December 2000 Newsletter
PSA Consult
Volume III No. 10
December 31, 2000

LABORATORY DIAGNOSIS OF BARTONELLA INFECTION
Overview, Epidemiology & Pathogenesis
Although a dozen Bartonella species have been described, only four cause human disease. B. henselae causes cat scratch disease in immunocompetent persons, or bacillary angiomatosis and peliosis in patients with defective cellular immunity. An estimated 24,000 cases of cat scratch disease yearly in the USA, with 2,000 hospital admissions, results in an estimated health care cost for this illness alone of $12 million per year. It also causes fever of unknown origin in immunocompetent and immunocompromised children and adults. B. quintana, the causative agent of trench fever in World War I, is transmitted through the bite of the body louse. This illness, characterized by fever, rash, bone pain and splenomegaly, has re-emerged in recent years as a cause of bacillary angiomatosis, largely in homeless people where the human body louse again plays a role in transmission. In contrast, bacillary angiomatosis in the immunocompromised patient due to either B. henselae or B. quintana is linked to exposure to cats, especially young cats infested with fleas. B. bacilliformis, the etiologic agent of conventional bartonellosis or Carrion’s disease, is endemic in the highlands of the Andes, where it is transmitted by the sand fly. It has an acute form with a febrile hemolytic anemia – Oroya fever, and a chronic form in which cutaneous vascular lesions – verruga peruana can resemble bacillary angiomatosis histologically, but with fewer organisms. B. elizabethae has been reported to cause "culture negative" endocarditis and bacteremia, as have the other listed species. The various Bartonella infections are listed in the table below, and the discussion which follows focuses primarily on cat scratch disease (CSD) and bacillary angiomatosis (BA).

Clinical Bartonella Syndromes
  • Cutaneous bacillary angiomatosis (BA)
  • Extracutaneous BA
  • Bacillary peliosis hepatis and splenis
  • Cat scratch disease
  • Trench fever
  • Bacteremia and endocarditis
  • Bartonellosis (Carrion’s Disease)
    • - Acute; Oroya fever
    • - Chronic; verruga peruana

Clinical Features
The severity and presentation is related to the immune status. In general, classical CSD occurs in otherwise healthy patients, whereas those immunocompromised by AIDS or immunosuppression tend to have systemic disease characterized by bacillary angiomatosis. However, systemic disease has been reported in healthy patients and cat scratch disease in AIDS patients.

Cat Scratch Disease typically presents clinically as regional lymphadenopathy preceded by an erythematous papule at the inoculation site in 25-95% of patients. These two findings plus positive serology and characteristic histopathologic features are keys to the diagnosis. About two weeks after the scratch, regional lymphadenopathy develops, which lasts two-four weeks and resolves spontaneously. For most patients this is the typical course, but in 1-2% of cases there is prolonged morbidity with persistent fever, expanding suppuration of nodes with rupture through the capsule and extension to the skin. Other complications include Parinauds ocularglandular syndrome, hepatic and splenic abscess, encephalopathy, pneumonia, arthralgia and various skin eruptions.

Bacillary Angiomatosis can involve almost any organ system, but cutaneous lesions are most common and number and distribution reflects the degree of immunosuppression. Papules and nodules range from skin colored to dark red, and can resemble lesions of Kaposi’s sarcoma, or pyogenic granuloma/hemangioma.
Subcutaneous lesions mimicking soft tissue tumors and osteolytic lesions also occur. Visceral lesions include peliosis hepatis and splenis. Any mucosal surface can be the site of BA, including the larynx, trachea, bronchi and esophagus. Ophthalmic and CNS lesions also occur.

Laboratory Diagnosis
Histo- and cytopathology in the skin and lymph nodes of BA & CSD is characteristic, but requires an invasive procedure. Fine needle aspiration biopsy of enlarged lymph nodes for smear, culture and molecular diagnosis has also been successful in CSD. Epithelioid cell clusters in a necroinflammatory background is a characteristic cytologic picture, but can be mimicked by other entities. Because the differential diagnosis includes other causes of suppurative granulomas, including lymphogranuloma venerium, Yersinial adenitis, tularemia, brucellosis, atypical mycobacterial and fungal infections, finding the organisms with silver impregnation stains or by PCR is key to the diagnosis.

Culture is time consuming, but does not require special media, is not technically difficult, and can be attempted with homogenates of tissues and aspirates. However, it is not very sensitive and probably not worthwhile except in AIDS patients or for suspected bacteremias.

Serologic Diagnosis by immunofluorescence and enzyme immunoassay tests for IgM and IgG antibodies have been described. In general, these tests have not performed well, but recent reports of EIA’s analyzed by Western Blots describe good sensitivity and specificity (for IgG 86% and 95%; for IgM 94% and 99%), correlate well with IFA and with clinical findings. Two commercial IFA tests (BION, Chicago IL; MRL, Cypress, CA) are available and have been evaluated. Both tests are sensitive but not specific for IgG antibodies to B. henselae, but titers of &Mac179; 256 in the appropriate clinical context can support the diagnosis of CSD. For IgM, sensitivity and specificity with the BION product was 88 and 95%; for the MRL kit 64 & 86%. These tests now offer an early noninvasive approach to the diagnosis of CSD lymphadenopathy in the appropriate clinical setting; however, it should be noted that antibody kinetics vary widely among CSD patients; for AIDS patients with bartonella infection, a significant antibody response may not occur. For most patients, however, serology probably offers the most cost effective approach to diagnosis if both IgG and IgM or paired serum specimens are tested.

Molecular Diagnosis by PCR was a key development reported by Relman in 1990 (NEJM 323: 1573), who sequenced the 16 S RNA from specimens of bacillary angiomatosis (16 S RNA is in all bacteria, but has a unique sequence for each species). B. henselae and B. quintana differ only by a few base pairs. PCR on paraffin section is available in a few reference laboratories. Molecular testing can confirm B. henselae in the majority of suspected CSD cases. A few of the negative cases will be due to MAI or other organisms, but some will remain unexplained. PCR may be useful also to confirm a Bartonella etiology in other situations (e.g. tissue fragments of vegetation in culture negative endocarditis).

Written by: Louis A. Rosati, M.D.

References

  1. Adal K, et al. Cat scratch disease, bacillary angiomatosis and other infections due to Rochalimea. N Engl J Med 1994; 330:1509-1515.
  2. Anderson BE, and Neuman MA. Bartonella spp as emerging human pathogens. Clin Micro Rev 1997; 10: 203-219.
  3. Cockerell CJ and Connor DH. Cat scratch disease in Pathology of Infectious Disease. Connor DH, Chandler FW (eds). Appleton and Lange, Stanford Ct. 1997, Chap 49, Vol I; pp461-468.
  4. Jacamo V, et al. Human infections caused by Bartonella spp. Pts I & II, Clin Microbiol Newsl. 2000; 22, Nos 1 & 2.
  5. Jacobs RF, et al. Bartonella henselae as a cause of prolonged fever and fever of unknown origin in children. Clin Infect Dis 1998; 26:80-84.
  6. Jackson LA, et al. Cat scratch disease in the United States: an analysis of three national databases. Am J Public Health 1993; 83:1707-1711.
  7. Koehler JE, et al. Molecular epidemiology of Bartonella infections in patients with bacillary angiomatosis – peliosis. N Engl J Med 1997; 337:1876-1881.
  8. LeBoit P. Bacillary angiomatosis in Pathology of Infectious Disease. Connor DH, Chandler FW (eds). Appleton and Lange, Stanford CT 1997; Chap 42, Vol I; pp 407-415.
  9. Litwin CM, et al. Immunologic response to Bartonella henselae as determined by enzyme immunoassay and Western Blot analysis. Am J Clin Path 1997; 108:202-209.
  10. Margileth AM. Antibiotic therapy for cat scratch disease. Clinical study of therapeutic outcome. Pediatr Infect Dis J. 1992; 11:474-8.
  11. Mouritsen Cl, et al. Rapid polymerase chain reaction-based detection of the causative agent of cat scratch disease (Bartonella henselae) in formalin-fixed, paraffin-embedded samples. Human Path. 1997; 28:820-826.
Laboratory Diagnosis of Bartonella Infections
Infection Bartonella species Diagnostic techniques available
Trench fever B. quintana Blood culture, serology
Oroya fever B. bacilliformis Blood culture, blood smear
Verruga peruana B. bacilliformis Biopsy & culture
Cat scratch disease B. henselae Biopsy, serology & PCR
Bacillary angiomatosis B. quintana
B. henselae		 Biopsy, culture & PCR
Peliosis hepatis B. henselae Biopsy, culture & PCR
Bacteremia in homeless B. quintana Blood culture
Endocarditis B. quintana
B. henselae
B. elizabethae		 Serology, blood culture, PCR

Modified from: Jacomo V & Raolt D. Clin Microbiol Newsl. 2000; 22 No. 2