Recovery of organisms from the handrails of escalators in the public metro rail system in Washington, D.C.

Introduction

Microorganisms can spread in the community through fomites. The potential hazards of such dissemination has been shown to be present in hospitals (1) and day care centers (2), but have not been well established in public places, such as the railway system.

The Metro railway system in Washington, D.C., is used daily by thousands of individuals who commute to work. Fomites that are touched by most passengers present a potential health risk for spread of bacterial and other pathogens. Many of the passengers use the handrails of the escalators leading to and from the train stations.

In this study, we attempted to find out whether those handrails were contaminated by bacteria.

Materials and Methods

Bacterial cultures were obtained from the handrails of the escalators in 12 stations in the underground train on the "Red Line" of the Metro rail system in Washington, D.C., on two weekdays between 4:00 p.m. and 6:00 p.m. (rush hours) on March 6 and 8, 1993. Sterile cotton swabs were dipped in sterile saline and were thereafter placed on the right side of the moving handrails, leading to the stations, for three seconds. All sampling by swabs were done by the same individual who maintained constant pressure. The moving handrails were made from rubber-type materials.

Each swab was then placed in a sterile plastic tube that contained 2 mL of sterile saline; the tip of the swab was broken and the contents were shaken vigorously by vortex machine for three seconds. The contents of the tubes were platted quantitatively on blood and McConkey's agar and incubated at 5% [CO.sub.2] for 48 hours at 37[degrees]C.

Quality control studies illustrated the ability of the method used in this study to isolate Gram-positive and Gram-negative bacteria from environmental sources (i.e., tables).

The number of colonies was counted, and the organisms were identified using the methods outlined in the Manual of Clinical Microbiology published by American Society for Microbiology (3).

Results

Microorganisms were isolated from samples collected from eight of the 12 stations on March 6, 1993, and from four of the 12 stations on March 8, 1993 (Table 1).

The number of colonies per swab varied from 1 to 16. Only one type of organism was isolated from each sample. All of the organisms isolated were Gram-positive cocci: 5 alpha hemolytic streptococci, 5 coagulase negative staphylococcus sp. and 2 Staphylococcus aureus. No Gram-negative bacilli were isolated.

[TABULAR DATA 1 OMITTED]

Discussion

The above results indicate that although some of the handrails in the Metro rail system harbor microorganisms, their number is relatively small. The organisms recovered were Gram-positive cocci, and two of them (alpha hemolytic streptococci and coagulase negative Staphylococcus sp.) are of low virulence. These organisms do not present a high health risk to the passengers.

The recovery of such a small number of organisms and the lack of recovery of Enterobacteriaceae was surprising, as the handrails are touched by numerous individuals each day. It is quite possible that the dry surface of the handrails does not enable the microorganisms to attach to it. It is also possible that the constant movement and friction of the handrails against their border mechanically remove microorganisms. An alternative hypothesis is that organism attachment is prevented because of the electrostatic buildup in the handrails.

Monitoring the cleanliness of community structures that are shared by the public has important health implications. Such structures can serve as a source of spread of potential pathogenic organisms in the community. It was reassuring to find that the handrails of the escalators in Washington's Metro railway system did not contain such pathogens.

References

(1.) Cozanitis D.A., J. Grant, and P. Makela (1978), "Bacterial contamination of telephones in an intensive care unit," Anaesthetist 27:439-442. (2.) Weniger B.G., J. Ruttenber, R.A. Goodman, D.O. Juranek, S.P. Wahlquist, and J.D. Smith (1983), "Fecal coliform on environmental surfaces in two day care centers," Appl Environ Microbiol 47:733-738. (3.) Lennette E.H., H.A. Balows, W.J. Hausler Jr., and H.J. Shadomy (eds.) (1985), Manual of Clinical Microbiology (4th ed.). American Society for Microbiology, Washington, DC.