Outbreaks caused by sprouts, United States, 1998-2010: lessons learned and solutions needed

After a series of outbreaks associated with sprouts in the mid-1990s, the U.S. Food and Drug Administration (FDA) published guidelines in 1999 for sprouts producers to reduce the risk of contamination. The recommendations included treating seeds with an antimicrobial agent such as calcium hypochlorite solution and testing spent irrigation water for pathogens. From 1998 through 2010, 33 outbreaks from seed and bean sprouts were documented in the United States, affecting 1330 reported persons. Twenty-eight outbreaks were caused by Salmonella, four by Shiga toxin-producing Escherichia coli, and one by Listeria. In 15 of the 18 outbreaks with information available, growers had not followed key FDA guidelines. In three outbreaks, however, the implicated sprouts were produced by firms that appeared to have implemented key FDA guidelines. Although seed chlorination, if consistently applied, reduces pathogen burden on sprouts, it does not eliminate the risk of human infection. Further seed and sprouts disinfection technologies, some recently developed, will be needed to enhance sprouts safety and reduce human disease. Improved seed production practices could also decrease pathogen burden but, because seeds are a globally distributed commodity, will require international cooperation.

Leptospirosis outbreak following severe flooding: a rapid assessment and mass prophylaxis campaign; Guyana, January-February 2005

BACKGROUND

Leptospirosis is a zoonosis usually transmitted through contact with water or soil contaminated with urine from infected animals. Severe flooding can put individuals at greater risk for contracting leptospirosis in endemic areas. Rapid testing for the disease and large-scale interventions are necessary to identify and control infection. We describe a leptospirosis outbreak following severe flooding and a mass chemoprophylaxis campaign in Guyana.

METHODOLOGY/PRINCIPAL FINDINGS

From January-March 2005, we collected data on suspected leptospirosis hospitalizations and deaths. Laboratory testing included anti-leptospiral dot enzyme immunoassay (DST), immunohistochemistry (IHC) staining, and microscopic agglutination testing (MAT). DST testing was conducted for 105 (44%) of 236 patients; 52 (50%) tested positive. Four (57%) paired serum samples tested by MAT were confirmed leptospirosis. Of 34 total deaths attributed to leptospirosis, postmortem samples from 10 (83%) of 12 patients were positive by IHC. Of 201 patients interviewed, 89% reported direct contact with flood waters. A 3-week doxycycline chemoprophylaxis campaign reached over 280,000 people.

CONCLUSIONS

A confirmed leptospirosis outbreak in Guyana occurred after severe flooding, resulting in a massive chemoprophylaxis campaign to try to limit morbidity and mortality.

Nonfoodborne Vibrio infections: an important cause of morbidity and mortality in the United States, 1997-2006

BACKGROUND

Infections due to Vibrio species cause an estimated 8000 illnesses annually, often through consumption of undercooked seafood. Like foodborne Vibrio infections, nonfoodborne Vibrio infections (NFVI) also result in serious illness, but awareness of these infections is limited.

METHODS

We analyzed illnesses occuring during the period 1997-2006 that were reported to the Centers for Disease Control and Prevention's Cholera and Other Vibrio Illness Surveillance system. The diagnosis of NFVI required isolation of Vibrio species from a patient with contact with seawater.

RESULTS

Of 4754 Vibrio infections reported, 1210 (25%) were NFVIs. Vibrio vulnificus infections were the most common (accounting for 35% of NFVIs), with 72% of V. vulnificus infections reported from residents of Gulf Coast states. Infections due to V. vulnificus resulted in fever (72% of cases), cellulitis (85%), amputation (10%), and death (17%). V. vulnificus caused 62 NFVI-associated deaths (78%). Recreational activities accounted for 70% of exposures for patients with NFVIs associated with all species. Patients with liver disease were significantly more likely to die as a result of infection (odds ratio, 7.8; 95% confidence interval, 2.8-21.9). Regardless of pre-existing conditions, patients were more likely to die when hospitalization occurred >2 days after symptom onset (odds ratio, 2.9; 95% confidence interval, 1.8-4.8).

CONCLUSION

NFVIs, especially those due to V. vulnificus, demonstrate high morbidity and mortality. Persons with liver disease should be advised of the risks associated with seawater exposure if a wound is already present or is likely to occur. Clinicians should consider Vibrio species as an etiologic agent in infections occurring in persons with recent seawater exposure, even if the individual was only exposed during recreational marine activities. Immediate antibiotic treatment with aggressive monitoring is advised in suspected cases.

Outbreak of multidrug-resistant Salmonella enterica serotype Typhimurium Definitive Type 104 infection linked to commercial ground beef, northeastern United States, 2003-2004

BACKGROUND

Multidrug-resistant Salmonella enterica serotype Typhimurium Definitive Type 104 (DT104) emerged in the 1990s and is associated with greater clinical severity than pansusceptible S. Typhimurium. Although infection with DT104 is common in the United States, it is rarely associated with outbreaks. From October to December 2003, a cluster of DT104 infections with indistinguishable pulsed-field gel electrophoresis patterns was identified in the northeastern United States.

METHODS

A case-control study that assessed exposures compared case patients to age- and geography-matched control subjects. Information on consumer purchasing and grocery store suppliers was used to trace the implicated food to its source.

RESULTS

We identified 58 case patients in 9 states by pulsed-field gel electrophoresis. Representative isolates were phage type DT104 and were resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline (R-type ACSSuT). Of 27 patients interviewed for the case-control study, 41% were hospitalized (median duration of hospitalization, 4 days). Compared with 71 healthy control subjects, case patients had more medical comorbidities (matched odds ratio, 4.3; 95% confidence interval, 1.5-12.7). Illness was associated with consuming store-bought ground beef prepared as hamburgers at home (matched odds ratio, 5.3; 95% confidence interval, 1.9-15.3) and with eating raw ground beef (P< or =.001). Seven case patients (27%), but no control subjects, ate raw ground beef. Product traceback linked cases to a single large ground beef manufacturer previously implicated in a multistate outbreak of highly drug-resistant Salmonella enterica Newport infections in 2002.

CONCLUSIONS

This first multistate outbreak of highly drug-resistant S. Typhimurium DT104 infection associated with ground beef highlights the need for enhanced animal health surveillance and infection control, prudent use of antimicrobials for animals, improved pathogen reduction during processing, and better product tracking and consumer education.