Gram +/-Cocci: Thao Nguyen, PHD Thao - Nguyen@Ttu - Edu.Vn
Gram +/-Cocci: Thao Nguyen, PHD Thao - Nguyen@Ttu - Edu.Vn
Gram +/-Cocci: Thao Nguyen, PHD Thao - Nguyen@Ttu - Edu.Vn
• Spherical, 1 μm
• Irregular clusters
• Young: G+; Old: G-
• Non motile
• No spore or flagella
• May have capsule
• Common of skin and
mucous membranes
Morphology identification-Growth
• Facultative anaerobe
• Optimum temp. at 37oC
• Form pigment best 20-25oC
• S. aureus: gray to deep golden
yellow, produces hemolysis
• S. epidermidis: gray to white
on primary isolation
• No pigment: anaerobically or in
broth
Morphology identification- Growth Characteristics
Consume: Many carbohydrates
Produce:
Catalase
b-lactamase
Lactic acid
No gas
Relatively resistant to drying, heat (alive at 50oC for 30
minutes), 9% sodium chloride
Readily inhibited by certain chemicals: 3% hexachlorophene
Antigenic Structure
• Catalase negative
• Group A, C, G β-hemolysis
• Transforms plasminogen into plasmin-> digest
fibrin and other proteins
• Interfered by nonspecific serum inhibitors and
by a specific antibody, antistreptokinase
• Given intravenously for treatment of venous
thrombosis (huyết khối)
Toxins and Enzymes
B. Streptodornase
• DNAse
• Facilitate the spread of streptococci in tissue by
liquefying pus (like streptokinase)
• Streptodornase+Streptokinase: liquefy exudates and
facilitate removal of pus and necrotic tissue
Toxins and Enzymes
C. Hyaluronidase
• Bacteremia, meningitis,
abdominal infection,
tooth abscesses
• Most serious is subacute
endocarditis
• Colonization of heart by
forming biofilms
Viridans Group
• S. mutans produce slime
layers that adhere to teeth,
basis for plaque
• Involve in dental caries
• Person with preexisting heart
conditions should receive
prophylactic antibiotics before
surgery or dental procedures
S. pneumoniae – the pneumococcus
• Cause 60-70% of all bacterial pneumonias
• Small, lancet shaped cells, pairs, short chains
• Growth induced by 5-10% CO2
• Culture dies in O2
• Catalase and peroxidases negative
S. pneumoniae – the pneumococcus
• All pathogenic strains form large capsules –
major virulence factor
• 90 capsular subtypes
• Cause pneumonia
• Otitis media in kids
S. pneumoniae – Epidemiology and
Pathology
• 5-50% of all people carry it in nasopharynx.
Infections are usually endogenous
• Very delicate, not survive long outside its
habitat
• Kids, elderly, immune compromised, those
with lung diseases/viral infections –
predisposed to pneumonia
Pneumonocci gain access to middle ear by
way of eustachian tube
S. pneumoniae – Cultivation and
Diagnosis
• Gram stain of specimen – presumptive
identification
• Quellung test or capsular swelling reaction
• a-hemolytic; optochin sensitivity, bile
solubility, inulin fermentation
Bile Optochin
test
S. pneumoniae – Treatment and
Prevention
• Traditionally use Penicillin G or V
• Increase drug resistance
• Two vaccines available for high risk individual
– Capsular antigen vaccine: older adults and high
risk individuals, 5 year effective
– Conjugate vaccine for children 2-23 months
What is the major virulence factor
of Streptococcus pneumoniae?
A) M protein
B) Pyogenic exotoxins
C) Capsule
D) DNase
E) Hyaluronidase
NEISSERIACEAE
central
nervous
system sexually transmitted
disease (STD)
irritation- gonorrhea
meningitis
Family Neisseriaceae
• G- cocci
• Residents of mucous membranes of warm
blooded animals
• Genera include Nesseria, Branhamella,
Moraxella
• 2 primary human pathogens
– Neisseria gonorrhoeae
– Neisseria meningitidis
Genus Neisseria
• G-, bean shaped, diplococci
• No flagella or spores
• Capsules on pathogens
• Pili
• Strict parasites, do not survive outside
hosts
• Aerobic/microaerophilic
• Catalase and cytochrome oxidase
positive
• Pathogenic spiecies require rich
complex media
NEISSERIA MENINGITIDIS
Não mô cầu (meningococcus)
• Epidemic cerebrospinal meningitis
• Causes life-threatening sepsis (meningococcemia)
and/or meningitis
Virulence factors
1. Capsule
• Polysaccharide
• Antiphagocytic
• Classified into 13 serogroups based on
different antigenic capsular polysaccharides:
A-E, H, I, K, L, X, Y Z
• Meningitis: usually by serogroups A, B, and C
Virulence factors
2. Endotoxin
• Lipopolysacharides (LPS)
• Causes blood vessel destruction (hemorrhage)
and sepsis
• Hemorrage on the skin (petechiae-petechial
rash): tiny, round, red dots
Virulence factors
3. IgA1 protease: cleaves IgA in half
4. Neisseria meningitidis can extract iron from
human transferrin via a non-energy requiring
mechanism
5. Pili: Attachment to nasopharyngeal cells;
Undergo antigenic variation to avoid attack by
the immune system
Epidemiology and Pathogenesis
• Prevalent cause of meningitis: sporadic or epidemic
• 5% of the population: normal flora of the nasopharynx;
asymptomatically => develop natural immunization
• Spreads via respiratory secretions
• High risk groups: infants (6m-3y); army recruits, college
freshman
• Disease happens when bacteria invade the
bloodstream, cross the blood-brain barrier, permeate
the meninges and grow in the cerebrospinal fluid
• Very rapid onset; neurological symptoms; endotoxin
causes hemorrhage and shock; can be fatal
Meningococcal Disease
1) Meningococcemia
• Spiking fevers, chills, arthralgia (joint pains),
• Muscle pains, petechial rash
• Meningococci rapidly disseminate throughout
the body => meningitis and/or Fulminant
meningococcemia
Meningococcal Disease
2) Fulminant meningococcemia (Waterhouse
Friderichsen syndrome, septic shock)
• Bilateral hemorrhage => adrenal insufficiency
• Hypotension, tachycardia
• Enlarging petechial skin lesions
• Disseminated intravascular coagulation (DIC)
• Coma
• Death can occur rapidly (6-8 hours)
Meningococcal Disease
3) Meningitis
• Most common
• Infants < 1 y/o:
chill, fever,
vomitting,
iritabilility,
lethargy, stiff neck
• Petechial skin
Diagnostic Laboratory Tests
• Specimens:
blood, cerebrospinal fluid, petechial scrapings
• Neisseria culture
– best on chocolate agar (heated blood agar)
– Thayer-Martin VCN (chocolate agar+Vancomycin,
Colistin+Nystatin)
– High CO2 concentration improves the growth
Diagnostic Laboratory Tests
• Oxidase test : positive
• Sugars fermentation
• Neisseria meningitidis can grow on maltose
while Neisseria gonorrhoeae cannot
• Agglutination with type-specific or polyvalent
serum
Treatment, Epidemiology and Control
• Penicillin G or Ceftriaxone: disseminated
meningococcemia
• Rifampin or Minocyclin: contacts with infected
patients
• Immunization with purified capsular
polysaccharides from certain strains (groups A, C,
Y, and W135)
• Duration of immunitiy in adults: 2-4 ys; in
children: does not induce immunity
NEISSERIA GONORRHOEAE
(Lậu cầu khuẩn-gonococcus)
• Second most common STD, gonorrhea
Virulence factors
1) Pili
• Complex genes coding for their pili, multiple
recombinations, hyper varitable amino acid
• changing antigens protect the bacteria from
our antibodies
• prevent phagocytosis, probably by holding the
bacteria so close to host cells
Virulence factors
2) Lipopolysaccharides
3) Protein I (Outer membrane protein porins,
PorA, PorB)
•form pores in the surface through which some
nutrients enter the cell
•preventing phagosome – lysosome fusion in
neutrophils
Phagocytosis
Virulence factors
4) Protein II (Opa Proteins)
• Membrane protein (rooted from the outer
membrane)
• Promote adhesion of gonococci within
colonies and to host cells
• Each strain has 11 or 12 genes for different
Opas, but expressions are occasionally
different (0, 1, 2..)
Virulence factors
5) Protein III (Rmp)
• Associates with Por in the formation of pores
in the cell surface
6) Other proteins (poorly defined roles)
• Lip (H8) is a surface exposed protein
• Fbp (ferric-binding protein), is expressed when
the available iron supply is limited
7) IgA1 protease
Gonococcal Disease in Men