Showing 7 results for Listeria Monocytogenes
S. Maktabi, M. Pourmehdi, M. Zarei, R. Moalemian ,
Volume 2, Issue 3 (9-2015)
Abstract
Background: Listeria monocytogenes is one of the most important food-borne bacteria causing septicemia, meningitis and encephalitis in humans. The objective of this study was to evaluate the occurrence and antibiotic resistance of the bacterium in retail minced beef in Ahvaz, South-West of Iran.
Methods: In this survey, 150 samples of minced beef were randomly obtained from retail butcheries in Ahvaz, Iran and tested for presence of L. monocytogenes. The procedure was one-step enrichment in Listeria enrichment broth followed by plating on oxford agar. Isolated colonies were subjected to subsequent biochemical tests and polymerase chain reaction (PCR) assay using the target iap-P60 gene encoding P60 protein. Susceptibility of the isolates to various antibiotics was investigated by Kirby-Bauer disk diffusion method. The results were analyzed by chi-square test and fisher’s exact test using SPSS 16.0 software.
Results: The incidence of Listeria spp. was 2.7% (4 of 150 samples) and only one sample (0.66%) was contaminated to L. monocytogenes. Statistical analysis showed no significant difference in prevalence of Listeria between various regions (p>0.05). The isolate was resistant to streptomycin and showed an intermediate susceptibility to tetracycline and penicillin. However, it was sensitive to other tested antibiotics.
Conclusion: Our findings showed the presence of antibiotic resistant L. monocytogenes strain among beef samples in this region of Iran and so, indicated the potential risk for public health from consumption of raw or undercooked beef which may increase the possibility of acquisition of resistance to antibiotics.
M. Zarei, A. Fazlara, M. Pourmahdi Borujeni, M. Karimi,
Volume 2, Issue 4 (12-2015)
Abstract
Background: Unlike industrially production, Iranian traditional doogh are not pasteurized after production. Hence, possible contamination with different pathogenic bacteria may occur during production or post-production of traditional doogh. The aim of the present study was to monitor the behavior of Escherichia coli O157:H7 and Listeria monocytogenes in traditional Iranian doogh at different temperatures and time periods.
Methods: Low acid and high acid doogh samples were inoculated with approximately 4 and 6 log cfu/ml of each pathogen separately and incubated at 4 ºC and 25 ºC. At different time interval, samples were taken to enumerate E. coli O157:H7 and L. monocytogenes and determine titratable acidity. Results were analyzed by ANOVA test using SPSS software (v. 16.0).
Results: Although the survival ability of E. coli O157:H7 in doogh samples was slightly higher than L. monocytogenes, both of them were detected in low acid doogh sample after 10-14 days at 4 ºC. However, they were not detected in low acid doogh samples for more than 2 days at 25 ºC. In contrast, in high acid doogh samples, the viability of E. coli O157:H7 and L. monocytogenes declined more quickly to undetectable level, both at 4 ºC and 25 ºC indicating less viability of these bacteria in high acid doogh samples compared to those of low acid ones (p<0.05).
Conclusion: Traditional Iranian doogh should be considered as a potential vehicle of transmission of E. coli O157:H7 and L. monocytogenes, especially in low acid doogh samples when stored under refrigeration.
E. Sadeghi, A. Mohammadi, M. Jamilpanah, M. Bashiri, S. Bohlouli,
Volume 3, Issue 1 (3-2016)
Abstract
Background: Listeria monocytogenes is an important Gram-positive disease-causing bacterium existing in milk and dairy products. Inhibitory effects of Mentha pulegium essential oil at concentrations of 0.03, 0.015, and 0.0075% on growth of L. monocytogenes were studied in Iranian white cheese during 60 days of storage.
Methods: Essential oil of M. pulegium plant, collected from north of Iran, was extracted by Clevenger apparatus and analyzed by gas chromatography mass spectrometry (GC-MS). The antibacterial effects of the oil were evaluated by growth of the microorganism in control and treatment cheese samples. Also, sensory properties of the cheese samples containing different concentration of M. pulegium were determined. Statistical analyses were performed by ANOVA and Fisher’s Least Significant Difference (LSD) procedure using SPSS 16.0 software.
Results: GC/MS analysis showed that the major compounds of M. pulegium essential oil were pulegone (36.68%), piperitenone (16.88%) and 1,8 cineole (14.58%). In control group, L. monocytogenes grew in 7 days and then their growth decreased gradually during 60 days. But, in all treated samples there is a log reduction in bacterium count while the maximum growth lasted for 14 days with a significant difference (p<0.05) compared with control samples. Although 0.03% concentration of mentha oil had the most strong antibacterial effects, but the samples with 0.015% essential oil had significantly higher organoleptic properties score comparing the other samples (p<0.05).
Conclusion: M. pulegium essential oil not only can improve organoleptic properties of cheese but also can reduce and postpone the growth of L. monocytogenes in this product.
L. Mansouri-Najand , S. Hamzeh Aliabad , N. Fatemi ,
Volume 4, Issue 4 (12-2017)
Abstract
Background: Listeria monocytogenes is a Gram-positive and facultative anaerobic food-borne bacterium which is capable of intra and extra cellular growth. L. monocytogenes usually can exist on different surfaces and instruments at production and processing sites of food products with animal origin. In Iran, the consumption of burger has increased recently, but its safety is still of great concern. Despite few reports from some areas of Iran, there is limited information about burger contamination in Kerman province. Therefore, this research was set to molecular identification of L. monocytogenes in hamburgers distributed in Kerman, Iran.
Methods: A total of 100 raw hamburgers were collected from 20 fast food/sandwich shops in Kerman city, Iran during summer 2014. The hamburgers stored in ice box and transported to the food hygiene laboratory. The samples were microbiologically analyzed for the presence of L. monocytogenes. The isolated bacteria were confirmed by molecular assay.
Results: Three out of 100 (3%) hamburger samples were biochemically diagnosed as Listeria contamination; however molecular identification assay confirmed that two of them were L. monocytogenes.
Conclusion: Although the prevalence rate of L. monocytogenes was not high in hamburger samples of Kerman, the risk of human listeriosis must not be ignored or underestimated. Further surveys are required in future for risk assessment of this pathogenic bacterium in other food products distributed in the country.
Y. Shahbazi, N. Shavisi,
Volume 5, Issue 3 (9-2018)
Abstract
Background: One of the most well-known Iranian traditional cheeses is Koozeh. The aim of present work was to evaluate the survival of L. monocytogenes during ripening of Iranian traditional Koozeh cheese made from raw ewe's milk.
Methods: A 2-factor experimental design was applied to study the effect of ripening conditions, including different temperatures (4, 9, and 14 °C) and different concentrations of NaCl (0, 8, 12, and 15%) on the survival of L. monocytogenes in the Koozeh cheese. Microbial analysis was carried out over a period of 150 days with sampling in every 10 days. SPSS software (v. 16.0) was used for statistical analysis.
Results: Three NaCl concentrations (8, 12, and 15%) significantly affect the inactivation L. monocytogenes (p<0.05). After inoculation, L. monocytogenes populations were reduced most rapidly during the first ten days of storage (~0.5-1.5 log Colony Forming Unit/g) at three mentioned temperatures; after that, the bacteria were continually decreased, being below the detection limit (1 log CFU/g) at the end of ripening. Numbers of L. monocytogenes were reduced more effectively at 14 °C storage temperature than 9 and 4 °C (p<0.05).
Conclusion: L. monocytogenes was declined drastically during ripening days and eliminated at the end of ripening of Koozeh cheese. L. monocytogenes counts were decreased during ripening of Koozeh cheese under adverse conditions such as high salt concentrations and high temperatures. However, since Iranian Koozeh cheese is made from raw and unpasteurized milk, there are still some concerns about health risk of L. monocytogenes in this product. Also, the effects of temperature and salting parameters on the sensorial properties of Koozeh cheese should be investigated in future.
DOI: 10.29252/jfqhc.5.3.109
C. Cardamone, F. Cirlincione, R. Gaglio , V. Puccio , F. Daidone , S. Sciortino , I. Mancuso , M.l. Scatassa ,
Volume 7, Issue 1 (3-2020)
Abstract
Background: Consumption of raw cheese may be associated with different diseases. This study aimed to evaluate behavior of four pathogenic bacteria during manufacture and ripening of Protected Designation of Origin (PDO) Pecorino Siciliano cheese.
Methods: The experimental cheese groups were inoculated with pathogenic bacteria, including Escherichia coli O157, Listeria monocytogenes, Salmonella Enteritidis, and Staphylococcus aureus. The cheese making processes were monitored from milk curdling until 3 months ripened cheeses and the levels of Lactic Acid Bacteria (LAB) and the four dairy pathogens were evaluated by plate counts. Randomly Amplified Polymorphic DNA (RAPD)-Polymerase Chain Reaction (PCR) analysis was applied to confirm that the colonies isolated during the several steps of production were the same strains added in milk. Statistical analysis was done using XLStat software.
Results: The levels of mesophilic and thermophilic coccus and rod LAB in curd were comparable in both trials and reached values between 8-9 log10 Colony Forming Unit (CFU)/g in cheeses at 90 days of ripening. The four pathogenic bacteria were found in experimental curd at levels higher than those inoculated in milk and completely disappeared after 60 days of ripening. The RAPD analysis clearly demonstrated the presence of the added strain during production and confirmed the results of plate counts.
Conclusion: This work showed that the production conditions of PDO Pecorino Siciliano cheese decreased growth of E. coli O157, L. monocytogenes, S. Enteritidis, and S. aureus.
DOI: 10.18502/jfqhc.7.1.2449
M. Raeisi , A. Afshari , H. Shirzad-Aski , S. Seifi , M. Hashemi , R. Khoshbakht , Z. Malvandi , O.r. Coban , S.m.a. Noori ,
Volume 10, Issue 2 (6-2023)
Abstract
Background: Given that controlling Listeria contamination is very important in food chain system, the knowledge of their prevalence in food is very important. Therefore, this study aims to examine the prevalence of important Listeria species in various food types and evaluate serotype distribution, as well as the study of the virulence factors of L. monocytogenes.
Methods: During July 2018 and January 2020, 900 food samples were collected in the North of Iran, including beef, chicken, fish, shrimp, milk and yogurt, green vegetables, mixed vegetable salad, Olivier salad, and cottage cheese. After isolation and identification steps, each bacterial DNA was extracted. Then, using specific primers, species, serotypes, and virulence genes of Listeria isolates were evaluated in the samples by Polymerase Chain Reaction (PCR) method.
Results: The test results of 136 samples (15.1%) were positive for Listeria spp. and the most contaminated food was beef (35%) followed by chicken (29%) and green vegetables (23%). The most isolated Listeria spp. was L. monocytogenes and L. ivanovii. Among L. monocytogenes isolates, the dominant serogroups were 1/2a and 4b; furthermore, all of the isolates of this species harbored four virulence genes, including hlyA, plc, iap, and actA.
Conclusion: These reports highlighted the importance of food safety in various food products, particularly raw meats and vegetables. Moreover, contamination of healthy foods such as fish and vegetables with Listeria is an indicator of public health.
DOI: 10.18502/jfqhc.10.2.12673
