Incidence and Trends of Infections with Pathogens Transmitted Commonly Through Food and the Effect of Increasing Use of Culture-Independent Diagnostic Tests on Surveillance - Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2013-2016.

Foodborne diseases represent a substantial public health concern in the United States. CDC's Foodborne Diseases Active Surveillance Network (FoodNet) monitors cases reported from 10 U.S. sites* of laboratory-diagnosed infections caused by nine enteric pathogens commonly transmitted through food. This report describes preliminary surveillance data for 2016 on the nine pathogens and changes in incidences compared with 2013-2015. In 2016, FoodNet identified 24,029 infections, 5,512 hospitalizations, and 98 deaths caused by these pathogens. The use of culture-independent diagnostic tests (CIDTs) by clinical laboratories to detect enteric pathogens has been steadily increasing since FoodNet began surveying clinical laboratories in 2010 (1). CIDTs complicate the interpretation of FoodNet surveillance data because pathogen detection could be affected by changes in health care provider behaviors or laboratory testing practices (2). Health care providers might be more likely to order CIDTs because these tests are quicker and easier to use than traditional culture methods, a circumstance that could increase pathogen detection (3). Similarly, pathogen detection could also be increasing as clinical laboratories adopt DNA-based syndromic panels, which include pathogens not often included in routine stool culture (4,5). In addition, CIDTs do not yield isolates, which public health officials rely on to distinguish pathogen subtypes, determine antimicrobial resistance, monitor trends, and detect outbreaks. To obtain isolates for infections identified by CIDTs, laboratories must perform reflex culture†; if clinical laboratories do not, the burden of culturing falls to state public health laboratories, which might not be able to absorb that burden as the adoption of these tests increases (2). Strategies are needed to preserve access to bacterial isolates for further characterization and to determine the effect of changing trends in testing practices on surveillance.

Cryptosporidiosis outbreak at an academic animal research laboratory-Colorado, 2014.

BACKGROUND: After cryptosporidiosis was reported in three workers caring for preweaned calves at an academic research laboratory, we sought to identify cases, determine risk factors, and implement control measures. METHODS: A cryptosporidiosis case was defined as diarrhea duration ≥72 hr, abdominal cramps, or vomiting in an animal research laboratory worker during July 14-July 31. A confirmed case had laboratory evidence of Cryptosporidium infection. Staff were interviewed regarding illness, potential exposures, training, and personal protective equipment (PPE) standard operating procedures (SOPs). RESULTS: The cryptosporidiosis attack rate (AR) was 74% (20/27); five were laboratory-confirmed. Median job training was 2 hr including respiratory-fit testing. No SOPs existed for doffing PPE. AR for workers who removed their gloves first was 84% (16/19) compared with 20% (1/5) for workers who removed gloves last (risk ratio = 4.2; P < 0.02). CONCLUSIONS: This outbreak highlights the importance of adequate training, enforced proper PPE procedures, and promoting a culture of safety. Am. J. Ind. Med. 60:208-214, 2017. © 2017 Wiley Periodicals, Inc.

Multistate outbreak of listeriosis associated with cantaloupe.

BACKGROUND: Although new pathogen-vehicle combinations are increasingly being identified in produce-related disease outbreaks, fresh produce is a rarely recognized vehicle for listeriosis. We investigated a nationwide listeriosis outbreak that occurred in the United States during 2011. METHODS: We defined an outbreak-related case as a laboratory-confirmed infection with any of five outbreak-related subtypes of Listeria monocytogenes isolated during the period from August 1 through October 31, 2011. Multistate epidemiologic, trace-back, and environmental investigations were conducted, and outbreak-related cases were compared with sporadic cases reported previously to the Listeria Initiative, an enhanced surveillance system that routinely collects detailed information about U.S. cases of listeriosis. RESULTS: We identified 147 outbreak-related cases in 28 states. The majority of patients (127 of 147, 86%) were 60 years of age or older. Seven infections among pregnant women and newborns and one related miscarriage were reported. Of 145 patients for whom information about hospitalization was available, 143 (99%) were hospitalized. Thirty-three of the 147 patients (22%) died. Patients with outbreak-related illness were significantly more likely to have eaten cantaloupe than were patients 60 years of age or older with sporadic illness (odds ratio, 8.5; 95% confidence interval, 1.3 to ∞). Cantaloupe and environmental samples collected during the investigation yielded isolates matching all five outbreak-related subtypes, confirming that whole cantaloupe produced by a single Colorado farm was the outbreak source. Unsanitary conditions identified in the processing facility operated by the farm probably resulted in contamination of cantaloupes with L. monocytogenes. CONCLUSIONS: Raw produce, including cantaloupe, can serve as a vehicle for listeriosis. This outbreak highlights the importance of preventing produce contamination within farm and processing environments.

Notes from the Field: Typhoid Fever Outbreak Associated with an Asymptomatic Carrier at a Restaurant - Weld County, Colorado, 2015.

On September 11, 2015, a single case of typhoid fever, caused by Salmonella Typhi infection, was reported to the Colorado Department of Public Health and Environment (CDPHE). Because the patient (patient A) had symptom onset September 2 and had traveled internationally for 4 days 60 days before symptom onset, the case initially was thought to be travel-associated* (1,2). On October 1, a second case of S. Typhi infection was reported in patient B, with symptom onset September 20. Patient B reported no international travel or contact with ill persons or known carriers. Patients A and B resided approximately 6 miles (10 kilometers) apart and had no discernible epidemiologic connection. Family members of patients A and B tested negative for S. Typhi. CDPHE and the Weld County Department of Public Health and Environment (WCDPHE) investigated to 1) determine whether these cases represented a larger outbreak, 2) identify common exposure sources, and 3) stop transmission. Investigators determined that the typhoid fever in both patients and in a third patient (patient C) was associated with eating in the same restaurant during a 5-day period.

Infection with Pathogens Transmitted Commonly Through Food and the Effect of Increasing Use of Culture-Independent Diagnostic Tests on Surveillance--Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2012-2015.

To evaluate progress toward prevention of enteric and foodborne illnesses in the United States, the Foodborne Diseases Active Surveillance Network (FoodNet) monitors the incidence of laboratory-confirmed infections caused by nine pathogens transmitted commonly through food in 10 U.S. sites. This report summarizes preliminary 2015 data and describes trends since 2012. In 2015, FoodNet reported 20,107 confirmed cases (defined as culture-confirmed bacterial infections and laboratory-confirmed parasitic infections), 4,531 hospitalizations, and 77 deaths. FoodNet also received reports of 3,112 positive culture-independent diagnostic tests (CIDTs) without culture-confirmation, a number that has markedly increased since 2012. Diagnostic testing practices for enteric pathogens are rapidly moving away from culture-based methods. The continued shift from culture-based methods to CIDTs that do not produce the isolates needed to distinguish between strains and subtypes affects the interpretation of public health surveillance data and ability to monitor progress toward prevention efforts. Expanded case definitions and strategies for obtaining bacterial isolates are crucial during this transition period.

Outbreak of salmonellosis linked to live poultry from a mail-order hatchery.

BACKGROUND: Outbreaks of human salmonella infections are increasingly associated with contact with live poultry, but effective control measures are elusive. In 2005, a cluster of human salmonella Montevideo infections with a rare pattern on pulsed-field gel electrophoresis (the outbreak strain) was identified by PulseNet, a national subtyping network. METHODS: In cooperation with public health and animal health agencies, we conducted multistate investigations involving patient interviews, trace-back investigations, and environmental testing at a mail-order hatchery linked to the outbreak in order to identify the source of infections and prevent additional illnesses. A case was defined as an infection with the outbreak strain between 2004 and 2011. RESULTS: From 2004 through 2011, we identified 316 cases in 43 states. The median age of the patient was 4 years. Interviews were completed with 156 patients (or their caretakers) (49%), and 36 of these patients (23%) were hospitalized. Among the 145 patients for whom information was available, 80 (55%) had bloody diarrhea. Information on contact with live young poultry was available for 159 patients, and 122 of these patients (77%) reported having such contact. A mail-order hatchery in the western United States was identified in 81% of the trace-back investigations, and the outbreak strain was isolated from samples collected at the hatchery. After interventions at the hatchery, the number of human infections declined, but transmission continued. CONCLUSIONS: We identified a prolonged multistate outbreak of salmonellosis, predominantly affecting young children and associated with contact with live young poultry from a mail-order hatchery. Interventions performed at the hatchery reduced, but did not eliminate, associated human infections, demonstrating the difficulty of eliminating salmonella transmission from live poultry.

Bacterial enteric infections detected by culture-independent diagnostic tests--FoodNet, United States, 2012-2014.

The increased availability and rapid adoption of culture-independent diagnostic tests (CIDTs) is moving clinical detection of bacterial enteric infections away from culture-based methods. These new tests do not yield isolates that are currently needed for further tests to distinguish among strains or subtypes of Salmonella, Campylobacter, Shiga toxin-producing Escherichia coli, and other organisms. Public health surveillance relies on this detailed characterization of isolates to monitor trends and rapidly detect outbreaks; consequently, the increased use of CIDTs makes prevention and control of these infections more difficult. During 2012-2013, the Foodborne Diseases Active Surveillance Network (FoodNet*) identified a total of 38,666 culture-confirmed cases and positive CIDT reports of Campylobacter, Salmonella, Shigella, Shiga toxin-producing E. coli, Vibrio, and Yersinia. Among the 5,614 positive CIDT reports, 2,595 (46%) were not confirmed by culture. In addition, a 2014 survey of clinical laboratories serving the FoodNet surveillance area indicated that use of CIDTs by the laboratories varied by pathogen; only CIDT methods were used most often for detection of Campylobacter (10%) and STEC (19%). Maintaining surveillance of bacterial enteric infections in this period of transition will require enhanced surveillance methods and strategies for obtaining bacterial isolates.

Preliminary incidence and trends of infection with pathogens transmitted commonly through food - Foodborne Diseases Active Surveillance Network, 10 U.S. sites, 2006-2014.

Foodborne illnesses represent a substantial, yet largely preventable, health burden in the United States. In 10 U.S. geographic areas, the Foodborne Diseases Active Surveillance Network (FoodNet) monitors the incidence of laboratory-confirmed infections caused by nine pathogens transmitted commonly through food. This report summarizes preliminary 2014 data and describes changes in incidence compared with 2006-2008 and 2011-2013. In 2014, FoodNet reported 19,542 infections, 4,445 hospitalizations, and 71 deaths. The incidence of Shiga toxin-producing Escherichia coli (STEC) O157 and Salmonella enterica serotype Typhimurium infections declined in 2014 compared with 2006-2008, and the incidence of infection with Campylobacter, Vibrio, and Salmonella serotypes Infantis and Javiana was higher. Compared with 2011-2013, the incidence of STEC O157 and Salmonella Typhimurium infections was lower, and the incidence of STEC non-O157 and Salmonella serotype Infantis infections was higher in 2014. Despite ongoing food safety efforts, the incidence of many infections remains high, indicating that further prevention measures are needed to make food safer and achieve national health objectives.

Incidence and trends of infection with pathogens transmitted commonly through food--Foodborne Diseases Active Surveillance Network, 10 U.S. sites, 2006-2013.

Foodborne disease continues to be an important problem in the United States. Most illnesses are preventable. To evaluate progress toward prevention, the Foodborne Diseases Active Surveillance Network (FoodNet) monitors the incidence of laboratory-confirmed infections caused by nine pathogens transmitted commonly through food in 10 U.S. sites, covering approximately 15% of the U.S. population. This report summarizes preliminary 2013 data and describes trends since 2006. In 2013, a total of 19,056 infections, 4,200 hospitalizations, and 80 deaths were reported. For most infections, incidence was well above national Healthy People 2020 incidence targets and highest among children aged <5 years. Compared with 2010-2012, the estimated incidence of infection in 2013 was lower for Salmonella, higher for Vibrio, and unchanged overall.† Since 2006-2008, the overall incidence has not changed significantly. More needs to be done. Reducing these infections requires actions targeted to sources and pathogens, such as continued use of Salmonella poultry performance standards and actions mandated by the Food Safety Modernization Act (FSMA). FoodNet provides federal and state public health and regulatory agencies as well as the food industry with important information needed to determine if regulations, guidelines, and safety practices applied across the farm-to-table continuum are working.

Increased recognition of non-O157 Shiga toxin-producing Escherichia coli infections in the United States during 2000-2010: epidemiologic features and comparison with E. coli O157 infections.

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) are an important cause of diarrhea and the major cause of postdiarrheal hemolytic uremic syndrome. Non-O157 STEC infections are being recognized with greater frequency because of changing laboratory practices. METHODS: Foodborne Diseases Active Surveillance Network (FoodNet) site staff conducted active, population-based surveillance for laboratory-confirmed STEC infections. We assessed frequency and incidence of STEC infections by serogroup and examined and compared demographic factors, clinical characteristics, and frequency of international travel among patients. RESULTS: During 2000-2010, FoodNet sites reported 2006 cases of non-O157 STEC infection and 5688 cases of O157 STEC infections. The number of reported non-O157 STEC infections increased from an incidence of 0.12 per 100,000 population in 2000 to 0.95 per 100,000 in 2010; while the rate of O157 STEC infections decreased from 2.17 to 0.95 per 100,000. Among non-O157 STEC, six serogroups were most commonly reported: O26 (26%), O103 (22%), O111 (19%), O121 (6%), O45 (5%), and O145 (4%). Non-O157 STEC infections were more common among Hispanics, and infections were less severe than those caused by O157 STEC, but this varied by serogroup. Fewer non-O157 STEC infections were associated with outbreaks (7% versus 20% for O157), while more were associated with international travel (14% versus 3% for O157). CONCLUSIONS: Improved understanding of the epidemiologic features of non-O157 STEC infections can inform food safety and other prevention efforts. To detect both O157 and non-O157 STEC infections, clinical laboratories should routinely and simultaneously test all stool specimens submitted for diagnosis of acute community-acquired diarrhea for O157 STEC and for Shiga toxin and ensure that isolates are sent to a public health laboratory for serotyping and subtyping.

Impacts of culture-independent diagnostic practices on public health surveillance for bacterial enteric pathogens.

For decades, culture has been the mainstay of diagnostic testing for bacterial enteric pathogens. This paradigm is changing as clinical laboratories adopt culture-independent methods, such as antigen-based tests and nucleic acid-based assays. Public health surveillance for enteric infections addresses 4 interrelated but distinct objectives: case investigation for localized disease control; assessment of disease burden and trends to prioritize and assess impact of population-based control measures; outbreak detection; and microbiologic characterization to improve understanding of pathogens, their virulence mechanisms, and epidemiology. We summarize the challenges and opportunities that culture-independent tests present and suggest strategies, such as validation studies and development of culture-independent tests compatible with subtyping, that could be adopted to ensure that surveillance remains robust. Many of these approaches will require time and resources to implement, but they will be necessary to maintain a strong surveillance system. Public health practitioners must clearly explain the value of surveillance, especially how outbreak detection benefits the public, and collaborate with all stakeholders to develop solutions.

Clinical laboratory practices for the isolation and identification of Campylobacter in Foodborne Diseases Active Surveillance Network (FoodNet) sites: baseline information for understanding changes in surveillance data.

BACKGROUND: Campylobacter is a leading cause of foodborne illness in the United States. Understanding laboratory practices is essential to interpreting incidence and trends in reported campylobacteriosis over time and provides a baseline for evaluating the increasing use of culture-independent diagnostic methods for Campylobacter infection. METHODS: The Foodborne Diseases Active Surveillance Network (FoodNet) conducts surveillance for laboratory-confirmed Campylobacter infections. In 2005, FoodNet conducted a survey of clinical laboratories to describe routine practices used for isolation and identification of Campylobacter. A profile was assigned to laboratories based on complete responses to key survey questions that could impact the recovery and isolation of Campylobacter from stool specimens. RESULTS: Of 411 laboratories testing on-site for Campylobacter, 97% used only culture methods. Among those responding to the individual questions, nearly all used transport medium (97%) and incubated at 42°C (94%); however, most deviated from existing guidelines in other areas: 68% held specimens in transport medium at room temperature before plating, 51% used Campy blood agar plate medium, 52% read plates at <72 hours of incubation, and 14% batched plates before placing them in a microaerobic environment. In all, there were 106 testing algorithms among 214 laboratories with a complete profile; only 16 laboratories were fully adherent to existing guidelines. CONCLUSIONS: Although most laboratories used culture-based methods, procedures differed widely and most did not adhere to existing guidelines, likely resulting in underdiagnosis. Given the availability of new culture-independent testing methods, these data highlight a clear need to develop best practice recommendations for Campylobacter infection diagnostic testing.

Estimates of enteric illness attributable to contact with animals and their environments in the United States.

BACKGROUND: Contact with animals and their environment is an important, and often preventable, route of transmission for enteric pathogens. This study estimated the annual burden of illness attributable to animal contact for 7 groups of pathogens: Campylobacter species, Cryptosporidium species, Shiga toxin-producing Escherichia coli (STEC) O157, STEC non-O157, Listeria monocytogenes, nontyphoidal Salmonella species, and Yersinia enterocolitica. METHODS: By using data from the US Foodborne Diseases Active Surveillance Network and other sources, we estimated the proportion of illnesses attributable to animal contact for each pathogen and applied those proportions to the estimated annual number of illnesses, hospitalizations, and deaths among US residents. We established credible intervals (CrIs) for each estimate. RESULTS: We estimated that 14% of all illnesses caused by these 7 groups of pathogens were attributable to animal contact. This estimate translates to 445 213 (90% CrI, 234 197-774 839) illnesses annually for the 7 groups combined. Campylobacter species caused an estimated 187 481 illnesses annually (90% CrI, 66 259-372 359), followed by nontyphoidal Salmonella species (127 155; 90% CrI, 66 502-219 886) and Cryptosporidium species (113 344; 90% CrI, 22 570-299 243). Of an estimated 4933 hospitalizations (90% CrI, 2704-7914), the majority were attributable to nontyphoidal Salmonella (48%), Campylobacter (38%), and Cryptosporidium (8%) species. Nontyphoidal Salmonella (62%), Campylobacter (22%), and Cryptosporidium (9%) were also responsible for the majority of the estimated 76 deaths (90% CrI, 5-211). CONCLUSIONS: Animal contact is an important transmission route for multiple major enteric pathogens. Continued efforts are needed to prevent pathogen transmission from animals to humans, including increasing awareness and encouraging hand hygiene.

Travel-associated enteric infections diagnosed after return to the United States, Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009.

BACKGROUND: Approximately 40% of US travelers to less developed countries experience diarrheal illness. Using data from the Foodborne Diseases Active Surveillance Network (FoodNet), we describe travel-associated enteric infections during 2004-2009, characterizing the patients, pathogens, and destinations involved. METHODS: FoodNet conducts active surveillance at 10 US sites for laboratory-confirmed infections with 9 pathogens transmitted commonly through food. Travel-associated infections are infections diagnosed in the United States but likely acquired abroad based on a pathogen-specific time window between return from international travel to diagnosis. We compare the demographic, clinical, and exposure-related characteristics of travelers with those of nontravelers and estimate the risk of travel-associated infections by destination, using US Department of Commerce data. RESULTS: Of 64,039 enteric infections reported to FoodNet with information about travel, 8270 (13%) were travel associated. The pathogens identified most commonly in travelers were Campylobacter (42%), nontyphoidal Salmonella (32%), and Shigella (13%). The most common travel destinations were Mexico, India, Peru, Dominican Republic, and Jamaica. Most travel-associated infections occurred in travelers returning from Latin America and the Caribbean (LAC). Risk was greatest after travel to Africa (75.9 cases per 100,000 population), followed by Asia (22.7 cases per 100,000), and LAC (20.0 cases per 100,000). CONCLUSIONS: The Latin America and Caribbean region accounts for most travel-associated enteric infections diagnosed in the United States, although travel to Africa carries the greatest risk. Although FoodNet surveillance does not cover enterotoxigenic Escherichia coli, a common travel-associated infection, this information about other key enteric pathogens can be used by travelers and clinicians in pre- and posttravel consultations.

Invasive listeriosis in the Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009: further targeted prevention needed for higher-risk groups.

BACKGROUND: Listeriosis can cause severe disease, especially in fetuses, neonates, older adults, and persons with certain immunocompromising and chronic conditions. We summarize US population-based surveillance data for invasive listeriosis from 2004 through 2009. METHODS: We analyzed Foodborne Diseases Active Surveillance Network (FoodNet) data for patients with Listeria monocytogenes isolated from normally sterile sites. We describe the epidemiology of listeriosis, estimate overall and specific incidence rates, and compare pregnancy-associated and nonpregnancy-associated listeriosis by age and ethnicity. RESULTS: A total of 762 listeriosis cases were identified during the 6-year reporting period, including 126 pregnancy-associated cases (17%), 234 nonpregnancy-associated cases(31%) in patients aged <65 years, and 400 nonpregnancy-associated cases (53%) in patients aged ≥ 65 years. Eighteen percent of all cases were fatal. Meningitis was diagnosed in 44% of neonates. For 2004-2009, the overall annual incidence of listeriosis varied from 0.25 to 0.32 cases per 100,000 population. Among Hispanic women, the crude incidence of pregnancy-associated listeriosis increased from 5.09 to 12.37 cases per 100,000 for the periods of 2004-2006 and 2007-2009, respectively; among non-Hispanic women, pregnancy-associated listeriosis increased from 1.74 to 2.80 cases per 100,000 for the same periods. Incidence rates of nonpregnancy-associated listeriosis in patients aged ≥ 65 years were 4-5 times greater than overall rates annually. CONCLUSIONS: Overall listeriosis incidence did not change significantly from 2004 through 2009. Further targeted prevention is needed, including food safety education and messaging (eg, avoiding Mexican-style cheese during pregnancy). Effective prevention among pregnant women, especially Hispanics, and older adults would substantially affect overall rates.

Moving Away from Population-Based Case-Control Studies during Outbreak Investigations.

Population-based case-control studies are a time- and labor-intensive component of foodborne outbreak investigations. One alternative is a binomial trial that asks the question "if the likelihood of each case's having eaten a given food is no different from that of the average person in the population, how often would we find, by chance alone, that x of n (or more) cases would have eaten this food?" Calculating a binomial trial requires background exposure data. We conducted case-control studies and binomial trials in two foodborne outbreaks and compared results. In both outbreaks, using binomial trials we found much less than a 5% probability that the number of cases eating the suspected food vehicle would have occurred by chance. These results were comparable with results of the case-control studies, but with considerably less effort. When background exposure data are available, binomial trials are an efficient way to explore hypotheses that can be further tested by traceback efforts to identify a common source.

Antimicrobial use and outcomes in patients with multidrug-resistant and pansusceptible Salmonella Newport infections, 2002-2003.

Multidrug-resistant Salmonella Newport with decreased susceptibility to ceftriaxone (MDR-AmpC) is becoming increasingly common in its food animal reservoirs and in humans. Few data exist on rates of antimicrobial use or differences in clinical outcomes in persons infected with MDR-AmpC or other Salmonella strains. We conducted a case-comparison analysis of data from a multistate population-based case-control study to identify antimicrobial treatment choices and differences in clinical outcomes in those infected with MDRAmpC compared to pansusceptible S. Newport. Of isolates from 215 laboratory-confirmed S. Newport cases, 54 (25%) were MDR-AmpC, 146 (68%) were pansusceptible, and 15 (7%) had other resistance patterns; 146 (68%) patients with S. Newport were treated with antimicrobial agents and 66 (33%) were hospitalized. Over two-thirds of cases at low-risk for serious complications received antimicrobial therapy, most commonly with fluoroquinolones, to which this strain was susceptible. There were no significant differences in symptoms, hospitalization, duration of illness, or other outcomes between the persons infected with MDR-AmpC and pansusceptible S. Newport. Although currently prevalent MDR-AmpC S. Newport strains remains susceptible to the antimicrobial most commonly prescribed for it, continued efforts to reduce unnecessary use of antimicrobial agents in food animals and humans are critical to prevent further development of resistance to quinolones and cephalosporins, which is likely to lead to substantial adverse outcomes.