BS537: STAPH & STREP

What type of bacteria are Staphylococcus and Streptococcus?

Gram-positive cocci

Where are most staph and strep found?

Normal flora of skin and oral cavity

When do staph and strep become pathogenic?

When host immunity is compromised

What are the two major pathogens in this group?

Streptococcus pyogenes and Staphylococcus aureus

What is the arrangement of Streptococcus?

Chains or pairs

Are streptococci motile?

No

Do streptococci form spores?

No

Are streptococci catalase positive or negative?

Catalase negative

What type of metabolism do streptococci have?

Facultative anaerobes

Do streptococci require enriched media?

Yes

How are streptococci classified?

Lancefield groups and hemolysis

What is Lancefield classification based on?

Cell wall antigens

What are hemolysis types?

Alpha beta gamma

What is beta hemolysis?

Complete lysis of RBCs

What is alpha hemolysis?

Partial lysis (green)

What is gamma hemolysis?

No lysis

Which streptococci are beta hemolytic?

Groups A B C G

Which are alpha hemolytic?

S. pneumoniae and viridans

What group is Streptococcus pyogenes?

Group A beta-hemolytic

What group is Streptococcus agalactiae?

Group B beta-hemolytic

What diseases are caused by S. pyogenes?

Strep throat cellulitis rheumatic fever

What virulence factor is most important in S. pyogenes?

M protein

What does M protein do?

Prevents phagocytosis

What does hyaluronic acid capsule do?

Prevents phagocytosis

What do fimbriae do?

Attachment

What are streptolysins?

Hemolysins that damage cells

What is streptolysin O?

Oxygen-labile toxin

What is streptolysin S?

Oxygen-stable toxin

What do pyrogenic toxins cause?

Fever and rash

What are superantigens?

Cause massive cytokine release

What enzymes are produced by S. pyogenes?

Streptokinase hyaluronidase DNase

What does streptokinase do?

Breaks down clots

What does hyaluronidase do?

Breaks down connective tissue

What does DNase do?

Breaks down DNA

What is the reservoir for S. pyogenes?

Humans

How is S. pyogenes transmitted?

Droplets contact food

Where does S. pyogenes enter the body?

Skin or pharynx

Who is most affected?

Children

What are skin infections of S. pyogenes?

Impetigo erysipelas

What is impetigo?

Superficial crusting skin infection

What is erysipelas?

Infection of dermis/subcutaneous tissue

What is strep throat?

Pharyngitis caused by S. pyogenes

What is scarlet fever?

Toxin-mediated rash from S. pyogenes

What is streptococcal toxic shock syndrome?

Severe toxin-mediated systemic illness

What immune complications follow S. pyogenes?

Rheumatic fever glomerulonephritis

What is rheumatic fever?

Autoimmune reaction affecting heart joints brain

What is glomerulonephritis?

Kidney inflammation after infection

Where is S. agalactiae found?

Vagina GI tract pharynx

What does S. agalactiae cause?

Neonatal sepsis pneumonia meningitis

How is S. agalactiae transmitted?

During birth

How is it prevented?

Screening and antibiotics in pregnancy

What are viridans streptococci?

Alpha hemolytic oral flora

Where are viridans found?

Mouth gums teeth

What diseases do viridans cause?

Dental caries endocarditis

What is S. mutans associated with?

Plaque and cavities

What is S. pneumoniae?

Alpha hemolytic diplococcus

What is its shape?

Lancet-shaped pairs

What is its major virulence factor?

Capsule

What does S. pneumoniae cause?

Pneumonia otitis media

Where is it found?

Nasopharynx

Who is at risk for pneumococcal pneumonia?

Elderly children immunocompromised

How is S. pneumoniae diagnosed?

Gram stain optochin sensitivity quellung test

How is it treated/prevented?

Penicillin vaccines

What is the arrangement of Staphylococcus?

Clusters

Are staphylococci catalase positive or negative?

Catalase positive

Where are staphylococci found?

Skin and mucous membranes

Do staphylococci form spores?

No

What is Staphylococcus aureus?

Major pathogenic staph species

Where is S. aureus found?

Nose and skin

What are growth characteristics of S. aureus?

Salt tolerant facultative anaerobe

What temperature does it grow best?

37°C

What enzyme is diagnostic for S. aureus?

Coagulase

What does coagulase do?

Clots plasma

What enzymes does S. aureus produce?

Hyaluronidase DNase lipase penicillinase

What does penicillinase do?

Breaks down penicillin

What toxins does S. aureus produce?

Hemolysins leukocidin enterotoxin exfoliative toxin TSST

What does leukocidin do?

Kills WBCs

What does enterotoxin cause?

Food poisoning

What does exfoliative toxin cause?

Skin peeling

What does TSST cause?

Toxic shock syndrome

Where is S. aureus commonly carried?

Anterior nares

What increases risk of infection?

Poor hygiene diabetes immunodeficiency

What is MRSA?

Methicillin-resistant S. aureus

What are localized staph infections?

Folliculitis furuncle carbuncle impetigo

What is folliculitis?

Hair follicle infection

What is a furuncle?

Boil

What is a carbuncle?

Cluster of boils

What systemic infections can S. aureus cause?

Osteomyelitis bacteremia endocarditis

What is osteomyelitis?

Bone infection

What is bacteremia?

Bacteria in blood

What toxigenic diseases does S. aureus cause?

Food poisoning scalded skin syndrome toxic shock

What is scalded skin syndrome?

Skin blistering and peeling

What are coagulase-negative staphylococci?

Less virulent opportunists

What is S. epidermidis associated with?

Endocarditis UTIs

What is S. saprophyticus associated with?

UTIs

How is Staphylococcus identified?

Culture catalase test coagulase test

What is treatment concern with staph?

Antibiotic resistance

What must be done for abscesses?

Drainage

How are staph infections prevented?

Hygiene and universal precautions