commonly found in municipal water systems (4-6), and since the nail care business is a $6 billion and growing industry in this country (7), we hypothesized that similar whirlpool footbath-associated RGM infections occurred sporadically but went unnoticed. Soon after we alerted the health communities to this outbreak, 3 cases of lower extremity RGM infections associated with 2 different nail salons were documented from southern California (8).

No study has been published on the prevalence of mycobacteria in whirlpool footbaths. To determine the prevalence of nontuberculous mycobacteria in this common nail salon equipment, we undertook a mycobacteriologic survey of footspas in nail salons in California from November to December 2000.

The Study

Five large counties from different parts of California (Alameda, Sacramento, Orange, Riverside, and San Diego) participated in the survey. Counties chosen served large populations and had multiple nail salons with whirlpool footbaths. In each county, a team including the regional investigator of the California Bureau of Barbering and Cosmetology and a local public health professional visited selected nail salons. They assessed footspa equipment, cleaning solutions, and cleaning techniques and frequencies. Swab samples were also collected.

In each participating county, a convenience sample of [greater than or equal to] 3 different nail salons equipped with whirlpool footbaths located in the town's main business section was randomly selected for the survey. Salon managers were questioned about cleaning and disinfection regimens of their footspas. Pedicure equipment time in service within the salon and make and model numbers of whirlpool pedicure equipment were noted. For each salon, 2 separate footspas were sampled, unless that salon only had 1 footspa, in which case only 1 swab was collected. Using a screwdriver, investigators removed the grate or filter screen covering the recirculation port in each footspa basin and inspected the area behind the screen for debris. A sterile, cotton-tipped culturette was used to swab this area and placed in standard transport medium.

At the California Microbial Disease Laboratory, each swab was removed from the transport medium, placed into a 50-mL tube containing 5 mL of sterile water, and the contents vortexed. The swab was then removed from the tube, and the remaining suspension was decontaminated with an equal volume of N-acetyl-L-cysteine-sodium hydroxide for 15 minutes, followed by neutralization with phosphate buffer and concentration by centrifugation (9). The sediment was spread onto Middlebrook 7H10 and Middlebrook 7H11/Mitchison 7H11 selective agar plates, Lowenstein-Jensen slants, Bactec 12B, and Bactec Mycobacteria Growth Indicator Tube 960 system (Becton-Dickinson, Sparks, MD, USA) liquid media.

The mycobacteria isolated were identified by [greater than or equal to] of the following methods: rapid DNA probes using nucleic acid hybridization (10), high performance liquid chromatography that produces mycolic acid patterns (11), and biochemical tests (9). M. simiae and M. lentiflavum were differentiated by urease activity and photochomogenicity; for both of these, M. simiae is positive and M. lentiflavum is negative (12). M. smegmatis group organisms were not differentiated to the species level. M. mageritense was identified by polymerase chain reaction restriction analysis at a Mayo Clinic laboratory and by DNA sequencing at the University of Texas Health Center in Tyler.