Managerial practices regarding workers working while ill

Surveillance data indicate that handling of food by an ill worker is a cause of almost half of all restaurant-related outbreaks. The U.S. Food and Drug Administration (FDA) Food Code contains recommendations for food service establishments, including restaurants, aimed at reducing the frequency with which food workers work while ill. However, few data exist on the extent to which restaurants have implemented FDA recommendations. The Centers for Disease Control and Prevention's Environmental Health Specialists Network (EHS-Net) conducted a study on the topic of ill food workers in restaurants. We interviewed restaurant managers (n = 426) in nine EHS-Net sites. We found that many restaurant policies concerning ill food workers do not follow FDA recommendations. For example, one-third of the restaurants' policies did not specifically address the circumstances under which ill food workers should be excluded from work (i.e., not be allowed to work). We also found that, in many restaurants, managers are not actively involved in decisions about whether ill food workers should work. Additionally, almost 70% of managers said they had worked while ill; 10% said they had worked while having nausea or "stomach flu," possible symptoms of foodborne illness. When asked why they had worked when ill, a third of the managers said they felt obligated to work or their strong work ethic compelled them to work. Other reasons cited were that the restaurant was understaffed or no one was available to replace them (26%), they felt that their symptoms were mild or not contagious (19%), they had special managerial responsibilities that no one else could fulfill (11%), there was non-food handling work they could do (7%), and they would not get paid if they did not work or the restaurant had no sick leave policy (5%). Data from this study can inform future research and help policy makers target interventions designed to reduce the frequency with which food workers work while ill.

Characterization and pathogenic potential of Listeria monocytogenes isolates from the smoked fish industry

This study was designed to evaluate the hypothesis that some of the Listeria monocytogenes subtypes associated with foods, specifically smoked fish, may have an attenuated ability to cause human disease. We tested this hypothesis by using two different approaches: (i) comparison of molecular subtypes found among 117 isolates from smoked fish, raw materials, fish in process, and processing environments with subtypes found among a collection of 275 human clinical isolates and (ii) the evaluation of the cytopathogenicity of industrial isolates. Ribotyping and PCR-restriction fragment length polymorphism typing of the hlyA and actA genes differentiated 23 subtypes among the industrial isolates and allowed classification of the isolates into three genetic lineages. A significantly higher proportion of human isolates (69.1%) than industrial isolates (36.8%) were classified as lineage I, which contains human sporadic isolates and all epidemic isolates. All other industrial isolates (63.2%) were classified as lineage II, which contains only human sporadic isolates. Lineage I ribotypes DUP-1038B and DUP-1042B represented a significantly higher proportion of the human isolates than industrial isolates (5.1%). Lineage II ribotypes DUP-1039C, DUP-1042C, and DUP-1045, shown previously to persist in the smoked fish processing environment, represented nearly 50% of the industrial isolates, compared to 7.6% of the human isolates. Representatives of each subtype were evaluated with a tissue culture plaque assay. Lineage I isolates formed plaques that were significantly larger than those formed by lineage II isolates. Isolates from the smoked fish industry representing three ribotypes formed no plaques or small plaques, indicating that they had an impaired ability to infect mammalian cells. While L. monocytogenes clonal groups linked to human listeriosis cases and outbreaks were isolated, our data also suggest that at least some L. monocytogenes subtypes present in ready-to-eat foods may have limited human-pathogenic potential.

Molecular studies on the ecology of Listeria monocytogenes in the smoked fish processing industry

We have applied molecular approaches, including PCR-based detection strategies and DNA fingerprinting methods, to study the ecology of Listeria monocytogenes in food processing environments. A total of 531 samples, including raw fish, fish during the cold-smoking process, finished product, and environmental samples, were collected from three smoked fish processing facilities during five visits to each facility. A total of 95 (17.9%) of the samples tested positive for L. monocytogenes using a commercial PCR system (BAX for Screening/Listeria monocytogenes), including 57 (27.7%) environmental samples (n = 206), 8 (7.8%) raw material samples (n = 102), 23 (18.1%) samples from fish in various stages of processing(n = 127), and 7 (7.3%) finished product samples (n = 96). L. monocytogenes was isolated from 85 samples (16.0%) using culture methods. Used in conjunction with a 48-h enrichment in Listeria Enrichment Broth, the PCR system had a sensitivity of 91.8% and a specificity of 96.2%. To track the origin and spread of L. monocytogenes, isolates were fingerprinted by automated ribotyping. Fifteen different ribotypes were identified among 85 isolates tested. Ribotyping data established possible contamination patterns, implicating raw materials and the processing environment as potential sources of finished product contamination. Analysis of the distribution of ribotypes revealed that each processing facility had a unique contamination pattern and that specific ribotypes persisted in the environments of two facilities over time (P < or = 0.0006). We conclude that application of molecular approaches can provide critical information on the ecology of different L. monocytogenes strains in food processing environments. This information can be used to develop practical recommendations for improved control of this important food-borne pathogen in the food industry.

Synthesis and characterization of a polycarbon organometallic cluster, [PPN]2[Fe6(CO)18C4]

The polycarbon metal cluster [Fe6(CO)18C4]2- is formed by the reaction of CF3SO3SO2CF3 with [Fe3(CO)9(CCO)]2-. Apparently, the SO2CF3 moiety abstracts an oxygen from the ketenylidene (CCO) ligand and C-C coupling occurs to form the C4 ligand. A single-crystal X-ray structure determination reveals that the pattern of C-C bond lengths of the C4 ligand in [Fe6(CO)18C4]2- mimic those in free butadiene.

Application of the BAX for screening/genus Listeria polymerase chain reaction system for monitoring Listeria species in cold-smoked fish and in the smoked fish processing environment

The cold-smoked fish industry was used as a model for the development of a system for monitoring Listeria spp. in foods and in the food processing environment. A total of 214 samples including raw fish, fish during the cold-smoking process, finished product, and environmental samples were collected from three processing facilities over two visits to each facility. Samples were screened for Listeria spp. using the BAX for Screening/genus Listeria polymerase chain reaction system (PCR) and by culture. Listeria spp., confirmed by the API Listeria test strip or by a PCR assay targeting the L. monocytogenes hlyA gene, were isolated from a total of 89 (41.6%) samples. Of these, 80 samples also tested positive for Listeria spp. using the BAX system. Specifically, 42 (55.3%) environmental samples (n = 76), 11 (25.6%) raw materials samples (n = 43), 20 (35.1%) samples from fish in various stages of processing (n = 57), and 7 (18.4%) finished product samples (n = 38) tested positive for Listeria spp. using the BAX system. Five (4.0%) of the 125 culture-negative samples yielded BAX system-positive results. Listeria isolates from each of nine culture-positive/BAX system-negative samples yielded a positive reaction when tested in pure culture by the BAX system, suggesting that our false-negative results were likely due to the presence of low Listeria numbers in the initial enrichment as opposed to nonreacting isolates. The employment of alternative enrichment protocols, such as the two-step enrichment recommended by the manufacturer, may increase the sensitivity of the assay.

Detection of viable Listeria monocytogenes with a 5' nuclease PCR assay

A 5' nuclease assay has been developed to detect viable Listeria monocytogenes. The assay targets the hemolysin A (hlyA) transcript, which is found only in L. monocytogenes. The single-tube, reverse transcriptase (RT), fluorogenic probe-based assay was formatted by using Tth DNA polymerase whose activity was modulated by using the manganese-chelating morpholinepropanesulfonic acid (MOPS) buffer. This assay was quantitative over a 3-log-unit range of template concentrations when tested with an in vitro-transcribed hlyA mRNA. The viability of L. monocytogenes was reduced by heating at various temperatures and times up to a maximum of a 9-D inactivation. The location of the primer had a pronounced effect on the utility of the assay, and primers located in the most distal regions of the hlyA transcript appeared to correlate with the number of CFU while primers located more internal on the amplicon overestimated the cell viability. The assay with primers that included the 3' end of the transcript was an accurate indicator of viability as measured by CFU determination or staining with 5-sulfofluorescein diacetate.