Gram Smear Appearance of Most Common Pathogens

Staphylococcus aureus

Gram-positive cocci in grape-like clusters

Streptococcus pyogenes (Group A strep)

Gram-positive cocci in chains

Streptococcus pneumoniae

Gram-positive lancet shaped diplococci surrounded by an unstained capsule

Enterococcus faecalis

Gram-positive cocci in pairs and short chains

Neisseria meningitidis/Neisseria gonorrhoeae

Gram-negative kidney shaped intracellular diplococci

Escherichia coli

Small Gram-negative rods

Klebsiella pneumoniae

Gram-negative rods surrounded by unstained capsule

Pseudomonas aeruginosa

Slender Gram-negative rods often in pairs

Haemophilus influenzae

Small gram-negative coccobacilli

Clostridium spp

Large Gram-positive rods, often with spores

Listeria monocytogenes

Small Gram-positive rods, sometimes in short chains

Is Staphylococcus aureus Gram-positive or Gram-negative

Gram-positive

Is Streptococcus pyogenes (Group A strep) Gram-positive or Gram-negative

Gram-positive

Is Streptococcus pneumoniae Gram-positive or Gram-negative

Gram positive

Is Enterococcus faecalis Gram-positive or Gram-negative

Gram-positive

Are Neisseria meningitidis/Neisseria gonorrhoeae Gram-positive or Gram-negative

Gram-negative

Is Escherichia coli Gram-positive or Gram-negative

Gram negative

Is Klebsiella pneumoniae Gram-positive or Gram-negative

Gram-negative

Is Pseudomonas aeruginosa Gram-positive or Gram-negative

Gram negative

Is Haemophilus influenzae Gram-positive or Gram-negative

Gram negative

Is Clostridium spp Gram-positive or Gram-negative

Gram positive

Is Listeria monocytogenes Gram-positive or Gram-negative

Gram positive

Gram-positive cocci in clusters "grape like"

Staphylococcus aureus

Gram-positive cocci in chains

Streptococcus pyogenes (Group A strep)

Gram-positive lancet shaped diplococci surrounded by an unstained capsule

Streptococcus pneumoniae

Gram-positive cocci in pairs and small chains

Enterococcus faecalis

Gram-negative kidney-shaped intracellular diplococci

Neisseria meningitidis/Neisseria gonorrhoeae

Small Gram-negative rods

Escherichia coli

Gram-negative rods surrounded by an unstained capsule

Klebsiella pneumoniae

Slender gram-negative rods often in pairs

Pseudomonas aeruginosa

Small Gram-negative coccobacilli

Haemophilus influenzae

Large Gram-positive rods often with spores

Clostridium spp

Small Gram-positive rods sometimes in short chains

Listeria monocytogenes

Which common pathogens are surrounded by an unstained capsule

1. Streptococcus pneumoniae

2. Klebsiella pneumoniae

Which common pathogens are intracellular

1. Neisseria meningitidis

2. Neisseria gonorrhoeae

Which common pathogens are Gram-positive

1. Staphylococcus aureus

2. Streptococcus pyogenes

3. Streptococcus pneumoniae

4. Enterococcus faecalis

5. Clostridium spp

6. Listeria monocytogenes

Which common pathogens are Gram-negative

1. Escherichia coli

2. Klebsiella pneumoniae

3. Pseudomonas aeruginosa

4. Haemophilus influenzae

5. Neisseria meningitidis

6. Neisseria gonorrhoeae