P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5
Bryanston Gate, 170 Curzon Road
Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za
Tel: +27 (011) 463 3260
Fax: +27 (011) 463 3036
Fax to Email: + 27 (0) 86-557-2232
e-mail : [email protected]
Please read this section first
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MICROBIOLOGY LEGEND
CYCLE 36 ORGANISM 1
Enterococcus casseliflavus
Enterococcus is a genus of lactic acid bacteria of the phylum Firmicutes. Enterococci are Gram-positive cocci
that often occur in pairs (diplococci) or short chains, and are difficult to distinguish from streptococci on
physical characteristics alone. Two species are common commensal organisms in the intestines of humans: E.
faecalis (90-95%) and E. faecium (5-10%) but are also important pathogens responsible for serious infections.
Rare clusters of infections occur with other species, including E. casseliflavus, E. gallinarum, and E.
raffinosus. With increasing antibiotic resistance, enterococci are recognized as feared nosocomial pathogens
that can be challenging to treat.
Enterococcus species are hardy, facultative anaerobic organisms that can survive and grow in many
environments. In the laboratory, enterococci are distinguished by their morphologic appearance on Gram
stain and culture (gram-positive cocci that grow in chains) and their ability to (1) hydrolyze esculin in the
presence of bile, (2) grow in 6.5% sodium chloride, (3) demonstrate pyrrolidonyl arylamidase and leucine
aminopeptidase, and (4) react with group D antiserum.
Members of the genus Enterococcus were classified as Group D Streptococcus until 1984, when genomic DNA
analysis indicated a separate genus classification would be appropriate. Though they are not capable of
forming spores, enterococci are tolerant of a wide range of environmental conditions like extreme
temperature (10-45°C) & pH (4.5-10.0). Enterococci typically exhibit gamma-hemolysis on sheep's blood agar.
Enterococcus faecalis and Enterococcus faecium are the most prevalent species cultured from humans,
accounting for more than 90% of clinical isolates. Other enterococcal species known to cause human infection
include Enterococcus avium, Enterococcus gallinarum, Enterococcus casseliflavus, Enterococcus durans,
Enterococcus raffinosus and Enterococcus mundtii. E. faecium represents most vancomycin-resistant
enterococci (VRE).
Pathology
Important clinical infections caused by Enterococcus include urinary tract infections, bacteraemia, bacterial
endocarditis, diverticulitis, and meningitis. Sensitive strains of these bacteria can be treated with ampicillin,
penicillin and vancomycin.
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Accredited to ISO 17043
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Page 1 of 3
P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5
Bryanston Gate, 170 Curzon Road
Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za
Tel: +27 (011) 463 3260
Fax: +27 (011) 463 3036
Fax to Email: + 27 (0) 86-557-2232
e-mail : [email protected]
From a medical standpoint, an important feature of this genus is the high level of intrinsic antibiotic
resistance. Some enterococci are intrinsically resistant to β-lactam-based antibiotics (penicillins,
cephalosporins, carbapenems), as well as many aminoglycosides. In the last two decades, particularly virulent
strains of Enterococcus that are resistant to vancomycin (vancomycin-resistant Enterococcus, or VRE) have
emerged in nosocomial infections of hospitalized patients, especially in the US. VRE may be treated with
quinupristin/dalfopristin (Synercid) with response rates of approximately 70%. Tigecycline has also been
shown to have anti-enterococcal activity as has rifampicin.
Mortality/Morbidity
In general, the virulence of enterococci is lower than that of organisms such as S. aureus. However,
enterococcal infections often occur in debilitated patients and as part of polymicrobial infections. These
factors limit the ability of investigators to determine the independent contribution of enterococcal
infections to mortality and morbidity.
Vancomycin-resistant bacteremia increases the length of hospital stay by an average of 2 weeks, and studies
calculate an attributable mortality rate of up to 37% from these infections. Mortality rates associated with
enterococcal infections may exceed 50% in critically ill patients, those with solid tumors, and some transplant
patients. Bacteremia caused by VRE strains carries higher mortality rates than does bacteremia due to
vancomycin-susceptible strains. Despite the availability of antimicrobial agents with greater potency against
VRE, one study of 113 patients with VRE bacteremia reported that such agents did not significantly change
clinical outcomes.
Sex
In general, enterococcal infections are distributed equally between the sexes. Although urinary tract
infections are more common in healthy women than in healthy men, enterococci are an uncommon cause of
uncomplicated cystitis in this setting.
Age
Enterococcal infections are more common in elderly patients because of various associated factors that are
more common in these patients. For example, urinary tract catheterization and instrumentation are more
common in elderly populations. Abdominal surgery for diverticulitis or biliary tract disease is also performed
more commonly in elderly persons. In a recent study, most cases of enterococcal endocarditis occurred in
elderly individuals.
In neonates, enterococci occasionally cause bacteremia and meningitis. Outbreaks of enterococcal infections,
including VRE infections, have been reported in neonatal ICUs, pediatric ICUs, and hematology/oncology
units, but, overall, VRE infections are less common in pediatric patients than in adults
Enterococcus casseliflavus
Physiology and classification
Enterococcus casseliflavus was formerly known as Streptococcus faecium subsp. casseliflavus or
Streptococcus casseliflavus. Ent. casseliflavus is normally pigmented and motile, but non-pigmented and nonmotile strains may occur.
Occurrence and habitat
Ent. casseliflavus is associated with plant material.
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Accredited to ISO 17043
Certificate available on request or at www.sanas.co.za
Page 2 of 3
P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5
Bryanston Gate, 170 Curzon Road
Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za
Tel: +27 (011) 463 3260
Fax: +27 (011) 463 3036
Fax to Email: + 27 (0) 86-557-2232
e-mail : [email protected]
Pathogenicity
This species is found infrequently in infections.
Identification
Pigmentation, motility and intrinsic vancomycin-low level resistance are most useful characteristics. The
differentiation from other yellow pigmented enterococci is shown in table 1 and the characteristics
distinguishing between this species and Ent. gallinarum in table 2.
E. casseliflavus
E. faecalis
Table 1: Tests useful in the differentiation of yellow
pigmented enterococci
Characteristics
Ent.
Ent.
Ent.
casseliflavus
mundtii
sulfureus
Table 2: Tests useful in the differentiation of members of
the Enterococcus gallinarum species group
Test
+
-
?
Yellow pigment
Hippurate
D+
-
-
Arginine dihydrolase
+
+
-
Group D antigen
+
+
-
L-Arabinose
+
+
-
Glycerol
-
D
-
Gluconate
+
-
+
Acid from
Sorbitol
Glycerol
Glycogen
Β-haemolysis on horse blood
agar
Α-haemolysis on sheep blood
agar
Inulin
+
-(D -?)
-
Vancomycin
resistance
Motility
Acid produced from
Α-Methyl-D-glucoside
Rhamnose
Sorbitol
+
-
+
D+
D+
-
-
D
-
Ent.
gallinarum
D+
Ent.
casseliflavus
+
1
D
D
D+
D
-
-
D+
D – Different or variable: D+ usually positive; D- usually negative
References
1. The Genera of Lactic Acid Bacteria edited by B.J. Wood, W.H.N Holzapfel
2. http://en.wikipedia.org/wiki/Enterococcus
Questions
1. Discuss how you would distinguish between E. faecalis and E. casseliflavus in your lab.
2. What are the morphological characteristics of the genus Enterococcus?
3. Discuss the pathophysiology of Enterococci.
\
Thistle QA is a SANAS accredited organisation, No: PTS0001
Accredited to ISO 17043
Certificate available on request or at www.sanas.co.za
Page 3 of 3