The Cocci of Medical

Importance

Chapter 18

MCB 2010

Palm Beach State College

Professor Duncombe

Pyogenic Cocci: stimulate pus

formation: 4 groups

• Staph

• Strept

• Entero

• Neisseria

• Skin

• Mucous membranes

• No spores, flagella

Staphylococcus aureus

Staphylococcus: Virulence Factors

• Skin

• Mucous membranes

• No spores, flagella

• Capsules?

• Body temp

• Facultative

• High salt, pH, temp

• Months of air drying

• Coagulase

• Hyaluronidase:

spreading factor

• Nuclease

• Lipase

• Penicillinase

Exotoxins

• Hemolysins

• Leukocidin

• Enterotoxins

• Exfoliative toxin

• TSS toxin (fever, vomiting,

shock, systemic organ

damage)

• MRSA: skin lesion contact

• Abscess

• Pneumonia, endocarditis

• Phagocytes

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Staphylococcus aureus

Streptococcus: chains

• No spores, motility

• Capsules

• Slime layers

• Facultative

• Fermenters

• Enriched media

• Sensitive to drying, heat, disinfectants

• Many drug-resistant

• Enterococcus

• Shared between humans and pets

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S.pneumoniae:

Most serious in humans: Impetigo

S. pyogenes/ S. pharyngitis

Streptococcus Surface Antigens

• Techoic acid: CHO: protect from host

lysozyme

• Lipoteichoic acid: adhesion

• M-protein: spikes; antiphago;adhesion

• Hyaluronic acid: capsule: can’t distinguish

from human HA; no immune response

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Streptococcus Toxins

• Streptolysins: hemolysins

• Erythrogenic/pyogenic toxin: scarlet fever

• Rheumatic fever/Acute glomerulonephritis

• Superantigens: toxins that evoke a severe

immune response: tumor necrosis factor:

vascular injury

Streptococcus Enzymes

• Streptokinase: digest

blood clots: invasion

• Hyaluronidase:

spreading

• DNase

• Strept pneumo

Streptococcus Infections

Identification of Streptococcus

• Blood hemolysis

• Gram +

• Catalase –

• Test Kits: cAMP,

bacitracin, PYR

(pyrolidonyl

aminopeptidase):

differentiate different

groups

• Treatment: penicillin

Neisseriaceae

• Gram –

• Mucous membranes

• Pairs, bean-shaped,

flat sides touching

• No spores, flagella

• Capsules, pili

• Parasitic

• Aerobic/microaero-

phile

Virulence Factors/Treatment

• Pili: attach, antiphagocytic

• Protease: antibody A

• Catalase

• Fermenter

• Oxidase

• Quinoline/tetracycline: other combos

• N. meningitidis: endotoxin from cell wall lyses

• Natural immunity: penicillin

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Fig18.24

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