A 33-year-old white male presented to our hospital with a 2-week history of subj

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A 33-year-old white male presented to our hospital with a 2-week history of subjective fevers, chills, and rigors. He also complained of a 20-to 30-lb weight loss, which he attributed to a decrease in appetite as well as to some nausea and vomiting. The patient had previously been seen at another hospital for these symptoms and was prescribed levofloxacin for possible pneumonia. He later returned to that hospital when his symptoms did not improve and a computed tomography (CT) scan of the thorax reportedly showed “spots on his lungs.” The patient was given more unknown antibiotics and sent home. Additionally, the patient reported having a dental procedure 6 months previously. His past medical history included diabetes mellitus type 2, gastroesophageal reflux disease, and schizoaffective disorder. He had no history of endocarditis or valvular heart disease. The patient smoked 1.5 packs of cigarettes per day for the past 20 years, consumed alcohol occasionally, and had a history of injection drug use, particularly cocaine. He last used injection cocaine 5 weeks prior to admission. On admission the patient had a temperature of 40.0°C, a pulse of 80 beats per minute, a respiratory rate of 19 breaths per minute, and a blood pressure of 130/80 mmHg. On physical exam, there was no jugular venous distention and there was a II/VI holosystolic murmur at the lower left sternal border that became louder with inspiration. Lungs were clear to auscultation bilaterally. White blood cell count was 15.1K cells per mL with 90.8% granulocytes and an increase in bands. Cardiac enzymes were normal. Chest radiograph revealed only a slight increased opacity in the right upper lobe of the lung but CT of the thorax showed multiple cavitary lesions in both lungs.. The remainder of the valves was normal. Initially, the patient was treated empirically for endocarditis with vancomycin and ceftriaxone to cover Staphylococcus aureus and Streptococcus. Anaerobic blood culture bottle, however, returned positive for branching gram positive bacilli and gram negative cocci. The therapy was then changed to penicillin G based on the usual sensitivities of these organisms. Blood cultures sent for the AACEK (Haemophilus species, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella species) organisms were negative after 6 weeks of incubation. Although the patient remained febrile after several days of penicillin G therapy, blood cultures before discharge were negative and the white blood cell count had decreased to 7.5K cells per mL with 74.8% granulocytes. The patient was then discharged with a central line for outpatient therapy. The patient continued to be febrile. After 6 days, the patient was readmitted to the hospital. The patient denied resumption of illegal injection drug use during his time at home. Blood cultures drawn at readmission again grew same two organisms isolated on first admission and additionally grew an anaerobic pigmented, gram negative bacilli. The patient was then treated with penicillin G and metronidazole. He became afebrile within 4 days and completed an uneventful 6-week in-patient course of therapy. Cardiothoracic surgery evaluation on admission and upon final discharge found no need for surgical intervention.

1. What three bacteria may be implicated in this patient's endocarditis based on the clinical history and laboratory isolation?

2. What is the pathogenicity of each organism?

3. How did the patient acquire these bacteria?

Explanation / Answer

1. ANS: Based on the clinical history and laboratory isolation of the endocarditis patient the three bacteria that are Cardiobacterium hominis, Haemophilus parainfluenzae and Staphylococcus aureus. These organisms generally occur in the saliva as normal flora. However, drug users who lick the blood on syringes ingest them and thus, they can casue polymicrobial endocarditis.

2. ANS: Pathogenicity of each organism:

A. Cardiobacterium hominis:It is Gram negative bacillus that occurs as normal flora of mouth and upper respiratory tract. The bacterium is grouped into HACEK group. The organism can cause inflammation of heart valves. It produces beta lactamases

B. Haemophilus parainfluenzae: Gram negative, pleomorphic, facultative anaerobes. The organism is mostly assocaited with upper respiratory tract infections and mitral valve inflammation. The organism is generally found in coinfection with Streptococcus.

C. Staphylococcus aureus: It is a virulent pathogen that is currently the most common cause of infections in hospitalized patients. S. aureus infection can involve any organ system. The bacteria are a leading cause of food poisoning, resulting from the consumption of food contaminated with enterotoxins.

3. ANS: The organisms are normally present as flora in the host. The patient acquired these bacteria due to the use of syringe drugs. Licking of the blood on the syringe, and sterilizing the syringe by licking makes the organism enter the sytem.

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