MICROBIO 5.2

Streptococcus

Strep gram status

Positive

Strep motility

Nonmotile

Strep shape

Cocci in pairs or chains

Strep catalase activity

Negative; no bubble (NOT Staph)

Oxygen requirements

Facultative anaerobe (like Staph)

Strep culturing plate

Blood agar plate

Strep virulence factor

• M protein —> membrane protein that disrupts body’s immune system; makes difficult for lysis

• Hylauronic acid capsule —> camaflouge bacteria & immune cells leave it alone

  • e.g. Strep pneumoniae

Hylauronic acid capsule

Sticky carbohydrate enriched layer

Camaflouges bacteria bc it’s found in body connective tissue

Helps adhesion to host cells and prevents immune cells from lysing

Strep that exhibit alpha hemolysis

Strep pneumoniae

*Alpha hemolysis —> green oxidized hemoglobin

Strep pneumoniae potential diseases

• pneumonia (lungs)

• sinusitis (sinuses)

• otitis media (middle ear)

• meningitis (membrane around brain/spinal cord)

• bacteremia (bacteria in bloodstream)

• sepsis (systemic response to infection)

• endocarditis (inner lining of heart)

• pericarditis (sac surrounding heart)

• brain abscess (localized collection of pus; infection in brain)

Strep that exhibit beta hemolysis

Group A, Group B, Group D Strep

Lancefield groupings

Based on antigens of bacterial cell wall

Example of GAS

Group A strep —> Strep pyogenes

• strep throat

• scarlet fever

• impetigo

• toxic shock syndrome

• cellulitis (deeper layers of skin)

• necrotizing fasciitis rapid tissue death)

• pyogenes = fever

Examples of GBS

Group B Strep —> Strep agalactiae

• blood infection

• pneumonia

• meningitis in newborn

Gamma hemolysis

No hemolysis —> enterococcus faecalis

Streptococcal pharyngitis

Strep throat

What is responsible for strep. pharyngitis?

GAS

S. pyogenes = 20% pharyngitis in adults, 30% in kids

**S. pyogenes is responsible for 90% of human Strep infections!

When do strep throat usually occur? (epidemiology)

Winter, early spring

Transmission type of Strep pharyngitis

Asymptomatic carriers & respiratory droplets

• humans are natural reservoirs for s. pyogenes

How does strep pharyngitis infection occur?

• When exposed to large enough amount of bacteria before body can produce antibodies

• immunocompromised

• microbiota decrease & body’s nutrients are BACTERIA’S

Signs & symptoms of strep. pharyngitis

• inflamed throat

  • swollen lymph nodes, fever, exudate (pus)

How do you diagnose strep. pharyngitis?

1. Throat is swabbed

2. Sample applied to antibody mixture

3. If antigen present in the sample, it binds to antibodies

4. If bind, it is positive test for bacteria being present

Complications of strep, pharyngitis

• otitis

• sinusitis

• pneumonia

• rheumatic fever

Rheumatic fever

Autoimmune disease that develops in 3% of untreated S. pyogenes, 2-3 weeks post infection

S pyogenes M protein stimulate antibody production in host —> antibodies to M protein are CROSS REACTIVE; attacks host tissues that are similar to M protein (e.g. heart valves, kidney, joints)

Cross reactive antibodies

Antibodies that bind to HOST’S tissues that bears proteins that resemble M protein

Treatment for strep. pharyngitis

Antibiotics

Treatment for rheumatic fever

Penicillin

Sepsis

Systemic inflammatory reaction to infection

Septicemia

Blood poisoning caused by bacterial infection in the blood

Causes of sepsis

GBS, E. coli, S. aureus, Pseudomonas, Klebsiella

GBS causes septicemia which causes sepsis

Location where infection occurs for sepsis

Lungs, urinary tract, GI, skin infection

Signs & symptoms of sepsis

Fever, chills, rapid breathing, elevated HR, increase in WBC, lymphangitis

Lymphangitis

Lymphatic vessels look like red streaks because of inflammation

Septic shock

Inflammation —> blood vessels dilate —> BP decreases (hypotension) —> cells not enough nutrients & waste not disposed —> tissue death —> organ failure

Treatment for sepsis

Antibiotics (decrease inflammation) and support (regulate temp, BP, O2 level)