Bacterial Infections

There are currently 11 known species of Bartonella, four of which are considered to be pathogenic in humans, namely B bacilliformis, B quintana, B henselae, and Bartonella elizabethae. B henselae and B elizabethae have only recently been isolated and identified, but B quintana and B bacilliformis have long been known as the causes of trench fever (B quintana) and Oroya fever and verruga peruana (B bacilliformis). The bartonellae establish intimate relationships with animal hosts, often within the vascular compartment but without causing disease. The relationship between B bacilliformis and the other three Bartonella species that are pathogenic in humans was established in the early 1990s.

Patients complain of fever, myalgias, malaise, headache, bone pain — particularly of the legs, and a transient macular rash. Usually the illness continues for 4-6 weeks.

The most common manifestation of bacillary angiomatosis is a dermal lesion (Table 1). Three types of lesions are seen: cutaneous papules, subcutaneous nodules, and hyperpigmented plaques, in decreasing order of frequency. Papules are usually red-purple in color and range in size from a few millimeters to several centimeters, often surrounded by a collarette of scale.

Rickettsialpox has been reported infrequently in the United States. This disease is a mild, self-limited illness caused by R akari and is transmitted to humans by a house mite.

RMSF is caused by Rickettsia rickettsii and is an acute tick-borne illness occurring during seasonal tick activity. The disease is characterized by acute onset of fever, headache, and a rash of the extremities spreading to the trunk. A. Epidemiology.

Ehrlichiosis is not a reportable disease, so its true incidence is unknown. The majority of cases of HME have been reported from the south, central, and southeastern United States. Cases have also been reported from Western Europe, Scandinavia, and Africa. In contrast, most cases of HGE have been reported from the upper midwestern and northeastern United States.

Once inside a host cell, Coxiella and Ehrlichia spp. remain within a vacuole where they progress through distinct developmental stages; in contrast, the Rickettsia spp. escape the endocytic vacuole and replicate within the host cell cytoplasm. Ehrlichia and Rickettsia spp. are transmitted by arthropod vectors. Coxiella burnetii is the causative agent of Query or Q fever.

Chlamydia trachomatis, Chlamydia psittaci, and Chlamydia pneumoniae are among the most prevalent microbial pathogens in humans worldwide. C trachomatis is responsible for a variety of sexually transmitted disease (STD) syndromes in both sexes. In addition, certain serotypes of C trachomatis are responsible for trachoma, the most common infectious cause of blindness in humans. C psittaci is a zoonotic pathogen associated with atypical pneumonia.

Pneumonia, pericarditis, myocarditis, and endocarditis have been attributed to C psittaci infection (psittacosis or ornithosis) (Box 5). The incubation period for the pneumonia is usually 1-2 weeks. Its onset is gradual with body temperature increasing over a period of 5-7 days; however, there are cases in which the onset is sudden with rigors and temperatures as high as 104 °F.