Antimicrobial resistance of Listeria monocytogenes and Salmonella Enteritidis isolated from vegetable farms and retail markets in Malaysia

Listeriosis and salmonellosis are the major foodborne illnesses worldwide. Over the last decade, increasing reports about the antibiotic resistance of Listeria monocytogenes and Salmonella from diverse sources have prompted public health concerns, especially in developing countries with over reliance or misuse of antibiotic drugs in the treatment of humans and animals. In this study, antibiotic susceptibility profiles of 58 L. monocytogenes and 12 Salmonella Enteritidis strains from vegetable farms and retail markets in Malaysia were tested by the standard disk diffusion method. Listeria monocytogenes isolates were found to exhibit 100% resistance to penicillin G. Also, high resistance patterns were observed for meropenem (70.7%) and rifampicin (41.4%). The multiple antibiotic resistance (MAR) index of L. monocytogenes isolates ranged from 0.11 to 0.56. Besides, the antibiogram results revealed that multidrug-resistant (MDR) S. Enteritidis were detected and all the S. Enteritidis isolates demonstrated resistance to at least four antibiotics. Ampicillin, amoxicillin, and trimethoprim failed to inhibit all the S. Enteritidis strains. Salmonella Enteritidis isolates also displayed high resistance to nalidixic acid (75.0%), trimethoprim-sulfamethoxazole (75.0%), and chloramphenicol (66.7%). Findings in this study indicated that vegetables could be potential sources of multidrug resistance of L. monocytogenes and S. Enteritidis, which can be a serious issue and a major concern for public health. Thus, there is a great need for surveillance programs in Malaysia to continuously monitor the antibiotic resistance profiles of important pathogens

Isolation of food-borne pathogen bacteriophages from retail food and environmental sewage

Bacteriophages are the viruses of bacteria and are widely distributed in the biosphere, exhibiting dramatic manifestations both in liquid cultures and on solid media. In this study, bacteriophages were isolated from different types of food (beef, chicken meats, cucumber, lettuce, clam, cockles and shrimp) and sewage samples using 6 reference pathogen strains (Salmonella Enteritidis, Salmonella Typhimurium, Campylobacter jejuni, Vibrio parahaemolyticus, Listeria monocytogenes and Escherichia coli). A total of 29 bacteriophage isolates were obtained and further examined for titer via agar overlay assay. The titers were determined within the range of 108 to 1011 PFU/mL. Our results showed that diverse of bacteriophages are naturally present in a variety of foods

Prevalence and antimicrobial susceptibility of Vibrio parahaemolyticus isolated from short mackerels (Rastrelliger brachysoma) in Malaysia

Numerous prevalence studies and outbreaks of Vibrio parahaemolyticus infection have been extensively reported in shellfish and crustaceans. Information on the quantitative detection of V. parahaemolyticus in finfish species is limited. In this study, short mackerels (Rastrelliger brachysoma) obtained from different retail marketplaces were monitored with the presence of total and pathogenic strains of V. parahaemolyticus. Out of 130 short mackerel samples, 116 (89.2%) were detected with the presence of total V. parahaemolyticus and microbial loads of total V. parahaemolyticus ranging from 105 MPN/g. Prevalence of total V. parahaemolyticus was found highest in wet markets (95.2%) followed by minimarkets (89.1%) and hypermarkets (83.3%). Pathogenic V. parahaemolyticus strains (tdh+ and/or trh+) were detected in 16.2% (21 of 130) of short mackerel samples. The density of tdh+ V. parahaemolyticus strains were examined ranging from 3.6 to >105 MPN/g and microbial loads of V. parahaemolyticus strains positive for both tdh and trh were found ranging from 300 to 740 MPN/g. On the other hand, antibiotic susceptibility profiles of V. parahaemolyticus strains isolated from short mackerels were determined through disc diffusion method in this study. Assessment of antimicrobial susceptibility profile of V. parahaemolyticus revealed majority of the isolates were highly susceptible to ampicillin sulbactam, meropenem, ceftazidime, and imipenem, but resistant to penicillin G and ampicillin. Two isolates (2.99%) exhibited the highest multiple antibiotic resistance (MAR) index value of 0.41 which shown resistance to 7 antibiotics. Results of the present study demonstrated that the occurrence of pathogenic V. parahaemolyticus strains in short mackerels and multidrug resistance of V. parahaemolyticus isolates could be a potential public health concerns to the consumer. Furthermore, prevalence data attained from the current study can be further used to develop a microbial risk assessment model to estimate health risks associated with the consumption of short mackerels contaminated with pathogenic V. parahaemolyticus

Evaluation of bacteriological quality of locally produced raw and pasteurised milk in Selangor, Malaysia

High demand for milk has been observed amongst the Malaysian public. Hence, research in milk is essential to assure food safety in milk consumption. This study evaluated the quality of locally-produced milk and present of bacterial hazards in cow and goat milk. A total of 120 milk samples including thirty raw cow milk, thirty pasteurized cow milk, thirty raw goat milk and thirty pasteurised goat milk were collected from dairy farms, delivery milkman, marts and markets in Selangor, Malaysia. The bacteriological quality of milk was evaluated for the presence of Escherichia coli, mesophilic, and coliform bacteria. An acceptable standard limit of < 1 x 105 CFU/mL for the total bacterial count was used to indicate good quality of milk. Overall, all type of milk exceeded 100,000 CFU/mL. The pasteurized raw goat milk showed the highest (7.16 log10 CFU/mL) in total plate count while the pasteurized cow milk recorded as the lowest (5.38 log10 CFU/mL) in total plate count. Approximately half of the milk samples were contaminated with coliform bacteria and a proportion has exceeded the acceptable limit of 50 CFU/mL. The presence of E. coli was detected in over 44% of the samples. Milk contaminated with the pathogenic E. coli can cause self-limited, watery to bloody diarrhea including severe diseases like haemolytic uremic syndrome (HUS). Hence, it is important to ensure the quality of milk for public health safety