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Aerococcus viridans Endocarditis
Aerococcus viridans Endocarditis FRANCIS D. PIEN, M . D . , Straub Clinic, Honolulu, Hawaii; WALTER R. W I L S O N , M . D . , Division of Infectious Diseases and Internal Medicine; KEVIN KUNZ, M . D . , Kailua Kona Medical Clinic, Kona, Hawaii; JOHN A. WASHINGTON II, M . D . , Section of Clinical Microbiology, Department of Laboratory Medicine Aerococcus viridans organisms are gram-positive cocci with a strong tendency to form tetrads. These bacteria have infrequently been encountered as a human pathogen, particularly in bacterial endocarditis. A review of the literature suggests that treatment of A. viridans endocarditis should be similar to that for endocarditis caused by penicillin-susceptible streptococci.
In 1953, Williams and associates' proposed the name Aerococcus viridans to describe a group of aerobic α-hemolytic, gram-positive cocci that have a strong tendency to form tetrads rather than clusters or chains. We report a case of A. viridans endocarditis. The patient was hospitalized and treated in Hawaii; the microorganism was identified and susceptibility tests were performed in Mayo Clinic laboratories. REPORT OF CASE A 28-vear-old man presented with a 6-month history of various rheumatic complaints, including pain in the shoulders, back, and left knee. He had a history of fever for 1 month, anemia, and microscopic hematuria. On admission to Straub Clinic Hospital, he was afebrile and had systolic and diastolic murmurs of aortic insufficiency which were loudest at the cardiac apex. The spleen was not palpable, and he had no physical signs of peripheral emboli or hypersensitivity phenomena. No clinical signs of cardiac failure were noted. The patient denied recent exposure to needles or dental work; he was employed as a hotel kitchen helper and a commercial fisherman. Six blood culture sets were positive for a slow-growing gram-positive coccus, which was identified as A. viridans by the Mayo Clinic Microbiology Laboratory on the basis of the following test results: gram-positive cocci in tetrads on Gram's stain, a negative catalase test, and a weakly positive bile-esculin reaction. The microorganism was subcultured, and repeat Cram's stain demonstrated characteristic grampositive cocci in tetrads. Results of antibiotic sensitivity tests done by agar- or broth-dilution methods were as follows: minimal inhibitory concentrations of 0.13 μg/ml for penicillin, 0.13 μg/ml for cephapirin, 1.0 μg/ml for vancomycin, and 1.0 μ^/ιηΙ for gentamicin. The minimal bactericidal concentra-
tion was 0.13 μg/ml for cephapirin. The patient was initially treated with several antibiotics elsewhere. Antimicrobial therapy at Straub Clinic was aqueous penicillin C (20 million U daily) and gentamicin (60 mg every 8 hours) administered intravenously for 2 weeks. An echocardiogram revealed a flail aortic leaflet with vegetations, aortic insufficiency, and left ventricular enlargement. On the eighth day of antimicrobial therapy, the patient underwent aortic valve replacement. Gram's stain of the large vegetations showed focal aggregates of grampositive cocci; cuItures of the aortic valve were negative for bacterial growth. Postoperatively, the patient received intravenous penicillin and gentamicin therapy for an additional week and then was dismissed with a 2-week oral regimen of phenoxymethyl penicillin (1 g three times daily). The patient was well during 6 months of outpatient follow-up. DISCUSSION Aerococci differ from streptococci because they are weakly catalase-positive organisms and tend to form tetrads rather than chains in broth media. These slowgrowing bacteria ferment maltose and mannitol and tolerate 40% bile, 10% salt, 0.25% crystal violet, and 0.01% potassium tellurite. 2 " 4 Unlike enterococci, aerococci are highly susceptible to many antibiotics and do not contain the group D streptococcal antigen. 4,5 Previously, A. viridans had beep termed Pediococcus homari or Gaffkya homari by some authors, but it is now considered to be a separate genus and species.2 A. viridans is ubiquitous in nature and may be isolated from dust, vegetables, and crustaceans.4~b In an environmental study of a hospital in North Carolina, this organism was frequently found on objects in the operating room, recovery room, nursery, intensive care unit, patient wards, and delivery suite. 7 Our patient may have
Address reprint requests to Dr. W. R. Wilson. Mayo Clin Proc 59:47-48, 1984
47
AEROCOCCUS
48
VIRIDANS
ENDOCARDITIS
Mayo Clin Proc, January 1984, Vol 59
Table 1.—Bacterial Endocarditis Caused by Aerococcus viridans Antibiotic sensitivities (μ&ΛηΙ)
Case
Reference no.
Age (yr) and sex
Predisposing heart disease
Infected valve
Penicillin
Cephalothin or cephapirin
Vancomycin
7.50
5.0
1
5
54
M
Mitral valve prolapse
Mitral
0.06
2
11
50
M
Rheumatic mitral insufficiency
Aortic
0.04
3
Current report
28
M
No history of heart disease
Aortic
0.13
been exposed to this microorganism during his work as a commercial fisherman. Human infections caused by A. viridans have been described. Nathavitharana and associates8 recently reported three cases of acute childhood Aerococcus meningitis from Sri Lanka. Colman 9 reported 10 clinical isolates from several European sources. These cases included three urinary tract infections, one case each of empyema, an infected wound, and a mouth isolate, and four cases of endocarditis. No clinical data were reported on the patients with endocarditis except that the isolates were reportedly susceptible to penicillin, streptomycin, erythromycin, and tetracycline. The minimal inhibitory concentrations of these isolates to benzyl penicillin were 1.6 U or less (1.0 μ8/ιηΙ). Parker and Ball' 0 reported four cases of endocarditis and three cases of bacteremia caused by A. viridans but provided no clinical information about their patients. These cases represented 1 % of the clinically important "streptococcal" isolates received by the Central Public Health Laboratory, Colindale, London, for the period 1972 through 1974. Table 1 includes our case and the only other two case reports 5, ' } of bacterial endocarditis caused by A. viridans for which we could find clinical data. Obviously, this environmental organism may cause serious medical consequences, including infective endocarditis. The few clinical reports available suggest that patients with A. viridans endocarditis may be treated successfully with
...
0.13
1.0
Antimicrobial therapy and outcome /Aqueous penicillin G, 18 x 10 6 U/day for 5 w k , then orally administered penicillin for 2 wk. Had osteomyelitis of lumbar spine 1Parenterally administered penicillin G plus streptomycin. Died of congestive heart failure. Postmortem cultures of cardiac vegetations sterile IParenterally administered penicillin plus gentamicin. Aortic valve replacement because of flail leaflet. Cure. (See text for details)
penicillin G or a cephalosporin in dosages similar to those for patients with endocarditis caused by penicillinsusceptible viridans streptococci. REFERENCES 1.
10. 11.
Williams REO, Hirch A, Cowan ST: Aerococcus, a new bacterial genus. ) Gen Microbiol 8:475-480, 1953 Buchanan RE, Gibbons NE: Bergey's Manual of Determinative Bacteriology. Eighth edition. Baltimore, Williams & Wilkins Company, 1974, pp 515-516 Whittenbury R: A study of some pediococci and their relationship to Aerococcus viridans and the enterococci. J Gen Microbiol 40:97-106, 1965 Evans )B, Kerbaugh MA: Recognition of Aerococcus viridans by the clinical microbiologist. Health Lab Sei 7:76-77, 1970 Untereker WJ, Hanna BA: Endocarditis and osteomyelitis caused by Aerococcus viridans. Mt Sinai J Med NY 43:248-252, 1976 Deibel RH, Niven CF Jr: Comparative study of Gaffkya homari, Aerococcus viridans, tetrad-forming cocci from meat curing brines, and the genus Pediococcus] Bacteriol 79:175-180, 1960 Kerbaugh MA, Evans )B: Aerococcus viridans in the hospital environment. Appl Microbiol 16:519-523, 1968 Nathavitharana KA, Arseculeratne SN, Aponso HA, Vijeratnam R, Jayasena L, Navaratnam C: Acute meningitis in early childhood caused by Aerococcus viridans. Br Med J 286:1248, 1983 Colman G: Aerococcus-like organisms isolated from human infections. ] Clin Pathol 20:294-297, 1967 Parker MT, Ball LC: Streptococci and aerococci associated with systemic infection in man. ) Med Microbiol 9:275-302, 1976 Janosek J, Eckert J, Hudäc A: Aerococcus viridans as a causative agent of infectious endocarditis. ] Hyg Epidemiol Microbiol Immunol (Praha) 24:92-96, 1980
In 1953, Williams and associates' proposed the name Aerococcus viridans to describe a group of aerobic α-hemolytic, gram-positive cocci that have a strong tendency to form tetrads rather than clusters or chains. We report a case of A. viridans endocarditis. The patient was hospitalized and treated in Hawaii; the microorganism was identified and susceptibility tests were performed in Mayo Clinic laboratories. REPORT OF CASE A 28-vear-old man presented with a 6-month history of various rheumatic complaints, including pain in the shoulders, back, and left knee. He had a history of fever for 1 month, anemia, and microscopic hematuria. On admission to Straub Clinic Hospital, he was afebrile and had systolic and diastolic murmurs of aortic insufficiency which were loudest at the cardiac apex. The spleen was not palpable, and he had no physical signs of peripheral emboli or hypersensitivity phenomena. No clinical signs of cardiac failure were noted. The patient denied recent exposure to needles or dental work; he was employed as a hotel kitchen helper and a commercial fisherman. Six blood culture sets were positive for a slow-growing gram-positive coccus, which was identified as A. viridans by the Mayo Clinic Microbiology Laboratory on the basis of the following test results: gram-positive cocci in tetrads on Gram's stain, a negative catalase test, and a weakly positive bile-esculin reaction. The microorganism was subcultured, and repeat Cram's stain demonstrated characteristic grampositive cocci in tetrads. Results of antibiotic sensitivity tests done by agar- or broth-dilution methods were as follows: minimal inhibitory concentrations of 0.13 μg/ml for penicillin, 0.13 μg/ml for cephapirin, 1.0 μg/ml for vancomycin, and 1.0 μ^/ιηΙ for gentamicin. The minimal bactericidal concentra-
tion was 0.13 μg/ml for cephapirin. The patient was initially treated with several antibiotics elsewhere. Antimicrobial therapy at Straub Clinic was aqueous penicillin C (20 million U daily) and gentamicin (60 mg every 8 hours) administered intravenously for 2 weeks. An echocardiogram revealed a flail aortic leaflet with vegetations, aortic insufficiency, and left ventricular enlargement. On the eighth day of antimicrobial therapy, the patient underwent aortic valve replacement. Gram's stain of the large vegetations showed focal aggregates of grampositive cocci; cuItures of the aortic valve were negative for bacterial growth. Postoperatively, the patient received intravenous penicillin and gentamicin therapy for an additional week and then was dismissed with a 2-week oral regimen of phenoxymethyl penicillin (1 g three times daily). The patient was well during 6 months of outpatient follow-up. DISCUSSION Aerococci differ from streptococci because they are weakly catalase-positive organisms and tend to form tetrads rather than chains in broth media. These slowgrowing bacteria ferment maltose and mannitol and tolerate 40% bile, 10% salt, 0.25% crystal violet, and 0.01% potassium tellurite. 2 " 4 Unlike enterococci, aerococci are highly susceptible to many antibiotics and do not contain the group D streptococcal antigen. 4,5 Previously, A. viridans had beep termed Pediococcus homari or Gaffkya homari by some authors, but it is now considered to be a separate genus and species.2 A. viridans is ubiquitous in nature and may be isolated from dust, vegetables, and crustaceans.4~b In an environmental study of a hospital in North Carolina, this organism was frequently found on objects in the operating room, recovery room, nursery, intensive care unit, patient wards, and delivery suite. 7 Our patient may have
Address reprint requests to Dr. W. R. Wilson. Mayo Clin Proc 59:47-48, 1984
47
AEROCOCCUS
48
VIRIDANS
ENDOCARDITIS
Mayo Clin Proc, January 1984, Vol 59
Table 1.—Bacterial Endocarditis Caused by Aerococcus viridans Antibiotic sensitivities (μ&ΛηΙ)
Case
Reference no.
Age (yr) and sex
Predisposing heart disease
Infected valve
Penicillin
Cephalothin or cephapirin
Vancomycin
7.50
5.0
1
5
54
M
Mitral valve prolapse
Mitral
0.06
2
11
50
M
Rheumatic mitral insufficiency
Aortic
0.04
3
Current report
28
M
No history of heart disease
Aortic
0.13
been exposed to this microorganism during his work as a commercial fisherman. Human infections caused by A. viridans have been described. Nathavitharana and associates8 recently reported three cases of acute childhood Aerococcus meningitis from Sri Lanka. Colman 9 reported 10 clinical isolates from several European sources. These cases included three urinary tract infections, one case each of empyema, an infected wound, and a mouth isolate, and four cases of endocarditis. No clinical data were reported on the patients with endocarditis except that the isolates were reportedly susceptible to penicillin, streptomycin, erythromycin, and tetracycline. The minimal inhibitory concentrations of these isolates to benzyl penicillin were 1.6 U or less (1.0 μ8/ιηΙ). Parker and Ball' 0 reported four cases of endocarditis and three cases of bacteremia caused by A. viridans but provided no clinical information about their patients. These cases represented 1 % of the clinically important "streptococcal" isolates received by the Central Public Health Laboratory, Colindale, London, for the period 1972 through 1974. Table 1 includes our case and the only other two case reports 5, ' } of bacterial endocarditis caused by A. viridans for which we could find clinical data. Obviously, this environmental organism may cause serious medical consequences, including infective endocarditis. The few clinical reports available suggest that patients with A. viridans endocarditis may be treated successfully with
...
0.13
1.0
Antimicrobial therapy and outcome /Aqueous penicillin G, 18 x 10 6 U/day for 5 w k , then orally administered penicillin for 2 wk. Had osteomyelitis of lumbar spine 1Parenterally administered penicillin G plus streptomycin. Died of congestive heart failure. Postmortem cultures of cardiac vegetations sterile IParenterally administered penicillin plus gentamicin. Aortic valve replacement because of flail leaflet. Cure. (See text for details)
penicillin G or a cephalosporin in dosages similar to those for patients with endocarditis caused by penicillinsusceptible viridans streptococci. REFERENCES 1.
10. 11.
Williams REO, Hirch A, Cowan ST: Aerococcus, a new bacterial genus. ) Gen Microbiol 8:475-480, 1953 Buchanan RE, Gibbons NE: Bergey's Manual of Determinative Bacteriology. Eighth edition. Baltimore, Williams & Wilkins Company, 1974, pp 515-516 Whittenbury R: A study of some pediococci and their relationship to Aerococcus viridans and the enterococci. J Gen Microbiol 40:97-106, 1965 Evans )B, Kerbaugh MA: Recognition of Aerococcus viridans by the clinical microbiologist. Health Lab Sei 7:76-77, 1970 Untereker WJ, Hanna BA: Endocarditis and osteomyelitis caused by Aerococcus viridans. Mt Sinai J Med NY 43:248-252, 1976 Deibel RH, Niven CF Jr: Comparative study of Gaffkya homari, Aerococcus viridans, tetrad-forming cocci from meat curing brines, and the genus Pediococcus] Bacteriol 79:175-180, 1960 Kerbaugh MA, Evans )B: Aerococcus viridans in the hospital environment. Appl Microbiol 16:519-523, 1968 Nathavitharana KA, Arseculeratne SN, Aponso HA, Vijeratnam R, Jayasena L, Navaratnam C: Acute meningitis in early childhood caused by Aerococcus viridans. Br Med J 286:1248, 1983 Colman G: Aerococcus-like organisms isolated from human infections. ] Clin Pathol 20:294-297, 1967 Parker MT, Ball LC: Streptococci and aerococci associated with systemic infection in man. ) Med Microbiol 9:275-302, 1976 Janosek J, Eckert J, Hudäc A: Aerococcus viridans as a causative agent of infectious endocarditis. ] Hyg Epidemiol Microbiol Immunol (Praha) 24:92-96, 1980