A total of 78 samples comprising different types of street foods, sold in different locations in Malaysia, were examined for the presence of Enterobacter cloacae. E. cloacae contamination was recorded in 9% of the samples examined. Tests for susceptibility to 12 different antibiotics showed that all were resistant to six or more antibiotics, but susceptible to chloramphenicol and gentamicin. Plasmids of four different sizes were detected from the three plasmid positive isolates. RAPD analysis using four primers yielded completely different banding patterns for all E. cloacae studied. In Malaysia, no published information on street foods in the epidemiological investigation of E.cloacae related disease is available. However, their occurrences have provided compelling evidence that the risk of disease transmission caused by E. cloacae through street foods is moderate.
Three restriction enzymes were used in Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) using the mitochondrial cytochrome b region to establish a differential diagnosis which detect and discriminate between three meat species: pork, cow and chicken. DNA was extracted from samples containing meat of a single animal such as raw pork (Sus scrofa domesticus), chicken (Gallus gallus) and cow (Bos taurus) as well as mixed samples of two species of animals in different ratios. The amplified 359 base pairs (bp) portion of the mitochondrial cyt b gene from pure or mixed samples in different ratios was cut using three different restriction enzymes resulting in species specific restriction fragment length polymorphism (RFLP). This technique proved to be extremely reliable in detecting the presence of low levels of target DNA obtained from a 0.25 mg component in a particular mixed meat sample. This revealed the cyt b region as highly conserved and consequently a good molecular marker for diagnostic studies. Thus, this technique can be applied to food authentication for the identification of different species of animals in food products.
Chicken is the most widely consumed meat in Malaysia as it is abundant, provides good nutrient and taste, and available at an affordable price. However, it is known to harbour various foodborne pathogens including faecal microorganism, Escherichia coli. There are various routes and factors that can cause contamination of E. coli in chicken. Furthermore, numerous reports have shown that over the past decades, the trends of antimicrobial resistance among foodborne pathogens have been increasing rapidly. Therefore, the present work aimed to assess the prevalence of E. coli contamination by examining various contributing factors and its antibiotic resistance in raw chicken meat sold in Klang Valley, Malaysia. Results showed that 74% of the samples were contaminated with E. coli with wet markets showing higher prevalence (17%) of E. coli than in hypermarkets. Univariate analysis within the same risk factor showed that packaging process, storage temperature, and antibiotics had significant effects on the prevalence of E. coli (∼ 6.097 log CFU/g). The E. coli loads were significantly influenced by market type and storage temperature as validated by Mann-Whitney tests. All E. coli isolates displayed multiple antibiotic resistance (MAR) index ranging from 0.33-1.00, and 35 E. coli isolates showed the highest MAR index (1.00), being resistant to 12 antibiotics. Furthermore, 90% of E. coli isolates contained extended-spectrum beta-lactamase (ESBL) genotypes that can subvert potent antibiotic, beta-lactam. The findings from the present work would help reduce the risk of foodborne illnesses by identifying the risk factors associated with E. coli prevalence in chicken and provide the basis to revise guidelines on antibiotic use in livestock to reduce antimicrobial resistance.
The present work investigated the profile and biodiversity of lactic acid bacteria (LAB) isolated from selected manufactured and homemade fermented foods in Malaysia. A total of 55 LAB were isolated from 20 samples, and identified based on the sequencing of 16S rRNA gene. The LAB isolates were identified as Lacticaseibacillus rhamnosus (34.5%), Lactiplantibacillus plantarum (20%), Limosilactobacillus fermentum (20%), Lacticaseibacillus paracasei (12.7%), Lacticaseibacillus casei (3.6%), Lactobacillus sp. (1.8%), Enterococcus faecalis (3.6%), Enterococcus faecium (1.8%), and Enterococcus durans (1.8%). Majority (94%) of the LAB isolates exhibited broad-spectrum antimicrobial activity against selected foodborne pathogens, and four isolates (L. fermentum SC1001, L. paracasei K2003, and L. rhamnosus KF1002 and MK2003) could produce bacteriocin-like inhibitory substance (BLIS). Lacticaseibacillus paracasei M1001 (homemade mozzarella) exhibited high-temperature tolerance and acid resistance, was homofermentative, and generated good antimicrobial activity, which strongly implied its potential for industrial applications. The present work results would potentially widen our knowledge of LAB diversity in Malaysian fermented foods and provide a potential for their applications in the food industry or other purposes.
Lactic acid bacteria (LAB) are known to exhibit various beneficial roles in fermentation, serving as probiotics, and producing a plethora of valuable compounds including compounds with antimicrobial activity including bacteriocin-like inhibitory substance (BLIS) that can be used as biopreservative to improve food safety and quality. However, the yield of BLIS is often limited, which poses a challenge to be commercially competitive with the current preservation practice. Therefore, the present work aimed to establish an optimised two-plasmid CRISPR/Cas9 system to redirect the carbon flux away from lactate towards compounds with antimicrobial activity by disrupting lactate dehydrogenase gene (ldh) on various strains of LAB. The lactic acid-deficient (ldhΔ) strains caused a metabolic shift resulting in increased inhibitory activity against selected foodborne pathogens up to 78% than the wild-type (WT) strain. The most significant effect was depicted by Enterococcus faecalis-ldh∆ which displayed prominent bactericidal effects against all foodborne pathogens as compared to the WT that showed no antimicrobial activity. The present work provided a framework model for economically important LAB and other beneficial bacteria to synthesise and increase the yield of valuable food and industrial compounds. The present work reported for the first time that the metabolism of selected LAB can be manipulated by modifying ldh to attain metabolites with higher antimicrobial activity.