Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (481 page)

   Noncholera
Vibrio
species may also cause human infection, most commonly diarrheal syndromes, albeit typically less severe than classic cholera. Extraintestinal infection is uncommon but well described.
Vibrio vulnificus
may cause significant infection after ingestion of contaminated seafood or traumatic inoculation. Preexisting liver disease, as seen with alcoholic cirrhosis, hepatitis, and hemochromatosis, predisposes patients to invasive infection. Cellulitis with formation of bullae is characteristic. Secondary
V. vulnificus
bacteremia is associated with high mortality.

   Laboratory Findings

Culture
: Isolates grow on routine laboratory media after overnight incubation; isolation is improved by the use of specific selective and differential media (e.g., TSCB) for specimens likely to be contaminated, like stool.

Core Laboratory
: In cholera, careful monitoring of core laboratory values to assess the patient’s state of hydration and metabolic status is critical.

YERSINIA
INFECTION

   Definition

Yersinia
species are nonfastidious, glucose-fermenting GNBs, but growth in culture may be slow. Yersiniosis is usually caused by infection with
Yersinia enterocolitica
presenting with acute gastroenteritis.
Yersinia enterocolitica
is widely distributed in nature and transmitted by the oral route. Swine have been implicated as a reservoir for human infections.

Yersinia pestis
is a significant pathogen. In naturally occurring infection, humans are incidental hosts, acquiring infection by exposure to the epizootic cycle between fleas and rodents (e.g., flea bite, contact with infected animal carcasses) or through care of patients with pneumonic plague.
Yersinia pestis
infection is now rare due to control of the normal rodent reservoir, but
Y. pestis
is considered a potential risk for development as a bioterror agent; public health officials must be contacted immediately if
Y. pestis
infection is suspected.

   Who Should Be Suspected?

Symptoms of
Y. enterocolitica
infection include acute enteritis (diarrhea and abdominal pain), mesenteric adenitis, and pseudoappendicitis.

There are three major clinical manifestations of human
Y. pestis
infection:

   
Bubonic
(approximately 90% of reported cases): Sudden onset of fever, chills, malaise. Patients develop pain and swelling of a regional lymph node, usually with edema and erythema. The inguinal nodes are most commonly affected, although the upper extremity or cervical nodes may be more commonly involved in infection transmitted by cats.

   
Septicemic
(approximately 10% of cases): Patients present with fever and sepsis without specific or localized symptoms. DIC and multiorgan failure develop as late complications.

   
Pneumonic
: Pneumonic plague may develop as a complication of bubonic plague through hematogenous spread or by direct inhalation of infectious aerosols. Patients present with a sudden onset of dyspnea, cough, and fever.

   Laboratory Findings

Culture
: Laboratories should have procedures in place for recognition and limitation of handling of
Y. pestis
isolates. The appropriate public health department should be alerted as soon as
Y. pestis
infection is suspected on the basis of clinical or laboratory findings. Further diagnostic testing should be performed under the direction of public health officials.

Yersinia
gastroenteritis is diagnosed by culture of infected material. Isolates may grow slowly on MAC and show an optimum incubation temperature of 25–32°C. Isolation may be improved by the use of special selective media and incubation, like cold enrichment, but in acute yersiniosis, the bacterial load is high in stool and is usually detected by routine enteric cultures if the laboratory has been alerted to rule out
Yersinia
. Because of their growth characteristics, automated identification and susceptibility testing may be unreliable.

Stool may contain increased WBCs and RBCs, but grossly bloody stool is uncommon. Bacteremia is uncommon but may occur in patients with disorders leading to iron overload, like beta-thalassemia.

Suggested Readings

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2005;41:969–974.

Brouwer MC, van de Beek D, Heckenberg SGB, et al. Community-acquired
Listeria monocytogenes
meningitis in adults.
Clin Infect Dis.
2006;43:1233–1238.

Cetinkaya Y, Falk P, Mayhall CG. Vancomycin-resistant enterococci.
Clin Microbiol Rev.
2000;13:686–707.

Coenye T, Vandamme P, Govan JRW, et al. Taxonomy and identification of the
Burkholderia cepacia
complex.
J Clin Microbiol.
2001;39:3427–3436.

Denton M, Kerr KG. Microbiological and clinical aspects of infection associated with
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.
Clin Microbiol Rev.
1998;11:57–80.

Gaynes R, Edwards JR; the National Nosocomial Infections Surveillance System. Overview of nosocomial infections caused by gram-negative bacilli.
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2005;41:848–854.

Gottlieb SL, Martin DH, Xu F, et al. Summary: the natural history of
Chlamydia trachomatis
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2010;201:S190–S204.