Original scientific paper
https://doi.org/10.15567/mljekarstvo.2018.0101
Influence of milk product type and its initial contamination on the efficiency of different methods for detection of Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli O157:H7
Boris Antunović
orcid.org/0000-0003-0052-3795
; University of J.J. Strossmayer, Faculty of Agriculture, Department for Animal Husbandry, Vladimira Preloga 1, 31000 Osijek, Croatia
Ivančica Kovaček
; Dr. Andrija Štampar Institute of Public Health, Department of Environmental Protection and Health Ecology, Division of Food and Consumer Goods Microbiology, Mirogojska cesta 16, 10000 Zagreb, Croatia
Kristina Gvozdanović
; University of J.J. Strossmayer, Faculty of Agriculture, Department for Animal Husbandry, Vladimira Preloga 1, 31000 Osijek, Croatia
Manuela Grčević
; University of J.J. Strossmayer, Faculty of Agriculture, Department for Animal Husbandry, Vladimira Preloga 1, 31000 Osijek, Croatia
Vesna Gantner
; University of J.J. Strossmayer, Faculty of Agriculture, Department for Animal Husbandry, Vladimira Preloga 1, 31000 Osijek, Croatia
Vedran Poljak
; Croatian Institute of Public Health, Department of Health Ecology, Rockefellerova 7, 10000 Zagreb, Croatia
Mario Ostović
; University of Zagreb, Faculty of Veterinary Medicine, Department of Animal Hygiene, Behaviour and Welfare, Heinzelova 55, 10000 Zagreb, Croatia
Željko Pavičić
; University of Zagreb, Faculty of Veterinary Medicine, Department of Animal Hygiene, Behaviour and Welfare, Heinzelova 55, 10000 Zagreb, Croatia
Nihada Ahmetović
; University of Tuzla, Faculty of Medicine, Univerzitetska 1, Tuzla 75000, Bosnia and Herzegovina
Abstract
This paper investigates differences in efficacy of isolating pathogenic bacteria Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli O157:H7 between conventional cultivation (ISO method) and immunomagnetic separation (IMS method) related to the types of dairy products and initial numbers of bacteria. Different milk products (dairy pudding- vanilla or chocolate; a mixture of yoghurt and pudding; solid, liquid and fruit yoghurt; AB culture - with or without fruit; cheese spread) were intentionally contaminated with different numbers (≈10 and ≈30) of live cells of the observed bacteria per mL. The obtained results showed that the classical ISO procedure still represents an equally adequate method for the detection of S. Enteritidis and L. monocytogenes in dairy products as well as the IMS method. However, the ISO method was found to be inefficient for determination of E. coli O157:H7 when the initial contamination was low (≈10 live cells per mL). In such cases, even the IMS method appeared to be inefficient when used for fermented dairy product analysis. Fermented dairy products in contrast to the non-fermented ones, still represent a challenge for the development of routine detection methods, especially for S. Enteritidis, whilst the detection of L. monocytogenes and E. coli O157:H7 has improved by introducing the IMS method. The largest difference in the ability to detect bacteria in dairy product samples with reference to the initial number of bacteria by both methods was in the detection of E. coli O157:H7. The choice of broth (non-selective fluid broth vs. selective fluid broth) did not matter in the in the detection of S. Enteritidis and L. monocytogenes by applying the IMS procedure. However, for the detection of E. coli O157:H7 the application of modified tripton-soya broth with novobiocin (mTSB+Nb) has proved to be superior when compared to using the buffered peptone water (BPW). The presented results may be of importance as a scientific basis for future determination of standard methods related to laboratory detection of pathogens in dairy products.
Keywords
milk; dairy products; Salmonella Enteritidis; Listeria monocytogenes; Escherichia coli O157:H7; immunomagnetic separation
Hrčak ID:
192294
URI
Publication date:
10.1.2018.
Visits: 3.052 *