Fatal Vibrio vulnificus Infection Associated with Eating Raw Oysters, New Caledonia

International audienceTo the Editor: The bacterium Vi-brio vulnifi cus is a marine fl ora sap-rophyte that can cause necrotic skin infection and septicemia in humans who eat shellfi sh. Symptoms of sep-ticemia (mortality rate >50%) have been described mostly in Florida and Japan among persons who ate raw fi lter-feeding shellfi sh when seawater temperatures are >20°C (1). V. vulnifi cus–related septicemia introduced through the digestive system appears within 7 days after inges-tion (2). Clinical signs and symptoms include fever, collapse, and metastatic necrotic skin lesions. We report 3 patients from New Caledonia who died after V. vulnifi cus infection, which they probably acquired by eating contaminated oysters. These patients were hospitalized during February–May 2008 at Noumea Hospital (Noumea, New Caledonia). Patient 1 was a 51-year-old man with fever, muscle pains, bleeding gums, and a history of alcohol abuse; within 48 hours after symptom onset, he died of septic shock, with diffuse ecchymoses and purpura. Patient 2 was a 67-year-old woman with no known concurrent conditions who was admitted to the hospital with chills, diarrhea, and vomiting; septic shock developed, with painful erythematous plaques on the lower limbs becoming foamy, confl uent, and necrotic. Patient 3 was a 74-year-old woman with untreated lupus who was hospitalized with lower-limb edema, hypotension, hypothermia, and erythematous skin lesions. All 3 patients received cepha-losporins but died of multiple organ failure within 12 hours after hospital admission. Peripheral blood aerobic–anaer-obic samples were taken from all patients , stored in BacT/Alert FA vials (bioMérieux, Marcy-l'Etoile, France), and incubated in the BacT/Alert 3D system (bioMérieux). Curved mobile gram-negative bacilli were isolated from blood samples cultured on conventional media without additional salt within 24 h after incubation at 37°C in a 5% CO 2-enriched atmosphere. V. vulnifi cus was identifi ed through the Vitek2 system (bioMérieux) and con-fi rmed by using the Api 20E system (bioMérieux). Strains were sent to the Centre National de Reference des Vibrions et du Choléra, (Institut Pasteur, Paris, France), which by PCR confi rmed the gene encoding virulence-associated hemolysin, a species-specifi c marker (3). Molecular typing by pulsed-fi eld gel electrophoresis was performed to assess possible clonality of the strains. Several studies have shown the genomic diversity among environmental and clinical V. vulnifi cus isolates. The use of genotyping methods has identifi ed >100 V. vulnifi cus strains in a single oyster (4) and notable hetero-geneity among clinical isolates from multiple patients, even if a unique pathogenic strain causes the infection in each patient. Thus, V. vulnifi cus infections within a large population at risk may result from rare events controlled more by the host than by the bacterial strain (5). Pulsed-fi eld gel electrophoresis genotype analysis enabled us to divide the strains into 2 groups. One group included the isolate from patient 1, and the other group included isolates from patients 2 and 3, which despite having slightly different NotI and Sfi I patterns refl ecting genetic rearrangement , clearly belonged to a single clone. Isolation of strains with such a high degree of homogeneity is not common, raising the question of the existence of V. vulnifi cus clones that are particularly virulent or adapted to humans. Currently, however, reliable markers for determining V. vulnifi cus virulence do not exist. Thus, no geno-typing system is likely to be useful for rapidly identifying strains that affect public health (6). V. vulnifi cus–related analysis requires the assumption that all strains are virulent. Epidemiologic information collected from patients' families indicated recent consumption of raw oysters. Two of the 3 cases occurred within a short time frame and were associated with eating local oysters harvested on the west coast of New Caledonia. The literature mentions few cases of V. vulnifi cus infection in the South Pacifi c. Cases described were isolated, rarely fatal, and involved infection through the skin (7–10). The V. vulnifi-cus infections we report may be related to the emergence of a new clone or to changes in the climate or environmental conditions. New Caledonia experienced unusual weather conditions during the fi rst half of 2008 (heavy rains and exceptionally high temperatures). These specifi c conditions may have favored higher sea surface temperatures, lower salinity, increased turbidity, and subsequent multiplication of V. vulnifi-cus in seawater. A range of projects were implemented to train practitioners to recognize potential V. vulnifi cus infections. Local health authorities issued criteria for defi ning suspected cases of V. vulnifi cus infection and recommendations for early medical care of patients with clinical symptoms. Methods of detecting the bacterium in human and animal health laboratories were improved , particularly by the systematic use of selective media in the event of suspected clinical V. vulnifi cus infection and standardized reporting of V. vulnifi cus isolation. Preventive measures , such as improving microbial surveillance and warning consumers about risks associated with eating raw seafood, are essential to help reduce the risk for V. vulnifi cus–induced illness. 136 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 1, January 2011 LETTERS Acknowledgments We thank Jacob Kool, Martha Iwa-moto, Rajal Mody, and Dominique Hervio-Heath for help in investigating these cases and for formulating recommendations

Incentivizing the Dynamic Workforce: Learning Contracts in the Gig-Economy

In principal-agent models, a principal offers a contract to an agent to perform a certain task. The agent exerts a level of effort that maximizes her utility. The principal is oblivious to the agent's chosen level of effort, and conditions her wage only on possible outcomes. In this work, we consider a model in which the principal is unaware of the agent's utility and action space. She sequentially offers contracts to identical agents, and observes the resulting outcomes. We present an algorithm for learning the optimal contract under mild assumptions. We bound the number of samples needed for the principal obtain a contract that is within $\epsilon$ of her optimal net profit for every $\epsilon>0$