Lab

Gram positive, spherical-shaped shaped bacteria, arranged in clusters

Staphylococcus spp.

To differentiate between staphylococcus and streptococcus

Catalase test

To differentiate between S. aureus and S. epidermidis

Coagulase test

Staphylococcus aureus on blood agar

Golden-yellow colonies with beta-hemolysis on blood agar

Differential media for:

Staphylococcus aureus, mannitol salt agar (MSA)

DNase test agar, used to identify S. aureus

Müller-Hinton agar used for antibiotic susceptibility testing

Differentiate between coagulase negative staphylococcus ( staphylococcus epidermidis and staphylococcus saprophyticus)

Picture 1: staphylococcus saprophyticus (resistant)

Picture 2: staphylococcus epidermidis (sensitive)

Gram positive, spherical-shaped bacteria, arranged in chain

Streptococcus spp.

A system of classification that classifies catalase-negative gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls

Lancefield grouping

Gram-positive, spherical-shaped bacteria, arranged in pairs (diplococci)

Streptococcus Pneumoniae

Bacitracin sensitivity test

Picture A: streptococcus pyogenes (Bacitracin sensitive)

Picture B: streptococcus agalactiae (Bacitracin resistant)

Optochin sensitivity test

Picture A: streptococcus pneumoniae (optochin sensitive)

Picture B: streptococcus viridans group (optochin resistant)

Selective and differential medium

Bile esculin agar, enterococci and group D streptococci

Enterococcus faecalis hydrolysis esculin in the presence of bile and turns more than half the medium into black

Gram negative, spherical-shaped bacteria arranged in pairs (diplococci)

Neisseria spp.

Bacillus on a blood agar

Ground glass appearance

Tellurite blood agar selective media for Corynebacteria Diphtheriae

Robertson’s cooked meat

Clostridium perfringens: saccharolytic anaerobes (turn the color of meat pieces into red)

Clostridium tetani: proteolytic anaerobes (blacking of the meat)

Oxidase test and sugar fermentation on Neisseria spp.

Both N. gonorrhoeae and N. meningitidis are oxidase positive

N. meningitidis: glucose (+), maltose (+), sucrose (-)

N. gonorrhoeae: glucose (+), maltose (-), sucrose (-)

Gram positive, rode shaped bacteria

Aerobic or anaerobic (under some conditions)

Most strains of Bacillus are not pathogenic for humans unlike Bacillus anthracis

B. cereus sometimes causes spoilage in canned foods and food poisoning