Phenotyping using semi-automated BIOLOG and conventional PCR for identification of Bacillus isolated from biofilm of sink drainage pipes

The presence of Bacillus in natural biofilms which develop in sink drainage pipes is not widely studied. Therefore, the main aim of this study was to isolate and identify Bacillus spp. using the BIOLOG GEN III system as a phenotypic fingerprint and polymerase chain reaction (PCR). A total of 61 biofilms samples were collected from sink drainage pipes in a kitchen and bathroom of different households in Helwan area and both laboratory and hospital collected from National Research Centre (NRC). Bacillus was isolated from the biofilms using HiCrome Bacillus Agar followed by isolates identification by both BIOLOG to the species level and PCR using genus specific primers to the genera level. Bacillus was detected in all tested biofilm samples (61 samples). The highest counts were observed in hospital sink drainage pipes (105 CFU/10 cm2) while; the lowest counts were observed in both bathroom and laboratory sink drainage pipes (102 CFU/10 cm−2). In total, 61% Bacillus isolates were identified by BIOLOG while, 67% isolates were confirmed by PCR. The diversity of Bacillus among species level using BIOLOG were 34% B. cereus, 23% B. subtilis ss subtilis, 17% B. thuringiensis, 16% B. licheniformis and 13% B. amyloliquefaciens. It can be concluded that; PCR is more sensitive than BIOLOG for identification of Bacillus. However, BIOLOG can identify Bacillus at species level and test 94 carbon and chemical sources on a microplate in one shot. Thus, the combination between phenotyping by BIOLOG and molecular approaches such as PCR for identification of bacterial isolates is recommended.