PHAR 541: Microbio Part II-Bacterial morphology and Gram Stain

gram stain info always include

• cell wall form: pos or neg

• shape: cocci, bacilli

• formation: diplococci, clusters, pairs, chains

Bacterial shape (cocci)

1. coccus/cocci: spherical

2. diplococci: cocci arranged in pairs

   1. streptococcus pneumoniae

   2. Neisseria ghonorrhoeae

3. Streptococci: cocci arranged in chains

   1. streptococcus pyogenes

   2. streptococcus agalctiae

4. Staphylococci: cocci that divide in multiple planes and form grape like clusters

   1. staphylococcus aureus

Bacterial shape (bacilli)

1. bacilli = rod-shaped

2. coccobacilli: oval and similar to a coccus

   1. Haemophilus influenzae

3. branching or filamentous: resembling stands of hair or spaghetti

   1. Nocardia spp

other bacterial shapes

1. vibrio: curved or comma-shaped rod

2. spirillum: a thick, rigid spiral

   1. helicobacter pylori

3. Spirochete: a thin flexible spiral

   1. treponema pallidum

4. pleomorphic: can take on various chapes

   1. mycoplasma spp

Positive cocci

1. coagulase pos

   1. staphylococcus aureus

2. coagulase neg

   1. staphylococcus epidermis

   2. staphylococcus saprophyticus

   3. staphylococcus hominis

   4. staphylococcus hemolyticus

   5. staphylococcus warneri

3. diplococci: PAIRS (pneumococci)

   1. streptococcus pneumoniae

4. streptococci: CHAINS

   1. B-hemolytic

   2. Streptococcus pyogenes

   3. streptococcus agalactiae

   4. Groups C,F,G

   5. alpha-hemolytic

   6. viridans streptococcus

   7. streptococcus pneumoniae

positive bacilli

1. small

   1. listeria

   2. Propionibacterium

   3. Corynebacterium

   4. Gardnerella

2. large

   1. spore-forming: Clostridium, Bacillus

   2. nonspore-forming: Lactobacillus

3. branching or filamentous

   1. nocardia

   2. actinomyces

   3. erysipelothrix

negative cocci

1. neisseria meningitidis

2. neisseria gonorrhoeae

3. veillonella

negative bacilli

lactose fermenter

1. (oxidase positive)

   1. aeromonas

   2. pasteurella

   3. vibrio

2. oxidase negative

   1. e. coli

   2. klebsiella spp

   3. enterobacter spp

   4. citrobacter spp

non-lactose fermenter

1. oxidase positive

   1. pseudomonas spp

   2. flavobacterium spp

   3. alcaligenes spp

   4. achromobacter spp

   5. moraxella spp

2. oxidase negative

   1. proteus spp

   2. proficendia spp

   3. serratia spp

   4. morhanella spp

1. salmonella spp

2. shigella spp

negative coccobacilli

1. haemophilus influenzae

2. moraxella catarrhalis

atypical microorganisms

1. do not stain on gram stain

2. lack of cell wall

   1. mycoplasma spp

   2. ureaplasma app

3. intracellular pathogens

   1. Chlamydophila pneumoniae

   2. chlamydia trachomatis

   3. legionella spp

qualitative

presence of absence of growth

semi-quantitative

grading of bacterial growth as rare (1+), few (2+), moderate (3+), or heavy (4+) on selected media → number corresponds to quadrant

quantitative

actual colony count is provided