Mlt Microbiology (Week 03A)

Front 1

Streptococcus & Enterococcus

Back 1

The two major genera of Streptococcaceae that are major pathogens.

Less common are: Aerococcus, Leuconostococcus, Pediococcus, & Gemmella.

Front 2

Streptococci vs Streptococcus

Back 2

Streptococcus is the correct name.

Front 3

Streptococcaceae

Back 3

Streps are catalase negative (doesn't produce catalase, no bubbles), non-motile, non-spore forming, do not reduce nitrates, and are facultative anaerobes.

Front 4

Lansfield's Classification

Back 4

Classified based upon C-carbohydrate in the cell wall.

Front 5

Important Species of Streptococcus & Enterococcus

Back 5

• Streptococcus pyogenes
  
• Streptococcus agalactiae
• Streptococcus pneumoniae
• viridans streptococci
• Enterococcus sp.

Front 6

Streptococci Morphology

Back 6

Streptococci are Gram positive cocci seen in chains. Colonies are gray-white and shiny.

Front 7

Testing & Identification of Strep

Back 7

• Strep pyogenes (GAS [Group A Strep])

Bacitracin (TAXO A) sensitivity test: streak plate for confluent growth and place test discs on top of organism. Tests for susceptibility to antibodies.

• SXT sesitivity

trimethoprim sulfamethoxazole. Groups A & B are resisitant, but other beta-hem groups are sensitive (ie, group C)

• Strep agalactiae (GBS)

Soft beta hemolysis (~50%) is characteristic but not unique.

• CAMP test (Christie, Atkins, Munch-Petersen)

results in a uniquely shaped extreme beta hemolysis. One line of Staph aureus drawn down the middle, with a positive control (GBS) line on one side, and a negative control (GAS) and your unknown on the other side. Growth will show results.

• Strep pneumoniae

morphology: flat, lancet shaped end-to-end pairs. Small, gray, translucent, checker-like, alpha appearance.

Bile solubility test, place one drop of 4% bile solution on colony, incubate for 20 minutes. If colony has dissolved, it is strep pneumoniae. If it has a capsule, it will resist the solution.

TAXO P (Optochin) ethyl hydrocupreine-HCL, place disc on confluent growth. Measure zome of no growth, if greater than 15mm it is strep pneumoniae.

• Enterococci vs Group D Strep

Will both be positive for BEM, but only Enterococci can tolerate the PYR/6.5% NaCl test.

Front 8

Beta-hemolytic Streptococci

Back 8

Group A: Strep pyogenes

Group B: Strep agalactiae

Group C: Lancefield group

(Enterococci are rarely beta, usually non or alpha)

Front 9

Alpha-hemolytic Strep

Back 9

Otherwise known as "viridans streptococci", because it is green. No C-carbohydrate, therefore no Lanecfield group.

Strep pneumoniae

Front 10

Enterococci & Group D Strep

Back 10

Enterococci:

Enterococcus faecalis

Enterococcus faecium

GDS:

Streptococcus bovis

Streptococcus equinus

Front 11

Streptococcus pyogenes associated diseases

Back 11

• Sore throat (biggest cause of strep throat!) (#1 cause of bacterial pharyngitis. Tonsillitis.) Follow up problems can include rheumatic fever and acute glomerulonephritis.
• Scarlet fever (starts with pharyngitis, SPE (strep pyogenic exotoxin) gets into blood stream and has a systemic effect, causing a red rash on trunk region.)
• Otitis media, sinusitis (middle ear infection)
• Pneumonia
• Erysipelas (skin infections, similar to impetigo.) Follow up problems include acute glomerulonephritis.
• Wound infections
• Puerpural infection (used to be a common cause of death from child birth)
• Bacteremia/Septiccemia
• Pericarditis, peritonitis, etc...

Front 12

Streptococcus agalactiae associated diseases

Back 12

• Can be NURF (normal upper respiratory flora) or NVF (normal vaginal flora) in some people.
• #1 cause of bacterial meningitis in full term infants.
• Bacteremia/Septicemia (often in older adults)
• Rarely pneumonia

Front 13

Antigenic structure of Strep pyogenes

Back 13

C-carbohydrate, M-protein (most pathogenic importance), and F-protein.

Front 14

Extracellular Enzymes & Toxins of Strep pyogenes

Back 14

Hemolysins (lyse RBCs)

• Streptolysin O (MOST IMPORTANT.) (Antigenic protein, not as active in presence of oxygen.)
• Streptolysin S (much less antigenic protein. Oxygen stable.)

Streptokinase

• Plasminogen --> Plasmin (inhibits/breaks down blood clots, breaks down fibrin)

Hyaluronidase

• Spreading factor (breaks down connective tissue with hyaluronic acid. Flesh eating.)

NADase

• Breaks down NAD

DNAase

• breaks down DNA