Pagers and stethoscopes as vehicles of potential nosocomial pathogens in a tertiary care hospital in a developing country

Introduction

In most hospitals health care-associated infections (HAI) are important causes of mortality, morbidity and economic burden. A recent report from intensive care units (ICUs) in eight developing countries showed that the overall device-associated infection rates were as high as 22.5 cases per 1000 ICU-days, and that the rates of specific device-associated infections substantially exceeded the rates reported from industrialized countries. ¹ Estimates from a retrospective case control study from India showed a 54% attributable mortality due to HAI along with a longer hospital stay, ICU stay and increased costs. ² The factors that determine the risk of acquiring an infection in health-care settings in developing countries are complex.

These infections are often caused by bacteria which are capable of surviving in the hospital environment and on inanimate objects. ³ These pathogens can then be transmitted to susceptible patients through direct or indirect contact on the hands of health-care workers (HCWs), resulting in infection or colonization.

Pagers are commonly used in hospitals and they can become contaminated, as shown in the study by Singh et al., ⁴ with bacteria from HCWs' hands and clothing as well as from the environment. Pagers and stethoscopes are often passed from one user to another and stethoscopes are often used on multiple patients. Hence, they are potential vehicles for the transmission of nosocomial pathogens from patients to the HCW and to other patients via the HCW. ⁵ There is, however, a lack of data on the role of such items in the transmission of HAI.

Methods employed to reduce this risk include intermittent cleaning of equipment and the use of dedicated equipment. An early randomized crossover trial showed that noscocomial Clostridium difficile diarrhoea rates were significantly reduced when disposable thermometers were used instead of electronic thermometers. There are no recommended guidelines for cleaning and/or disinfecting multiple user pagers.

We report the findings from a study which assessed pager and stethoscope contamination in a tertiary care hospital in India.

Methods

This prospective study was conducted in the Christian Medical College, Vellore, Tamilnadu, India, over an one-year period, during 2002–2003. This is a tertiary level hospital with 2234 inpatient beds, situated in South India. In this study, 60 pagers and 40 stethoscopes were included. Of the 60 pagers, 16 were handled by individual doctors and the rest were shared by four to eight doctors. The pagers belonged to doctors working in different specialties and subspecialties of medicine, surgery, child health, obstetrics and gynaecology.

Without prior notice, the investigators visited various clinical units and collected pagers from doctors at various career levels. The pagers were removed from their cases and the four surfaces were pressed gently onto the surface of a sheep blood agar plate for about 10 s each; pager cases were treated similarly. The pagers and their cases were also swabbed using cotton swabs and inoculated in a thioglycollate broth. Stethoscopes were swabbed and cultured on blood agar and MacConkey's agar plates. The plates and the broth were followed up by routine bacteriological procedures for isolating and identifying aerobic bacteria. Susceptibility testing was done using disc diffusion tests following the National Committee for Clinical Laboratory Standards criteria. ⁶

The study was approved by the institutional review board and funding was provided by research grants from the institution.

Results

Fifteen (25%) of the 60 pagers and 11 (27.5%) of the 40 stethoscopes examined yielded potential pathogens (Table 1). Gram-positive cocci were isolated from 18 (18%) items, with Enterococcus spp (10; 10%) being the most frequently found isolate. Stethoscopes were more likely to carry Enterococci compared to pagers (20% versus 3.3%; P = 0.013; 95% confidence interval [CI] 1.3–52.9). Staphylococcus aureus was isolated from 8% of the items and pagers were more often contaminated, although this was not statistically significant (11.6% versus 2.5% of stethoscopes; P = 0.14; 95% CI 0.59–115.97). One isolate of Enterococcus faecium was a high level gentamicin resistant (HLGR) organism but none of the isolates of S. aureus were methicillin-resistant.

Of the seven isolates of Enterobacteriaceae, six were from pagers. One Klebsella pneumoniae isolate was resistant to cefotaxime, indicating extended spectrum beta-lactamase production. ⁶

As shown in Table 2, contamination with potential pathogens was found in two of the 16 personal pagers and 11 of the 44 shared pagers were similarly contaminated, although the difference was not statistically significant (P = 0.16).

Discussion

Our data show that at least a quarter of the pagers and stethoscopes used in the hospital carried potential nosocomial pathogens. Antimicrobial-resistant nosocomial pathogens, such as HLGR Enterococci and extended spectrum beta-lactamases (ESBL)-producing Klebsiellae were also isolated. Enterococci and ESBL-producing K. pneumoniae are implicated in nosocomial bacteremias and outbreaks of HAI. ⁷ The differences in carriage rates between shared pagers and personal pagers were not statistically significant. This could possibly be due to the small number studied.

We found significantly higher rates of enterococcal colonization among the stethoscopes. However, there was no significant difference in the rates of carriage of S. aureus between pagers and stethoscopes. Beer et al. found all pagers to be contaminated with bacteria such as S. aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella spp. and methicillin-resistant Staphylococcus aureus (MRSA). ⁸ Nunez et al. isolated coagulase negative Staphylococci together with 13 other potentially pathogenic microorganisms, including S. aureus, Acinetobacter sp. and Enterobacter agglomerans. ⁹

There is evidence to show that Gram-positive cocci such as Staphylococci and Gram-negative bacilli can survive on inanimate objects for as long as 7 months and 30 months, respectively. ¹⁰ The high rate of contamination with the bacteria capable of surviving long periods is a cause for concern. It is therefore necessary to develop a practical method of decontaminating pagers and stethoscopes between users. Cleaning with 60% spirit has been proven to reduce colony counts substantially and has been described as beneficial. ^8–10 Disinfection, coupled with strict adherence to hand hygiene during handling of pagers and stethoscopes, may reduce the transmission of nosocomial pathogens through this route and thereby avoid nosocomial infections.