1. Cocci
Gram Positive cocci
Gram Negative cocci
Ver 2011-1

2. Gram Negative cocci:
• Neisseriaceae - only • produces “cytochrome
aerobic family oxidase” - Oxidase
• Genus Neisseria, Test
Kingella, Eikenella, • N. gonnorhea
Simonsiella & (gonococcus ) -
Allysiella venereal disease
• diplococci • N. meningitidis
• exhibits “twitching” (meningococcus) -
type of movement meningitis

3. Antigenic Structure
• Pili – fimbriae that enhance cell attachment
• Por – protein that occurs in trimers thru which
some nutrients enter the cell
• Opa – proteins for adhesion of gonococci within
colonies and expression of CD66
• Rmp (Protein III) – antigenically conserved,
associates with Por in formation of pores
• LOS – Lipooligosaccharide –responsible for
toxicity of gonococcal infections

4. • Neisseria gonorrhoeae is
a fastidious organism
requiring growth factors
which are present in
hemolyzed blood cells.
Thayer-Martin chocolate
agar plates have VCN
antibiotics which prevent
growth of most organisms
while supporting N.
gonorrhoeae growth

5. • As a group, the Neisseria species are non-
sporulating, non-flagellated, gram
negative diplococci (a distinct bean shape
arranged in pairs) that may or may not have
a capsule and/or pili that facilitate
attachment to mucus membranes. They are
sensitive to cold, desiccation, light, and
acidity; most require complex enriched
media (e.g., chocolate agar, or modified
Thayer-Martin media) and high O2.

6. N. meningitidis (associated with
cerebrospinal meningitis: inflammation of
the meningeal layers of the brain promoted
by the capsule, released endotoxin, and IgA
protease).
N.lactimica is a weak nasopharyngeal
pathogen that is sometimes mistaken for
N.meningitidis , lactose fermenter &
usually found in children

7. Moraxella catarrhalis
• Previously named Branhamella catarrhalis
& before that Neisseria catarrhalis.
• Found in 40-50% of normal school children
• May cause bronchitis, pneumonia, sinusitis,
otitis media and conjunctivitis
• Concerned as a cause of infection for
immunocompromised patients

9. Gram negative cocci :
• Veillonellaceae - • found in the
only anaerobic gastrointestinal tracts
family of animals, but
• genus Veillonella, Veillonella are found
Acidaminococcus, in considerable
Megasphaera numbers within the
• forms pairs or short oral cavity
chains but smaller • mostly non-pathogenic
than Neisseria

11. Gram + cocci -
Peptostreptococcus
• Gram + coccus of variable size and shape
found on the skin and as part of the normal
flora of mucous membrane
• Formerly called peptococcus
• Frequently found in mixed infections due to
normal flora
• Occassionally, cultures from breast, brain,
or pulmonary infections

12. Gram positive cocci :
• Micrococcus-
– obligate aerobes found
in water & soil
– pigmented types
– morphologically
similar to
staphylococcus
– unlike streptococcus
acid is produced thru
aerobic oxidation &
not fermentation

13. Staphylococcus
can be both aerobic & anaerobic
found primarily in mammalian
skin & anterior nares
most important strain : S.aureus,
epidermidis & saprophyticus
S. aureus secretes enterotoxin
which causes food poisoning

14. General Characteristics
• Staph. are resistant to
drying & high salt
concentration
(halophilic)
• S. aureus also
produces coagulase,
an enzyme w/c clots
plasma & distinguish
it from S.
epidermidis

15. Morphology & Identification:
• Spherical about 1um in diameter arranged
in irregular clusters
• Can occur singly, pairs, tetrads and chains
in liquid culture
• Develop rapid resistance to many
antimicrobial agents & present difficult
therapeutic problems
• Contains around 35 species

16. Culture
• Grow readily on most medium
• Young culture stain strongly gram +, on
ageing become gram negative
• Non-motile, non-spore forming
• Lysed with penicillin
• Grows in BAP with resistance to nafcillin
• Exhibits “coagglutination” , some strains
are encapsulated

17. Streptococcus
- appear in chains of varying
length
- grow in the presence or
absence of air
- several species are
indigenous in animals & man
found in skin, oral cavity,
respiratory tract

18. - some specie also found in plants & dairy
products
-classified by Lancefield from Group A to H,
K-U based on a group specific carbohydrate
known as C substance in the cell envelope
and determined by an amino sugar

19. Classification of strep is based on
• Colony morphology & reaction to blood agar
• Serologic specificity of cell wall/antigens
• Biochemical reactions & resistance to factors
• Ecologic features

20. Typing usually done for Groups
A, B, C, F & G
• Strep A – rhamnose N-acetylglucosamine
• Strep B – rhamnose glucosamine
polysaccharide
• Strep C – rhamnose N-acetylgalactosamine
• Strep D – glycerol techoic acid

21. Characteristic of medically
significant strep:
Disease
Name Group Hemolysis
S. Pyogenes A Beta Pharyngitis
S. Agalactiae B Beta Meningitis
S. Dysgalactiae C,G Beta Similar to A
E. Faecalis D Alpha UTI.
Endocarditis
S. Bovis D Gamma Endocardits,
colon
S. Anginosus F Alpha, beta Brain abscess
Viridans group NONE Alpha Dental caries
S. Pneumoniae NONE Alpha Pneumonia
Peptostreptococcus NONE Alpha Abscesses

22. Antigenic structure & toxins:
• M Protein – major virulence factor of Strep A
• T substance – acid labile, heat labile
• Nucleoproteins – P substance
• Streptokinase – Fibrinolysin
• Streptodornase – depolymerizes DNA
• Hyaluronidase – splits hyaluronic acid
• Pyrogenic Exotoxins – Exotoxins A, B, C
• Hemolysins - Streptolysin O & S

23. Medically important gram + cocci
• Staphylococcus aureus,
(staphylococcal scalded skin
syndrome, skin infections -
e.g. boils etc., toxic shock
syndrome, food poisoning,
osteomyelitis, septic
arthritis, pneumonia, and
endocarditis)

24. • Staphylococcus epidermidis
(artificial valve
endocarditis, catheter and
shunt infections, prosthetic
infections)
• Staphylococcus
saprophyticus, (urinary
tract infection in young
sexually active females

25. • Streptococcus
pyogenes (Lancefield
group A) (pharyngitis,
scarlet fever, toxic
shock syndrome, skin
infections, post
infectious sequelae -
rheumatic fever and
glomerulonephritis

26. • Streptococcus
agalactiae(meningitis,
pneumonia and bacteremia
in the newborn)
• Group D streptococci
including the enterococcus
(the enterococci are
responsible for nosocomial
urinary tract infections,
bacteremia)

27. • Streptococcus pneumoniae
(pneumonia - community
acquired, sinusitis,
meningitis, bacteremia,
otitis media)
• Viridans streptococci
– (dental caries - S.
mutans, endocarditis,
bacteremia)

28. Diseases attributable to invasion
by S pyogenes, B-hemolytic
Group A Streptococcus
• Erypelas
• Cellulitis
• Necrotizing Fasciitis
• Puerperal Fever
• Bactermia/Sepsis

29. Properties that help distinquish
between Staphylococcus and
Streptococcus/Enterococcus
• Catalase activity
• Coagulase Activity
• Novobiocin
• Hemolysis
– Alpha (Bile solubility & Optochin), Beta &
Gamma
• Bacitracin sensitivity– inhibits cell wall
synthesis