Download Volume 26 - No 23: Nutrionally Deficient Streptococcus

JOHNS HOPKINS
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Department of Pathology
600 N. Wolfe Street / Baltimore MD 21287-7093
(410) 955-5077 / FAX (410) 614-8087
Division of Medical Microbiology
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER Vol. 26, No. 23
Tuesday, November 11, 2007
A. Provided by Emily Luckman, Division of Outbreak Investigation, Maryland Department
of Health and Mental Hygiene.
4 outbreaks were reported to DHMH during MMWR Week 49 (Dec. 2- Dec. 8, 2007):
2 Foodborne Gastroenteritis outbreaks
1 outbreak of FOODBORNE GASTROENTERITIS associated with a Restaurant (Montgomery Co.)
1 outbreak of FOODBORNE GASTROENTERITIS associated with an Office Luncheon (Montgomery Co.)
2 Rash illness outbreaks
1 outbreak of NORWEGIAN SCABIES associated with a Nursing Home (Baltimore City)
1 outbreak of SCABIES associated with a Shelter (Cecil Co.)
B. The Johns Hopkins Hospital, Department of Pathology, Information provided by,
Wang (Steve) Cheung, M.D., Ph.D.
Case Presentation
The patient is a 58-year-old woman with a history of mitral value prolapse (MVP). In 2004, while
preparing for a hike to Kilimanjaro, she was found to have MVP in a routine physical exam. She had no
symptoms associated with it until recently she was found to have mitral regurgitation and pulmonary
hypertension. She decided to have her mitral valve repair. During the surgery, a soft sterile vegetation
was noted; hence, a bacterial culture and routine histology of the leaflets were sent. The histology showed
acute endocarditis with special stains demonstrating the presence of Gram positive cocci along the surface
of the vegetation. Both the blood and tissue culture grew out nutritionally deficient streptococcus.
Organism
The nutritionally deficient streptococci are Gram positive cocci with alpha hemolysis on blood
agar that was originally described by Frenkel and Hirsch in 1961. They were described as streptococci
that form satellites around other types of bacteria; hence, its old name was satelliting streptococcus. Later,
other names were given due to its nutrient dependence such as thiol-requiring streptococci, vitamin B6 or
pyridoxal-dependent streptococci, and nutritionally variant streptococci (NVS). In 1989, Bouvet et al used
DNA-DNA hybridization to show that NVS were highly related to streptococci and renamed two NVS
species as Streptococcus adjacens and Streptococcus defectivus. However, sequence analysis of the 16S
rRNA gene revealed that these two species were not related to any species; therefore, a new genus
Abiotrophia was created (Kawamura et al, 1995). Interestingly, further studies have converted most of the
members of Abiotrophia genus into the Granulicatella genus (Collins and Lawson, 2000). In summary,
the original nutritionally deficient streptococci or nutritionally variant streptococci (NVS) are now
Abiotrophia and Granulicatella species.
Clinical Significance
Abiotrophia and Granulicatella species are part of normal flora found in the upper respiratory
mucosa, urogenital tract, and gastrointestinal tract. They can cause sepsis and bacteremia and are
responsible for 3-6% of streptococcal infective endocarditis. Other infections such as meningitis and
epidural abscesses caused by NVS were found in patients with previous neurosurgical procedures.
Interestingly, these bacteria can produce neuraminidase and aminopeptidases which contribute to their
virulence.
Unfortunately, infective endocarditis caused by NVS has a higher rate of complications than that
caused by other types of streptococci. In one study, embolization occurred in 27% of cases and surgery was
required in 38% of cases (Stein and Nelson, 1987). Besides neuraminidase, NVS can produce an
exopolysaccharide that binds to fibronectin and extracellular matrix with high affinity. These virulence
factors along with longer generation times (2 to 3 hours versus 45 minutes for other streptococci) could
decrease the effectiveness of beta-lactam antibiotics.
Laboratory Diagnosis
When the Gram stain for blood culture or tissue (heart valve) culture shows streptococci with
failure to grow on subsequent subculture, NVS should be suspected. As described earlier, NVS need
pyridoxal (vitamin B6) to grow and many of the commercially available media, especially chocolate agar,
do contain pyridoxal. Alternatively, subculturing on blood agar plates streaked with S. aureus can support
the growth of nutritionally variant streptococci near the streak since staphylococci contain enzymes that can
make pyridoxal. For identification purposes, the same streak method can be used with Haemophilus spp
instead of staphylococci or placing a disk containing pyridoxal for the satellite test.
With any streptococci (i.e. catalase negative Gram positive cocci in chain), the type of hemolysis on
blood agar dictates the work-up. For beta-hemolytic streptococci (complete lysis of the red cells), a rapid
latex agglutination-based antigen test can be used to identify Lancefield Group A, B, C, D, F, and G
streptococci. For gamma-hemolytic (non-hemolytic) streptococci, both Group D non-enterococci and
enterococci are bile esculin positive (i.e. can grow in 40% bile and can hydrolyze esculin to esculetin).
However, only enterococci can grow in higher salt concentration (6.5%). As for the alpha-hemolytic
streptococci (partial hemolysis or greening), the pneumococci can be distinguished by being positive (or
sensitive) on the Optochin (P disk) and positive on the Quellung test. With no zone or less than 14 mm
zone of inhibitory growth on the P disk, the viridans strep group organisms are usually also negative on
pyroglutamic aminopeptidase (PYR). However, for NVS which is alpha-hemolytic, it is positive for leucine
aminopeptidase (LAP), similar to streptococci; but unlike other streptococci, NVS is positive for (PYR).
Other biochemical tests can be performed either individually or using the API Rapid Strep commercial kit
for identification. Molecular analyses can also be done for further identification of Abiotrophia and
Granulicatella species (or NVS).
Treatment
Management of Abiotrophia and Granulicatella bacteremia usually involves the use of systemic
antibiotic beginning with Penicillin. However, due to the increasing resistance to Penicillin, other
antibiotics can be used such as clindamycin, erythromycin, rifampin and vancomycin. As for NVS infective
endocarditis, the majority of these cases do require surgical procedure to repair or replace the infected heart
valve (usually the mitral valve).
REFERENCES:
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Lin CH, Hsu RB (2007). Infective endocarditis caused by nutrionally variant streptococci. Am J Med Sci
334:235-239.
Stein DS, Nelson KE (1987). Endocarditis due to nutrionally deficient streptococci: therapeutic dilemma. Rev
Infect Dis, 9:908-16.
Frenkel A, Hirsch W (1961). Spontaneous development of L forms streptococci requiring secretions of other
bacteria or sulphydryl compounds for normal growth. Nature 191:728-30.
Bouvet A, Grimont F, Grimont PAD (1989). Streptococcus defectivus sp nov and Streptococcus adjacens sp
nov nutrionally variant streptococci from human clinical specimens. Int J Syst Bacteriol 39:290-4.
Kawamura Y et al. (1995). Transfer of Strep adjacens and Strep defectivus to Abiotrophia gen nov. Int J Syst
Bacteriol 45:798-803.
Shenep J (2000) Virdians-group streptococcal infection in immunocompromised hosts. Int J Antimicro Agent
14:129-135.