Isolation and Characterization of Salmonella Species from Street Food and Clinical Samples

The aims of this study were to isolate and characterize Salmonella spp. from food sampled randomly from street vendors in Selangor, Malacca, Kuala Lumpur and Negeri Sembilan, and from clinical samples in a hospital in Klang, Selangor (collected from January to September 2004). A total of 24 Salmonella strains, belonging to seven different serotypes, were isolated from 129 different street-vended foods and drinks and 12 rectal swabs from hospital patients suspected with salmonellosis. The most frequently encountered serotype from street foods was Salmonella Biafra (66.7%) while the most frequently encountered serotype from clinical samples was Salmonella Typhi (66.7%). To the best of our knowledge, this is the first reported occurence of Salmonella Biafra in street foods in Malaysia. Other serotypes isolated from street foods were Salmonella Braenderup (25%) and Salmonella Weltevreden (8.3%), and from clinical samples were Salmonella Typhimurium (17%), Salmonella Paratyphi A (0.08%) and Salmonella Paratyphi B (0.08%). All isolates were tested for their resistance to the following 14 antibiotics: streptomycin, trimethoprim, sulphamethoxazole, tetracycline, cefuroxime, ciprofloxacin, ampicillin, chloramphenicol, gentamicin, rifampin, penicillin, nalidixic acid, norfloxacin and erythromycin. All strains (100%) were found resistant to the antibiotic rifampin. None of the strains were however resistant to cefuroxime. A dendrogram was generated for antibiotic resistances of the isolates, and six clusters were defined, with similarity levels ranging from 18.8% to 100%. Generally, street foods and clinical isolates tend to cluster apart. A dendrogram to cluster the antibiotics was also generated, and they could be grouped according to their classes based on mode of inhibition: cell wall synthesis, protein synthesis, or nucleic acid synthesis. The most related compounds were chloramphenicol and tetracycline (46.6% similarity), which is acceptable as they share the same mode of inhibition. Ampicillin was grouped in the same cluster at 13.5% similarity although of different inhibition mode, possibly due to cross-resistance. Out of the 24 isolates screened for the presence of plasmid, 15 harbored plasmids. The plasmid sizes ranged from 3.0 to 38.5 MDa. Randomly amplified polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC) analysis were performed for the molecular genetic typing of the strains. RAPD fingerprinting with the primers OPAR3 and OPAR8 produced a combination of 21 fingerprint patterns, while ERIC fingerprinting generated 19 patterns. Cluster analysis of S. Biafra showed that similar serotypes were found in different food samples collected at different locations. The likely source of this result was cross contamination during food handling. Cluster analysis of S. Typhi showed that all the serotypes were different, even though the location of sampling was the same. The results indicate multiple source of S. Typhi infection of the patients. From this study, RAPD was found to be more discriminative than ERIC

Consumers' consumption practices of ready-to-eat foods and food safety knowledge

The purpose of this study was to examine consumers’ consumption practices of ready-to-eat foods and their food safety knowledge. Convenience sampling was done by giving questionnaires to 258 ready-to-eat food consumers in Klang Valley, Kuala Lumpur, Malaysia. Based on the results, the biggest motivator for consumers to purchase RTE foods was convenience (47.3%). Most respondents (40.7%) consume RTE foods more than twice a week, and purchased RTE food at restaurants and cafes (36.8%). A majority (54.3%) of the respondents purchased RTE foods for their lunch, and spent RM11-RM20 per person (48.1%). Overall, the respondents had good food safety knowledge. A majority (81%) knew that diarrhea is the common symptom of foodborne disease, and knew about the correct temperature for refrigeration (42.2%). Most of the respondents knew that bacteria will grow quickly at body temperature (36.4%), and that room temperature encourages multiplication of bacteria (66.7%). Respondents knew that raw and cooked food should be separated to prevent transfer of bacteria (60.9%), and that placing raw meat in the plastic bag before putting it into the grocery basket decreases chance of foodborne illness (62%). However, not many respondents (10.1%) knew that the best way to clean a cutting board after using it for raw meat is by washing with bleach and water. This study could help RTE food marketers gain better insights into consumers’ attitude and behavior patterns towards RTE food. Knowing the baseline knowledge of consumers in food safety is essential for the development of effective educational health

Molecular characterization of clinical isolate of Vibrio cholera isolated from outbreaks cases in Malaysia

A total of 32 clinical strains of Vibrio cholerae, including members of the 01 and 0139 serogroup were collected from Klang, Selangor; Penang Island; Samarahan, Sarawak and Miri, Sarawak in Malaysia. In general, all the isolates except the 0139 serotype expressed low resistance to all the antibiotics tested with their Multiple Antibiotic Resistance (MAR) indices ranged from 0.10 to 0.48. The presence of ctx gene that encoded the cholera toxin was confirmed in all these clinical isolates by polymerase chain reaction. The results from the RAPD-PCR were analyzed using the RAPDistance software (Version 1.04). From the dendrogram generated, two main groups were observed which were subdivided into two clusters each. The Selangor's isolates and the 0139 Penang's isolates formed one group whereas the Samarahan, Sarawak isolates and the Miri, Sarawak isolates made up the other group, thus delineating their different sources of origin based on their geographical location

Time course study on the growth of Salmonella Enteritidis on raw vegetables used in sandwiches

A time course study on the growth of Salmonella Enteritidis on raw vegetables used a part of the ingredients for sandwiches at room temperature and at 4°C, with initial microbial load of log 3 and log 1 spiked onto the lettuce and cucumber slices. The growth of Salmonella Enteritidis were higher at room temperature and were dose dependent. The information obtained in this study may contribute towards food handling solutions in order to be able to control the food safety of fresh produce

Detection of Listeria monocytogenes in foods

Listeria monocytogenes is a gram positive, facultative intracellular pathogen with the capacity to cause food poisoning outbreaks as well as severe illness in vulnerable human population groups. It can cause a rare but serious disease called listeriosis with high fatality rates (20–30%) compared with other foodborne microbial pathogens. Although Listeria monocytogenes is infective to all human population groups, it is more likely to cause severe problems among pregnant women, immunocompromised individuals, the elderly and neonates. There are a variety of phenotyphic and genotyphic methods for the detection of Listeria monocytogenes in foods. Recent technological advances have increased the ability of scientists to detect Listeria monocytogenes. The purpose of this review is to discuss molecular characteristics of the Listeria monocytogenes pathogen, standard detection methods of this pathogen in foods based on culture methods, confirmation of species and subtyping based on phenotypic and genotyphic methods

Characterization of Enterobacter cloacae isolated from street foods

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

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

Occurrance and antibiotic resistance of Campylobacter jejuni and Campylobacter coli in retail broiler chicken

Broiler part samples (80 fresh and 80 chilled) were examined for the prevalence and numbers of C. jejuni and C. coli by employing most-probable-number (MPN) and polymerase chain reaction (PCR) techniques. The prevalence of the bacteria was high where C. jejuni was detected in 92.5% fresh and 53.8% chilled samples while C. coli in 80.0% fresh and 56.3% chilled. The number of these bacteria in the positive fresh and chilled samples was from 3 to more than 2400 MPN/g and from 3 to 290 MPN/g, respectively. Antibiotic resistance test (using Kirby-Bauer disc diffusion method) on 10 C. jejuni and 13 C. coli isolates toward ampicillin, tobramycin, enrofloxacin, ciprofloxacin, tetracycline, cephalothin, gentamicin and norfloxacin revealed high resistance toward all antibiotics (20.0% - 100.0%). All isolates were resistant to at least two antibiotics. This study highlights the potential of multidrug-resistant C. jejuni and C. coli transmission to humans through fresh and chilled broiler parts. Consecutive studies with bigger sample sizes and covering all over Malaysia are warranted in future

Characterisation of L. monocytogenes strains isolated from salad vegetables

Seventy-one strains of L. monocytogenes isolated from raw salad vegetables consumed in the minimally processed state in Malaysia were characterised by serotyping, random amplified polymorphic DNA-polymerase chain reaction analysis (RAPD-PCR) and antimicrobial susceptibility testing. Based on serotyping, only one strain belonged to serotype 4 while the rest were from serotype 1. RAPD-PCR typing was carried out using two primers, i.e., OPAR-8 and GEN 1-50-09. Based on RAPD-PCR fingerprinting, the strains could be grouped into six composite profile groups and a solitary isolate. The isolates were also evaluated against 16 antibiotics. Excluding nalidixic acid and oxacillin for which L. monocytogenes has natural resistance, the highest prevalence of resistance was against cephalexin. None of the isolates were resistant against imipenem and kanamycin. The multiple antibiotic resistance index (MARI) ranged from 0.06 to 0.63. It was found that most (82%) isolates were susceptible to antibiotics commonly used in veterinary and human listeriosis treatment

Characterization of Salmonella enterica isolated from street food and clinical samples in Malaysia

Salmonella enterica is one of the major causes of bacterial foodborne infection. The aims of this study were to determine the antibiotic resistance and the genetic diversity of Salmonella enterica isolated from street foods and clinical samples and to understand the correlation between the prevalence of serovars and genotypes with their source (street food and clinical samples) and geographic origin (Negeri Sembilan, Malacca and Selangor in Peninsular Malaysia). The enterobacterial repetitive intergenic consensus (ERIC) PCR analysis distinguished the Salmonella isolates into 19 ERIC types, with one untypable isolate. Dendrograms were specifically constructed for the S. Biafra and S. Typhi isolates. Identical or very similar ERIC types among the S. Biafra isolates from street food samples indicate transmission of the S. Biafra among the street foods, as well as possible cross-contamination of the street foods. In addition, the identical or very similar ERIC types among the S. Typhi isolates from human samples examined suggest possible similarity in their source of infection. All the twenty four isolates were resistant to rifampin and none were resistant to cefuroxime. Most isolates displayed multiple resistances. Dendrogram of antibiotic resistances produced six clusters, with similarity levels between 18.8% and 100%. Generally, street food and clinical isolates tend to cluster apart. Dendrogram to cluster the antibiotic groups showed that they could be grouped according to classes based on mode of inhibition. The findings suggest that street food contaminated with drug-resistant Salmonella enterica can be an important factor in the continuous emergence of antibiotic resistant Salmonella enterica