Investigation of diagnostic equipment as reservoirs for microbial growth and sources of microbial transfer, hygiene practices of students and efficacy of disinfectants
Authors:   , Logtenberg Johmari 
Published: October 2021

Background: Healthcare-associated infections (HCAIs) are a global concern as they affect millions of people worldwide. Poor hygiene practices and the use of microbial contaminated medical equipment by healthcare workers (HCWs) are common contributing factors to the development of HCAIs, which result in additional hospital costs, prolonged hospital stays, development of antibacterial resistance and increases in mortality and morbidity. Because Chiropractic students (CSs) at the Durban University of Technology Chiropractic Day Clinic (DUT CDC) make use of diagnostic equipment during their consultations with patients, this study aimed to determine if the stethoscopes and sphygmomanometers that were used in the DUT CDC served as reservoirs for bacterial growth, including antibiotic-resistant bacteria, and to correlate the findings with the hygiene practices of CSs and the efficacy of disinfectants. Method: This quantitative study comprised of two phases: a phase one pre-test post-test design and a phase two cross-sectional descriptive questionnaire design. Phase one required the collection of bacterial samples from the stethoscopes and sphygmomanometers of 29 CSs before and after performing the physical assessments on new patients (58 samples). These bacterial samples were incubated and analysed. The bacterial isolates were enumerated, identified and, where appropriate, tested for antibiotic-resistance. The modified AOAC use dilution method was used to test the efficacy of the selected disinfectants. Phase two required 29 CSs to complete the research questionnaire. The data were initially captured onto Excel spreadsheets and subsequently analysed using IBM SPSS version 24.0 (p-value <0.05 was considered statistically significant), with the application of Spearman’s rank correlation, an one-way ANOVA evaluation, Tukey post hoc and paired t-tests. Results: Although the majority of the CSs was knowledgeable and regarded disinfection as important, only 13.8% applied adequate disinfection practices. The most common reasons that were stated were inadequate education or training, forgetfulness, lack of time, and disinfectant unavailability. Bacterial growth was present on 96.6% and 100.0% of the pre-test and post-test stethoscope samples respectively, and on 94.8% and 100.0% of the pre- and post-test sphygmomanometer samples respectively. The total colony-forming units (CFUs) for both the post- test readings were higher compared to their respective pre-test samples. Paired t-tests indicated significantly (p< 0.01) higher mean values for the post-stethoscope group only, with a greater distribution of the total CFUs for stethoscope samples at the diaphragms’ edge. The bacteria that were isolated from both sets of pre- and post-test samples consisted predominantly of coagulase negative staphylococci (CoNS), Micrococcus spp. and Staphylococcus aureus, while the minority consisted of Bacillus spp., Corynebacterium spp., coliforms and Escherichia coli. Overall, the majority of the bacteria was considered potentially pathogenic, except for the post-test sphygmomanometer sample. The disinfectant efficacy testing revealed results that were in contrast with the literature, which caused the researcher to question the validity and reliability of the modified AOAC use dilution method in this study. Chloramphenicol was the most effective antibiotic with a bacterial susceptibility rate of 95.7%, (Ciprofloxacin (93.2%), Vancomycin (80.8%), Amoxicillin (AMO) (69.5%) and Erythromycin (57.7%)). The resistance of Micrococcus spp. isolates to the various antibiotics was of concern. The high resistance levels of CoNS and S. aureus to AMO suggests the presence of methicillin-resistant Staphylococcus aureus and methicillin-resistant CoNS isolates. The most susceptible specie in general was Micrococcus spp. at 60.9%, followed by S. aureus at 59.6%, E. coli at 53.8%, and CoNS at 48.7%, while the least susceptible was coliforms at 36.9%. No correlations (p> 0.05) were identified between the mean CFU isolates from the CSs’ equipment and their reported average disinfection rate. Conclusions and recommendations: Both stethoscopes and sphygmomanometers were contaminated with non-pathogenic and potential pathogenic bacteria (some were resistant to multiple antibiotic classes). Although knowledgeable about equipment disinfection procedures, only 13.8% of the CSs reported disinfecting their pieces of equipment after examining every patient. The provision of adequate equipment disinfection education, the placement of visual reminders and accessible disinfectants will assist in improving the practice of adequate equipment disinfection. Moreover, equipment disinfection before and after every patient consultation will minimise cross- contamination and thus the risk of the development of HCAIs.