Isolation, identification and characterization of microbial contaminants in selected biosafety laboratories in Kenya
Moses, Dennis Nyachae
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Microbial contamination in laboratories and hospitals is becoming serious problem worldwide and characterization of such contaminants offer hope for treating some hospital and laboratory acquired infections (LAI). Microbial contaminants on benches, floors, media and in equipment can be influenced by temperature, humidity, nutrient media used in the laboratories as well as storage conditions of the media. Therefore there is need to determine the microbial sources, isolate and identify the contaminants when performing standard microbiological manipulations. The study was carried out at the International Livestock Research Institute (ILRI), Kenya Agriculture and Livestock Research Organization (KALRO) Biotechnology center, Nairobi and Kenyatta University Plant Transformation Laboratory (KUPTL). KUPTL and KALRO are ISOcertified institutions in Kenya. KALRO, KUPTL and ILRI are biosafety level II laboratories The objectives of this study were (i) to determine sources of microbial contaminants in selected biosafety laboratories in Kenya (ii) to identify the bacterial and fungal contaminants in selected biosafety laboratories based on morphological and biochemical characteristics and (iii) to determine the genetic identity of persistent bacteria in the biosafety laboratories sites after disinfection with sodium hypochlorite. Isolation of pure cultures was carried out based on morphological differences where colony form, elevation, pigmentation and size were used to distinguish bacteria and fungi contaminants. Specific microbes were further authenticated using differential and selective media. Gram staining was performed to determine cell wall characteristics. Isolated fungi were identified using microscopic observations of size, and shape. Molecular analysis was carried out using PCR followed by Restriction Fragment Length Polymorphism (RFLP) where the persistent bacteria isolates were positively identified compared to known standards. The results showed (i) the laboratory sites sampled were contaminated with various microbes (ii) macroscopic and microscopic observations of fungi confirmed presence of Cladosporium sp, Penicillium sp, Aspergillus sp and Alternaria sp on tables, door knobs, preparation rooms, gloves and in biosafety cabinets and (iii) the persistent bacteria identified were Shigella sp, Pseudomonas aeruginosa, Corynebacteria sp, Bacillus sp and Staphylococci aureus. The contaminants were similar to standard strains but there was a significant difference in contamination in all three selected laboratories (Analysis of Variance (ANOVA P=0.00). The size of PCR product was 996 bp and RFLP patterns of bacterium were the same as standard strains. It is concluded that despite disinfection with sodium hypochlorite, bacterial and fungal contaminants persist in laboratory surfaces and equipment, hence need to increase the concentration or change the disinfectant.