Vibrio Parahaemolyticus and Vibrio vulnificus
المؤلف:
Stefan Riedel, Jeffery A. Hobden, Steve Miller, Stephen A. Morse, Timothy A. Mietzner, Barbara Detrick, Thomas G. Mitchell, Judy A. Sakanari, Peter Hotez, Rojelio Mejia
المصدر:
Jawetz, Melnick, & Adelberg’s Medical Microbiology
الجزء والصفحة:
28e , p265-266
2025-09-03
408
In addition to V. cholerae O1 and O139, several other Vibrio species have clearly been associated with infections in humans. Among the non-halophilic vibrios, the non-O1/ O139 V. cholerae strains are associated with a wide spectrum of diarrheal illness ranging from severe watery diarrhea to milder traveler’s diarrhea. Among the halophilic vibrios, V. parahaemolyticus and V. vulnificus are probably the most commonly encountered organisms.
V. parahaemolyticus is a halophilic bacterium that causes acute gastroenteritis after ingestion of contaminated seafood such as raw fish or shellfish. After an incubation period of 12–24 hours, nausea and vomiting, abdominal cramps, fever, and an explosive watery diarrhea occur. Except in severe cases, grossly evident blood and/or mucus is not found in stool specimens. Clinically, the enteritis ranges from mild watery diarrhea to a forthright, dysentery-like syndrome, but then tends to subside spontaneously within 1–4 days with no treatment other than restoration of water and electrolyte balance. No enterotoxin has yet been isolated from this organ ism. Because V. parahaemolyticus is ubiquitous in coastal waters, gastroenteritis due to this organism occurs worldwide, with highest incidence in Asia. In the United States, V. parahaemolyticus is the most often Vibrio species isolated in laboratories in Louisiana and in Florida; overall, in the United States, illnesses due to pathogenic, halophilic Vibrio species are more frequently encountered between the months of April and October, likely reflecting seasonal changes associated with shellfish consumption and recreational water activities. V. parahaemolyticus is a facultatively anaerobe, Gram-negative rod, and does not grow well on some of the routine differential media used to grow salmonellae and shigellae, but it does grow well on blood agar. The organism grows well on TCBS agar, where it yields green colonies (does not ferment sucrose). The final organism identification is achieved by use of various standard biochemical tests. Usually no specific treatment other than rehydration is required since the gastroenteritis is self-limited. However, antimicrobial therapy could be considered for patients in whom the diarrheal illness does not resolve within 5 days; doxycycline and/or fluoroquinolones are appropriate choice for antibiotic therapy and would shorten the duration of the illness.
Among the various non-cholera vibrios, V. vulnificus is a particularly virulent species and is primarily known to cause severe wound and soft tissue infections, as well as bacteremia/sepsis, rather than gastroenteritis. It is a free-living bacterium and part of the normal marine microbiota in association with bivalves and crustaceans. In the United States, V. vulnificus is found along the Atlantic and Pacific Coasts, and especially the Gulf Coast. Infections due to V. vulnificus have been noticed to increase in the United States, particularly in association with Gulf Coast oyster consumption. The organism’s association with oysters has long been noticed, and studies found that almost all oysters harvested during the summer months from the Chesapeake Bay contain this pathogen, as do approximately 10% of the crabs. The two most common clinical presentations of V. vulnificus infection are rapidly progressive wound infections due to skin/soft tissue injuries following exposure to contaminated seawater and primary bacteremia/sepsis following the consumption of contaminated raw oysters. Following the consumption of contaminated food (eg, oysters), V. vulnificus can invade the bloodstream without causing gastrointestinal symptoms; the clinical picture of the ensuing sepsis is characterized by abrupt onset of chills, fever, followed by hypotension and the development of “metastatic” cutaneous lesions. Such lesions begin as erythematous discolorations of the skin that rapidly progress to hemorrhagic vesicles and bullae and then necrotic ulcerations. V. vulnificus septicemia has a fatality rate of greater 50%. Additional risk factors for developing V. vulnificus septicemia other than consumption of contaminated/raw seafood have been described. Such risk fac tors include cirrhosis, other liver diseases, hemochromatosis, hemolytic anemia, malignancies, immunosuppression, and chronic renal failure. Wound infections due to V. vulnificus often develop when a superficial wound comes in contact with contaminated seawater; infections develop and spread rapidly in both healthy as well as immunocompromised patients. Wound infections initially present with erythema and swelling, but quickly develop into an intense cellulitis, with bullous skin lesions, myositis, ulceration, and necrosis; mortality in patients with V. vulnificus wound infections ranges from 20% to 30%. Because of the rapid progression of the infection, it is often necessary to treat with appropriate antibiotics before culture confirmation of the etiology can be obtained. Diagnosis is by culturing the organism on standard laboratory media (eg, blood agar and MacConkey agar); TCBS agar is the preferred medium for stool cultures, where most strains produce blue-green (sucrose-negative) colonies. Definitive, species-level organism identification is achieved by use of various biochemical tests.
Wound infections caused by V. vulnificus respond well to appropriate antimicrobial agents; fluoroquinolones, third-generation cephalosporins (eg, ceftriaxone), and doxycycline are highly active against V. vulnificus; however, in severe cases debridement of all devitalized and/or necrotic tissue or even amputations may be necessary and lifesaving.
الاكثر قراءة في البكتيريا
اخر الاخبار
اخبار العتبة العباسية المقدسة
