Comparison of Vibrio parahaemolyticus isolates from aquatic products and clinical by antibiotic susceptibility,virulence, and molecular characterisation

Vibrio parahaemolyticus is a common foodborne pathogen found in aquatic products and represents a major threat to human health worldwide. Though not all this bacteria were harmful to human beings, the pathogenic V. parahaemolyticus always harbors either tdh (the thermostable direct hemolysin) or trh (TDH-related hemolysin) gene, or both. Additionally, the extensive use of antibiotics has been shown to be a contributing factor to the increasing incidence of antimicrobial-resistant strains. In this study, thirty-one clinical isolates were examined and compared with 95 (38.0%) aquatic product isolates (fishes, n = 28; shrimps, n = 67) collected from 250 samples in Guangdong, China. All isolates were studied by antibiotic susceptibility analysis, tdh and trh genes detection, serotyping and molecular typing (ERIC-PCR). The antimicrobial resistance patterns of these aquatic product isolates to 12 antimicrobial agents revealed that most of the isolates were resistant to streptomycin (90.53%). The isolates were also resistant to follow by ampicillin (33.68%) and cephalothin (30.53%). For clinical isolates, they were resistant to streptomycin (93.55%), ampicillin (87.10%), and cefazolin (64.52%). All isolates showed no resistance to azitromycin, chloramphenicol, ciprofloxacin, or nalidixic acid. The clinical isolates were positive for tdh (100%) and trh gene (77.42%), with ratios of only 2.11% and 28.42%, respectively in the aquatic product isolates. Serotyping detected shown that the isolates contained O1, O2, O3, O4, and O11, with the O3 serotype being the most common among the clinical isolates (48.39%), while the O2 (41.05%) makes the maximum proportion on aquatic product isolates. ERIC-PCR results demonstrated the isolates (n = 126) were classified into eight clusters, revealing genetic variation and relatedness between clinical and aquatic product isolates. This study provided a foundation for understanding the distinction between aquatic product and clinical isolates and yielded basic information for achieving food safety through control of V. parahaemolyticus contamination.     

Comparison of antibiotic resistance patterns in Listeria monocytogenes and Salmonella enterica strains pre-exposed and exposed to poultry decontaminants

Recent opinions expressed by European Union Scientific Committees suggest there is a potential for poultry decontaminants to increase resistance to antibiotics. At this moment there is no scientific information available to estimate this risk accurately. Four strains (Listeria monocytogenes serovar 1/2a, Listeria monocytogenes serovar 4b, Salmonella enterica serotype Typhimurium and Salmonella enterica serotype Enteritidis) were repeatedly exposed to increasing sub-inhibitory concentrations of decontaminants (trisodium phosphate, acidified sodium chlorite, citric acid, chlorine dioxide or peroxyacetic acid) and tested against 15 antibiotics by means of a standard disc-diffusion technique (NCCLS). The antibiotic resistance patterns of strains were compared before and after exposure to decontaminants. Intra-specific differences in antibiotic resistance patterns were found among strains. Increases in resistance to various antibiotics were observed in L. monocytogenes and S. enterica strains after exposure to chemicals (especially ASC). These results raise concerns over the application of certain poultry decontaminants, since they could contribute to the development of microbial resistance mechanisms. However, these are preliminary results derived from laboratory-based experiments. Additional studies under practical field conditions would be needed to substantiate these findings.     

A small study of Yersinia enterocolitica in pigs from birth to carcass and characterisation of porcine and human strains

The objectives of this study were to investigate the present of Yersinia enterocolitica at the different stages of production from birth to chilled carcasses; to characterise the isolates in terms of bioserotype, virulence factors (ail, ystA, ystB, inv, yadA and virF) and antibiotic resistance profiles and to examine strains causing diarrheal illness in Ireland. Rectal, throat, floor, partition, wall and/or carcass swabs and water samples were testing for Y. enterocolitica using the bacteriological analytical method. Presumptive positive isolates were confirmed using API 20E strips. The isolates were then combined with 10 clinical strains, biotyped, serotyped, their antibiotic resistance phenotypes determined by disc diffusion and tested for the presence of ail, ystA, ystB, inv, yadA and virF genes using multiplex PCR assays. Y. enterocolitica had an overall prevalence rate of 0.55% (4/726). Y. enterocolitica 2/O:9 and 1A/O:9 were detected on the farm and/or in the abattoir. The clinical isolates were 1A/O:5, 1A/O:8, 1A/O:9, 2/O:9 or 4/O:9. All biotype 1A strains were ail, ystA, yadA and virF negative but carried the ystB gene. All biotype 2 and 4 strains were ail, ystA, yadA and virF positive. Resistant to cephalothin, ampicillin and amoxicillin/clavulanic acid was common and one 2/O:9 strain was resistant to compound sulphonamides and tetracycline. Intermediate resistance to neomycin and streptomycin was also observed. The data presented may explain the low incidence of yersiniosis in Ireland and suggests that biotype 1A may present a public health risk. Neomycin and tetracycline resistance have rarely been reported in Y. enterocolitica and should be monitored in future surveillance studies.     

Occurrence and antibiotic resistance profiles of Listeria monocytogenes isolated from seafood products and market and processing environments in Iran

This study was designed to determine the occurrence of Listeria monocytogenes in popular seafood products and their market and processing environments. The frequency of L. monocytogenes contamination was found to be 4.83% in raw and 14.5% in RTE seafood products. In raw products, the prevalence of L. monocytogenes was significantly higher (P < 0.05) in freshwater fish (11.4%) than in seawater fish (1.80%) and shrimp (1.69%). Cold-smoked fish had the highest frequency of L. monocytogenes contamination among the RTE products. The microbial load of L. monocytogenes in seafood products was in the range of <0.3 to 1100 MPN/g; and did not exceed 100 MPN/g in most of the examined samples. The incidence of L. monocytogenes in environmental and personnel samples was 17.1% and 16.2% in markets, and 21.3% and 18.2% in processing plants, respectively. It was found that contamination of processed fish fillets and shrimp flesh with L. monocytogenes mainly originated from the processing environments, rather than the raw materials. In addition, the implemented cleaning procedures were insufficient to eliminate L. monocytogenes from the market and processing environments. Serological examinations revealed that serotype 1/2a (45.7%) was the predominant serotype of L. monocytogenes followed by 4b (40.3%), 1/2c (5.39%), 1/2b (4.68%), and 4c (3.96%). Regarding seasonal variability, 1/2a was the dominant serotype during warm seasons, whereas 4b was the most prevalent serotype during cold seasons. The isolates of L. monocytogenes were highly resistant to penicillin, ampicillin, tetracycline, and vancomycin. The results indicate that prevalence of L. monocytogenes serotypes 1/2a and 4b, which are associated with foodborne outbreaks of human listeriosis; and their resistance to commonly used antibiotics for treatment of human listeriosis could be a public health concern.     

Antimicrobial resistance and virulence genes of Arcobacter isolates recovered from edible bivalve molluscs

The goals of this study were to assess the prevalence, antimicrobial susceptibility and the presence of virulence genes of arcobacters recovered from edible bivalve molluscs. A total of 106 samples (21 clams, 18 mussels, 20 oysters, 20 razor clams, 11 scallops and 16 surf clams) were analysed by culture between 2010 and 2013. The obtained colonies were identified by multiplex PCR and PCR-RFLP and genotyped by ERIC-PCR. Furthermore, nine putative virulence genes (cadF, ciaB, cjl349, irgA, hecA, hecB, mviN, pldA and tlyA) were assessed by PCR and the antimicrobial resistance was tested by the dilution agar method. The global prevalence was 40.5%, with the highest value in surf clams (87.5%) followed by razor clams (65.0%), mussels (33.3%), clams (23.8%), scallops (18.0%) and oysters (15.0%). The most commonly found species was Arcobacter butzleri (62%) followed by Arcobacter cryaerophilus (21%), Arcobacter skirrowii (16%) and Arcobacter defluvii (1%). A high resistance was found to nalidixic acid and ampicillin, while the predominant detected virulence genes were mviN (83.8%), ciaB (82.8%) and tlyA (72.7%). Our results indicate a high prevalence of arcobacters in shellfish and the pathogenic potential of the recovered isolates suggests that this type of food could be a plausible transmission route of virulent strains to humans.     

Occurrence,antimicrobial resistance and biofilm formation of Salmonella isolates from a chicken slaughter plant in China

An investigation was undertaken to determine the occurrence, antibiotic resistance and biofilm formation of Salmonella spp. isolated from a chicken slaughter plant in Anhui, China. A total of 104 samples (52 from chicken carcasses and 52 from processing contact-surfaces) were collected from three processing points in a chicken slaughterhouse. The 23 isolates (22.1%, 23/104) were confirmed for Salmonella and belonged to six different serotypes, including S. Indiana (n = 9), S. Infantis (n = 4), S. Derby (n = 3), S. Heidelberg (n = 2), S. Agona (n = 2) and S. Typhimurium (n = 1), whereas two isolates (n = 2) were non-typable. Significant differences in occurrence were found between post-evisceration, post-chilling and post-grading processing points. A total of 20 (87%, 20/23) isolates were resistant to at least one antibiotic, of which 19 isolates (95%, 19/20) showed 13 multiple antibiotic resistance patterns against 11 different antibiotics. Resistance to ampicillin (78.3%, 18/23) was the most common. The multiple antibiotic resistance (MAR) index varied from 0.27 to 0.91. The Salmonella isolates from the chicken plant and from humans in the same area who were suffering Salmonella infections showed similar antimicrobial resistance patterns, namely resistance to ampicillin, trimethoprim/sulfamethoxazole, gentamicin, chloramphenicol and tretracycline, and abbreviated as “ATsGCT”. Meanwhile, Salmonella isolates exhibited variation in biofilm-forming behavior with regards to the incubation media and serotypes, a relatively high biofilm production was observed for S. Agona incubated in MTLB (meat thawing-loss broth) at 72 h. There was no significant correlation between antimicrobial resistance and biofilm formation of isolates. Our findings provide baseline information on the distribution of Salmonella serovars in this plant, and provide support to the need for improved farming practice and for more prudent use of antimicrobial agents.     

Prevalence,antibiotic resistance and genetic diversity of Listeria monocytogenes isolated from retail ready-to-eat foods in China

Listeria monocytogenes is a major foodborne pathogen that is well known as high mortality rate upon infected. This study aimed to investigate the prevalence of L. monocytogenes isolates from retail ready-to-eat (RTE) foods in China and characterize the isolates of L. monocytogenes by antibiotic resistance, serotyping, ERIC-PCR and REP-PCR subtyping analyses. From September 2012 to January 2014, a total of 364 retail RTE foods were obtained. Using the qualitative and quantitative methods, 25 samples (6.87%) were positive for L. monocytogenes. The identity of isolates of L. monocytogenes was confirmed by PCR. All 80 isolates in this survey were sensitive to penicillin and mezlocillin, the highest resistance is clindamycin (51.25%), followed by cephalothin (23.75%) and ampicillin (12.5%). Twenty-seven isolates were susceptible to all 14 tested antibiotics; seventeen isolates were resistant to more than two antibiotics, including six multiresistent strains resist to more than 10 antibiotics. L. monocytogenes isolates belonged to serovar types 1/2a (3a), 4b (4d, 4e), 1/2b (3b, 7) and 1/2c (3c). 29 L. monocytogenes isolates were selected by serotyping. At the relative similarity coefficient of 0.80, it grouped 29 isolates and 5 reference strains into 2 clusters and 3 singletons, 4 clusters and 1 singleton by ERIC-PCR and REP-PCR, respectively. Our study reflects the potential risk of L. monocytogenes infection in China. We also provide a comprehensive surveillance on its incidence on the RTE foods of L. monocytogenes and ensure more accurate treatment of human listeriosis with effective antibiotics.     

Prevalence and antimicrobial resistance of Staphylococcus aureus isolated from raw milk and dairy products

The objectives of this study were to determine the prevalence and antimicrobial resistance of Staphylococcus aureus isolated from raw milk (cow and sheep) and dairy products (traditional cheese and kashk) in Mazandaran Province, Iran. A total of 2650 samples, including 1930 raw milk and 720 dairy products were purchased from retail stores. Out of 2650 samples, S. aureus was detected in 328 samples (12.4%) in which 53 (16.2%) were positive for methicillin-resistant S. aureus. The S. aureus isolates showed resistance to tetracycline (56.1%), followed by penicillin G (47.3%), oxacillin (16.2%), lincomycin (11.9%), clindamycin (11.3%), erythromycin (7.9%), streptomycin (5.8%), cefoxitin (5.5%), kanamycin (4%), chloramphenicol (3.7%), and gentamicin (2.1%). A high frequency of blaZ (46%) and tetM (34.8%) resistance genes was found in S. aureus isolates. The findings of this study revealed consumption of raw milk and dairy products as a potential risk of foodborne infection in this region.     

Prevalence,acquired antibiotic resistance and bacteriocin production of Enterococcus spp. isolated from tunisian fermented food products

In this study, a total of 100 fermented food products including dairy (Lben, Rayeb, Rigouta, and Jben) olive and vegetable products, harvested in Northwestern Tunisia, were investigated for the presence of Enterococcus spp. Our results showed high levels of contamination with Enterococcus spp., identified according to standard bacteriological, biochemical and phenotypic criteria. 143 isolates were recovered; E. faecium (46.15%) was the predominant species, followed by E. faecalis (27.27%), E. casseliflavus (12.58%), E. durans (8.39%) and E. mundtii (5.59%). None of the isolates showed acquired resistance againts clinically relevant drugs used for enterococcal infections treatment in human medicins, and no haemolytic activity was demonstrated. Furthermore, over 50% of the isolates within each species exhibited antilisterial bacteriocin production. Further data are needed to enhance understanding of bacteriocin production of enterococci in fermented food products as well as the potential risks to quality and safety, including possible transmission of antibiotic resistant organisms to human consumers.     

Trends in the occurrence and characteristics of Campylobacter jejuni and Campylobacter coli isolates from poultry meat in Northern Poland

The aim of this study was to investigate the occurrence of Campylobacter spp. in poultry meat available in retail stores in the northern part of Poland during a five-year period (2009–2013). A total of 742 poultry meat samples were collected from butcher shops and supermarkets including the following types of samples: chicken breast filets (n = 133), turkey breast filets (n = 112), chicken wings (n = 135), chicken leg quarters (n = 128), chicken drumsticks (n = 115), and chicken giblets (n = 119).The results indicated that 41.6% of the samples were positive for Campylobacter spp., and Campylobacter jejuni was predominant in this study. The prevalence of Campylobacter spp. changed during the study period, decreasing from 60.2% in 2009 to 32% in 2013.The characterization of the isolates revealed a high prevalence of Campylobacter virulence genes. All Campylobacter spp. isolates from poultry meat contained the cadF gene, which is responsible for adherence. The flaA gene, which is involved in motility, was present in all C. jejuni and Campylobacter coli strains. The cdtB, which is associated with toxin production, was present in 93.3% of C. jejuni strains and 89.6% of C. coli strains. The iam gene, which is associated with the invasiveness of Campylobacter spp., was predominant in C. coli strains (95.6%) compared to C. jejuni strains (84.5%).Resistance to four antimicrobials was also examined. The prevalence of resistance among the obtained C. jejuni and C. coli isolates was as follows: ciprofloxacin (62.8% and 72.2%, respectively), tetracycline (42.3% and 42.6%, respectively), erythromycin (3% and 1.7%, respectively) and azithromycin (1%). Multidrug resistance was more frequent among C. jejuni isolates (29.8%) than among C. coli isolates (18.2%).In conclusion, the results of this study demonstrated the importance of poultry meat as a source of Campylobacter spp., especially macrolide-resistant strains. The trend of decreasing Campylobacter spp. occurrence in retail poultry meat in this region of Poland requires further investigation, and monitoring.     

Occurrence and factors associated with aflatoxin contamination of raw peanuts from Lusaka district's markets,Zambia

Peanuts, one of the most susceptible crops to aflatoxin (AF) contamination, are widely produced and consumed in Zambia. This cross-sectional study was designed to determine the levels of AFs in raw peanuts sold in Lusaka district's markets as well as identify factors associated with increased AF presence. Raw peanut samples were collected from open markets and supermarkets and analyzed for aflatoxin contamination using high performance liquid chromatography (HPLC). A questionnaire was also administered to the peanut vendors to investigate factors contributing to increased levels of AFs in peanuts. Of the 92 samples, 51 (55.4%; 95% CI: 44.9–65.4) tested positive for presence of AFs. The overall median and geometric mean ± standard deviation (SD) concentration for AF were 0.23 ppb (range: 0.014–48.67 ppb) and 0.43 ± 9.77 ppb, respectively. The association between market types and presence of AFs was not statistically significant (Pearson Χ² = 0.0587, p = 0.809). Of 51 samples that tested positive to AF, 6.5% and 12% were above the maximum permissible limits (MPLs) set by the Codex Alimentarius Commission and European Union standards, respectively. There was a significant difference in the levels of AF between Chalimbana and Kadononga (p<0.0001), and also Chalimbana and Makulu red (p<0.0001). Chalimbana was the most at risk of AF contamination, when compared to other peanut varieties. The high level of AFs in raw peanuts from both supermarkets and open markets samples constitutes a health hazard for the population of Lusaka district. Therefore, intervention strategies that reduce the levels of AF contamination in peanuts should be given priority.     

Prevalence and characterization of Escherichia coli O157:H7 from samples along the production line in Chinese beef-processing plants

This work investigated the prevalence of Escherichia coli O157:H7 and the antibiotic susceptibility, genetic diversity and virulence genes of isolated strains from four beef slaughter plants in China. A total of 510 samples (feces, hide, carcasses and raw meat) were tested for E. coli O157:H7 using enrichment, immunomagnetic separation, and plating on selective media. The prevalence of E. coli O157:H7 in the feces, hide, pre-evisceration carcass, post-evisceration carcass, post-washing carcass, chilled carcass, and raw meat samples was 1.43%, 1.43%, 0%, 0%, 0%, 1.25%, and 0%, respectively. Multiplex PCR assays were used for serotype confirmation and virulence gene detection. stx₂, eaeA and EHEC-hlyA genes were present in all six of the strains, and the stx₁ gene was not present. Fluorescence amplified fragment length polymorphism (FAFLP) was used to determine the genetic diversity of E. coli O157:H7 and revealed a high similarity between the strains isolated from feces and those isolated from carcasses. None of the isolated strains were found to be resistant to sixteen commonly used antimicrobial agents. The results of this study indicate that although E. coli O157:H7 contamination in the Chinese beef industry is sporadic and not as common as reported in other counties, all of the isolates contained three major virulence genes, presenting a high risk of disease for humans. The current research provides baseline information on E. coli O157:H7 prevalence and character profiles in Chinese beef-processing plants that can be used for future studies.     

Occurrence of aflatoxin M1 in white cheese samples from Tehran, Iran

This study was undertaken to determine the occurrence of aflatoxin M₁ (AFM₁) in 50 white cheese samples from 2 dairy factories in summer 2008 and winter 2009. Enzyme-linked immunosorbent assay (ELISA) method was used for analysis of the samples. Aflatoxin M₁ was found in 60% of the cheese samples, ranging from 40.9 to 374 ng/kg. Toxin levels in 6% of the samples exceeded the Iranian national standard limit i.e. 200 ng/kg. Considering seasonal variability, mean concentration of AFM₁ in the samples collected in winter was significantly (P < 0.03) higher than those collected in summer. Therefore, high occurrence of AFM₁ in cheese samples could be a potential hazard for public health.     

Prevalence and characterization of Yersinia enterocolitica isolated from retail foods in China

Yersinia enterocolitica is an important food-borne enteropathogen that causes gastrointestinal syndromes. The aims of this study were to identify Y. enterocolitica in food samples in China, and to assess the pathogenic potential and antimicrobial resistance, and to characterize the genotypes of the isolates. From July 2011 to May 2014, a total of 2320 food samples were obtained, and 47 (2.03%) were found positive for Y. enterocolitica, while 706 retail-level ready-to-eat products and 249 vegetable samples were negative. A total of 58 Y. enterocolitica strains were isolated. All isolates belonged to biotype 1A, and the primary serotype was O:8. All strains lacked the ail, virF, ystA, and ystC virulence genes, but harbored the ystB, fepD, ymoA, fes, and sat genes. All 58 strains were sensitive to kanamycin and sulfonamide, but were resistant to two or more antibiotics. Most of the strains expressed the β-lactamase genes; the presence of blaA and blaB was detected in 97% and 100% of isolates, respectively. Many strains were resistant to trimethoprim/sulfamethoxazole (79.3%), ampicillin (91.4%), and cephalothin (91.4%). The 58 strains were grouped into three clusters and one singleton by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) at a similarity coefficient of 70%, and each cluster was largely organized by geographical region. This study provides a valuable accounting of the prevalence of Y. enterocolitica from a nationwide survey of foods in China, and highlights the seasonal effects of Y. enterocolitica prevalence in foods in China for the first time.     

北萨哈林盆地油气成藏主控因素及有利区带分析

北萨哈林盆地属于中新生代弧后盆地,发育中、上中新统奥科贝凯组页岩、上中新统努托瓦组下段页岩、下中新统威宁组和中、下中新统达吉组含煤层系3套烃源岩。主力产层为中、下中新统的达吉组砂岩和上中新统努托瓦组下段砂岩。圈闭类型为背斜、复杂断背斜和断块。统计分析表明,平面上油气主要聚集在盆地东北萨哈林次盆,并且海上油气储量、油气田规模均大于陆上;垂向上油气主要分布在中新统达吉组和上中新统努托瓦组。油气成藏条件综合评价分析认为,盆地油气分布主要受构造和储层两方面因素的控制：上新世晚期形成的构造圈闭是油气聚集的主要场所,上新世晚期—全新世萨哈林褶皱幕对早期形成的圈闭起调整或破坏作用;中、下中新统达吉组和上中新统努托瓦组下段砂岩的展布控制了油气藏的纵横向分布。油气勘探结果表明,东北萨哈林次盆陆上部分勘探程度较高,海上是近几年的储量增长区,也是今后最具勘探潜力的地区,其勘探目的层主要为努托瓦组和达吉组,勘探目标主要为构造—地层型圈闭和地层型圈闭。     

Safety aspects, genetic diversity and technological characterisation of wild-type Streptococcus thermophilus strains isolated from north Italian traditional cheeses

Antibiotic susceptibility, antimicrobial activity, genotypic and technological properties of 52 Streptococcus thermophilus isolates, collected from four north Italian traditional cheeses, was investigated. RAPD-PCR, was used to study genetic variability and distinguish closely related strains; the results showed a high degree of heterogeneity among isolates. With regard to technological properties, after 6 h of incubation in milk 25% of the streptococcal strains could be defined as fast acid producers, while after 24 h the majority of isolates (79%) displayed only weak acidification activity. Reduction activity was generally low; in fact, none of these S. thermophilus strains showed a Eh < −102 mV). All the studied S. thermophilus were susceptible to ciprofloxacin, levofloxacin, penicillin G, ampicillin, mupirocin, nitrofurantoin, quinupristin/dalfopristin and rifampicin. Nine isolates were classified as resistant to tetracycline, 6 to streptomycin, 5 to oxacillin, 3 to erytromycin, 3 to vancomycin and only one to chloramphenicol. PCR-based detection did not identify any of the common genetic determinants for vancomycin (vanA, vanB, vanC1, vanC2, vanC3, vanD, vanE, vanG) or erythromycin (ermB and ermC). The genetic basis of the tetracycline resistance phenotype in these strains was linked to tetS-tetL genes (8 isolates) or the tetM gene (1 isolate), and the integrase element int of the Tn916/Tn1545 family of transposons was negative. Four strains were able to produce antimicrobial compounds against Clostridium tyrobutyricum. The study provides new evidence of the resistance of S. thermophilus to antimicrobial agents, confirming the importance of including an accurate safety assessment of phenotypic/biotechnological data when carrying out strain selection for dairy applications.     

Occurrence of Vibrio spp. in sea fish, shrimps and bivalve molluscs harvested from Adriatic sea

One hundred and seventeen samples of sea fish (100), shrimps (10) and bivalve molluscs (7) were sampled at fish markets (100 samples) and hotels (17 samples) along the sea side in Croatia within the period from May to July 2000. The samples were tested for the presence of Vibrio spp. Vibrio spp. was isolated in 23 (19.65%) of total count of samples. The most frequently found were V. parahaemolyticus (9.40%), V. vulnificus (6.84%) and V. alginolyticus (3.42%). A significantly larger number of positive findings involved the samples collected at hotels (35.29%) as compared to those collected at fish markets (17.00%). The isolation was conducted by a conventional cultivation with the enrichment in alkaline peptone water and on TCBS Kobayashi agar (“Biolife”).     

Occurrence of Listeria monocytogenes and Salmonella spp. in meat processed products from industrial plants in Southern Italy

The main goal of the present investigation was to assess the microbiological safety of two typical meat-derived products, i.e. raw pork sausages and entrails lamb rolls, produced in Salento (Apulia, Southern Italy). Analyses were carried out for 7 years (from 2008 to 2014) and a total number of 6720 samples was collected by specialized personnel. The presence of Listeria monocytogenes and Salmonella spp. was detected by a PCR-based assay, combined with culturing in enrichment broth. The prevalence of L. monocytogenes was assessed in 2.4% entrails lamb rolls and in 4.2% raw pork sausages samples, whereas the occurrence of Salmonella spp. was revealed in 2.7% lamb rolls and in 3.5% pork sausages. A statistically significant seasonal variation was found in the occurrence of L. monocytogenes; in fact a higher number of samples contaminated by this pathogen was recorded in spring and autumn. On the contrary, no significant seasonal changes occurred in the prevalence of Salmonella spp. The data reported indicate that, due to the presence of these pathogens, the Italian food processors need to improve the microbiological monitoring of the processing chains, in order to guarantee health safety.     

Comparison of Oxford Agar, PALCAM and Listeria monocytogenes Blood Agar for the recovery of L. monocytogenes from foods and environmental samples

This work had as the main objective a comparison between Listeria monocytogenes Blood Agar (LMBA) and the conventional selective agar media, Oxford and PALCAM, relative to its efficacy in the detection of L. monocytogenes in naturally contaminated food and environmental samples. 173 environmental samples and 272 samples of foods were analysed. A higher sensitivity for detection of L. monocytogenes was verified for LMBA than for PALCAM and Oxford. In LMBA L. monocytogenes could be distinguished from other Listeria spp. by detection of hemolysis. In Oxford and PALCAM this distinction was not possible. The higher growth rate of L. innocua cf. L. monocytogenes in selective liquid media could result in a high number of false negatives (non-detection of the target organism on plates, although its presence was observed by other tests, eg. mini-VIDAS LMO). The need for specific media for the detection of L. monocytogenes in food was confirmed. LMBA could be an alternative medium to use together with PALCAM or Oxford.