A study was conducted at Haramaya district in east Hararghe Zone of Oromia Regional State, Ethiopia to determine the prevalence of E. coli on Ethiopia Birr (ETB) paper currency notes handled by various food type handlers with E. coli. Simple random sampling technique was applied both on the food handlers and the notes types of currency at Haramaya University (HU) and the surrounding, and at Haramaya town.
The sample of currency was collected from meat seller at butcher, milk handler both at open market and dairy station, fruit and vegetables sellers’ at supermarket, and bread and the related seller’s at cafeteria. A random of Birr 1, Birr 5, Birr 10, Birr 50, and Birr 100 currency notes were collected from each notes. Age and sex of handlers were also considered. Using 95 % confidence interval (CI) with required 5 % precision (Thrusfield 2005) sample size was calculated. A total of 384 ETB notes were sampled. During each sampling occasion, 10 each ETB currency notes were directly collected from Automatic Teller Machines (ATM) and Commercial Bank of Ethiopia branch in the study area for control purpose.
All samples were collected aseptically by letting the selected individuals to drop a selected currency note into sterile polythene bags while substitution with equal currency. The polythene bags were promptly sealed, immediately labeled and transported to Microbiology Laboratory, College of Veterinary Medicine, Haramaya University (HU) for microbiological analysis.
Both surfaces of each sampled currency were thoroughly swabbed aseptically using sterile Buffered Peptone Water (BPW) (Merck, Germany) soaked cotton on pre-sterilized aluminum foil. The swab was dipped into 10 ml BPW and incubated for 24 h at 37 °C. After which a loop full was streaked on Eosin Methylene Blue (EMB) agar (Oxoid, UK) and incubated overnight at 37 °C. Characteristic metallic shine E. coli presumptive colony was transferred into Nutrient Agar for biochemical test using Indole production, Methylene red reduction, Voges Proskauer reaction and Citrate utilization (IMViC) tests according to Quinn et al. (2004). Escherichia coli ATCC® 25922™ (USA) was used as a control cultures. Antimicrobial susceptibility test was done on 43 randomly selected isolates by the Kirby-Bauer disk diffusion method (Bauer et al. 1966; CLSI 2007). The tested bacterium was taken from an overnight freshly grown culture and inoculated into 5 ml Brain Heart Infusion Broth (Merck, Germany). The inoculated broth was incubated for 4 h to approximately 106 CFU/ml at McFarland 0.5 % level of turbidity (CLSI 2007). With this culture, a bacterial lawn was prepared on Mueller–Hinton agar (Oxoid, UK). Antimicrobials against (Oxoid, UK) including chloramphenicol (C 30 µg), neomycin (N 30 µg), oxytetracycline (OT 30 µg), polymyxin-B (PB 300 IU) and trimethoprim-sulfamethoxazole (SXT 1.25/23.75/µg) were used for test. Result was interpreted using the diameter of zone of bacterial growth inhibition surrounding the disc (CLSI 2007).
The data obtained from laboratory examination was recorded in Microsoft excel 2007, analyzed using STATA 11 version and IBM SPSS 20. Percentage was calculated to evaluate for E. coli prevalence at all study variables. Significances of associated study factors/variables were compared using one way ANOVA. Significance of differences was considered at 95 % confidence interval (P < 0.05) for study variables such as sample sources, currency note denomination and food types for E. coli positive.