Biofilm forming ability and time course study of growth of Salmonella Typhi on fresh produce surfaces

This study aimed to determine the biofilm formation ability by Salmonella Typhi on cucumber, mango and guava surface, as well as to determine the relationship between time contact and biofilm formation. Crystal violet assay was performed to quantify the biofilm formation based on the value of optical density at 570 nm of the destaining crystal violet at the specific interval time. The result showed that the attachment of the bacterial cells on the fresh produce surface increased with the contact time. The readings of OD 570 at time 12 h for cucumber, mango and guava surfaces were 0.824, 0.683 and 0.598, respectively, indicating that the biofilm formation by Salmonella Typhi on different fresh produce surface varied with time. Since the result showed that Salmonella Typhi formed biofilm on fresh produce surfaces, hygienic practice from farm to fork including handling, processing, distribution and storage of the fresh produce should be of concern

Performance characteristics and estimation of measurement uncertainty of two plating procedures for Listeria monocytogenes enumeration in chicken meat

The objectives highlighted in the present study were to determine the estimates of measurement uncertainty associated with PALCAM and CHROMagar TM Listeria media, to compare the efficacy between both media in relation to their measurement uncertainties. In addition, this study was carried out to assess the performance characteristics of spread and spiral plating procedures based on the comparison of Listeria monocytogenes enumeration between PALCAM and CHROMagar TM Listeria media. This work involved pure culture experiment, artificially contaminated samples experiment and naturally contaminated samples experiment. In pure culture experiment, PALCAM performance was relatively inferior to CHROMagar TM Listeria medium for both plating procedures. From the artificially contaminated samples, the results revealed that the values of repeatability, reproducibility, and measurement uncertainty at 95% confidence interval were comparable between both media under evaluation. However, at the level of naturally contaminated samples, the performance of CHROMagar TM Listeria medium was refutable as the presence of high number of competitive microorganisms reduced the clarity of the medium. The current emphasis in ensuring microbiological safety which requires use of accredited laboratories has led to measurable need for measurement uncertainty to ensure reliability of test results for global acceptance

Prevalence of Listeria monocytogenes in frozen burger patties in Malaysia

A total of 112 burger patties (35 beef burger patties, 39 chicken burger patties and 38 fish burger patties) which are commercially available at retail level were investigated for the presence and number of Listeria monocytogenes. These samples were analyzed using MPN-PCR method and conventional culturing methods. L. monocytogenes was detected in 33.3% of chicken burger patties, 22.9%of beef patties, and 10.5% of fish patty samples. From all contaminated raw burger patties, the estimated count of L. monocytogenes was ranged from 3 to 75 MPN/g. The results suggest that burger act as a potential source of listeriosis if the contaminated burger patty is consumed without adequate cooking. The risk associated with consumption of these samples was found to be high particularly for processed food at retail level in Malaysia. Therefore, food manufacturers play an importantrole in monitoring the manufacturing process and conduct a periodical surveillance on microbiological quality assessment on the processing plants. Besides, there is a need to increase awareness ofconsumers and food handlers to practice proper cooking of the burger patties before the point of consumption, to reduce the risk of listeria infection

Antibiogram pattern among cultures of Listeria monocytogenes isolated from frozen burger patties in Malaysia

orty-one isolates of Listeria monocytogenes, which were obtained from raw burger patties, were tested for their susceptibility against eleven antibiotics by using standard disc diffusion method. In particular, 31.7% of the isolates were found to be not resistant to any of the antibiotic tested while the rest showed resistance to at least one antibiotic. The result showed that resistance to tetracycline was the most common (46.3%), followed by erythromycin (36.6%), amikacin (31.7%), and sulfamethoxazole-trimethoprim (17.1%). All the isolates of Listeria monocytogenes were sensitive towards imipenem and gentamicin. The findings of the present study revealed the presence of multidrug-resistant Listeria monocytogenes isolates in the processed meat products and hence suggested the emergence of antibiotic resistance in bacterial strains in the food chain

Biofilm formation by Salmonella Typhi and Salmonella Typhimurium on plastic cutting board and its transfer to dragon fruit

Adhesion of microorganism to food contact surface can become a source of microbial contamination.Enhanced resistances to environmental stresses are exhibited by biofilm producers. In this study, biofilm formation by Salmonella Typhi and Salmonella Typhimurium on plastic cutting board was accessed before the evaluation of the transfer of these two pathogens from plastic cutting board to dragon fruit. By using crystal violet assay, it was found that the adhesion on plastic cutting board by these two pathogens was the greatest at time 12 h. Results showed that Salmonella adhesion is strain-dependent and varied with time. The mean transfer rate from contaminated plastic cutting board to dragon fruit was examined to be 0.79 and 0.72 for Salmonella Typhi and Salmonella Typhimurium, respectively. This indicated that there is a risk of cross-contamination which should be concerned

Antibiotic resistance and biosafety of Vibrio cholerae and Vibrio parahaemolyticus from freshwater fish at retail level

A total of 49 isolates of V. parahaemolyticus and 8 isolates of V. cholerae isolated from freshwater fish of patin (Pangasius hypopthalmus) and red tilapia (Oreochromis sp.) were purchased from different retail level in Selangor, Malaysia. All of the isolates showed a multiple resistances towards all 15 antibiotics tested. Some of the isolates show a high resistance to different antibiotics including bacitracin, vancomycin, tetracycline, furazididone, cephalothin and erythromycin. However, both species was susceptible towards imipenem. Overall antibiotics resistance patterns of all isolates were resistant from 2 to 14 resistance patterns with multiple antibiotic resistance (MAR) index ranging from 0.13 to 0.93 respectively. As the results obtained in the dendrogram produced from both species had indicates that these antibiotics were intensively used whether in the aquaculture farm through feeds during culture or at the hatchery production of seed. Thus, this study will provides an essential information of the MAR index and also the clustering analysis in order to determine the biosafety of Vibrio spp. in freshwater aquaculture fish sold at different retail level in Malaysia

Salmonella: a foodborne pathogen

Salmonellosis continues to be a major public health problem worldwide. It also contributes to negative economic impacts due to the cost of surveillance investigation, treatment and prevention of illness. As such, research on Salmonella has gained great interest and concern from scientists. The purpose of this review is to discuss the classification and nomenclature, characteristic, clinical manifestation, epidemiology, transmission vehicles, antibiotic resistance and quorum sensing of Salmonella

Using RAPD-PCR as molecular assessment on the performance of CHROMAgar™ Listeria and PALCAM agar on isolation of Listeria spp. and L. monocytogenes from foods

In this study, Listeria spp. were isolated from naturally contaminated samples of beef burger, minced beef and sliced cheese using PALCAM and CHROMagar™. Samples were enriched with FDA-BAM method and plated on PALCAM and CHROMagar™ Listeria before confirmation using PCR on hlyA and LLO toxin genes specific to L. monocytogenes. Identification of isolates showed a total of 45 isolates of Listeria spp. and two L. monocytogenes. All the 47 isolates were then subjected to RAPD analysis using two oligomers (OPA14 and OPA15) and fingerprint clustering was able to cluster the L. monocytogenes from Listeria spp. based on isolation from agar types as well as L. monocytogenes from Listeria spp. Studies showed that OPA14 and OPA15 are useful for rapid discrimination of Listeria spp. and L. monocytogenes . The differences observed on the isolation of Listeria spp. from PALCAM and CHROMagar™ Listeria that may have an impact on epidemiological studies

Biosafety assessment of Listeria monocytogenes in vegetarian burger patties in Malaysia

The aim of this study was to examine vegetarian burger patties manufactured by two producers in Malaysia for the presence of Listeria monocytogenes. Brand A was produced by an established food manufacturer while Brand B was produced by a small-scaled food producer. A total of 108 samples of vegetarian burger patties produced by both manufacturers were sampled from retail market and were analyzed by combined MPN-PCR and MPN plating method. Of all the samples tested, ten (9.3%) were found to be contaminated with L. monocytogenes. The L. monocytogenes contamination level in vegetarian burger patties manufactured by producer A (20.9% of the samples were contaminated with 3-1100 MPN/g of L. monocytogenes) was significantly higher (P<0.05) than vegetarian burger patties manufactured by producer B (1.5% of the samples harbored 9.2 MPN/g of L. monocytogenes). Based on the detection and isolation rate obtained with MPN-PCR and MPN-plating, the recovery rate of the L. monocytogenes was estimated to be only 40.0% by MPN-plating approach

Random amplified polymorphism DNA profile of Listeria monocytogenes from raw and ready-to-eat foods in Malaysia

Listeria monocytogenes subtyping is important in food processing environment or in epidemiological studies in order to identify the contamination sources and spreading routes, and to investigate the food-borne outbreaks. This study employs the combination of serotyping and random amplified polymorphism DNA (RAPD) analysis methods to characterize the isolated L. monocytogenes strains in food samples from local markets. Listeria antisera kit was used in serotyping which grouped L. monocytogenes isolates based on the expression of somatic and flagellar antigens. The L. monocytogenes serovars were further classified into RAPD types based on polymorphic banding patterns generated by using 10 random RAPD primers. The 23 isolated strains were divided into four different serotypes consisting 4b (43.5%), 1/2b (34.8%), 4d (8.70%) and 4e (4.35%) with two untypable isolates (8.70%). 11 banding patterns were obtained from each selected primer, OPA10 and OPA14 with DNA fragments ranging from approximately 0.15 kb to 1.1 kb. The constructed dendograms showed similarity percentage of 4% to 100% for OPA10, 12% to 100% for OPA14 and 4% to 100% for combination of primers. At a comparative genetic similarity of more than 90%, 21 distinguish RAPD profiles were obtained. The discriminatory of RAPD analysis method was proven as it could distinguish the isolates from the same serovar. However, between the two primers used, OPA14 provide better discriminatory results than OPA10 although it failed to type one isolate. These findings suggest that the application of RAPD analysis could be a useful tool in characterization of L. monocytogenes isolated from foods as it may provide important information on cross-contamination potential sites. Thus, the microbial monitoring should be applied and continuously performed in order to control listeriosis infection. The data may be useful for the food producers or epidemiological and public health studies of Listeria spp