DEPARTMENT OF PATHOLOGY
The Johns Hopkins Medical Institutions


Vol. 21, No. 16
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Tuesday, May 14, 2002

  1. Provided by Karen Fujii, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.


    2. 5 outbreaks were reported to DHMH during MMWR Week 19 (May 5 - May 11):

    3 outbreaks (1 with a lab-confirmed Salmonella case) associated with restaurants in Anne Arundel Co.
    1 scombroid poisoning outbreak associated with a restaurant in Montgomery Co.
    1 outbreak of methicillin-resistant Staphylococcus aureus abscesses at a hospital in Anne Arundel Co.
     

  2. The Johns Hopkins Hospital, Department of Pathology, Information provided by, Lynette S. Nichols, MD.
Case description: The patient is a 66 year old male with a history of hypertension who initially presented with right upper quadrant pain and cholelithiasis requiring a cholecystectomy. He subsequently developed bitemporal headache, right ear pain with diminished hearing, and intense orbital pressure bilaterally. There were no fevers, sweats, or chills. The right ear pain continued for weeks ultimately progressing to near complete hearing loss bilaterally. Antibiotics were initiated for a presumed ear infection, and 6 weeks later, the right ear pain subsided, however, the hearing did not improve and he began having headaches, loss of appetite and weight loss. He underwent diagnostic audiograms that revealed bilateral mild hearing loss at all frequencies. As a result, an MRI was performed revealing multiple white matter lesions and unusual enhancing lesions in the region of the left sylvian fissure. The patient subsequently began to experience weakness in both legs. CSF cytology, flow cytometry, and cultures revealed no abnormalities. A brain biopsy was performed which revealed extensive necrosis and acute and chronic inflammation. Organisms were not identified by special stains. The patient’s condition continued to decline. A repeat MRI revealed an abscess in the region of the previous biopsy which ultimately required drainage. A culture of the brain abscess revealed Brucella melitensis.

Organism: Brucella melitensis was first recovered from the spleens of British Army personnel who died of an illness called Malta fever in 1887 by Sir David Bruce, who named the agent Micrococcus melitensis. Soon thereafter, Brucella was recognized as a cause of infectious abortion in cattle and was identified in domesticated livestock in many countries. There are six species of Brucella currently recognized, four of which including B. melitensis cause disease in humans.

Epidemiology: Brucellosis is predominantly a zoonotic disease, causing contagious abortion or other reproductive problems in domesticated animals. Humans acquire the infection by direct contact of infected tissues or body fluids with conjunctivae or broken skin, by ingestion of contaminated meat or dairy products, and by inhalation of infectious aerosols. In the United States implementation in 1945 of the Federal-State Co-operative Brucellosis Eradication Program (requiring that cattle be tested for brucellosis and slaughtered if infected), immunization of cattle with live, attenuated Brucella abortus vaccine, and mandatory pasteurization of dairy products have greatly reduced the prevalence of brucellosis in humans.

Clinical Manifestations: The clinical manifestations of brucellosis depend on the overall health of the person and the species involved. Disease caused by Brucella melitensis is typically the most severe. Disease usually manifests 1 week to several months after exposure and usually begins gradually with sweats, chills, fever, weakness, malaise, headache, and anorexia. Weight loss, myalgias, arthralgias, and back pain develop in 25 to 50% of cases, splenomegaly in 20 to 30%, and lymphadenopathy in 10 to 20%. Disease recurs, owing to relapse or reinfection, in about 5% of the cases.

Laboratory Diagnosis: Brucella grows on sheep blood and chocolate agar, however an infusion base agar supplemented with 5% heated horse or rabbit serum provides optimal recovery. Agar plates should be incubated at 35 C containing 5 to 10% CO2. Biphasic blood cultures are recommended. Agar plates are held 3 weeks and blood cultures 4 weeks before being discarded as negative. Brucella grow slowly, forming pinpoint, translucent, convex, smooth, nonhemolytic colonies with a glistening surface after 3-7 days. Smears show gram-negative coccobacilli. The organisms are immotile, catalase positive, and oxidase positive. Most will hydrolyze urea rapidly, but they do not ferment lactose or glucose. The differentiation of species of Brucella that infect humans is listed in the chart below using traditional phenotypic tests. Our isolate was definitively identified in the laboratory through the use of cellular fatty acid analysis and 16S ribosomal RNA gene sequencing.
 
   
SPECIES
    
Characteristics
B. melitensis
B. abortus
B. suis
B. canis
         
CO2 required for growth
-
+/-
-
-
H2S produced
+
+
-
-
Time to urease positive
2 hr
2 hr
15 min
15 min
Growth on dye medium containing:        
Basic fuchsin
+
+
-
-
Thionin
+
-
+
+

Treatment: Doxycycline plus rifampin is the treatment recommended by the World Health Organization. Rifampin is used to treat pregnant women, and trimethoprim-sulfamethoxazole has been used in children. Rifampin plus a third generation cephalosporin has been recommended to treat central nervous system involvement.

References:

  1. Koneman et al. Color Atlas and Textbook of Diagnostic Microbiology, 5th Edition, Lippincott-Raven, Philadelphia, 1997.

    2.  

     
     
     

    Woods et al. Diagnostic Pathology of Infectious Diseases, Lea and Febiger, Philadelphia, 1993.

    Help | Feedback | Pathology Home | Previous Menu | Tool Box* | Search

    Copyright © 2002 THE JOHNS HOPKINS UNIVERSITY