Bartonella quintana: What a Lousey Bug!

Abstract & Commentary

Synopsis: Bacteremia due to B quintana is prevalent among homeless individuals in many cities and is often asymptomatic and chronic or intermittent.

Source: Foucault C, et al. Bartonella quintana bacteremia among homeless people. Clin Infect Dis. 2002;35:684-689.

Foucault and colleagues in Marseilles, France, evaluated homeless individuals presenting either to the emergency departments of the University Hospital as well as those admitted to medical facilities at shelters in order to determine the prevalence of Bartonella quintana bacteremia. One milliliter of whole blood was plated onto sheep blood agar while the remainder was inoculated into an aerobic blood culture bottle. After 7 days of incubation, 1 mL was removed from the blood culture bottles and plated on sheep blood agar plates, which, like those directly inoculated, were examined weekly for 3 months. Isolates from blood and body lice were identified by PCR methods.

Of the 126 individuals studied, all of whom were HIV-negative, 42 (33%) had B quintana bacteremia. Lice were detected on 18 (43%) of the bacteremic and 18 (21%) of the nonbacteremic subjects (OR, 2.75). B quintana was detected by PCR in lice more frequently from bacteremic than nonbacteremic individual (56% vs 6%; OR, 21.25). Sixty-five percent of the bacteremic and 20% (OR, 7.66) of the nonbacteremic subjects had elevated antibody titers to B quintana.

Approximately one-third of both the bacteremic and nonbacteremic patients were febrile, and the groups were similar in most other characteristics as well, with the exception of a greater frequency of sweats (22% vs 5%) among the former. The WBC was normal in all subjects.

Only one of the serial blood cultures was positive in 22 of the 42 bacteremic homeless subjects, but at least 2 consecutive cultures obtained at weekly intervals were positive in 16, while 5 had intermittently positive cultures. Bacteremia persisted for 17, 53, and 78 weeks in 1 subject each and was intermittent for periods of 4-58 weeks in another 4.

No evidence of endocarditis was detected in the 14 patients who underwent echocardiography, although a transthorac procedure was performed in only 7 of these. Six of 8 patients treated with either amoxicillin, amoxicillin/clavulanate, or benzathine penicillin remained bacteremic, as did 2 of 4 treated with doxycycline. None of 4 given gentamicin plus doxycycline had bacteremia at follow-up.

Comment by Stan Deresinski, MD, FACP

Pediculus humanus, the human body louse, is the only known vector of B quintana, which may cause, in addition to the chronic and often asymptomatic bacteremia described in this study, trench fever, endocarditis and some cases of bacillary angiomatosis. P humanus infests only humans and is the vector for at least 2 pathogens, in addition to B quintana Rickettsia prowazekii, the agent of epidemic typhus, and the spirochete, Borrelia recurrentis, a cause of relapsing fever.1 High seroprevalence rates indicating B quintana infection have been described among homeless in Paris,2 Baltimore,3 and Seattle,4 and the organism has been detected in 12.3% of body lice examined in Russia.5

B quintana infects erythrocytes where it may persist for the life of the individual red blood cell and, in addition, may infect endothelial cells.6-8 Bacteremia may persist for as long as 8 years.9 In contrast to infection with Bartonella bacilliformis, which also infects erythrocytes, B quintana infection is not associated with hemolysis. Asymptomatic B quintana bacteremia has its counterpart in the domestic cat, a large proportion of which in some locations has chronic asymptomatic bacteremia due to B henselae, the agent of cat scratch disease whose vector is the cat flea.10,11

A high index of suspicion must be maintained in order to make a bacteriological diagnosis of bloodstream infection with B quintana if for no other reason than the difficulty most of us currently have in convincing our microbiology laboratories to do any work over and above the routine minimum. As indicated above, recovery from blood requires prolonged incubation since detectable growth often takes 20-40 days.12 Serological tests are, of course, less specific than microbiological diagnosis.

Although the data from this study are nonrandomized and very limited, they do suggest that a combination of doxycycline and gentamicin may be a preferred regimen. Others have recommended monotherapy with doxycycline, erythromycin, or azithromycin for 4-6 weeks if the infection is uncomplicated, with the addition of either a third-generation cephalosporin or an aminoglycoside for the first 2-3 weeks in patients with endocarditis.12

All of this begs the question of what to do when next confronted with a homeless individual, whether symptomatic or not, in an area where B quintana infection is prevalent. In this study, only one-third had a temperature higher than 37.5°C. Reliance on serological screening would also be of limited value; while 65% of the bacteremic patients in this study had an elevated antibody titer to B quintana antigens, so did 20% of the nonbacteremic group. On the other hand, the presence of very high titers ( > 1:800) was a better discriminator between the groups but was quite insensitive, with only 23% of bacteremic subjects having such a titer.

Furthermore, in the absence of endocarditis, it is unclear that there is any clinical benefit to treatment, which, at any rate, may often fail.

Finally, sending the individuals back to their previous environment is likely to subject them to reinfection. Thus, the question of when to badger our microbiology laboratories to appropriately handle blood cultures in order to detect B quintana bacteremia remains, in most circumstances, unclear.

Dr. Deresinski, Clinical Professor of Medicine, Stanford; Associate Chief of Infectious Diseases, Santa Clara Valley Medical Center, is Editor of Infectious Disease Alert.


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10. Bergmans AM, et al. Prevalence of Bartonella species in domestic cats in The Netherlands. J Clin Microbiol. 1997;35:2256-2261.

11. Jameson P, et al. Prevalence of Bartonella henselae antibodies in pet cats throughout regions of North America. J Infect Dis. 1995;172:1145-1149.

12. Ohl ME, Spach DH. Bartonella quintana and urban trench fever. Clin Infect Dis. 2000;31:131-135.