Bacteria unit lecture notes, Study notes of Microbiology

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G R A M P O S I T I V E N O N - M O T I L E M A Y B E P I G M E N T E D C O M P L E T E L Y H A R M L E S S U B I Q U I T O U S

Micrococcus

Staphylococcus

 Gram positive  Appear as clusters of spherical cells that resemble grapes  Resistant to drying out  Normal flora  Nosocomial infections

Staphylococcus aureus is responsible for:

 Forming abscesses with pus producing lesions, boils, acne, impetigo, and caruncles associated with the skin

S aureus is responsible for:

 Pnuemonia  Osteomyelitis (bone and bone marrow abscesses)  (endocarditis-inflamed endocardium)

S aureus can produce these toxic end products

 Coagulases- form blood clots that surround and protect the organism  Leukocidin- lyses white blood cells  Hemolysins- lyses red blood cells  Enterotoxin- causes gastroenteritis

S aureus can produce these nontoxic end

products

 Dnase- breaks down DNA  Lipase- breaks down lipids  Gelatinase- degrades gelatin  Staphylokinase- a fibrinolysin

VRSA

 Vancomycin resistant Staphylococcus aureus  Treatment:  Linezolid- very harsh- inhibits protein synthesis  Side effects-  thrombocytopenia- abnormally small number of platelets resulting in the potential for increased bleeding and decreased ability for clotting.  Elevates liver enzymes  GI upsets- which are severe

Streptococcus

 Cocci that divide in a single plane forming chains  Circular translucent to opaque pinpoint colonies  Gram positive  Aerotolerant  encapsulated

Streptococcus can cause a variety of extracellular

metabolites:

 Hemolysins (alpha and beta)- act on RBCs  Leucocidins- destroy pathogens  Erythrogenic toxin – causes scarlet fever rash  Hyaluronidase- hydrolyzes tissue cement  Streptokinase- a fibrinolysin  Nucleases- destroy viscous tissue debris

Bacillus

 Gram positive  Ubiquitous in nature  Natural flora  Opportunistic pathogen  Endospore former- spore producing  Environment- soil  Antibiotics

Bacillus and antibiotics

 Bacillus brevis- is the organism that is the source of the antibiotics gramicidin and tyrocidin  Bacillus polymyxa- is a saprophytic soil and water organism that produces the antibiotic polymyxin B

Clostridium

 Gram positive  Anaerobic- obligate anaerobes  Spore former  Found in soil  Secrete powerful exotoxins

Corynebacterium

 Gram positive  Club shaped rods- pleomorphic with one or both ends swollen  Corynebacterium diptheriae- the causative agent of diptheria

Lactobacillus

 Gram positive  Commonly found in yogurt  Lactic-acid producing bacteria  Located in the vagina, intestinal tract, and oral cavity  Commercially used for production of sauerkraut, pickles, buttermilk, and yogurt.