A Multistate Outbreak of Salmonella enterica Serotype Saintpaul Infections Linked to Mango Consumption: A Recurrent Theme

Sir—We read with interest the report of a multistate outbreak of Salmonella enterica serotype Newport infection in 1999 by Sivapalasingam et al. [1]. The outbreak was associated with the consumption of mangoes imported from a single farm in Brazil. An environmental investigation at the farm revealed that inadequately chlorinated water was used in the hot water immersion treatment to exterminate fruit fly larvae. At the time, the importance of adequately chlorinating the treatment water had not been recognized [1, 2]. We write to report a second outbreak of S. enterica infection associated with consumption of mangoes; however, the serotype in this outbreak was Saintpaul. Also imported, these mangoes were possibly contaminated through a mechanism similar to that described by Sivapalasingam et al. [1]. In March of 2001, the Massachusetts and Connecticut departments of public health reported 19 patients with culture-confirmed S. Saintpaul infections. The PFGE patterns of the DNA from these isolates were indistinguishable, suggesting an outbreak. By 31 March 2001, S. Saintpaul isolates from 7 additional patients, including residents of California, Delaware, New Jersey, New York, and Rhode Island, were identified. The mean age of patients was 35 years (range, 1–89 years); 48% were female. To identify risk factors for infection, we conducted a case-control study with 13 cases and 25 controls frequency-matched for age, sex, and city of residence. Telephone interviews were conducted by state health department and Centers for Disease Control and Prevention officials using a standardized questionnaire. Raw mango consumption was the only exposure significantly associated with illness (OR, 28.8; 95% CI, 2.1–888; P = .003). Three patients had adequate purchase records for the US Food and Drug Association (FDA) to initiate a “trace-back” investigation; however, only 1 patient's purchase could be traced beyond the retail seller. This patient's receipt indicated that the mangoes were imported from Peru, but there was inadequate information obtained to complete the trace-back to the farm level. During an unrelated site-visit to mango-producing regions in Peru, US Animal and Plant Health Inspection Service (APHIS) inspectors noted that producers were using untreated water in the final step of the fruit fly control program (P. C. Witherell, US Department of Agriculture, APHIS-Plant Protection and Quarantine, personal communication). Subsequent to the outbreak of mango-associated S. Newport infection in 1999 reported by Sivapalasingam et al. [1], APHIS recommended a concentration of 50–200 ppm chlorine in the water used for the hot water immersion treatment [1]. This change was not published until 2002 [3]. It is likely that the mango producers in Peru had not yet learned of the need to chlorinate the water used for hot water immersion treatment, and a second outbreak occurred before the recommendation became widely adopted. In conclusion, mangoes were implicated as the vehicle during a multistate outbreak of S. Saintpaul in February and March of 2001. These mangoes were likely exposed to inadequately chlorinated water, which may have led to contamination with S. Saintpaul. APHIS recommendations currently include using adequately chlorinated water in mango processing for the prevention of fruit fly infestation [3]. As of 1 January 2003, no subsequent foodborne outbreaks have been associated with mangoes. The outbreak we report demonstrates the need for thorough microbiologic evaluation of new methods of food processing prior to their implementation, as Sivapalasingam et al. [1] suggest.