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Background: Colistin has become a last-resort antibiotic for the management of multidrug-resistant gram-negative bacteria. The disk diffusion test is cheap and easy to perform but may be unreliable for colistin susceptibility testing due to poor diffusion of the large colistin molecule. An improved agar diffusion test would increase the reliability of colistin susceptibility testing. This study aimed to modify Muller-Hinton agar (MHA) to improve colistin diffusion in agar., Methods: MHA was modified by reducing the agar concentration from 100% to 30% and supplementing with protamine. We tested 60 gram-negative clinical isolates of Pseudomonas aeruginosa (N=27) and Acinetobacter calcoaceticus-baumannii complex (N=33). Disk diffusion test results were interpreted based on minimum inhibitory concentrations determined by broth microdilution., Results: The modified MHA yielded the best performance metrics, including 94.7% sensitivity, 100% specificity, and an area under the curve of 0.995 (95% confidence interval, 0.982-1.000), P <0.001, at a cut-off point of 13 mm., Conclusions: A reduction of the agar concentration from 100% to 30% and the addition of protamine improved colistin diffusion in agar and allowed routine colistin susceptibility testing in a clinical microbiology laboratory, but should be handled with caution., Competing Interests: None., (© The Korean Society for Laboratory Medicine.)

Background: Electronic devices have become one of the most essential accessories being used in daily lives including schools. Those devices increase the communication and using them makes learning much easier. Microbial contamination of electronic devices and inanimate surface of electronic equipment at INES-Ruhengeri can have a significant role for transmission of pathogenic bacteria. Aim: The aim of this study was to isolate and identify bacteria from electronic devices used by students and staffs at INES-Ruhengeri University. Methodology: This cross-sectional study was done on 40 electronic devices such as computers, microscopes, global positioning system (GPS) and total stations A random sampling method was applied from sterile swab soaked in peptone water solution by the technique of bearing on the surface of the entire devices and then placed in a transport medium. Collected samples were then taken in INES-Ruhengeri Microbiology laboratory for further experiments. Results: All 40 electronic devices were contaminated with bacteria. The most predominant bacteria isolated from electronic devices was S.aureus (25.9%) followed by Bacillus spp(24.1%), K.pneumonia(12.9%), S.epidermis(12.9%), Micrococcus spp(7.4%), P.aeruginosa(5.5%), E.coli(3.3%), Salmonella spp(3.3%) and Shigella spp(3.3%). Antimicrobial susceptibility pattern of selected antibiotics was performed. Norfloxin was the most sensitive antibiotic on all isolated bacteria. Chloramphenicol antibiotic shown no activity over any of the isolated bacteria, to imply that all bacteria had resistance on it. Conclusion: This study shown that there is bacterial contamination to all devices and antibiotic susceptibility test shown that some antibiotics were sensitive and resistant to the isolated bacteria. [ABSTRACT FROM AUTHOR]