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Besides its health and spoilage hazards, Escherichia coli is a process hygiene indicator for cheeses made from milk that has undergone heat treatment. Hence, its ability to persist in cheesemaking plant environment and equipment is important. In total, 120 samples from two producing plants were analysed and 72 E. coli isolates were obtained. The target was to find out whether there is a difference in heat-resistance between persistent and non-persistent E. coli strains. The strains were selected using macrorestriction analysis and recurrent detection in cheesemaking plants hereby: one strain persisting in brine for blue-veined cheeses, two strains persisting in brine for hard cheeses and one non-persistent strain from raw material. Their D(50)-values were 196; 417; 370 and 182 min, respectively, D(59)-values ranged from 20 to 32 min and z-values were 7.5; 6.6; 8.1 and 9.0 °C, respectively. The non-persistent strain was the least resistant to heating to 50 °C but it was not the least resistant generally. All tested strains were highly heat-resistant and carried genes of the heat resistance locus LHR1 and/or LHR2. Our results emphasise the need to screen for the presence of LHR genes and the occurrence of heat-resistant E. coli in cheese production where they could survive subpasteurisation temperatures and contaminate the manufacturing environment and finished products. [ABSTRACT FROM AUTHOR]

The study investigated population structure of Listeria monocytogenes strains originating from human listeriosis cases and from ready-to-eat (RTE) foods in the Czech Republic in 2013-2016. A total of 117 isolates, both from sporadic and epidemic cases, and 128 isolates mainly from meat and dairy products were characterized using serotyping and multilocus sequence typing (MLST). Serotypes 1/2a, 1/2b, 1/2c and 4b were detected with serotype 1/2a prevailing both in the human population (57.3 %) and in foods (54.7 %). MLST detected 32 sequence types (STs) belonging to 28 clonal complexes (CCs) with STs occurring exclusively in humans, in foods and simultaneously in foods and humans. Phylogenetic analysis revealed strains belonging to the evolutionary lineages I and II. The population structure of L. monocytogenes showed a high level of heterogeneity. Strains of lineage I and II showed the same potential to cause listeriosis in human population. Strains of ST8 (serotype 1/2a) and ST6 (serotype 4b) were dominant among human isolates. Strains of ST121 (1/2a), ST8 (1/2a), ST2 (4b) and ST3 (1/2b) prevailed in food isolates. Within the study, 16 STs were detected, the presence of which in RTE foods can pose an increased risk of illness to consumers in the Czech Republic. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the prevalence and characteristics of Listeria monocytogenes in ripened and steamed cheeses from the retail market in the Czech Republic examined between 2007 and 2016. The examination to detect and enumerate L. monocytogenes in samples was carried out at the time of purchase and at the end of the shelf-life. The isolates recovered from the samples were characterized by serotyping, clonogrouping by polymerase chain reaction (PCR) and by macrorestriction analysis. L. monocytogenes was detected in 20 of 387 (5.2%) originally packaged cheeses from different producers. The counts of L. monocytogenes did not exceed the limit of 100 CFU·g-1 in any of the samples. L. monocytogenes was detected most frequently in blue-veined cheeses from one producer (28.9%). Probably persistent L. monocytogenes strains were found in blue-veined cheeses and smear-ripened cheeses from two producers. With respect to the fact that L. monocytogenes is able to persist in food-processing facilities, it is necessary to carry out regular monitoring of Listeria occurrence in the food-processing environment. As L. monocytogenes can multiply at refrigeration temperatures, it is necessary to set the appropriate use-by date and provide information to consumers. [ABSTRACT FROM AUTHOR]

Nitroaromatic compounds are toxic and rather recalcitrant pollutants of water and soil. Microbial degradation of the individual nitroaromatic compounds has already been well described in the literature. However, because several compounds often occur in the environment mutually influencing each other’s degradation, further research into the biodegradation of their mixtures is still needed. We investigated the degradation of a mixture of 4-nitrophenol (4-NP) and 4-nitrotoluene (4-NT) by a mixed microbial culture immobilized in a continuously operated packed-bed reactor (PBR) and by free suspended cells in shake flasks. Each compound was at first degraded separately, then in a mixture, and their degradation characteristics were compared. When treated separately, 4-NP and 4-NT were degraded with efficiency over 99 and 95%, respectively. When in a mixture, 4-NP was still completely removed from the media but the 4-NT removal efficiency dropped by a half and remained about the same during the whole experiment regardless the increasing 4-NP concentration at the PBR inlet. The shake flask experiments corroborated our finding that 4-NP negatively influenced 4-NT degradation by competitive inhibition and also indirectly on the adaptation level. [ABSTRACT FROM PUBLISHER]

The present study was designed to assess heterogeneity of virulence factors among strains of Listeria monocytogenes isolated from the food chain and humans in the Czech Republic. The virulence characteristics, presence of Listeria pathogenicity island 1 (LIPI-1) as well as inlA, inlB, inlC and inlJ genes of tested strains of L. monocytogenes from foods and food processing plants were comparable with human strains independently of particular serotypes. Restriction polymorphism of inlA gene confirmed a correlation between the restriction fragment length polymorphism (RFLP) profiles and the serotypes. Strains of serotype 1/2a and 1/2c with RFLP profiles, which may be characterized by production of a truncated internalin A, were detected not only in food strains, but also in 44% of strains isolated from clinical cases of listeriosis. Premature stop codon (PMSC mutation type 3) in the inlA gene associated with the production of truncated internalin A was detected in one L. monocytogenes strain from a ready-to-eat fish product. Considering food safety, all tested food strains should still be considered as pathogenic to humans even though some of these showed reduced virulence on the basis of genotyping results. [ABSTRACT FROM AUTHOR]

The emergence of plasmid-mediated colistin resistance carried by mcr genes and polymyxin resistance in carbapenem-resistant bacteria poses a threat to antibiotic therapy of bacterial infections. The worldwide spread of colistin resistance carried by mcr genes, particularly in Enterobacteriaceae, points to the possibility of the spread of this type of resistance also in non-fermenting Gram-negative bacteria such as Pseudomonas aeruginosa or Acinetobacter baumannii. This study provides information on the first described occurrence of the mcr-4 gene in A. baumannii isolated from imported turkey liver obtained in the retail market of the Czech Republic.

Plasmid-mediated resistance to colistin is a recently described phenomenon. The study reports this new type of colistin resistance in food isolates of Escherichia coli in the Czech Republic. Strains with phenotypically determined colistin resistance were studied for presence of the mcr-1 and mcr-2 genes. A positive finding of E. coli harboring the mcr-1 gene was confirmed in a sample of raw minced turkey meat imported from Poland. Two different strains of E. coli carrying the mcr-1 gene were detected in the same sample. This is the first reported case of this type of resistance in E. coli strains isolated from foods at retail in the Czech Republic.

The study objective was to investigate whether the strain of L. monocytogenes serotype 1/2c isolated from neonatal listeriosis carries a premature stop codon (PMSC) mutation in the inlA gene. The strain was characterized by serotyping, macrorestriction analysis after digestion with the restriction enzyme AscI, and sequencing of the inlA gene. The tested strain of serotype 1/2c and pulsotype 1 possesses a new type of point mutation leading to a PMSC in the inlA gene and production of truncated internalin A. The case of early onset form of neonatal listeriosis caused by serotype 1/2c with a PMSC mutation in the inlA gene confirmed the transplacental transmission potential of this strain.

Background: To assess the incidence of antimicrobial resistance of L. monocytogenes strains isolated from humans and foods in the Czech Republic in the period of 2001 to 2012., Material and Methods: Phenotypic resistance testing has been monitored by the disk diffusion method and complemented by the assessment of minimum inhibitory concentration by E-test method and genes encoding resistance by the PCR method., Results: All tested strains (678) were susceptible to ampicillin, penicillin, gentamicin, trimethoprim, vancomycin and chloramphenicol. Resistance to tetracycline (2/509) and erythromycin (1/509) was detected sporadically in strains of food origin., Conclusions: Very good and so far stable susceptibility of tested strains of L. monocytogenes isolated from humans and foods to antibiotics used in the therapy of listeriosis was found in the monitoring period. Sporadic occurrence of resistance was detected only in strains from foods.