Evaluation of Diagnostic PCR for the Detection of Listeria monocytogenes in Food Products

Conventional methods for the detection of Listeria in foodstuffs are generally cumbersome and time consuming. The use of primary enrichment in ½ strength Fraser broth and the use of Oxford and RAPID’L. mono agars were assessed in comparison with polymerase chain reaction (PCR) for their ability to accurately detect and confirm the presence of L. monocytogenes in food products. Of the 27 food samples tested, 74 % were presumptively positive for Listeria on Oxford agar, while 44 % were presumptively positive for L. monocytogenes on RAPID’L. mono. Only 37 % of samples were confirmed to be positive for L. monocytogenes by PCR amplification of the hly gene (732 bp). PCR was able to eliminate the false positives and detect all L. monocytogenes in the food products, unlike the conventional methods used in the industry. In addition to the fact that the incidence of Listeria species was higher than L. monocytogenes on selective media, there was also the presence of Listeria-like organisms. These organisms had the typical appearance of Listeria on selective media, but were non-Listeria species, as confirmed by the PCR and API Listeria (bio- Mérieux). PCR proves to be a sensitive and rapid technique to be included in the procedure of detection of L. monocytogenes in food products

Evaluation of Diagnostic PCR for the Detection of Listeria monocytogenes in Food Products

Conventional methods for the detection of Listeria in foodstuffs are generally cumbersome and time consuming. The use of primary enrichment in ½ strength Fraser broth and the use of Oxford and RAPID’L. mono agars were assessed in comparison with polymerase chain reaction (PCR) for their ability to accurately detect and confirm the presence of L. monocytogenes in food products. Of the 27 food samples tested, 74 % were presumptively positive for Listeria on Oxford agar, while 44 % were presumptively positive for L. monocytogenes on RAPID’L. mono. Only 37 % of samples were confirmed to be positive for L. monocytogenes by PCR amplification of the hly gene (732 bp). PCR was able to eliminate the false positives and detect all L. monocytogenes in the food products, unlike the conventional methods used in the industry. In addition to the fact that the incidence of Listeria species was higher than L. monocytogenes on selective media, there was also the presence of Listeria-like organisms. These organisms had the typical appearance of Listeria on selective media, but were non-Listeria species, as confirmed by the PCR and API Listeria (bio- Mérieux). PCR proves to be a sensitive and rapid technique to be included in the procedure of detection of L. monocytogenes in food products

Antimicrobial-resistant Klebsiella species isolated from free-range chicken samples in an informal settlement

Sub-therapeutic doses of antimicrobial agents are administered routinely to poultry to aid growth and to prevent disease, with prolonged exposure often resulting in bacterial resistance. Crossover of antibiotic resistant bacteria from poultry to humans poses a risk to human health. In this study, 17 chicken samples collected from a vendor operating in an informal settlement in the Cape Town Metropolitan area, South Africa were screened for antimicrobial-resistant Gram-negative bacilli using the Kirby Bauer disk diffusion assay. In total, six antibiotics were screened: ampicillin, ciprofloxacin, gentamicin, nalidixic acid, tetracycline and trimethoprim. Surprisingly, Klebsiella ozaenae was identified in 96 and K. rhinoscleromatis in 6 (n = 102) of the samples tested. Interestingly, ~40% of the isolated Klebsiella spp. showed multiple resistance to at least three of the six antibiotics tested. Klebsiella ozaenae and K. rhinoscleromatis cause clinical chronic rhinitis and are almost exclusively associated with people living in areas of poor hygiene.Web of Scienc

The use of ultraviolet radiation as a non-thermal treatment for the inactivation of alicyclobacillus acidoterrestris spores in water, wash water from a fruit processing plant and grape juice concentrate

Alicyclobacillus acidoterrestris is a non-pathogenic, spore-forming bacterium that can survive the commercial pasteurisation processes commonly used during fruit juice production. Surviving bacterial endospores germinate, grow and cause spoilage of high acid food products. Fruit juices can be treated using ultraviolet light (UV-C) with a wavelength of 254 nm, which has a germicidal effect against micro-organisms. In this study, A. acidoterrestris was inoculated into water, used wash water from a fruit processing plant and grape juice concentrate. Ultraviolet dosage levels (J L−1) of 0, 61, 122, 183, 244, 305 and 367 J L−1 were applied using a novel UV-C turbulent flow system. The UV treatment method was shown to reliably achieve in excess of a 4 log10 reduction (99.99%) per 0.5 kJ L-1 of UV-C dosage in all the liquids inoculated with A. acidoterrestris. The applied novel UV technology could serve as an alternative to thermal treatments of fruit juices for the inactivation of Alicyclobacillus spores as well as in the treatment of contaminated wash water used in fruit processing.Department of HE and Training approved lis

Effect of colony age on near infrared hyperspectral images of foodborne bacteria

Near infrared hyperspectral imaging (NIR-HSI) and multivariate image analysis were used to distinguish between foodborne pathogenic bacteria, Bacillus cereus, Escherichia coli, Salmonella Enteritidis, Staphylococcus aureus and a non-pathogenic bacterium, Staphylococcus epidermidis. Hyperspectral images of bacteria, streaked out on Luria–Bertani agar, were acquired after 20 h, 40 h and 60 h growth at 37 °C using a SisuCHEMA hyperspectral pushbroom imaging system with a spectral range of 920–2514 nm. Three different pre-processing methods: standard normal variate (SNV), Savitzky–Golay (1st derivative, 2nd order polynomial, 15-point smoothing) and Savitzky–Golay (2nd derivative, 3rd order polynomial, 15-point smoothing) were evaluated. SNV provided the most distinct clustering in the principal component score plots and was thus used as the sole pre-processing method. Partial least squares discriminant analysis (PLS-DA) models were developed for each growth period and was tested on a second set of plates, to determine the effect the age of the colony has on classification accuracies. The highest overall prediction accuracies where test plates required the least amount of growth time, was found with models built after 60 h growth and tested on plates after 20 h growth. Predictions for bacteria differentiation within these models ranged from 83.1 % to 98.8 % correctly predicted pixels

Microbial quality of springbok (Antidorcas marsupialis) meat in relation to harvesting and production process

Prevalent bacteria on springbok (Antidorcas marsupialis) carcasses were investigated. Twelve springbok carcasses were swabbed around the incision area after in-field evisceration; carcasses were swabbed again after skinning and after chilling at the deboning area. Swab samples taken after skinning portrayed a presence of Escherichia coli and Enterobacteriaceae counts. Springbok carcasses swabbed after chilling indicated a high level of aerobic bacteria, Clostridium spp. and lactic acid bacteria (LAB). In contrast, swab samples taken at the incision area tend to be lower in counts than samples taken at the processing plant. Previous studies have found a reduction in microbial counts as temperature decreases. This was not the case for this study, as both Clostridium spp. and LAB counts increased after springbok carcasses had been kept at 2 degrees C for 24 hours. Further investigation in the abattoir is warranted, as results obtained during the study indicate that contamination may be due to poor processing and hygiene practice in the processing plant

Prevalence of Campylobacter and Arcobacter species in ostriches from Oudtshoorn, South Africa

ABSTRACT: Cloacal swabs were obtained from live ostriches reared on 30 different farms situated in South Africa (Oudtshoorn) during the period of June 2018 to July 2019 to determine the prevalence of Campylobacter and Arcobacter species. PCR (n = 168 pooled cloacal swabs), the Cape Town protocol (n = 836 cloacal swabs), International Organization for Standardization ISO 10272-1:2006 (n = 836 cloacal swabs), and a selective Arcobacter spp. method (n = 415 cloacal swabs) were used for detection. PCR determined an average prevalence of 24.63% for species belonging to the Campylobacteraceae family. The ISO 10272-1:2006 method determined a Campylobacter spp. prevalence level of 16.83%, while the Cape Town protocol could not detect Campylobacter spp. For Arcobacter spp., a prevalence of 18.80 and 39.14% was determined with the Cape Town protocol and the selective Arcobacter spp. method, respectively. Results showed that prevalence levels could be influenced by season, the source of water, and the presence of wild water birds. Higher prevalence levels for Campylobacter spp. (23.38%) and Arcobacter spp. (68%) were detected in ostriches sampled during spring and autumn, respectively. Higher prevalence levels for Campylobacter spp. (25.23%) and Arcobacter spp. (44.50%) were detected in ostriches reared on farms that made use of borehole water. Higher prevalence levels for Arcobacter spp. (44.38%) were seen in ostriches reared on farms with wild water birds. This research shows that ostriches from South Africa can be considered as potential carriers of species belonging to the Campylobacteraceae family

The microbial quality of black wildebeest (Connochaetes gnou) carcasses processed in a South African abattoir

The aim of this study was to investigate the microbial quality of black wildebeest (Connochaetes gnou) carcasses from the point of slaughter until the deboning process, allowing for the determination of possible points of contamination during the slaughter process. Carcasses were sampled at three processing points (skin on, skin off and post chilling) at four different carcass sites (rump, flank, brisket and neck). Before skinning, aerobic bacteria, Enterobacteriaceae, and Escherichia coli were enumerated from hide samples, counts ranged from 0.92 to 7.84 log cfu/g. After skinning the same bacteria were enumerated on the carcass. Counts ranged from 0.93 to 6.12 log cfu/g. A decrease in bacterial counts was seen after chilling of the carcasses. Significant differences between sites' bacterial loads were seen. For aerobic bacteria differences were prominent for flank (after skinning) and neck (after chilling), whilst for Enterobacteriaceae and E. coli noticeable differences between sites were noted for flank samples after chilling. Clostridium spp. showed an increase in counts after skinning, but this was not statistically significant. All samples were negative for Salmonella spp. The results from this study allow identifying when and on which area of the carcass contamination events occur

Determination of the microbial population of blesbok (Damaliscus pygargus phillipsi) meat in South Africa

The aim of this study was to investigate the microbial population and their prevalence on blesbok meat after slaughter and dressing of the carcasses. Animals were harvested from the University of Stellenbosch's experimental farm in the Western Cape, South Africa. Eight animals were shot and bled out in the field where after they were transported to the slaughter facility on the farm where dressing of the carcasses was done and two meat samples were taken. Surface swabs of the meat samples were used for analyses. All samples were tested for the presence of total coliforms, aerobic count, Staphylococcus aureus and Escherichia coli. Total aerobic count was in the range of 1.6-5.1 log cfu/cm(2) whereas all total coliform count was above 5 log cfu/cm(2). E. coli counts ranged from 0-2.19 log cfu/cm(2) and lastly S. aureus were all considerably low except for blesbok seven that was excessively contaminated. It was therefore evident to see that cross contamination took place during the slaughter process including during removal of the hide

Antimicrobial-resistant Klebsiella species isolated from free-range chicken samples in an informal settlement

A b s t r a c t Introduction: Sub-therapeutic doses of antimicrobial agents are administered routinely to poultry to aid growth and to prevent disease, with prolonged exposure often resulting in bacterial resistance. Crossover of antibiotic resistant bacteria from poultry to humans poses a risk to human health. Material and methods: In this study, 17 chicken samples collected from a vendor operating in an informal settlement in the Cape Town Metropolitan area, South Africa were screened for antimicrobial-resistant Gram-negative bacilli using the Kirby Bauer disk diffusion assay. Results: In total, six antibiotics were screened: ampicillin, ciprofloxacin, gentamicin, nalidixic acid, tetracycline and trimethoprim. Surprisingly, Klebsiella ozaenae was identified in 96 and K. rhinoscleromatis in 6 (n = 102) of the samples tested. Interestingly, ~40% of the isolated Klebsiella spp. showed multiple resistance to at least three of the six antibiotics tested. Conclusions: Klebsiella ozaenae and K. rhinoscleromatis cause clinical chronic rhinitis and are almost exclusively associated with people living in areas of poor hygiene