Lactococcus garvieae endocarditis: first case report in Latin America

Abstracts

Lactococcus garvieae, patógeno zoonótico emergente, é responsável por mastite em ruminantes e septicemia em peixes. Embora seja considerado oportunista e raramente causar infecções em humanos, sua incidência deve estar subestimada devido à dificuldade do diagnóstico. Há pouquíssimos relatos de osteomielite, abscesso hepático e peritonite, e apenas nove casos descritos na literatura mundial de endocardite. Relatamos o primeiro caso de endocardite por Lactococcus garvieae da América Latina em paciente portadora de prótese valvar metálica, com quadro de febre diária, calafrios, nodos de Osler e seis hemoculturas positivas para Lactococcus garvieae, que preenchiam os critérios de Duke para o diagnóstico de "endocardite infecciosa definitiva"

Endocardite bacteriana; diagnóstico; Lactococcus garvieae; próteses valvares cardíacas

Lactococcus garvieae, patógeno zoonótico emergente, es responsable por mastitis en rumiantes y septicemia en peces. Aunque sea considerado oportunista y raramente cause infecciones en humanos, su incidencia debe estar subestimada debido a la dificultad del diagnóstico. Hay poquísimos relatos de osteomielitis, absceso hepático y peritonitis, y apenas nueve casos descriptos en la literatura mundial de endocarditis. Relatamos el primer caso de endocarditis por Lactococcus garvieae de América Latina en paciente portadora de prótesis valvar metálica, con cuadro de fiebre diaria, escalofríos, nódulos de Osler y seis hemocultivos positivos para Lactococcus garvieae, que llenaban los criterios de Duke para el diagnóstico de "endocarditis infecciosa definitiva"

Endocarditis bacteriana; diagnóstico; Lactococcus garvieae; prótesis valvares cardíacas

CASE REPORT

^IFGM - Clínica Paulista de Doenças Cardiovasculares, São Paulo, SP - Brasil

^IIHospital Beneficência Portuguesa de São Paulo, São Paulo, SP - Brasil

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ABSTRACT

Lactococcus garvieae, an emerging zoonotic pathogen, is responsible for mastitis in rodents and sepsis in fish. Although deemed opportunistic and hardly ever causing infections in humans, its incidence is probably underestimated due to the difficulty in diagnosis. There are very few reports of osteomyelitis, liver abscess, and peritonitis, and only nine cases of endocarditis described in worldwide literature. We describe the first case of Lactococcus garvieae endocarditis in Latin America, in a female patient with metallic prosthetic heart valve who presented with daily fever, chills, Osler nodes and six positive blood cultures for Lactococcus garvieae, which met Duke's criteria for the diagnosis of "definitive infective endocarditis".

Keywords: Endocarditis, bacterial; diagnosis; Lactococus garvieae; heart valve prosthesis.

Introduction

Lactococcus garvieae, an emerging zoonotic pathogen, was originally isolated in mastitis in rodents and is responsible for sepsis in fish; it is deemed opportunistic and shows low virulence in humans, with very few reports of endocarditis (nine cases in the worldwide literature)^1-7, osteomyelitis⁸, liver abscess⁹, sepsis, and peritonitis⁵. However, the difficult differential diagnosis with Enterococcus may lead to underestimation of its incidence and real importance. In the present study, we report the first case of Lactococcus garvieae endocarditis in Latin America, the tenth in the worldwide literature.

Case report

A 58-year-old female Caucasian patient, a former smoker previously hypertensive, with type-2 diabetes, dyslipidemia, underwent mitral valve replacement by a metallic prosthetic valve six months earlier due to severe mitral stenosis of rheumatic etiology. Upon arrival at the hospital, the patient had a history of daily fever for six days (38.5º C), chills, diaphoresis, erythematous nodules in hands and legs, myalgia and weakness. As regards her nutritional habits, she often consumed several types of fish and reported having eaten white cheese recently. Despite denying dental treatment in the past few months, the patient had a dental prosthesis and had had a gingival perforation with a "fish bone" five days prior to the onset of symptoms.

On admission, she had fever (38.2º C), Osler nodes on her left hand and legs, and poor dentition. The remainder of her physical examination was unremarkable. Laboratory tests showed alterations in inflammatory tests, with PCR = 81.9 and VHS = 47.1, with no leukocytosis. No focus of infection was identified, despite extensive diagnostic investigation.

In samples for blood cultures drawn from three different sites, Gram-positive cocci were isolated and further identified as Lactococcus garvieae by means of biochemical tests and confirmed by genetic studies. The pathogen was isolated again in three other blood cultures samples drawn five days later. The antibiotic susceptibility test showed resistance only to clindamycin, and sensitivity to penicillin, gentamicin, vancomycin and other antibiotics.

Two transesophageal echocardiograms were performed, revealing absence of vegetation and competent mitral valve prosthesis. However, according to Duke's modified criteria, the patient was diagnosed with endocarditis and was treated with vancomycin 1 g every 12 hours for 28 days, due to confirmed penicillin allergy. There was complete remission of signs and symptoms, as well as normalization of laboratory tests; control blood cultures were negative.

In an attempt to identify the source of the infection, the white cheese consumed by the patient was sent for microbiologic testing. In the search for an "entrance door", due to the family history of intestinal polyposis, the patient also underwent barium enema. However, both tests were normal.

The patient was discharged with no symptoms after 30 days of hospitalization, and was referred for cardiology outpatient follow-up.

Discussion

Lactococcus garvieae is one of the eight species belonging to the Lactococcus genus, originally known as the lactic group of the Streptococcus genus, from which it was split in 1985, after genetic analysis¹⁰.

Formed by facultatively anaerobic catalase-negative Gram-positive cocci, these bacteria produce lactic acid, which provide them with fermentation ability and bactericidal property; thus, it is used in the food industry for fermentation and preservation of food¹⁰.

However, it is known that some species may be pathogenic to animals and humans, especially Lactococcus garvieae and Lactococcus Lactis¹⁰.

Considered an emerging zoonotic pathogen, Lactococcus garvieae is responsible for mastitis in rodents, and sepsis in fish. Infected fish which do not develop the disease may contribute to dissemination⁵.

It is considered an uncommon pathogen in humans; it is opportunistic and shows low virulence. Very few cases have been described in the literature with Lactococcus garvieae being the causal agent of endocarditis^1-7, osteomyelitis⁸, liver abscess⁹, sepsis and peritonitis⁵. There are nine cases of endocarditis reported in worldwide literature: in four of them prosthetic valves^1,3 are affected, and in the other five, native heart valves are^2,4,5,7.

This is the first case report of Lactococcus garvieae endocarditis in Latin America in a patient with metallic prosthetic valve in the mitral position who met the modified Duke criteria for the diagnosis of "definitive endocarditis" (Table 1).

Pathogenicity and infectivity of Lactococcus garvieae remain inconclusive. It is known that lactococci are not typically a part of the human flora³, but the intake of milk or contaminated fish may be sources of infection⁵. They have also been isolated in manufactured food due to their use in food products. However, gastric acidity, pancreatic enzymes, gallbladder and intestinal secretions, peristalsis, and epithelial cell integrity are protective factors against oral and gastrointestinal infections. The existence of gastrointestinal disorders such as ulcers, polyps or diverticula may act as facilitators of bacterial infectivity.

In the case described, the source of infection may have been the fish routinely consumed by the patient; the wound may have been caused by the "fish bone" and her poor dentition which may both been the entrance door. However, no data confirm this hypothesis.

It is difficult to distinguish L. garvieae from Enterococcus, because their phenotypes are similar. It is also challenging to distinguish Lactococcus garvieae from L. lactis. Some studies suggest the use of antibiotic susceptibility tests, because L. garvieae is resistant to clindamycin, whereas L. lactis is always sensitive to this antibiotic: this proved true in the present case.

In relation to the echocardiogram, few reports are found in the literature of patients presenting with vegetations in the native valve², and cases without abnormalities both in the transthoracic and transesophageal test of patients with endocarditis in prosthetic valves⁸, as in the present case report.

The gold-standard test for the identification of Lactococcus gavieae, despite its high cost, is the genetic study with confirmation of its DNA sequence¹⁰.

Conclusion

Lactococcus garvieae endocarditis is extremely uncommon, this being the tenth case described in worldwide literature, and its pathogenesis remains inconclusive. Possible sources of infection are contaminated milk and fish, with reports of growth of these bacteria in manufactured food. Gastrointestinal comorbidities and poor oral conditions may facilitate infectivity of this pathogen. Prosthetic heart valves are also predisposing factors, and this implies the need to advise patients on the importance of oral hygiene and dental treatment in the prevention of endocarditis. Gastrointestinal disorders should also be investigated whenever necessary.

Phenotypic similarities between Lactococcus and Enterococcus make it difficult to establish a microbiological diagnosis, so that genetic studies are still necessary for the definite identification of Lactococcus garvieae. The fact that these tests are unavailable in most of the medical centers worldwide probably cause Lactococcus garvieae to be underdiagnosed, so its clinical significance may be far greater than is thought.

Potential Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Sources of Funding

There were no external funding sources for this study.

Study Association

This study is not associated with any post-graduation program.

References

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• 4. Vinh DC, Nichol KA, Rand F, Embil JM. Native-valve bacterial endocarditis caused by Lactococcus garvieae. Diagn Microbiol Infect Dis. 2006;56(1):91-4.
• 5. Wang CY, Shie HS, Chen SC, Huang JP, Hsieh IC, Wen MS, et al. Lactococcus garvieae infections in humans: possible association with aquaculture outbreaks. Int J Clin Pract. 2007;61(1):68-73.
• 6. Yiu KH, Siu CW, To KK, Jim MH, Lee KL, Lau CP, et al. A rare cause of infective endocarditis; Lactococcus garvieae. Int J Cardiol. 2007;114(2):286-7.
• 7. Li WK, Chen YS, Wann SR, Liu YC, Tsai HC. Lactococcus garvieae endocarditis with initial presentation of acute cerebral infarction in a healthy immunocompetent man. Intern Med. 2008;47(12):1143-6.
• 8. James PR, Hardman SM, Patterson DL. Osteomyelitis and possible endocarditis secondary to Lactococcus garvieae: a first case report. Postgrad Med J. 2000;76(895):301-3.
• 9. Mofredj A, Baraka D, Kloeti G, Dumont JL. Lactococcus garvieae septicemia with liver abscess in an immunosuppressed patient. Am J Med. 2000;109:513-4.
• 10. Facklam R, Elliott JA. Identification, classification, and clinical relevance of catalase-negative, Gram-positive cocci, excluding the streptococci and enterococci. Clin Microbiol Rev. 1995;8(4):479-95.

Lactococcus garvieae endocarditis: first case report in Latin America

Tatiana Franco Hirakawa^I,II; Fernando Augusto Alves da Costa^I,II; Marcos Cairo Vilela^I,II; Micheli Rigon^I,II; Henry Abensur^II; Maria Rita Elmor de Araújo^II

Publication Dates

• Publication in this collection
  20 Dec 2011
• Date of issue
  Nov 2011

History

• Reviewed
  20 Aug 2010
• Received
  05 June 2010
• Accepted
  09 Sept 2010