Endocarditis in injection drug users is usually right sided and most commonly involves the tricuspid valve.1
Right-sided endocarditis presents with a syndrome of persistent fever and pulmonary symptoms due to septic emboli including cough, dyspnea, and hemoptysis. The peripheral stigmata of endocarditis caused by immunologic vascular events are not classically found in right-sided endocarditis.3
The most common organism isolated is Staphylococcus aureus
The case presented here and a review of the literature, however, demonstrates that it is important to consider other more fastidious causes of infection in this population. IDUs may be exposed to a variety of microbes due to their drug injection practices. For example, IDUs are subject to infection from normal oropharyngeal flora from the habit of cleaning their needles with saliva and using saliva to dissolve the drug. A case of endocarditis from 1 oral microbe, Neisseria sicca
, has been reported in an IDU who licked the blood off the needle of an unsuccessful “stick” before the next attempt.4
Raucher et al.5
reports cases of polymicrobial endocarditis with Haemophilus parainfluenzae
and other organisms of the normal oral flora. In this case series, several patients admitted to blowing into or sucking on their needles before injection. Endocarditis from Pseudomonas
species has been associated with washing needles in contaminated water.6
The bacteria implicated in this patient's endocarditis are Actinomyces odontolytica
species, and Prevotella melaninogenica
. They are all anaerobes predominantly found in the human oral cavity. They are all more commonly associated with other infections and abscesses but they can cause endocarditis in patients with predisposing conditions such as valvular heart valve disease and injection drug use.7,8,9
As in other previously described cases, we believe that this patient was exposed to these organisms through his habit of licking the needle prior to injection. Interestingly, 1 study identifies our organisms, Actinomyces odontolyticus
, Veillonella parvula
, and Prevotella melaninogenica
, as a part of a cluster of organisms that are particularly abundant in saliva and on the dorsal and lateral surfaces of the tongue.10
This information, the patient's history, and the absence of other organisms on blood culture confirm that these bacteria are the likely cause of the polymicrobial endocarditis in our patient. In a similar case, Mah and Shafran reported about an IDU with polymicrobial endocarditis involving Veillonella
species in which salivary contamination was suspected as the source of infection.11
There are no reports, however, of polymicrobial endocarditis in IDUs with the other organisms in this discussion.
In this case, penicillin G and metronidazole were the chosen treatments to cover all 3 organisms. Initially, however, assumptions regarding the source of his infection delayed the initiation of appropriate therapy. Being unaware of the patient's particular drug use habits, we assumed that coverage for skin flora would be adequate. In fact, it was entirely inadequate. In response to similar situations, some authors propose empirically treating for polymicrobial infection in all IDUs with endocarditis.11
They point out that in some instances valve vegetation cultures grow additional organisms beyond what is found on blood cultures.11
We, however, do not advocate that all cases of endocarditis in IDUs be empirically treated for polymicrobial infection. Rather, we recommend that a detailed history of injection drug use be taken. This history should delve into the user's habits and reveal the exact actions of the user from acquisition to disposal of the needle and the drug. It is critical that the examiner approach the patient nonjudgementally so as to elicit an honest history. If the history reveals exposure to other microbes in addition to skin flora, the empiric therapy should be adjusted to cover these organisms. The question that remains is whether this coverage should be dropped if blood cultures do not support infection by a non-skin flora organism. But in the event that the patient does not rapidly recover during the usual empiric therapy, a good history of injection drug use habits may point the physician to another antimicrobial agent.
In summary, we present a case of IE from Actinomyces odontolytica, Veillonella species, and Prevotella melaninogenica in a patient with a history of injection drug use. His habit of licking the needle to gauge the strength of the injection exposed him to infection by these oral microbes. Clearly, contamination from non-skin flora and polymicrobial endocarditis should be considered in an IDU with nonsterile injection drug use practices. Thus, we emphasize the importance of obtaining a detailed history of the injection drug use habits of the patient. This may reveal a risk factor for more unusual infections and alter the empiric therapy of endocarditis.