The document discusses Enterococci, including its natural habitats, morphology, general properties, medically important species, culture characteristics, virulence factors, pathogenicity, laboratory diagnosis, biochemical tests, Lancefield grouping, antibiotic resistance, and treatment options. Key points include that Enterococci normally inhabit the intestinal tract, oral cavity, and vaginal canal of humans and animals. The most common medically important species that cause nosocomial infections are Enterococcus faecalis and E. faecium. Laboratory identification involves culture, biochemical tests like catalase and sugar fermentation reactions, and determining Lancefield grouping. Antibiotic resistance is a concern, especially for vancomycin and penicillin.

1. Sharq Elneil College
School of Medical Laboratory Sciences
Department of Microbiology
Medical Bacteriology course
Enterococci
Dr.Mahadi Hassan Mahmoud
mahadi2010sd@yahoo.com
Bsc, Msc, MIBMS Microbiology

2. The Natural habitat
Normal components of the flora of:
 Intestinal tract
 Oral cavity
 Vaginal canal of humans and
animals

3. Morphology
 Gram-positive cocci (0.5 and
1.25 micrometers in diameter)
usually occur in pairs or short
chains
Non-capsulate
Non-motile.

4. General properties:
production of gas from glucose
(most enterococci are negative)
Have ability to grow at both
45°C and 10°C temperatures).
Can grow on media containing
Bile aesculin,

5. Medically Important species
At least 12 different species have
been associated with various illnesses
Enterococcus faecalis and E.
faecium — have emerged as a major
cause of nosocomial infections

6. Culture &chaacteristics:
Enterococci are aerobic organisms
capable of growing over a wide
temperature range,
10–45 ºC
On blood agar,
Enterococci are mainly nonhaemolytic
but some strains show alpha or beta-
haemolysis

7. ON MacConkey &CLED
Ferments lactose, producing small dark-
red magenta colonies on MacConkey aga
small yellow colonies on CLED (cysteine
lactose electrolyte-deficient) agar

8. Enterococcus species are also
able to grow in the presence of 6.5%
sodium chloride and 40% bile.
 When grown on media containing
aesculin, enterococci hydrolyze the
aesculin, producing black colonies.

10. Virulence Factor
 Polysaccharides on the surface of
enterococci represent an effective way to
prevent phagocytosis.
 Secreted factors (cytolysin/hemolysin,
gelatinase and serine protease)
 cell surface-located proteins or
adhesins (Esp) and the adhesin of
collagen Adhesins (Acm and SagA)

11. Pathogeicity:
Enterococcus faecalis, causing about 95% of
enterococcal infections including infections
of the
Urinary tract infection
 Biliary tract,ulcers (e.g. bed sores)
 Wounds (particularly abdominal)
 Occasionally endocarditis or meningitis

12. Laboratory diagnosis
specimens:
Collection of Spacimen
Direct Exam
Culture
Identificaion
Serology
Molecular characterization

13. Biochemical Tests
Catalase negative
Ferment lactose (also
mannitol and other sugars).
Hydrolyze aesculin
Reduce litmus milk

14. grow on reduce sorbitol glycerol, D- L- melibios
0.4% tetrazol tagatose arabinos e
telluride ium to e
formaz
an
E. yes Yes Acid Acid Acid No Acid No Acid
faecalis
E. No No No Acid No Acid No Acid Acid Acid
faecium

15. Lancefield Grouping
Enterococci possess Lancefield
Group D antigen (as also some
streptococci).
The Group D antigen of enterococci
is unlike that of other Lancefield
groups.
It is not extracted by traditional acid
extraction techniques. Enzyme
techniquesbased on Maxted’s enzyme
are required.

16. Antibiotic Resistant
Most enterococci are susceptible to
ampicillin and resistant to
cephalosporins.
Resistance is shown against
penicillin. Vancomycinand ampicillin
resistance appear to be
emerging,associated particularly with
hospital infections.

17. Penicillin or Ampicillin
Vancomycin
For urine isolates
Fluoroquinolones
Nitrofurantoin
Fosfomycin
Vancomycin-resistant strains
(VRE)

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