Closing the Brief Case: Safe To Go Back in the Water? Vibrio parahaemolyticus Wound Infection Associated with Brackish Water

ANSWERS TO SELF-ASSESSMENT QUESTIONS

1. Which of the following biochemical patterns is characteristic of V. parahaemolyticus?

   • (a) Non-lactose fermenting, sucrose fermenting, oxidase positive.
   • (b) Non-lactose fermenting, non-sucrose fermenting, oxidase positive.
   • (c) Lactose fermenting, non-sucrose fermenting, oxidase positive.
   • (d) Lactose fermenting, sucrose fermenting, oxidase negative.

Answer: b. V. parahaemolyticus is oxidase positive and almost always non-lactose fermenting and non-sucrose fermenting. In contrast, V. vulnificus and V. metschnikovii ferment lactose in 85 and 50% of cases, respectively. V. metschnikovii is unique among Vibrio species in being oxidase negative. The ability of V. cholerae to ferment sucrose distinguishes it from V. parahaemolyticus, which does not ferment sucrose.

1. A wound sustained in which of the following settings would be most likely to become infected with V. parahaemolyticus?

   • (a) A freshwater pond in summer.
   • (b) A brackish stream in late autumn.
   • (c) A hot tub in winter.
   • (d) An ocean beach in late spring.

Answer: d. V. parahaemolyticus thrives in saltwater and brackish environments and is most abundant when the water is warm.

1. Which of the following antibiotics is frequently a component of antimicrobial therapy for Vibrio infections?

   • (a) Erythromycin.
   • (b) Ciprofloxacin.
   • (c) Penicillin.
   • (d) Vancomycin.

Answer: b. Data on optimal antimicrobial regimens for V. parahaemolyticus are limited, and most cases of gastroenteritis require only supportive therapy. When antibiotic treatment is indicated for minor skin and soft tissue infections caused by V. parahaemolyticus, an oral fluoroquinolone (e.g., ciprofloxacin [answer b]) or tetracycline is generally chosen for minor skin and soft tissue infections, while the combination of an expanded-spectrum cephalosporin with a fluoroquinolone or tetracycline is preferred for more severe infections.

TAKE-HOME POINTS.

• V. parahaemolyticus can cause three clinical presentations: gastroenteritis, wound infections, and septicemia.

• Infections with V. parahaemolyticus are acquired through consumption of raw seafood or inoculation of wounds sustained in saltwater or brackish environments, particularly when the water is warm.

• Most Vibrio species are oxidase and catalase positive and require salt for growth. Thiosulfate citrate bile salts sucrose agar and chromogenic CHROMagar Vibrio agar are selective and differential media that can be used to detect and distinguish among Vibrio species. V. parahaemolyticus is almost always non-lactose fermenting and non-sucrose fermenting.

• Gastroenteritis due to V. parahaemolyticus is generally managed with supportive therapy. Mild wound infections can be treated with an oral tetracycline or fluoroquinolone. For severe wound infections and septicemia, the combination of an expanded-spectrum cephalosporin with either a tetracycline or a fluoroquinolone is usually recommended. Surgical debridement may also be required in the case of wound infection.

(See page 1414 in this issue [doi:10.1128/JCM.02660-15] for case presentation and discussion.)