Survivability of Bacteria on Blood Glucose Testing Strips
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Type of Work16 pages
Objective: Our research focus is to determine exactly how long clinically significant organisms, Escherichia coli 0157:H7, Pseudomonas aeruginosa, methicillin resistant Staphylococcus aureus (MRSA), and vancomycin resistant Enterococcus faecalis (VRE) survive on blood glucose testing strips. Design: Four separate tubes oftrypticase soy broth (TSB) were inoculated with each of the chosen test organisms and then incubated at 3 7°C overnight. The next day they were removed from incubation to slow down their growth. To determine the number of colony forming units (CFU) in each sample, dilutions of each organism were plated onto Mueller Hinton agar. The dilution with the most reliable colony count was used to calculate the dilution needed to create a 100,000 CFU/mL of phosphate buffered saline (pH 7.2) organism load. The blood glucose testing strips were inoculated with 1 0µL of inoculate at the non-electrical end of the strip and 1 0µL of inoculate was pipetted onto the blood collection site directly for a total of 20µL. Every day thereafter, a strip corresponding to each organism was pressed to a designated section on a CHROMagar™ plate for 30 seconds and then removed in order to replicate how long a blood glucose test strip would be handled in a clinical setting. The plate was then incubated at 3 7°C for 24 hours and observed for growth. Above the strip placement site, a reference sample consisting of a pure culture of each organism was swabbed onto the agar as a positive control. The phosphate buffered saline diluent served as a negative control. Setting: This research took place in the Medical Laboratory Science Program laboratories at Salisbury University, Maryland. Results: Each organism survived as follows: Escherichia coli 0157:H7, only one colony per day for days 42-45; Pseudomonas aeruginosa, colonies were too numerous to count for the first five days and then their number greatly declined to less than five colonies until day 11; methicillin resistant Staphylococcus aureus (MRSA), colonies were too numerous to count; and vancomycin resistant Enterococcus faecalis (VRE), colonies were also too numerous to count. Conclusion: Even though the surfaces of a blood glucose strip are non-nutritive and desiccated, clinically significant organisms survive for many days, making these strips a potentially important source of infection when they become contaminated.