Comparative evaluation of direct plating and most probable number for enumeration of low levels of Listeria monocytogenes in naturally contaminated ice cream products.

A precise and accurate method for enumeration of low level of Listeria monocytogenes in foods is critical to a variety of studies. In this study, paired comparison of most probable number (MPN) and direct plating enumeration of L. monocytogenes was conducted on a total of 1730 outbreak-associated ice cream samples that were naturally contaminated with low level of L. monocytogenes. MPN was performed on all 1730 samples. Direct plating was performed on all samples using the RAPID'L.mono (RLM) agar (1600 samples) and agar Listeria Ottaviani and Agosti (ALOA; 130 samples). Probabilistic analysis with Bayesian inference model was used to compare paired direct plating and MPN estimates of L. monocytogenes in ice cream samples because assumptions implicit in ordinary least squares (OLS) linear regression analyses were not met for such a comparison. The probabilistic analysis revealed good agreement between the MPN and direct plating estimates, and this agreement showed that the MPN schemes and direct plating schemes using ALOA or RLM evaluated in the present study were suitable for enumerating low levels of L. monocytogenes in these ice cream samples. The statistical analysis further revealed that OLS linear regression analyses of direct plating and MPN data did introduce bias that incorrectly characterized systematic differences between estimates from the two methods.

Prevalence and Level of Listeria monocytogenes in Ice Cream Linked to a Listeriosis Outbreak in the United States.

A most-probable-number (MPN) method was used to enumerate Listeria monocytogenes in 2,320 commercial ice cream scoops manufactured on a production line that was implicated in a 2015 listeriosis outbreak in the United States. The analyzed samples were collected from seven lots produced in November 2014, December 2014, January 2015, and March 2015. L. monocytogenes was detected in 99% (2,307 of 2,320) of the tested samples (lower limit of detection, 0.03 MPN/g), 92% of which were contaminated at <20 MPN/g. The levels of L. monocytogenes in these samples had a geometric mean per lot of 0.15 to 7.1 MPN/g. The prevalence and enumeration data from an unprecedented large number of naturally contaminated ice cream products linked to a listeriosis outbreak provided a unique data set for further understanding the risk associated with L. monocytogenes contamination for highly susceptible populations.

Laboratory, Environmental, and Epidemiologic Investigation and Regulatory Enforcement Actions in Response to an Outbreak of Salmonella Bredeney Infections Linked to Peanut Butter.

Background. In September 2012, the Centers for Disease Control and Prevention (CDC), U.S. Food and Drug Administration (FDA), and state and local partners investigated an outbreak of Salmonella enterica serovar Bredeney linked to peanut butter (PB). Methods. A case was defined as infection with the outbreak strain of Salmonella Bredeney between June 1, 2012 and October 31, 2012. Food exposure questionnaires were analyzed by the CDC to determine the food vehicle. The FDA reviewed production information from Retail Chain A's sole supplier of PB, Company A. The PB samples collected from case-patients and Company A were tested for Salmonella. Results. Forty-two case-patients from 20 states were identified. Of 33 case-patients from whom food exposure information was obtained, 25 (76%) shopped at Retail Chain A and 25 (100%) purchased Company A PB. Three state health departments isolated the outbreak strain from opened jars of PB collected from case-patients. The FDA investigators identified multiple deficiencies in current Good Manufacturing Practices (cGMPs) in Company A's manufacturing facility and determined that internal controls were insufficient to prevent shipment of contaminated product. The FDA isolated the outbreak strain of Salmonella Bredeney from implicated product collected at the firm and the environment of the firm's food production facility. Conclusions. Timely laboratory, investigational, and epidemiologic data led to the voluntary recall of PB by Company A. The FDA suspended Company A's food facility registration, prohibiting the firm from introducing food into interstate commerce. This outbreak underscores the need for effective preventive controls, including robust internal environmental monitoring programs, appropriate action in response to contamination findings, and an improved understanding of food safety at the managerial and corporate levels.

Draft Genome Sequence of Bivalent Clostridium botulinum Strain IBCA10-7060, Encoding Botulinum Neurotoxin B and a New FA Mosaic Type.

Here we report the genome sequence of a Clostridium botulinum strain IBCA10-7060 producing botulinum neurotoxin serotype B and a new toxin serotype. Multilocus sequence typing analysis revealed that this strain belongs to a new sequence type, and whole-genome single nucleotide polymorphism analysis showed that this strain clustered with strains in lineage 2 from group I.

Whole-genome single-nucleotide-polymorphism analysis for discrimination of Clostridium botulinum group I strains.

Clostridium botulinum is a genetically diverse Gram-positive bacterium producing extremely potent neurotoxins (botulinum neurotoxins A through G [BoNT/A-G]). The complete genome sequences of three strains harboring only the BoNT/A1 nucleotide sequence are publicly available. Although these strains contain a toxin cluster (HA(+) OrfX(-)) associated with hemagglutinin genes, little is known about the genomes of subtype A1 strains (termed HA(-) OrfX(+)) that lack hemagglutinin genes in the toxin gene cluster. We sequenced the genomes of three BoNT/A1-producing C. botulinum strains: two strains with the HA(+) OrfX(-) cluster (69A and 32A) and one strain with the HA(-) OrfX(+) cluster (CDC297). Whole-genome phylogenic single-nucleotide-polymorphism (SNP) analysis of these strains along with other publicly available C. botulinum group I strains revealed five distinct lineages. Strains 69A and 32A clustered with the C. botulinum type A1 Hall group, and strain CDC297 clustered with the C. botulinum type Ba4 strain 657. This study reports the use of whole-genome SNP sequence analysis for discrimination of C. botulinum group I strains and demonstrates the utility of this analysis in quickly differentiating C. botulinum strains harboring identical toxin gene subtypes. This analysis further supports previous work showing that strains CDC297 and 657 likely evolved from a common ancestor and independently acquired separate BoNT/A1 toxin gene clusters at distinct genomic locations.

Draft Genome Sequence of a Clostridium botulinum Isolate from Water Used for Cooling at a Plant Producing Low-Acid Canned Foods.

Clostridium botulinum is a pathogen of concern for low-acid canned foods. Here we report draft genomes of a neurotoxin-producing C. botulinum strain isolated from water samples used for cooling low-acid canned foods at a canning facility. The genome sequence confirmed that this strain belonged to C. botulinum serotype B1, albeit with major differences, including thousands of unique single nucleotide polymorphisms (SNPs) compared to other genomes of the same serotype.

National outbreak of type a foodborne botulism associated with a widely distributed commercially canned hot dog chili sauce.

BACKGROUND: On 7 and 11 July 2007, health officials in Texas and Indiana, respectively, reported 4 possible cases of type A foodborne botulism to the US Centers for Disease Control and Prevention. Foodborne botulism is a rare and sometimes fatal illness caused by consuming foods containing botulinum neurotoxin. METHODS: Investigators reviewed patients' medical charts and food histories. Clinical specimens and food samples were tested for botulinum toxin and neurotoxin-producing Clostridium species. Investigators conducted inspections of the cannery that produced the implicated product. RESULTS: Eight confirmed outbreak associated cases were identified from Indiana (n = 2), Texas (n = 3), and Ohio (n = 3). Botulinum toxin type A was identified in leftover chili sauce consumed by the Indiana patients and 1 of the Ohio patients. Cannery inspectors found violations of federal canned-food regulations that could have led to survival of Clostridium botulinum spores during sterilization. The company recalled 39 million cans of chili. Following the outbreak, the US Food and Drug Administration inspected other canneries with similar canning systems and issued warnings to the industry about the danger of C. botulinum and the importance of compliance with canned food manufacturing regulations. CONCLUSIONS: Commercially produced hot dog chili sauce caused these cases of type A botulism. This is the first US foodborne botulism outbreak involving a commercial cannery in >30 years. Sharing of epidemiologic and laboratory findings allowed for the rapid identification of implicated food items and swift removal of potentially deadly products from the market by US food regulatory authorities.

A national outbreak of Salmonella serotype Tennessee infections from contaminated peanut butter: a new food vehicle for salmonellosis in the United States.

BACKGROUND: Salmonella serotype Tennessee is a rare cause of the estimated 1 million cases of salmonellosis occurring annually in the United States. In January 2007, we began investigating a nationwide increase in Salmonella Tennessee infections. METHODS: We defined a case as Salmonella Tennessee infection in a patient whose isolate demonstrated 1 of 3 closely related pulsed-field gel electrophoresis patterns and whose illness began during the period 1 August 2006 through 31 July 2007. We conducted a case-control study in 22 states and performed laboratory testing of foods and environmental samples. RESULTS: We identified 715 cases in 48 states; 37% of isolates were from urine specimens. Illness was associated with consuming peanut butter more than once a week (matched odds ratio [mOR], 3.5 [95% confidence interval {95% CI}, 1.4-9.9]), consuming Brand X peanut butter (mOR, 12.1 [95% CI, 3.6-66.3]), and consuming Brand Y peanut butter (mOR, 9.1 [95% CI, 1.0-433]). Brands X and Y were produced in 1 plant, which ceased production and recalled products on 14 February 2007. Laboratories isolated outbreak strains of Salmonella Tennessee from 34 Brands X and Y peanut butter jars and 2 plant environmental samples. CONCLUSIONS: This large, widespread outbreak of salmonellosis is the first linked to peanut butter in the United States; a nationwide recall resulted in outbreak control. Environmental contamination in the peanut butter plant likely caused this outbreak. This outbreak highlights the risk of salmonellosis from heat-processed foods of nonanimal origin previously felt to be low risk for Salmonella contamination.

Detection and confirmation of Clostridium botulinum in water used for cooling at a plant producing low-acid canned foods.

Our laboratory tested water samples used for cooling low-acid canned foods at a canning facility under investigation by the U.S. Food and Drug Administration. We used an enzyme-linked immunosorbent assay with digoxigenin-labeled antibodies (DIG-ELISA) and real-time PCR as screening methods and confirmed the presence of neurotoxin-producing Clostridium botulinum in the samples by mouse bioassay.

International outbreak of severe botulism with prolonged toxemia caused by commercial carrot juice.

BACKGROUND: On 8 September 2006, 3 Georgia residents presented with symptoms of food-borne botulism, a potentially fatal illness caused by Clostridium botulinum neurotoxins. METHODS: Investigators reviewed medical records and interviewed patients and family members. Foods from patients' homes and samples of the implicated commercial beverage were tested for botulinum toxin and C. botulinum by standard methods. RESULTS: The patients presented with cranial neuropathies and flaccid paralysis; all patients required mechanical ventilation. The 3 Georgia patients had consumed carrot juice from the same bottle before illness onset. An additional case in Florida and 2 in Ontario, Canada, were subsequently identified in patients who had consumed carrot juice. Serum samples obtained from 5 patients tested positive for botulinum toxin type A-in one patient, 12 days after illness onset, and in another patient, 25 days after illness onset. Carrot juice produced by 1 manufacturer, recovered from patients' homes in Georgia, Florida, and Ontario, yielded type A toxin. The juice contained no added sugar, salt, or preservative; inappropriate refrigeration likely resulted in botulinum toxin production. CONCLUSION: This outbreak was caused by commercially produced, internationally distributed carrot juice that was contaminated with botulinum toxin. When toxemia persists, treatment for botulism should be considered even if diagnosed weeks after illness onset. The implicated pasteurized carrot juice had no barriers to growth of C. botulinum other than refrigeration; additional protective measures for carrot juice are needed to prevent future outbreaks. The US Food and Drug Administration has since issued industry guidance to reduce the risk of C. botulinum intoxication from low-acid refrigerated juices.