6141 Microbiology Lecture 2

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Streptococci: gram negative or gram positive?

Gram positive

Streptococci: coagulase negative or positive?

Coagulase negative

What type of Strep is in group A?

Strep. pyogenes (over 130 different strains (M-protein types))

What type of Strep is in group B?

Strep agalactiae

What type of Strep is in group D?

Strep bovis

What are some examples of pyogenic disease caused by Strep. pyogenes?

pharyngitis, impetigo, erisypelas, cellulitis, pneumonia

What are some examples of immune-related disease caused by Strep pyogenes?

Rheumatic fever, glomerulonephritis

What are some toxinoses caused by Strep pyogenes?

Scarlet fever, streptococcal toxic shock syndrome, necrotizing fasciitis

What is the significance of M proteins when discussing Streptococcus?

M proteins help determine the type of Group A Strep present. Different types cause different diseases.

What causes Erysipelas?

Bacterial enzymes (inflammation related and degradative): hyaluronidase, nucleases, hemolysins

Describe Strep pyogenes related cellulitis.

Infection of deeper tissue, erysipelas is more superficial.

What are the symptoms of rheumatic fever?

fever, rash, carditis (heart valve damage afterwards), and arthritis

What causes rheumatic fever?

Strep pyogenes: anti-M protein antibodies cross-react with heart and joint tissue antigens

What causes glomerulonephritis?

Antigen-antibody complexes accumulate on the glomerular basement membrane

What are the symptoms of glomerulonephritis?

hypertension, edema of the face and ankles, bloody urine

What causes Scarlet fever?

Streptococcus pyogenes: erythrogenic toxin, a pyogenic exotoxin.

What are the symptoms of scarlet fever?

diffuse red sunburn-like rash on the neck, trunk, and extremities

History of Strep pyogenes - 18th and 19th centuries

Streptococcal fasciitis in wounded soldiers, puerperal fever (women), blood poisoning

History of Strep pyogenes - late 19th to early 20th centuries

Scarlet and rheumatic fever

History of Strep pyogenes - 1940s to present

Scarlet and rheumatic fever virtually disappear

History of Strep pyogenes - Late 20th century

Scarlet fever outbreaks, TSS, fasciitis, pneumonia, nosocomial wound infections, invasive systemic infections

What is another name for necrotizing fasciitis?

Flesh-eating bacteria

Name several pathologies caused by Strep pneumoniae (pneumococcus)

Meningitis, Acute pneumonia, Otitis media

What causes meningitis?

Strep pneumoniae adheres to endothelial cells of the meninges (the membranes surrounding the brain and the spinal cord

What are some predisposing factors of acute pneumonia?

Repressed cough reflex (drugs and alcohol), respiratory tract infection (influenza virus) or damage (smoking), abnormal circulatory dynamics (heart/lungs), chronic diseases (sickle-cell anemia, nephrosis), head injuries (for meningitis)

In individuals less than 1 mo. of age, which organisms are most likely to cause infection?

Streptococcus group B (69.5%) and Listeria monocytogenes (21.8%)

In individuals 1-23 mo. of age, which organisms are most likely to cause infection?

Streptococcus pneumoniae (45.2%) and Neisseria meningitidis (30.8%)

In individuals 2-29 years, which organisms are most likely to cause infection?

Neisseria meningitidis (59.8%) and Streptococcus pneumoniae (27.2%)

In individuals 30-50 years, which organisms are most likely to cause infection?

Streptococcus pneumoniae (60.6%) and Neisseria menigitidis (18.2%)

In individuals 60+ years of age, which organisms are most likely to cause infection?

Streptococcus pneumoniae (68.6%) and Listeria monocytogenes (21.7%)

What is one of Strep penumoniae's virulence factors?

The capsule: inhibits lysis by phagocytes, over 85 different capsular antigen types

What is the most common cause of the most common childhood infection?

The most common cause: Strep pneumoniae
The most common childhood infeciton: Otitis media

What infections are caused by Strep agalactiae?

meningitis, pneumonia, and bacteremia in neonates

What infections are caused by Strep bovis (Group D)?

nosocomial UTIs, and endocarditis

What infections are caused by Strep mutans (Viridans group)?

causes dental caries, endocarditis, and bacteremia; enters blood stream during dental procedures

What are two species of Enterococcal infections?

Enterococcus faecalis and enterococcus faecium

What are some characteristics of enterococcal infections? (Where organism resides, pathogenesis...)

Reside in colon, nosocomial (second only to Staph aureus), UTIs, bacteremia, wound infections, endocarditis

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