for mbbs students

1. Group B
and Group D
Streptococci

2. Streptococcus
• Gram + Ve cocci
• Arranged in chains/pairs
• Important human pathogens: pyogenic
infection
• Tendency to spread
• Acute rheumatic fever; Glomerulonephritis

3. Classification
O2 requirement
Aerobes & facultative anaerobes Obligate anaerobes
Peptostreptococci
Hemolysis
α β γ
(Viridans gp) (Hemolytic) (Enterococcus)
Lancefield grouping
& Griffith typing
(Serological)

4. Beta hemolysis
Alpha hemolysis No hemolysis

5. Hemolysis Patterns of Streptococci

6. Group B streptococcus
(Streptococcus agalctiae)
– Important pathogen of cattle &
produce bovine mastitis
– Commensal of female genital tract
– Septic abortion & pueperal sepsis
– Neonatal septicemia & meningitis in
west

7. Differentiation between -hemolytic streptococci
CAMP test
Bacitracin
sensitivity
Hemolysis
Negative
Susceptible

S. Pyogenes
(Gp A)
Positive
Resistant

S. Agalactiae
( Gp B)
Inulin
Fermentation
Bile
solubility
Optochin
sensitivity
Hemolysis
Not ferment
Soluble
Sensitive
(≥ 14 mm)

S. pneumoniae
Ferment
Insoluble
Resistant
(≤13 mm)

Viridans strep
Differentiation between -hemolytic streptococci

8. Streptococcus agalctiae
• Gram-positive diplococcus
• Produces a narrow zone of -hemolysis on
blood agar
• Most strains are bacitracin resistant
• Positive CAMP test

9. Streptococcus agalctiae (cont-)
• Serologic Strains
– Type Ia, Ib, Ic, II, III, IV, V, VI, VII, and VIII
– Early onset disease can be due to any strain & can
be fatal
– Late onset disease is due to Type III in >90% of
cases

10. Epidemiology
• Colonizes ~20% of pregnant women
– Usually asymptomatic but can have UTIs,
chorioamnionitis, or endometritis
• 40-70% of infants born to colonized mothers are
colonized
• Nearly 50% of sexual partners of colonized women
are colonized 0.2-3.7/1000 live births
– Rates are diminishing with prophylaxis
• 0.5-2% of newborn infants born to colonized mothers
• Gets colonized.

11. Maternal Risk Factors
• Preterm labour < 37 weeks
• Preterm prom at 37 weeks
• Fever during labor
• Previous delivery of sibling with invasive gbs
disease
• Multiple births
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12. GBS COLONIZATION
• IN MOTHER
• LOWER GENITAL TRACT
• ANORECTUM
• URINARY TRACT
• IN NEONATES
• EXTERNAL EAR (IN FIRST 24 H )
• ANTERIOR NARES, THROAT
• ANORECTUM
• UMBILICUS
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13. Risk Factors for Colonization
• Heavily colonized mothers
• Mothers younger than 20
• African Americans
• Lower socioeconomic groups
• PROM
• Prolonged labor
• Maternal Chorioamnionitis
• Previous delivery with GBS disease

14. Early Onset v. Late Onset
• Occurs within the 1st
week of life (usually
<72 hours)
• Attack rate more in low
birth weight
• Accounts for 20%
• Cases appearing up to 6
months of age
• Cases after 1 month of
age occur primarily in
premature and
immunodeficient infants

15. Early Onset v. Late Onset
• Vertical transmission
• Ascending infection
(duration of ROM 
incidence of infection)
• During passage through
a colonized birth canal
• Maternal transmission
• Nonmaternal sites:
– Nursery
– Personnel
– Community
• Pathophysiology due to
weakened host defense

16. Early Onset v. Late Onset
• Pneumonia with
bacteremia
• Pulmonary HTN
Meningitis
• Bacteremia without a
focus (55%)
• Meningitis (35%)
• Osteomyelitis and
arthritis

17. Laboratory Findings
• Isolation and identification from normally
sterile sites
– CSF
– Gastric or tracheal aspirates
– Skin or mucous membranes

18. CAMP test
• Principle:
– Group B streptococci produce extracellular protein (CAMP factor)
– CAMP act synergistically with staph. -lysin to cause lysis of RBCs
• Procedure:
– Single streak of Streptococcus to be tested and a Staph. aureus are made
perpendicular to each other
– 3-5 mm distance was left between two streaks
– After incubation, a positive result appear as an arrowhead shaped zone of
complete hemolysis
– S. agalactiae is CAMP test positive while non gp B streptococci are
negative

19. Hemolysis on Blood agar
-hemolysis
-hemolysis
-hemolysis

20. CAMP test

21. CAMP test
Staph. aureus
Gp B
Streptococcus
Gp A
Streptococcus

22. GBS MENINGITIS
• MORTALITY RATE 50 - 75 %
• 21 % OF SURVIVORS HAVE MAJOR
PERMANENT NEUROLOGIC SEQUELAE
– MENTAL RETARDATION (USUALLY PROFOUND)
– SPASTIC QUADRIPLEGIA
– CORTICAL BLINDNESS
– DEAFNESS
– UNCONTROLLED SEIZURES
– HYDROCEPHALUS
– HYPOTHALAMIC DYSFUNCTION
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23. GBS MENINGITIS
• 20 % OF SURVIVORS HAVE MILD TO
MODERATE NEUROLOGIC SEQUELAE
• BORDERLINE MENTAL RETARDATION
• LANGUAGE DELAY
• UNILATERAL HEARING LOSS
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24. GBS BACTEREMIA WITHOUT FOCUS
• LATE ONSET DISEASE
• UNCOMPLICATED PERINATAL COURSE
• NON-SPECIFIC SIGNS IN FIRST FEW WEEKS OF
LIFE
– FEVER
– POOR FEEDING
– IRRITABILITY
– RINORRHEA
• “R/O SEPSIS” WORKUP
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25. PREVENTION OF GBS INFECTION
• CHEMOPROPHYLAXIS
• IMMUNOPROPHYLAXIS
25

26. Bacitracin sensitivity
• Principle:
– Bacitracin test is used for presumptive
identification of group A
– To distinguish between S. pyogenes
(susceptible to B) & non group A such as S.
agalactiae (Resistant to B)
– Bacitracin will inhibit the growth of gp A Strep.
pyogenes giving zone of inhibition around the
disk
• Procedure:
– Inoculate BAP with heavy suspension of tested
organism
– Bacitracin disk (0.04 U) is applied to inoculated
BAP
– After incubation, any zone of inhibition around
the disk is considered as susceptible

27. Differentiation between -hemolytic streptococci
CAMP test
Bacitracin
sensitivity
Hemolysis
Negative
Susceptible

S. pyogenes
Positive
Resistant

S. agalactiae
Inulin
Fermentation
Bile
solubility
Optochin
sensitivity
Hemolysis
ferment
Soluble
Sensitive
(≥ 14 mm)

S. pneumoniae
Not-fermented
Insoluble
Resistant
(≤13 mm)

Viridans strep
Differentiation between -hemolytic streptococci

28. Enterococcus: Microbiological
Properties
• Gram-positive cocci (round to oval-shaped,
occasionally elongated)
• Catalase negative
• Growth on 5% sheep blood agar with optimal
growth for occasional strains in the presence
of 5-10% CO2
• -hemolysis (E. faecium) and no hemolysis or
narrow zone of  hemolysis (E. faecalis)
• Most strains are bacitracin resistant

29. Enterococcus
1. They are relatively heat resistant & can withstand heat
at 60°C for 30 minutes (heat test or heat resistant test)
2. Their abiliy to grow in the presence of 6.5% sodium
chloride.
3.Their abiliy to grow at 45°C and at pH 9.6
4. They are PYR test positive.
5. They are resistant to SXT (Trimethoprim &
sulphamethoxazole).
On MacConkey’s medium they grow as tiny deep pink
colonies.
On Gram staining, enterococci appears oval cocci in short
chains.

30. Enterococcus ( Cont-)
• The identification of the species is based on
biochemical reactions. E. faecalis is the most
commonly isolated enterococcus from human
sources.
• Other enterococci are E. faecium & E. durans
E. faecalis can be identified by fermentation of
mannitol, sucrose, aesculin & sorbitol, and by
producing black colonies when grown on tellurite
blood agar.
-Sub acute bacterial endocarditis
-Septicaemia, biliary tract infection
-peritonitis

31. Enterococcus (Cont-)
Strains resistant to Penicillin & other antibiotics
occur frequently.
-Vancomycin is the primary alternative drug
-Vancomycin resistant strains has also been
isolated.
-Resistance is most common in E. faecium, but
Vancomycin resistant strains of E. faecalis also
occurs.

33. Streptococcus: Types of Infectious
Disease
• Streptococcus pyogenes is one of the
most virulent bacterial pathogens, and
causes acute pharyngitis, impetigo,
cellulitis, necrotizing fasciitis and
myositis (flesh-eating bacteria),
pneumonia, bacteremia, and
streptococcal toxic shock syndrome

34. Enterococcus: Types of Infectious Disease
• High-level vancomycin resistance results from vanA gene
coding for abnormal peptidoglycan precursors having
terminal D-alanyl-D-lactate (normal = D-alanyl-D-alanine)
with decreased vancomycin binding affinity and diminshed
inhibition by vancomycin of cell wall peptidoglycan synthesis
for VRE strains (VRE=vancomycin-resistant enterococci)
• Associated with resistance to high concentrations of
vancomycin (vancomycin minimal inhibitory concentrations
> 256-µg/ml) and treatment failure in VRE infection
• Prevalent with Enterococcus faecium, unusual for
Enterococcus faecalis

35. Species Identification of Group II
Enterococcus (Facklam’s Scheme)1
MAN SOR ARG ARA PIG
E. faecalis + – + – –
E. faecium + – + + –
E. casseliflavus2 + – + + +
E. gallinarum2 + – + + –
1MAN=mannitol, SOR=sorbose, ARG=argininie,
ARA=arabinose, PIG=yellow pigment
2Motile (E. faecalis and E. faecium non-motile)

36. Bile-Esculin Hydrolysis Test
Positive in Gp D streptococci &enterococci
• The bile-esculin hydrolysis test
measures the ability of an isolate to
hydrolyze the -glycoside bond of
esculin with production of esculetin and
glucose in the presence of 40% bile.
Free esculetin reacts with the iron salt
ferric citrate to form a brown to black
precipitate.

38. Test Enterococcus Group ‘D’
streptocoocus
1. Growth in
the presnce of
6.5% NaCl
+ -
2. PYR test + -
3. Sensitivity
to SXT
R S
4. Ability to
grow at 45°C
+ _
Differences between enterococcus & Group D streptococcus

39. Some characteristic features of
different groups of streptococci
Lancefiel
d group
Species or common
name
Diagnostic test Diseases caused
A Str. Pyogenes Bacitracin sensitive, PYR
positive, resistant to SXT
Upper respiratory tract
infections, skin
infections, Ac
Rheumatic fever, Ac
glomerulonephritis
B Str. agalactiae CAMP test positive, hippurate
hydrolysis positive, resistant to
SXT
Neonatal septicaemia &
meningitis
C Str. equisimilis Ribose fermented, trehalose
fermented
Pharyngitis,
endocarditis
D (i) Enterococcus sp. ( E.
faecalis & other
enterococci)
Heat test positive, growth in
the presence of 6.5% NaCl, PYR
negative, Sensitive to SXT
Urinary tract infections,
woun infections
(ii)
Non-enterococcal
No growth in 6.5%, PYR
negative, Sensitive to SXT
Genitourinary infections
Not
typed
Viridans streptococci( Str.
Salivarius, Str. Mutans &
Optochin resitant, species
differentiation on biochemical
Endocarditis, dental
caries