Bacterial Biofilm Formation in Milking Equipments in Lilongwe, Malawi

Some microorganisms can adhere to food handling surfaces forming biofilms that pose a safety challenge. This study was done to evaluate bacterial biofilm formation in milking equipments in Lilongwe, Malawi.

Pooled milk (n=54) and water (n=60) samples were collected from households and milk bulking groups in Lilongwe, Malawi. Swabbing (n=46) and rinsing (n=16) were done on milk handling containers after cleaning. Biofilm determination on the containers was done by detecting biofilm indicator bacteria, including Bacillus spp., Salmonella spp., and Pseudomonas spp. The strength of biofilm was determined by the tube method. Data were analyzed by SAS software version 9.1.3.  

Prevalence rates of Gram-negative rods were significantly (p<0.05) higher than the Gram-positive rods and the Gram-positive cocci. Of the 176 cases, contamination rates were 36 (20.4%), 32 (18.2%), and 18 (10.2%) for Salmonella spp., Bacillus spp., and Pseudomonas spp., respectively. The biofilm indicator organisms were significantly (p<0.05) more prevalent in dairy farmer households compared with the milk bulking centers. Fourteen out of 86 (16.3%) microbial isolates formed strong/high biofilms, whereas 18 out of 86 (20.93%) of isolates did not form any biofilm. The rate of isolates forming strong/high biofilms in households (17.6%) was significantly (p<0.05) higher than that of milk bulking centers (11.1%).

Biofilm formation on milk handling container surfaces in Lilongwe, Malawi could serve as a source of microbial pathogens and spoilage organisms.