Prevalence and characteristics of Listeria monocytogenes in meat, meat products, food handlers and the environment of the meat processing and the retail facilities of a company in Northern Greece

In this study, we investigated the incidence of Listeria monocytogenes in the receiving meat, the meat products, the personnel and the environment of a vertically integrated company in Northern Greece owing a processing plant and three trading facilities. A total of 303 samples were examined from the receiving raw meat, raw meat preparations, ready-to-eat meat products, processing surfaces and the environment of these facilities as well as the food handlers' hands and nasal cavities. MALDI-TOF MS was used for Listeria identification; from the 22 (7·26%) positive to Listeria spp. isolates, 12 (3·96%) identified as L. monocytogenes, eight (2·64%) as Listeria innocua and two (0·66%) as Listeria welshimeri. Molecular serotyping of L. monocytogenes isolates by multiplex PCR revealed 11 strains belonging to serogroup IIa (1/2a and 3a) and one to IIc (1/2c and 3c). The assay for the detection of the virulence-associated genes revealed eight isolates carrying all the examined genes (inlA, inlB, inlC, plcA, prfA, actA, hlyA and iap) and four carrying all except the actA gene. Eleven (91·7%) of the isolates showed a strong ability to form biofilm. All isolates were multidrug resistant. The MALDI-TOF Main Spectrum Profile (MSPs), revealed three clusters: one with five isolates (four from environmental samples and one from a food handler), one with five isolates (all from environmental samples) and one with two isolates (both from raw meat products). MALDI-TOF MS seems to be a reliable tool for the identification of niches and contamination routes in processing plants, contributing also to the evaluation and improvement of the applied preventive measures to control L. monocytogenes.

Characterization of Listeria monocytogenes from encephalitis cases of small ruminants from different geographical regions, in Greece

AIMS

The aim of this study was to evaluate the genetic diversity and resistance phenotypes of Listeria monocytogenes strains isolated from clinical encephalitis cases, and compare this population to isolates derived from tank milk of healthy animals.

METHODS AND RESULTS

A total of 57 L. monocytogenes strains isolated from ruminant's listeriosis cases (n = 31) and from tank milk of healthy ruminants (n = 26) were characterized by species PCR, molecular serotyping, PCR detection of virulence genes, pulsed-field gel electrophoresis and antimicrobial susceptibility testing. All strains possessed inlA, inlC, inlJ, plcA, actA, hlyA and iap virulence-associated genes while serotyping analysis revealed that they were mainly assigned into IVb group. Genotyping revealed 50 pulsotypes among the 57 strains assigned into seven clusters while indistinguishable pulsotypes between clinical and milk strains were not identified. Resistance of L. monocytogenes isolates to 14-16 antimicrobial agents tested was observed and 23 antimicrobial resistance profiles (ARPs) were defined while no apparent predominant ARP type was observed among isolates.

CONCLUSIONS

Small ruminants are exposed to a broad range of antimicrobial-resistant as well as genetically diverse strains of L. monocytogenes carrying virulence-associated genes but not all of them associated with the disease. Pulsed-field gel electrophoresis analysis suggests that pulsotypes associated with encephalitis are found in farms only in association with listeriosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings are valuable in understanding the ecology of this important food-borne pathogen and creating awareness for the emerging antimicrobial resistance.

Comparative study of all Salmonella enterica serovar Enteritidis strains isolated from food and food animals in Greece from 2008 to 2010 with clinical isolates

The aim of the present work was to study the epidemiology of Salmonella enterica serovar Enteritidis (S. Enteritidis) in Greece, comparing all the food and food animal isolates during a 3-year period with clinical isolates. Submission of the generated data to the PulseNet Europe database was carried out in order to study the population structure of this particular serovar and indicate possible connections with European strains. One hundred and sixty-eight (168) S. Enteritidis strains of human, animal, and food origin, isolated during the period 2008-2010 in Greece, were studied. Strains were characterized by phenotypic (antibiotic resistance) and molecular [pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST)] methods. PFGE revealed 39 XbaI, 48 BlnI, and 80 XbaI-BlnI distinct pulsotypes, suggesting several clones circulating through the food chain and multiple sources of transmission. Submission to the PulseNet Europe database indicated that PFGE profile SENTXB.0001, the most common PFGE profile in Europe, was also predominant in Greece (33.3 %). MLST showed that all the strains studied shared the same sequence type (ST11), representing the most common ST in Europe. High rates of resistance to nalidixic acid were observed among human and poultry isolates (~25 %), indicating the potential fluoroquinolone treatment failure. Our data suggest that strains originating from multiple reservoirs circulated in Greece through the food chain during the study period. Predominant profiles in Greece were common to PulseNet Europe profiles, indicating similarities between the S. Enteritidis populations in Greece and Europe.

Phenotypic and molecular characterization of multidrug-resistant Salmonella enterica serovar Hadar in Greece, from 2007 to 2010

All 120 strains of Salmonella enterica serovar Hadar isolated during 2007-2010 in Greece were characterized by phenotypic and molecular methods. High rates of resistance to nalidixic acid (92%) and low levels of ciprofloxacin resistance (88%) were observed. Pulsenet-pulsed field gel electrophoresis profile SHADXB.0001 was predominant in Greece (58%) as in Europe but PT1, a rare phage type in Europe, was frequent in Greece (56%). The SHADXB.0001 and PT1 clone (38%) were found in humans, animals and food of animal origin with R-type ApSpTNxpCp being predominant (25%). The data indicate that this clone (possibly endemic) was circulating through the food chain in Greece during the study period.

Isolation of methicillin-resistant Staphylococcus spp. from ready-to-eat fish products

A hundred samples from ready-to-eat (RTE) fish products were examined for the presence and antimicrobial susceptibility of Staphylococcus spp. Staphylococci were isolated from 43% of these samples (n = 100). The identified species in the samples were Staphylococcus aureus (7%), Staphylococcus epidermidis (13%), Staphylococcus xylosus (12%), Staphylococcus sciuri (4%), Staphylococcus warneri (3%), Staphylococcus saprophyticus (2%), Staphylococcus schleiferi (1%) and Staphylococcus auricularis (1%). Two Staph. aureus (MRSA) isolates, three Staph. epidermidis (MRSE), five Staph. xylosus, four Staph. sciuri, one Staph. schleiferi and one Staph. saprophyticus isolates were resistant to oxacillin and all of them carried the mecA gene. The two MRSA isolates belonged to the spa types t316 (ST359) and t548 (ST5) and none of them was able to produce enterotoxins. Pulsed field gel electrophoresis for Staph. aureus and Staph. epidermidis isolates revealed 6 and 11 distinct PFGE types, respectively, reflecting diversity. The presence of methicillin-resistant staphylococci, especially MRSA and MRSE, in RTE fish products may constitute a potential health risk for consumers.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides the first data on the occurrence of methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci in salted and smoked fish products in Greece. These results are important and useful for Staphylococcus spp. risk assessment and management programmes for ready-to-eat fish products.

Culture phenotypes and molecular characterization of Mycobacterium avium subsp. paratuberculosis isolates from small ruminants

In this study the suitability of different solid media was investigated for the isolation of Mycobacterium avium subsp. paratuberculosis (Map) in order to identify the optimum single or combination of media to permit the isolation of all strain types from small ruminants. A subset of these Map strains was then further characterized by molecular typing methods to assess the genetic diversity of Map strains in the study area (Northern Greece). Map strains were isolated from tissues and faeces of infected goats (n=52) and sheep (n=8) and were analysed for polymorphisms in IS1311 to classify the strain type as Type C or S. The study found that M7H11 supplemented with mycobactin j, OADC and new born calf serum (M7H11+Mj) is the best single choice of medium for the primary isolation of Map of both Type C and S from small ruminants. The combination of M7H11+Mj and Herrolds egg yolk medium supplemented with mycobactin j and sodium pyruvate allowed the detection of all Map isolates in this study. Nineteen Map isolates were characterised by pulsed-field gel electrophoresis and the isolates demonstrated significant genetic diversity. Twelve different SnaBI and 16 distinct SpeI profiles were detected of which 25 have not been described previously and are new profiles. The combination of both enzyme profiles gave 13 different multiplex profiles. Ten different multiplex profiles were detected in goats and three in sheep. One ovine isolate gave the same multiplex profile as a caprine isolate and two different profiles were found within a single goat herd.

Diversity of vanA-type vancomycin-resistant Enterococcus faecium isolated from broilers, poultry slaughterers and hospitalized humans in Greece

OBJECTIVES

This study investigated the prevalence of vancomycin-resistant enterococci (VRE) in the broiler production environment after the avoparcin ban and their epidemiological relationship with human clinical VRE from the same geographical regions in Greece.

METHODS

Caecal contents from broilers (n = 500) from eight livestock farms and faecal samples from poultry slaughterers (n = 50), all collected in two slaughterhouses during 2005-08, were analysed for species and vancomycin resistance gene identification using multiplex PCR. Sixty-three human clinical vancomycin-resistant Enterococcus faecium (VREF) isolates, obtained during 2006-09, were also examined. Discriminant analysis (DA) was used to establish the relationship of antimicrobial resistance profiles (ARPs) among broiler, poultry slaughterer and human clinical VREF. PFGE was conducted to study the genetic relatedness among VREF from the different sources.

RESULTS

A total of 120 VRE were recovered from 113 (22.6%) broiler samples. VREF carrying the vanA gene were predominant, being recovered from 72 (14.4%) samples from five (62.5%) broiler farms. Concerning poultry slaughterers, VREF were recovered from 10 (20%) samples. Susceptibility testing revealed that broiler VREF were consistently resistant to tetracycline, whereas 93.7% of clinical VREF were resistant to ampicillin. Furthermore, 92.1% of clinical VREF compared with 54.4% of broiler VREF were multiresistant (resistant to at least five antimicrobial classes). DA classified broiler and human clinical VREF into their corresponding source with high classification rates (100% and 85.7%, respectively), while the classification rate of poultry slaughterer VREF was relatively low (50%), with 40% of them classified closely to broiler VREF. PFGE patterns were clearly related to the source of the VREF, with broiler isolates being clustered distinctly from all human isolates.

CONCLUSIONS

A remarkable persistence of VREF was observed in the broiler production environment even >10 years after the avoparcin ban. Human and broiler VREF belonged to clearly unrelated populations, strongly indicating no clonal spread of VREF among the different sources, even between broilers and poultry slaughterers, despite them sharing common ARPs, as also supported by DA.

Effectiveness of ozonation and chlorination on municipal wastewater treatment evaluated by a battery of bioassays and biomarkers

A battery of bioassays, including biological toxicity as well as in vitro mouse spleen lymphoproliferative responses and cytokine production, was conducted to compare the effectiveness of tertiary treatment methods such as coagulation (Coag) and absorption on granular activated carbon (GAC) and disinfection processes such as chlorination and ozonation in removing toxic or stress inducing agents from reclaimed wastewater. Whole effluent toxicity (WET) testing of secondary treated (ST) wastewater using as test species Vibrio fischeri, Daphnia magna and Tetrahymena thermophila as well as phytotoxicity revealed moderate toxicity effects that depend on the organism used. All bioassays exhibited decrease of the ecotoxicological responses after tertiary treatment. However, mitogenic responses were proved to be more sensitive. Endotoxin present in ST samples may be responsible for the increased strong lymphoproliferative activity as well as interleukin-1 (IL-1) production by mouse splenocytes. Tertiary treatment of ST with coagulation and/or adsorption on granular activated carbon (GAC) in combination with ozonation reduced WET to control levels. Ozonation alone or in combination with any other treatment removed endotoxin more efficiently than chlorination and thus reduced spleen lymphoproliferative responses and IL-1 production.

Bioassays and biomarkers for ecotoxicological assessment of reclaimed municipal wastewater

The aim of this work was to examine the ecotoxicity of reclaimed wastewater by the use of bioassays and the determination of immunological parameters. Secondary and tertiary mucicipal wastewater samples were examined for their physicochemical and microbiological characteristics as well as for their endotoxin concentrations. The ecotoxicological characteristics were assessed by a battery of bioassays, using Vibrio fischeri, Daphnia magna and Tetrahymena thermophilla as test species and phytotoxicity. The mitogenic responses of mouse splenocytes were as well used as bioassay. The cytokines of IL-1, IL-2, IL-10, IFNgamma and TNFalpha, were also determined in the supernatant of splenocyte cultures and served as molecular biomarkers. All bioassays exhibited decrease of the ecotoxicological responses after tertiary treatment. However, mitogenic responses were proved to be more sensitive. IL-1 increased, while IL-2 production was unaffected. The fact that IL-10 production increased in response to secondary treated effluents in conjunction with the increased endotoxin levels, suggest Th2 type immune responses. Although results obtained from the toxicity bioassays after the tertiary treatment showed comparable results to those of controls, cytokine levels indicated the induction of immune response even after tertiary treatment. Consequently, cytokine production could be used as a sensitive biomarker for the evaluation of treatment efficiency of the reclaimed wastewaters intended for reuse.

The effect of environmental conditions on the ability of a constructed wetland to disinfect municipal wastewaters

Constructed wetlands are widely used all over the world for the treatment of municipal wastewaters, which are characterized by high concentrations of pathogens. The objectives of this study were (1) to study the effect of solar radiation and temperature on the ability of a constructed wetland to reduce the concentration of total coliforms (TC), and (2) to evaluate the relationship between the presence of Salmonella spp. in the outflow and the concentration of TC. The results of this study showed that under Mediterranean environmental conditions, the percentage reduction in coliforms was lower during winter compared to all other seasons. Maximum removal of coliforms was achieved under conditions of high solar radiation and temperature. In addition, solar radiation was found to play a greater role in coliform die-off at low temperatures than at high temperatures. Finally, it was found that the probability of Salmonella spp. appearance in the outflow of the wetland was related to the concentration of TC. The increase in coliform bacteria in the effluents also increased the chances of Salmonella appearance. The risk of Salmonella spp. appearance in the outflow is minimized when the concentration of TC is below 10(2)/100 mL.

Evaluation of two assays, MSRV and RV, for the isolation of Salmonella spp. from wastewater samples and broiler chickens

The Rappaport Vassiliadis (RV) and the Modified Semi-solid Rappaport Vassiliadis (MSRV) methods were evaluated in 130 municipal wastewater samples and 30 flocks of broilers. Analysis of the results showed that 71 Salmonella serotypes were isolated in wastewater samples. The positivity of the MSRV method was 33% and of the RV method, 45%. The sensitivity was 95% and 83% with the MSRV and RV, respectively. The concordance between the two methods was 89% (k = 0785). One hundred serotypes were isolated from broiler internal organs and 50 from intestinal samples. For internal organs, the positivity of MSRV was 56% and of RV, 45%. For intestinal samples, the respective percentages were 28 and 22. For internal organs, the sensitivity was 100% with MSRV and 81% with RV, whereas for intestinal samples, the sensitivity was 100% with MSRV and 80% with RV. The specificity was 100% in all cases. The concordance between the two methods was 89% (k = 0790) for internal organs and 94% (k = 0851) for intestinal samples.

Copper concentrations in sheep liver and kidney in Greece

Copper liver and kidney concentrations were evaluated from sheep grazing at 2 areas: A (sampling points A1, A2, A3) and B. One hundred forty specimens were measured by flame atomic absorption spectroscopy after wet digestion for the February through April 1995 sampling period. Mean liver concentrations were: Area A (A1 = 99.48, A2 = 62.28, A3 = 23.02 mg/kg ww) and Area B 74.07 mg/kg ww. Copper concentrations in kidneys from all areas were in the normal range.