Most Common Foodborne Pathogens and Mycotoxins on Fresh Produce: A Review of Recent Outbreaks.

Every year millions of people are affected and thousands of them die due to infections and intoxication as a result of foodborne outbreaks, which also cause billions of dollars' worth of damage, public health problems, and agricultural product loss. A considerable portion of these outbreaks is related to fresh produce and caused by foodborne pathogens on fresh produce and mycotoxins. Escherichia coli O104:H4 outbreak, occurred in Germany in 2011, has attracted a great attention on foodborne outbreaks caused by contaminated fresh produce, and especially the vulnerability and gaps in the early warning and notification networks in the surveillance systems in all around the world. In the frame of this paper, we reviewed the most common foodborne pathogens on fresh produce, traceback investigations of the outbreaks caused by these pathogens, and lastly international early warning and notification systems, including PulseNet International and Rapid Alert System for Food and Feed, aiming to detect foodborne outbreaks.

Antimicrobial drug resistance patterns among cattle- and human-associated Salmonella strains.

During the year 2004, 178 human and 158 bovine clinical Salmonella isolates were collected across New York State to better understand the transmission dynamics and genetic determinants of antimicrobial resistance among human and bovine hosts. Serotyping, sequence typing, and pulsed-field gel electrophoresis typing results have been reported previously. Here we tested all isolates for phenotypic susceptibility to 15 antimicrobial drugs that are part of the National Antimicrobial Monitoring System bovine susceptibility panel. PCR was performed on a representative subset of unique isolates (n = 53) to screen for the presence of 21 known antimicrobial resistance genes (i.e., ampC, blaTEM-1, blaCMY-2, blaPSE-1, cat1, cat2, cmlA, flo, aadA1, aadA2, aacC2, strA, strB, aphA1-IAB, dhrfI, dhrfXII, sulI, sulII, tetA, tetB, and tetG); selected fluoroquinolone- and nalidixic acid-resistant (n = 3) and -sensitive (n = 6) isolates were also tested for known resistance-conferring mutations in gyrA and parC. Genes responsible for antimicrobial resistance were shared among isolates of human and bovine origin. However, bovine isolates were significantly more likely than human isolates to be multidrug resistant (P < 0.0001; Fisher's exact test). Our analyses showed perfect categorical agreement between phenotypic and genotypic resistance for beta-lactam and chloramphenicol. Our data confirm that resistance profiles of amoxicillin-clavulanic acid, chloramphenicol, kanamycin, and tetracycline were strongly associated with the presence of blaCMY or ampC, flo, aphA1-IAB, and tetA, respectively. Our findings provide evidence for the clinical value of genotypic resistance typing if incorporating multiple known genes that can confer a phenotypic resistance profile.

The prevalence of multidrug resistance is higher among bovine than human Salmonella enterica serotype Newport, Typhimurium, and 4,5,12:i:- isolates in the United States but differs by serotype and geographic region.

Salmonella represents an important zoonotic pathogen worldwide, but the transmission dynamics between humans and animals as well as within animal populations are incompletely understood. We characterized Salmonella isolates from cattle and humans in two geographic regions of the United States, the Pacific Northwest and the Northeast, using three common subtyping methods (pulsed-field gel electrophoresis [PFGE], multilocus variable number of tandem repeat analysis [MLVA], and multilocus sequence typing [MLST]). In addition, we analyzed the distribution of antimicrobial resistance among human and cattle Salmonella isolates from the two study areas and characterized Salmonella persistence on individual dairy farms. For both Salmonella enterica subsp. enterica serotypes Newport and Typhimurium, we found multidrug resistance to be significantly associated with bovine origin of isolates, with the odds of multidrug resistance for Newport isolates from cattle approximately 18 times higher than for Newport isolates from humans. Isolates from the Northwest were significantly more likely to be multidrug resistant than those from the Northeast, and susceptible and resistant isolates appeared to represent distinct Salmonella subtypes. We detected evidence for strain diversification during Salmonella persistence on farms, which included changes in antimicrobial resistance as well as genetic changes manifested in PFGE and MLVA pattern shifts. While discriminatory power was serotype dependent, the combination of PFGE data with either MLVA or resistance typing data consistently allowed for improved subtype discrimination. Our results are consistent with the idea that cattle are an important reservoir of multidrug-resistant Salmonella infections in humans. In addition, the study provides evidence for the value of including antimicrobial resistance data in epidemiological investigations and highlights the benefits and potential problems of combining subtyping methods.

Salmonella enterica serotype 4,5,12:i:-, an emerging Salmonella serotype that represents multiple distinct clones.

The prevalence, among human clinical cases, of Salmonella enterica serotype 4,5,12:i:-, a serotype antigenically similar to Salmonella enterica serotype Typhimurium but lacking second-phase flagellar antigens, has increased considerably over the last 10 years. To probe the evolution and ecology of this emerging serotype, we characterized 190 Salmonella isolates initially classified as Salmonella serotypes 4,5,12:i:- (n = 90) and Typhimurium (n = 100) and obtained from various sources in the United States and Spain. These isolates were characterized into six sequence types (determined by multilocus sequence typing [MLST]) and 79 pulsed-field gel electrophoresis types. The majority of Salmonella serotype 4,5,12:i:- and Typhimurium isolates (85 and 84 isolates, respectively) represented a single MLST type. Existing genome information revealed different genome deletions (which included genes responsible for phase 2 flagellum expression) in four Spanish Salmonella serotype 4,5,12:i:- isolates and one U.S. Salmonella serotype 4,5,12:i:- isolate. Fifty-nine isolates of both serotypes, representing different sources and geographical locations as well as different molecular subtypes, were thus screened for the presence of six genes and one specific region, all of which were previously found to show variable presence among Salmonella serotype 4,5,12:i:- and Typhimurium strains. All Salmonella serotype 4,5,12:i:- isolates lacked the phase 2 flagella genes fljA and fljB, which were present in all Salmonella serotype Typhimurium isolates. While all Spanish Salmonella serotype 4,5,12:i:- isolates carried the same deletion surrounding fljAB, all but two U.S. isolates showed a different genomic deletion; the two atypical U.S. isolates represented the "Spanish" deletion genotype and a unique deletion genotype. Salmonella serotype 4,5,12:i:- thus appears to represent at least two common clones, which cannot easily be differentiated with standard diagnostic procedures.

Assessing genetic heterogeneity within bacterial species isolated from gastrointestinal and environmental samples: how many isolates does it take?

Strain typing of bacterial isolates is increasingly used to identify sources of infection or product contamination and to elucidate routes of transmission of pathogens or spoilage organisms. Usually, the number of bacterial isolates belonging to the same species that is analyzed per sample is determined by convention, convenience, laboratory capacity, or financial resources. Statistical considerations and knowledge of the heterogeneity of bacterial populations in various sources can be used to determine the number of isolates per sample that is actually needed to address specific research questions. We present data for intestinal Escherichia coli, Listeria monocytogenes, Klebsiella pneumoniae, and Streptococcus uberis from gastrointestinal, fecal, or soil samples characterized by ribotyping, pulsed-field gel electrophoresis, and PCR-based strain-typing methods. In contrast to previous studies, all calculations were performed with a single computer program, employing software that is freely available and with in-depth explanation of the choice and derivation of prior distributions. Also, some of the model assumptions were relaxed to allow analysis of the special case of two (groups of) strains that are observed with different probabilities. Sample size calculations, with a Bayesian method of inference, show that from 2 to 20 isolates per sample need to be characterized to detect all strains that are present in a sample with 95% certainty. Such high numbers of isolates per sample are rarely typed in real life due to financial or logistic constraints. This implies that investigators are not gaining maximal information on strain heterogeneity and that sources and transmission pathways may go undetected.

Multilocus sequence typing supports the hypothesis that cow- and human-associated Salmonella isolates represent distinct and overlapping populations.

A collection of 179 human and 156 bovine clinical Salmonella isolates obtained from across New York state over the course of 1 year was characterized using serotyping and a multilocus sequence typing (MLST) scheme based on the sequencing of three genes (fimA, manB, and mdh). The 335 isolates were differentiated into 52 serotypes and 72 sequence types (STs). Analyses of bovine isolates collected on different farms over time indicated that specific subtypes can persist over time on a given farm; in particular, a number of farms showed evidence for the persistence of a specific Salmonella enterica serotype Newport sequence type. Serotypes and STs were not randomly distributed among human and bovine isolates, and selected serotypes and STs were associated exclusively with either human or bovine sources. A number of common STs were geographically widespread. For example, ST6, which includes isolates representing serotype Typhimurium as well as the emerging serotype 4,5,12:i:-, was found among human and bovine isolates in a number of counties in New York state. Phylogenetic analyses supported the possibility that serotype 4,5,12:i:- is closely related to Salmonella serotype Typhimurium. Salmonella serotype Newport was found to represent two distinct evolutionary lineages that differ in their frequencies among human and bovine isolates. A number of Salmonella isolates carried two copies of manB (33 isolates) or showed small deletion events in fimA (nine isolates); these duplication and deletion events may provide mechanisms for the rapid diversification of Salmonella surface molecules. We conclude that the combined use of an economical three-gene MLST scheme and serotyping can provide considerable new insights into the evolution and transmission of Salmonella.

[Treatment of metastatic renal adenocarcinomas with combined recombinant alpha-2a interferon and vinblastine]. / Traitement des adénocarcinomes rénaux métastatiques par l'association interféron recombinant alpha-2a et vinblastine.

The results of treatment of metastatic renal cell carcinoma have so far been very poor. Many phase II studies have shown that interferon alpha therapy is active in a significant proportion of patients (approximately 10 to 15% complete and partial remission). In the hope of improving these results we have conducted a phase I-II study of the combination of interferon alpha-2a and vinblastine in 21 patients with metastatic renal cell cancer. Side-effects were pronounced and the mean tolerated doses were 12.5 x 10(6) U/m2 interferon alpha three times per week and 0.10 mg/kg vinblastine once every three weeks. We observed a 43% response rate, with 1 complete remission, 8 partial remissions, 4 stabilizations and 8 progressions. These very encouraging results need to be confirmed by large scale studies.