Ch16 - Bacteria

Gram Stain

Laboratory technique used to quickly identify bacteria in a sample and classify them into two main categories: Gram-positive (purple) or Gram-negative (pink/red)

Gram stain (Positive Purple)

Bacteria with a thick cell wall. They appear colored under a microscope because they retain the crystal dye.

Gram stain (Negative Pink)

Thin peptidoglycan layer and an outer lipid membrane that prevents them from retaining the primary crystal stain, causing them to appear a different color under a microscope

Anthrax (Bacillus anthracis)

gram + rods (aligned end-to-end in chains) spore-forming

Strep throat (Streptococcus pyogenes)

gram + cocci (aligned in chains or pairs)

Cholera (Vibrio cholera)

gram – curved rod (looks like a comma)

Tuberculosis (Mycobacterium tuberculosis)

does not gram stain well (stains fuchsia with acid fast stain)

Bubonic plague (Yersinia pestis)

gram - rod

Tetanus (Clostridium tetanii)

gram + rod (looks like drumsticks) spore-forming

Diphtheria (Corynebacterium diphtheriae)

gram + rod (look like Chinese characters)

Botulism (Clostridium botulinum)

gram + rod spore-forming

Flesh eating disease (Streptococcus pyogenes) (Also strep throat)

gram + cocci (aligned in chains or pairs)

Bacteria pneumonia (Streptococcus pneumoniae)

gram + diplococci (sometimes aligned in chains)

Hemorrhagic colitis (Escherichia coli O157:H7)

gram - rod

Lyme disease (Borrelia burgdorferi)

gram - spirillum

Gonorrhea (Neisseria gonorrhoeae)

gram - diplococcus

Syphilis (Treponema pallidum)

gram - spirillum

Leprosy (Mycobacterium leprae)

does not gram stain well (stains pink with carbol fuchsin stain)

Obligate anaerobic bacteria

die if exposed to oxygen