Isolation and detection of Listeria monocytogenes in poultry meat by standard culture methods and PCR

Listeria is the genus of a bacteria found in soil and water and some animals, including poultry and cattle. It can be present in raw milk and food made from raw milk. It can also live in food processing plants and contaminate a variety of processed meats. Microscopically, Listeria species appear as small, Gram-positive rods, which are sometimes arranged in short chains. In direct smears, they can be coccoid, so they can be mistaken for streptococci. Longer cells can resemble corynebacteria. Flagella are produced at room temperature but not at 37 degrees C. Haemolytic activity on blood agar has been used as a marker to distinguish Listeria monocytogenes among other Listeria species, but it is not an absolutely definitive criterion. Further biochemical characterization is necessary to distinguish between the different Listeria species. The objective of this study was to detect, isolate and identify Listeria monocytogenes from poultry meat. Within a period of six months from January to June 2017, a total of 15 samples were collected. Three samples were positive for the presence of Listeria monocytogenes. Biochemical and microbiological tests as well as PCR technique using specific primers were used to confirm L. Monocytogenes in the samples

Histamin u ribi dostupnoj na tržištu Srbije u 2018. godini

Histamine is a biogen amin, which is formed by decarboxylation of the histidine amino acid, under the action of the L-histidine-decarboxylase enzyme. High level of free histidine in fish meat, bacterial histidin decarboxylase activity and high temperature of storage elevate the level of histamine. Among the most important factors that can affect the level of histamine in fish meat are the type of fish and the method of its preservation. In order to determine this dependence, 1030 samples of frozen fish (tuna, mackerel, sardines and sprat) and 167 samples of canned fish (tuna, sardines and mackerel) were monitored for histamine content by ELISA method. It was determined a lower concentration of histamine in frozen fish (from 5.71 mg/kg to 18.03 mg/kg) compared to canned fish (from 15.03 mg/kg to 110.6 mg/kg). The highest histamine concentrations were found in the mackerel samples, regardless of the preservation method (110.6 mg/kg in canned mackerel and 18.03 mg/kg in frozen mackerel), which were significantly higher compared to the histamine levels found in cans of tuna and sardines (p ˂0.0001). Of the total number of samples, three samples (two samples of canned sardines and one sample of canned mackerel) were declared unsafe for human health. In most of the analyzed samples, the level of determined histamine was relatively low, which confirms adequate implementation of control protocols and efficant surveillance of products placed on the Serbian market.Histamin je bioaktivni amin, koji nastaje u reakciji dekarboksilacije aminokiseline histidina, pod dejstvom enzima Lhistidin dekarboksilaze. Visok nivo slobodnog histidina u mesu ribe, aktivnost enzim produkujućih bakterija i visoke temperature skladištenja deluju predisponirajuće na sintezu histamina. Među najznačajnije faktore koji utiču na koncentraciju histamina u mesu ribe jesu vrsta ribe i metod njenog konzervisanja. U cilju utvrđivanja ove zavisnosti, uzorci zamrznute ribe (tune, skuše, sardine i papaline) i ribe u konzervi (tune, sardine i skuše) su analizirani ELISA metodom. Utvrđene su niže koncentracije histamina u uzorcima zamrznute ribe (od 5.71 mg/kg do 18.03 mg/kg) u poređenju sa konzervama od ribe (od 15.03 mg/kg do 110.6 mg/kg). Najviše koncentracije histamina su ustanovljene u uzorcima skuše, bez obzira na metod konzervisanja (110.6 mg/kg u konzervama od skuše i 18.03 mg/kg u zamrznutoj skuši), koje su bile i statistički značajno veće u odnosu na konzerve tune i konzerve sardine (p ˂0.0001). Od ukupnog broja uzoraka, samo tri uzorka (dva uzorka sardine u konzervi i jedan uzorak skuše u konzervi) su proglašeni nebezbednim za zdravlje ljudi. U najvećem broju ispitanih uzoraka izmerene su relativno niske koncentracije histamina, što ukazuje na adekvatno sprovođenje kontrole i nadzora nad proizvodima koji se plasiraju u promet na srpskom tržištu

Listeria monocytogenes contamination in ready to eat foods

Listeria monocytogenes is a food-borne pathogen responsible for listeriosis, a sickness with a high mortality rate. Listeriosis is largely associated with ready-to-eat (RTE) foods. It is well established that foods that pose the greatest risk of foodborne listeriosis are those RTE foods that have intrinsic characteristics such as pH and water activity that support the growth of L. monocytogenes. RTE foods can also become re-contaminated during further processing and handling. Increased handling leads to a higher probability of contamination. Sources of contamination can be food contact surfaces, processing machinery and workers. In our research, L. monocytogenes was detected in a RTE salad. Food safety criteria for Listeria monocytogenes in RTE foods have been applied from 2006 (Commission Regulation (EC) 2073/2005). Still, human invasive listeriosis was reported to increase during 2009-2013 in the European Union and European Economic Area. Time series analysis for the 2008-2015 period in this area showed an increasing trend of the monthly notified incidence rate of confirmed human invasive listeriosis of the over 75 age groups and female age group between 25 and 44 years old (probably related to pregnancies)