SOME CHARACTERISTICS OF Bartonella henselae AN OPPORTUNISTIC PATHOGEN IN ACQUIRED IMMUNE DEFICIENCY SYNDROME

Abstract

Cat-scratch disease (CSD) is an infectious disease, implicated as an opportunistic infection in human immunodeficiency virus (HIV) patients. So far, Bartonella henselae (Rochalimaea henselae), remains the most acceptable causative agent with infections reported in Europe, Asia and the United States, but not in Africa. The transmission cycle of the organism is not well understood, but cats are a suggested reservoir host. Distribution of B.henselae and other Bartonella species antibodies in humans and animals, as well as some biological characteristics of the organisms and applicability of line blot assay for diagnosis of CSD using four different antigen preparation. Both B.henselae and B.quintana grew better on heart infusion agar with rabbit blood (HIA/RB) than on trypticase soy agar (TSA) with different colony morphology. However, B.henselae grew more readily. Using IFA test, 4.4% of 1564 human sera from Africa were positive for antibody to B.henselae and B.aquintana or both, with a range of 3.2 to 5.6% in sera from different locations. Antibody prevalence of 11.6% (n-=353) in HIV positive individuals was significantly higher than in the general population. When 300 of the HIV samples that had been screened for HIV antibodies by the wellcozyme test were retested by the Genetic systems kit only 247 demonstrated antibodies. Of 1011 serum samples from cats, 31.4% were positive to B.heaselae antibodies, while 29.6% to B.quintana antibodies. The highest B.henselae antibody prevalence of 32.4% (n=953) was in cats from the USA, of which 2 were from a breeding house. Seroconversion occurred in 22.5% of all cats tested (n=151). Of 1886 Rodents and insectivores tested, 3 (0.3%) were positive for B. henselae, 7(0.3%) for B.quintana none for B.vinsonii and 6(0.3%) for R.rickettsii, while none of the insectivores and 78 Mastomys species tested from Nigeria were positive. Of 209 dogs from from the USA tested, 2.9% were antibody positive for B.henselae or B. quiniana suggesting dogs are susceptible to infection with these organisms. Experimental B.henselae infection Of CD-1 mice did not produce

disease and organism was not recovered from blood or organs of infected mice. Similarly, DNA was not detected in polymerase chain reaction (PCR). However, a significant antibody response was obtained in adult mice intraperitoneally inoculated. Infected weanling mice showed low antibody response and those allowed to mature produced antibody positive sucklings indicative of maternally acquired immunity. Results of line blot assays showed the test could easily be adapted for diagnosis of CSD. The best B.henselae antigens being those from E6 cell line, agar or treated with 20% sodium dodecyl sulfate (SDS), while nonidet 40 treated antigens were poor. Tissue culture studies showed BHK-21, MDCK and HEK, but not Hep2 cell lines were sensitive to B.henselae. Heat stability study showed the organism to be stable at -70⁰C for 6 months, -20⁰C for one month, 35°C for 3 hours, 22⁰C for 24 hours and +4°C for 72 hours, while chemical treatment showed that the organism was sensitive to 1% acetic acid, Chloroform, Formaldehyde and phenol. These studies demonstrated that there is a possibility that Bartonella infections may already be present in Africa. Thus, Bartonella henselae could be one of several opportunistic pathogens in HIV patients in Africa and line blot assay could be a useful diagnostic tool for Bartonella infections. Also rodents may be accidental rather than reservior hosts.