To assess the stethoscope cleaning practices, microbial load and efficacy of cleaning stethoscopes with alcohol-based disinfectant in a tertiary care hospital

Abstract

Background:

The objectives of our study were to study the stethoscope cleaning practices of medical personnel and to assess the microbial load on stethoscopes and efficacy of cleaning stethoscopes with alcohol-based disinfectant.

Methodology:

A questionnaire-based cross-sectional study was conducted among medical personnel at a tertiary care hospital in India to assess their knowledge and cleaning practices regarding stethoscope disinfection. Samples from the stethoscopes were collected before and after cleaning with alcohol-based disinfectant.

Results:

Out of 62 participants, 53.22% individuals had never cleaned their stethoscope. All the initial swab samples showed bacterial growth. There was mixed growth in the samples taken from 35 stethoscope bells and 31 diaphragms. Bacteria included coagulase negative staphylococci, bacillus species, diptheroids, S. aureus, Acinetobacter and Klebsiella pneumoniae. After cleaning with an alcohol-based disinfectant, there was a significant decrease in the average number of bacterial colony-forming units.

Conclusions:

Regular cleaning practices should be followed to prevent growth and transmission of potentially pathogenic organisms.

Background

The World Health Organization (WHO) defines a healthcare-associated infection (HCAI) as an infection occurring in a patient in a hospital or other healthcare facility, in whom the infection was not present or incubating at the time of admission (WHO, 2002). A survey conducted by the WHO in 55 hospitals across 14 countries revealed an average of 8.7% hospitalised patients suffering from HCAIs. The risk of HCAI in developing countries is 2–20 times higher than in developed countries (WHO, 2010). The impact of HCAI implies prolonged hospital stay, long-term disability, increased resistance of microorganisms to antimicrobials, a massive additional financial burden for health systems, high costs for patients’ families and increased mortality.

HCAIs are caused by bacteria, fungi or viruses through various sources including person-to-person contact via the hands of healthcare providers and visitors, personal equipment, airborne transmission, environmental contamination and colonised hospital staff (Gastmeier et al., 2005). Stethoscopes are an integral part of the physical examination of patients. They are a potential vector for nosocomial infections (Jones et al., 1995) with an increased risk of transmitting antibiotic resistant microorganisms because following contact with the skin, pathogens can attach and establish themselves on the diaphragms/bells of stethoscopes and subsequently be transferred to other patients if the stethoscope is not disinfected regularly.

Objectives

1. To study the stethoscope cleaning practices of healthcare personnel in a tertiary care hospital in Central India;

2. To study the microbial load on the stethoscopes of healthcare personnel;

3. To study the efficacy of cleaning with alcohol-based disinfectant on microbial load on stethoscopes.

Methodology

Study design: Cross-sectional study

Study setting: Outpatient department (OPD)/inpatient department (IPD)/intensive care unit (ICU)/nursing stations/operating theatres (OTs) at a tertiary care hospital in Central India where stethoscopes were being used

Study participants: Faculty members, resident doctors, medical students and paramedical personnel who were working in clinical care settings at a tertiary care setting. The medical personnel who use stethoscopes regularly in their clinical practice and those who consented were recruited in the study. Since the study was conducted in a new institutional set-up where the staff strength was lower, universal sampling was carried out and all the doctors/staff nurses engaged in clinical care were approached.

Sample size: All the doctors (faculty members and residents), nurses and medical students engaged in active patient care who use their individual stethoscopes in the various areas of the hospital were eligible to participate in the study. The eligible candidates were approached by two final-year medical students and were explained about the study in detail. None of the approached staff denied consent and 100% response rate was achieved. The students distributed the questionnaire and collected it from the participants. These students also collected the swabs from the stethoscopes. A total of 62 participants were included.

Inclusion criteria

The stethoscopes used individually by the

1. Faculty members engaged in patient care;

2. Senior residents of clinical departments engaged in patient care;

3. Nurses working in medical and surgical service wards, OTs and ICUs;

4. Nurses at the blood pressure measurement stations;

5. Medical students who examine patients during their clinical postings.

Exclusion criteria

The stethoscopes shared by multiple personnel in the common area were excluded.

Ethics issues

Written informed consent was obtained from the participants at time of the survey and all the information was kept confidential. The Institute Human Ethical Committee reviewed and approved our study protocol.

Methods

In order to assess the knowledge and cleaning practices regarding the disinfection of stethoscopes, the healthcare personnel were administered a questionnaire at the same visit while collecting samples from their stethoscopes. The stethoscope diaphragm (D) and bell (B) were divided into two equal parts and the initial samples (labelled S₀D and S₀B, respectively) were collected using sterile swabs moistened with sterile saline from one half of the stethoscope to document the baseline microbial load on the diaphragm. The stethoscope was then cleaned by alcohol-based disinfectant (Sterillium), commonly used as hand disinfectant in the hospitals. After cleaning and allowing the stethoscope to dry for 30 s, two samples were further collected using sterile swabs (labelled S₁D and S₁B) from the other half of the stethoscope’s diaphragm and bell. This division of the stethoscope into two parts was done to obviate the effect of physical removal of microbes by the first swab, thereby affecting the assessment of reduction in microbial load after cleaning, if any. In order to eliminate confusion and maintain uniformity, one of the researchers collected the samples from the stethoscopes whereas another researcher cleaned the stethoscope and administered the questionnaire.

Both the swabs were labelled with the date and time of collection along with the clinical area of work of the participant. The participants were assigned a unique identification number. The collected samples were immediately transported to the microbiology laboratory and were cultured on Nutrient agar medium and incubated for 24 h at 37 °C . Identification of the isolates was done by Gram stain and standard biochemical tests (Catalase test, Coagulase test, Indole test, Methyl red test, Voges-Proskauer test, Citrate test, Oxidase test and Urease test).

Results

Out of 62 participants, 87% believed that the stethoscope is a potential source of carrying infections from one individual to other. Thirty-three individuals (53.22%) had never cleaned their stethoscopes, 15 (24.2%) cleaned their stethoscopes > 8 weeks previously, two (3.2%) cleaned their stethoscopes 5–8 weeks previously, six (9.6%) cleaned their stethoscopes 1–4 weeks previously and only six (9.6%) individuals had cleaned their stethoscopes < 1 week ago. None of the participants cleaned their stethoscopes after seeing each patient. Among the individuals who cleaned their stethoscopes, only one participant cleaned his/her stethoscope daily. Among the individuals who cleaned their stethoscopes, the majority (86.2%, 25/29 participants) used alcohol-based disinfectant (Sterillium), followed by a plain cloth (10.3%, 3/29 participants) and soap and water (3.5%, 1/29 participants).

All the initial swab samples taken from the 62 stethoscopes showed bacterial growth. The samples taken from 35 stethoscope bells and 31 stethoscope diaphragms showed mixed growth. On the stethoscope bells, 96 organisms were isolated which comprised of eight different genera. Out of the 96 organisms isolated from stethoscope bells, 80 were Gram-positive cocci (GPC) and 16 were Gram-negative bacilli (GNB). Among the 96 isolates, 25 were potentially pathogenic and the rest were skin commensals. On the stethoscope diaphragm, a total of 92 organisms were isolated comprising eight different genera. Out of the 96 organisms isolated from stethoscope diaphragm, 79 were GPC and 13 were GNB. Among the 92 isolates, 22 were potentially pathogenic and the rest of the isolates were skin commensals. Potentially pathogenic isolates were S. aureus, Acinetobacter spp. and K. pneumoniae.

Figure 1 shows the frequency of stethoscope bells and diaphragms of the healthcare personnel with bacterial isolates.

Figure 1.

Frequency of stethoscope bell and diaphragm with bacterial isolates.

After cleaning with an alcohol-based disinfectant, K. pneumoniae was isolated from one of the stethoscope bells used in an ICU, while on the diaphragm of the stethoscope used in an ICU, two strains of K. pneumoniae and one Coagulase-negative staphylococcus (CoNS) were isolated and two strains of CoNS were isolated from the stethoscopes of medical students.

Out of 62 stethoscopes, 25 had potentially pathogenic bacterial growth before cleaning stethoscopes with alcohol-based disinfectant. However, after cleaning the stethoscopes, only two had pathogenic growth of isolates. This finding is statistically significant with P < 0.01.

Table 1 shows the relationship between the stethoscope cleaning practices and the presence/absence of potentially pathogenic isolates. An odds ratio (OR) of 4.7 (1.58–15.01) indicates that there is significant correlation between the presence/absence of potentially pathogenic isolates and cleaning practices.

Table 1.

Relationship between the stethoscope cleaning practices and presence/absence of potentially pathogenic isolates.

Cleaning practice	Bacterial isolates		Total
	Yes	No
Absent (never cleaned)	20	13	33
Present (ever cleaned)	7	22	29
Total	27	35	62

P value < 0.05; odds ratio = 4.7 (1.58–15.01).

Table 2 depicts the relationship of stethoscope cleaning frequency with the presence of potentially pathogenic isolates. It was seen that the stethoscopes that were never cleaned had the maximum numbers of polymicrobial growth.

Table 2.

Relationship of stethoscope cleaning frequency with the presence of potentially pathogenic isolates.

Cleaning frequency	Growth of bacterial isolates		Mixed growth	Total
	Pure growth	No growth
Cleaned 1 week previously	0	0	6	6
Cleaned 1–4 weeks previously	0	0	6	6
Cleaned 5–8 weeks previously	1	0	1	2
Cleaned > 8 weeks previously	4	2	9	15
Never cleaned	4	16	13	33

Table 3 shows the bacterial load on the stethoscopes before and after cleaning with alcohol-based disinfectant. There was a marked reduction in the number of colony-forming units of all isolates after cleaning with alcohol-based disinfectant.

Table 3.

Average number of colony-forming units (CFUs) of isolates before and after cleaning the stethoscopes.

Bacterial isolates	Bell before cleaning (CFUs)	Bell after cleaning (CFUs)	Diaphragm before cleaning (CFUs)	Diaphragm after cleaning (CFUs)
Coagulase negative Staphylococcus (CoNS)	200–300	0	300–400	5
Bacillus species	100–150	0	150–200	0
Diphtheroids	100–150	0	50–100	0
S.aureus	50–100	0	100–150	0
Acinetobacter	100–150	0	200–300	0
Micrococci	400–500	0	> 500	0
Klebsiella pneumoniae	50–100	10–50	100–150	50–100

Discussion

The responses obtained from the questionnaire illustrate that the majority (n = 54) of healthcare personnel had good knowledge regarding the role of stethoscopes in the transmission of hospital-acquired infections. These results are similar to those obtained from previous studies (Gazibara et al., 2015; Jain et al., 2013). Despite the adequate knowledge, the practice of cleaning the stethoscopes was poor.

In our study, 33 (53.22%) individuals had never cleaned their stethoscope. It was observed that about 10% of the participants cleaned their stethoscope < 1 week previously which was not in concordance with previous studies where 50–80% cleaned their stethoscopes < 1 week previously (Gazibara et al., 2015; Jones et al., 1995; Uneke et al., 2010). None of the participants cleaned his/her stethoscope after seeing each patient, as observed in previous studies (Genné et al., 1996; Jain et al., 2013). A study done in London by Whittington et al. (2009) shows that 91% of healthcare workers clean their stethoscopes after seeing each patient. This may be explained by the fact that the average number of patients seen per day by a physician in the developed world is much less compared to their counterparts in our country, who are overwhelmed with patient numbers. The doctor–patient ratio in India is 1:1379 compared to 1:356 in the UK (Global Health Observatory, 2018).

We observed that alcohol-based disinfectant was the most common agent used for cleaning the stethoscopes. These results are similar to previous studies (Gazibara et al., 2015; Jain et al., 2013; Jones et al., 1995; Uneke et al., 2010). The Centers for Disease Control and Prevention (CDC) recommends cleaning of stethoscopes with 70% ethyl alcohol or isopropyl alcohol (CDC, 2008).

All 62 stethoscopes revealed some bacterial growth before cleaning. This is similar to previous studies (Marinella et al., 1997; Núñez et al., 2000) where all the stethoscopes had some growth before the application of cleaning agent. However, Rao et al. (2017) in their study found that only 51.6% of the stethoscopes had some growth. The most common organisms found in our study were coagulase-negative Staphylococcus (50%), bacillus species (14%) and diptheroids (14%). Coagulase-negative Staphylococcus and diphtheroids are common skin commensals and are as likely to have come from the user as much as a patient and are not pathogenic when transferred to intact skin. Similarly, bacillus is an environmental organism and does not pose a risk in this situation.

Among the potentially pathogenic organisms, the most common organisms isolated were S. aureus and Acinetobacter species. Some studies (Marinella et al., 1997; Núñez et al., 2000) also found that S. aureus is the most common pathogenic organism on the stethoscope. In one of the studies (O’Flaherty and Fenelon, 2015), P. aeruginosa and vancomycin-resistant enterococci were cultured from the stethoscope; these were absent in our study. K. pneumoniae was cultured in 8% of the stethoscopes and this is in accordance with the result obtained in many studies conducted previously (Hoşbul et al., 2012; Shiferaw et al., 2013). Further analysis shows that there was a significant association between cleaning practices and presence of pathogenic growth (P < 0.05, OR = 4.7). Those who had never cleaned their stethoscopes were more likely to harbour potentially pathogenic organisms, i.e. S. aureus, Acinetobacter, K. pneumoniae.

After cleaning the stethoscopes with alcohol-based disinfectant, there was a significant decrease in the growth of pathogenic organisms (P value < 0.01). However, even after cleaning with alcohol-based disinfectant, there was a persistence of Klebsiella growth in the stethoscopes obtained from an ICU. This is most likely due to resistance of the nosocomial Klebsiella isolates to disinfectants (Gebel et al., 2002). For such resistant pathogens, hydrogen peroxide-based disinfectants have been shown to have maximum efficacy (Solutions Designed for Healthcare, 2014).

The CDC also recommends cleaning the stethoscope after seeing each patient (CDC, 2008). This may not be feasible in developing countries given the large number of patients per doctor and also the scarcity of resources (alcohol-based disinfectant in this setting). In our study, there was no growth of potentially pathogenic microorganisms in individuals who cleaned their stethoscopes < 4 weeks previously.

However, our study has certain limitations. First, the sample size was small. Second, as our study focused only on aerobes, other microorganisms (anaerobes, viruses and fungus) have not been studied. Another limitation is that, samples were not obtained from the tubings of the stethoscope. Further studies are needed to draw guidelines for minimum standards for frequency of stethoscope cleaning in order to prevent HCAIs.

The strengths of our study were that we divided the stethoscope into two parts so that the effect of physical removal of microbes was obviated, and we estimated the microbial load before and after cleaning the stethoscopes so that a reduction in the load was demonstrated.

Conclusions

Stethoscope cleaning practices were far from satisfactory in the study population. Regular cleaning practices should be followed to prevent growth and transmission of pathogenic organisms and thereby prevent hospital-acquired infections. Alcohol-based disinfectant is an efficacious agent for cleaning the stethoscopes.