|Year : 2016 | Volume
| Issue : 3 | Page : 182-183
Citrobacter freundii : A rare cause of native valve endocarditis
Maria Koshy, Ravikar Ralph, Kundavaram Paul Prabhakar Abhilash, George M Varghese
Department of Medicine I and Infectious Diseases, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Web Publication||28-Sep-2016|
Kundavaram Paul Prabhakar Abhilash
Department of Medicine I and Infectious Diseases, Christian Medical College, Vellore - 632 004, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Citrobacter species are usually intestinal tract colonizers and occasionally cause nosocomial infections such as urinary tract, respiratory tract, and wound infections. However, native valve endocarditis due to these organisms is extremely rare. We report a human immunodeficiency virus-infected individual with Citrobacter freundii endocarditis of the native aortic valve.
Keywords: Citrobacter freundii, endocarditis, infective endocarditis
|How to cite this article:|
Koshy M, Ralph R, Abhilash KP, Varghese GM. Citrobacter freundii : A rare cause of native valve endocarditis. J Med Soc 2016;30:182-3
| Introduction|| |
Members of Citrobacter genus are facultative anaerobic Gram-negative Bacilli belonging to the Enterobacteriaceae family. These organisms often colonize human and animal intestinal, urinary, and respiratory tracts. Citrobacter freundii is the common species linked to human disease. Infections are commonly reported in neonates, the elderly, and immunocompromised hosts, and include respiratory tract infections, urinary tract infections, bloodstream infections, wound and burn infections, meningitis, endocarditis, and peritonitis, which are most often nosocomially acquired. Endocarditis due to C. freundii, though reported in literature, is extremely rare. We report the first case of native valve C. freundii endocarditis from India in an immunocompromised patient.
| Case report|| |
A 42-year-old homemaker from West Bengal was admitted with a history of high-grade fever for 2 weeks. She had been diagnosed to have tuberculous lymphadenitis for the past year and completed 6 months of antituberculous therapy. Physical examination revealed pallor and a mild hepatomegaly. The cardiovascular system did not reveal any murmurs and the rest of the systemic examination was unremarkable. Complete blood count showed a total white blood cell count of 4400/cumm (70% neutrophils, 23% lymphocytes, and 7% monocytes), hemoglobin of 7.5 g%, and platelet count of 175,000/cumm. Three sets of blood culture were taken, each half an hour apart and from different sites. About 5-8 ml of blood was collected in adult blood culture bottles (BacT® /Alert) using standard precautions and processed by semi-automated blood culture system (BacT® /Alert; BioMérieux, MarcyΎ Etoile, France). Cultures flagged positive for growth within 12 h were identified using conventional methods (colony morphology and biochemical tests). Two sets of blood cultures grew C. freundii. Antimicrobial susceptibility testing was performed using disc diffusion method, which showed susceptibility to ciprofloxacin, gentamicin, amikacin, piperacillin-tazobactam, imipenem, and colistin. Transesophageal echocardiography revealed 5 mm × 3 mm mobile vegetation on the aortic valve. There was no other valvular abnormality. A diagnosis of C. freundii-infective endocarditis was thus confirmed and the patient was initiated on intravenous ciprofloxacin. She was also found to have human immunodeficiency virus (HIV) infection with a CD4 count of 57 cells/μl. The patient was successfully treated with a 6-week course of intravenous ciprofloxacin, and blood cultures taken after 2 weeks of antibiotics were sterile. Antiretroviral therapy was also initiated for advanced HIV infection after ruling out the possible underlying opportunistic infections.
| Discussion|| |
The genus Citrobacter is named after the organism's ability to use citrate as its sole carbon source. Citrobacter species are primary inhabitants of the intestinal tract and are often found in human feces. The genus Citrobacter has 11 different species and three among them such as C. freundii, Citrobacter koseri (Citrobacter diversus), and Citrobacter amalonaticus are known to cause human disease. In patients with Citrobacter infections, the bacteria can be transmitted vertically from mother or horizontally from carriers or other hospital sources.  The most common sources of Citrobacter isolates are urine, sputum, and soft tissue exudates. The urinary tract is the most frequent site from which Citrobacter is cultured and is usually associated with an indwelling catheter. Majority of Citrobacter infections (87.6%) are nosocomial-acquired and C. koseri is usually the predominant species.  Citrobacter species were isolated from 35.4% of the patients admitted in a tertiary referral burn center in Iran.  Although the incidence of bacteremia is low (0.3-0.9%), the mortality rate may be high.  Nosocomial neonatal septicemia due to C. freundii resulting in disseminated intravascular coagulation and hepatitis has been frequently reported.  Other rare complications of C. freundii include psoas abscess, spontaneous bacterial peritonitis, and septic arthritis. ,, Infective endocarditis due to C. freundii has been previously reported in patients with chronic liver disease, intravenous drug abusers, and those with a valvulopathy.  Our patient had advanced HIV infection and hence was vulnerable for bacteremic seeding of the previously normal aortic valve.
Of late, Citrobacter species are being isolated with an increasing frequency in hospital settings, and emergence of multidrug resistant strains is a serious concern. Resistance to multiple antibiotics is a result of plasmid-encoded resistance genes. Most species belonging to the Citrobacter, Enterobacter, Serratia, and Pseudomonas genera, as well as indole-positive Proteus species, commonly referred to as the "SPICE" organisms, have chromosomally inducible beta-lactamases (AmpC). This enzyme acts by either hydrolyzing or by simply binding the β-lactam that reaches the periplasmic space. The introduction of third-generation cephalosporins has led to the unexpected increase of resistance to β-lactams in the members of these genera. Metri et al. reported 76-94% of resistance to cephalosporins and 65-75% of resistance to fluoroquinolones.  Most of the studies have shown imipenem to have the maximum sensitivity.  Different species of Citrobacter demonstrate different antimicrobial susceptibility profiles. C. freundii is generally much more resistant to antimicrobial agents than the other species. The C. freundii isolate in our patient was a susceptible strain.
| Conclusion|| |
Although rare, infective endocarditis should be suspected in patients with C. freundii bacteremia, especially in immunocompromised individuals. As these infections are associated with a high mortality rate, prompt recognition of this complication and administration of antibiotics may be lifesaving.
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