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Bacterial endocarditis due to Lactococcus lactis subsp. cremoris: case report

1996; Elsevier BV; Volume: 2; Issue: 3 Linguagem: Inglês

10.1016/s1198-743x(14)65148-x

1469-0691

Giampietro Pellizzer, P. Benedetti, Francesca Biavasco, Vinicio Manfrin, Marzia Franzetti, Mariuccia Scagnelli, Claudio Scarparo, Fausto de Lalla,

Diphtheria, Corynebacterium, and Tetanus

Lactococci are catalase-negative, Gram-positive cocci formerly classified as group N streptococci (lactic streptococci) and, more recently, transferred to the genus Lactococcus [1Schleifer KH Kraus J Dvorak C Kilpper-Bälz R Collins MD Fischer W Transfer of Streptococcus lactis and related streptococci to the genus Lactococcus gen.nov. Syst Appl Microbiol. 1985; 6: 183-195Crossref Scopus (355) Google Scholar]. Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris- the two main subspecies of L. lactis, the type species of the new genus—are widely used in the dairy industries as cheese starters and commonly included in foodstuffs. Although Lactococcus species are generally thought to be non-pathogenic for humans, the isolation of several strains of lactococci from human sources has been reported [2Facklam RR Elliott JA Identification, classification, and clinical relevance of catalase-negative, gram-positive cocci, excluding the streptococci and enterococci.Clin Microbiol Rev. 1995; 8: 479-495PubMed Google Scholar, 3Facklam RR Pigott N Collins MD Identification of Lactococcus species from human sources.in: Orefici G New perspectives on streptococci and streptococcal infections. Gustav Fischer Verlag, Stuttgart1992: 110-111Google Scholar]. In particular, cases of endocarditis caused by L. lactis subsp. lactis (formerly Streptococcus lactis) have been described [4Wood HF Jacobs K McCarty M Streptococcus lactis isolated from a patient with subacute bacterial endocarditis.Am J Med. 1955; 18: 345-347Abstract Full Text PDF PubMed Scopus (31) Google Scholar, 5Mannion PT Rothburn MM Diagnosis of bacterial endocarditis caused by Streptococcus lactis and assisted by immunoblotting of serum antibodies.J Infect. 1990; 21: 317-318Abstract Full Text PDF PubMed Scopus (47) Google Scholar, 6Clark I Burnie JP Immunoblotting and culture positive endocarditis.J Clin Pathol. 1991; 44: 152-156Crossref PubMed Scopus (13) Google Scholar]. We report herein a case of endocarditis caused by L. lactis subsp. cremoris, which is to our knowledge the first documented case of endocarditis due to this particular subspecies. A 56-year-old man was admitted to our department in March 1994 with moderate intermittent fever (maximum 38.5 °C), arthromyalgias, and cough, for more than 1 month. The patient was a civil employee in a military base and denied ingestion of raw milk and/or unprocessed dairy products, alcohol consumption, drug addiction and any potential risk for blood-borne infections. He suffered from mild chronic glomerulonephritis and chronic gouty arthritis. No antibiotic treatment had been administered over 3 months prior to observation. Physical examination revealed moderate hepatomegaly and spleen enlargement. A grade IV systolic ejection murmur radiated into the axilla and an additional diastolic sound was audible in the third left intercostal space. The admittance screening for fever of unknown origin did not yield significant findings. In particular, dental and sinus foci were excluded by radiologic examination. Chest X-ray revealed moderate cardiac enlargement but the electrocardiogram was normal. An echocardiogram disclosed evident mitral valve prolapse and very moderate aortic regurgitation, no endocardial vegetation being revealed; repeated echocardiography after 1 and after 2 weeks, showed no modification. The patient refused a transesophageal echocardiogram. Five days after admission, crops of petechiae and apparent Janeway lesions were observed on the patient's soles. An entire set of seven blood cultures, the first and last of which had been drawn 5 days apart, yielded positive results: catalase-negative, Gram-positive cocci, occurring singly, in pairs, or in short chains. Colonies on blood agar were small, circular, smooth, entire, and weakly α-hemolytic. The strain was originally identified as L. lactis subsp. cremoris using Api 20 STREP galleries (Bio Mérieux, Marcy-l'Étoile, France), and the identification was confirmed by additional laboratory tests. In particular, identification to the genus level was supported by the following characteristics [2Facklam RR Elliott JA Identification, classification, and clinical relevance of catalase-negative, gram-positive cocci, excluding the streptococci and enterococci.Clin Microbiol Rev. 1995; 8: 479-495PubMed Google Scholar]: susceptibility to vancomycin (22-mm zone of inhibition around a 30-μg disk); no gas production from glucose; no growth in 6.5% NaCl; growth at 10°C but not at 45°C; pyrrolidonyl arylamidase test negative; leucine aminopeptidase test positive; and Voges-Proskauer test positive. Further identification to the species and subspecies level was supported by the following characteristics [1Schleifer KH Kraus J Dvorak C Kilpper-Bälz R Collins MD Fischer W Transfer of Streptococcus lactis and related streptococci to the genus Lactococcus gen.nov. Syst Appl Microbiol. 1985; 6: 183-195Crossref Scopus (355) Google Scholar]: growth in 2% but not in 4% NaCl; no growth at 40 °C; arginine dihydrolase test negative; acid production from galactose and lactose; no acid production from maltose, raffinose, and ribose. Lancefield group D antigen reactivity was found to be negative by the Streptex latex agglutination test (Murex Diagnostics, Dartford, UK). No reactivity was observed with the AccuProbe Enterococcus chemiluminescence assay (Gen-Probe, San Diego, CA). The whole cell protein pattern, determined essentially according to Elliott et al. [7Elliott JA Facklam RR Richter CB Whole-cell protein patterns of nonhemolytic group B, type Ib, streptococci isolated from humans, mice, cattle, frogs, and fish.J Clin Microbiol. 1990; 28: 628-630PubMed Google Scholar], was consistent with the identification of the isolate as belonging to the species L. lactis [8Elliott JA Collins MD Pigott NE Facklam RR Differentiation of Lactococcus lactis and Lactococcus garviae from humans by comparison of whole-cell protein patterns.J Clin Microbiol. 1991; 29: 2731-2734PubMed Google Scholar, 9Descheemaeker P Pot B Ledeboer AM Verrips T Kersters K Comparison of the Lactococcus lactis differential medium (DCL) and SDS-PAGE of whole-cell proteins for the identification of lactococci to subspecies level.Syst Appl Microbiol. 1994; 17: 459-466Crossref Scopus (16) Google Scholar]. MICs were determined by the agar dilution method as recommended by the National Committee for Clinical Laboratory Standards [10National Committee for Clinical Laboratory StandardsMethods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 3rd edn. Approved standard M7-A3. National Committee for Clinical Laboratory Standards, Villanova, PA1993Google Scholar]. The isolate was susceptible to penicillin G (MIC, 0.05 μg/mL), amoxicillin-clavulanate (MIC, 0.2 μg/mL), cefazolin (MIC, 0.1 μg/mL), erythromycin (MIC, 0.02 μg/mL), clarithromycin (MIC, 0.02 μg/mL), trimethoprim-sulfamethoxazole (MIC, 0.06 μg/mL), ciprofloxacin (MIC, 0.4 μg/mL), vancomycin (MIC, 2 μg/mL), and teicoplanin (MIC, ≤ 0.125 μg/mL). The patient was initially treated with intravenous penicillin G 10 million IU four times a day; 12 days after commencement, an alternative treatment with intravenous clarithromycin 300 mg twice a day was administered for 18 days, since the patient had exhibited an evanescent rash, bilaterally on his legs, that was believed to be due to penicillin. Fever was absent after the first week of antimicrobial treatment, and no rebounds were observed. No breakthrough bacteremia was recorded when blood cultures were repeated after treatment. Urine and throat cultures were constantly negative. During his hospital stay, the patient repeatedly complained of painful acute arthritis, mainly located in the right metatarsal joints; based upon laboratory findings and clinical presentation, these episodes seemed scarcely suggestive of gout and better mimicked an Oslerian arthritis. No outpatient antibiotic maintenance was prescribed. The patient was seen monthly for one semester, and one year and a half after discharge he remained in good health. Previously reported infections due to lactococci include three cases of infective endocarditis originally ascribed to strains of S. lactis [4Wood HF Jacobs K McCarty M Streptococcus lactis isolated from a patient with subacute bacterial endocarditis.Am J Med. 1955; 18: 345-347Abstract Full Text PDF PubMed Scopus (31) Google Scholar, 5Mannion PT Rothburn MM Diagnosis of bacterial endocarditis caused by Streptococcus lactis and assisted by immunoblotting of serum antibodies.J Infect. 1990; 21: 317-318Abstract Full Text PDF PubMed Scopus (47) Google Scholar, 6Clark I Burnie JP Immunoblotting and culture positive endocarditis.J Clin Pathol. 1991; 44: 152-156Crossref PubMed Scopus (13) Google Scholar], which should probably now be regarded as strains of L. lactis subsp. lactis. In the case described here, the following clinical findings appear to be strongly suggestive of subacute bacterial endocarditis: long-lasting fever, predisposing heart condition, petechiae, Janeway lesions, absence of demonstrable extracardial septic foci, signs of Oslerian arthritis, and persistent bacteremia. Based upon these signs, this case entirely meets the Duke criteria for the clinical diagnosis of infective endocarditis [11Durack DT Lukes AS Bright DK the Duke Endocarditis ServiceNew criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings.Am J Med. 1994; 96: 200-209Abstract Full Text PDF PubMed Scopus (2195) Google Scholar] and, on the basis of a review of the medical literature, it appears to be the first documented infective endocarditis due to L. lactis subsp. cremoris. The potential pathogenetic role of the Lactococcus genus, which had already been suspected to cause septic arthritis secondary to the ingestion of raw milk [12Campbell P Dealler S Lawton JO Septic arthritis and unpasteurised milk.J Clin Pathol. 1993; 46: 1057-1058Crossref PubMed Scopus (25) Google Scholar] seems, therefore, to have been definitely established.