lab 13- bacterial pathogens : gram positive cocci, genus staphylococcus

Staphyloccoci

divide in more than one plane to produce the streptococcus cell arrangement.

Streptococci and Enterococci

Gram-positive, facultatively anaerobic cocci found in the human intestine. They are leading causes of nosocomial (hospital-acquired) infections, particularly urinary tract infections (UTIs)

Staphylococci, Streptococci and Enterococci

bacteria genera which include species that are commonly found on epithelial surfaces such as skin and mucous membranes and are often cultured from patient samples during the process of disease diagnosis.

Pyogenic(pus forming)

gram positive cocci

Staphylococcus aureus

most common pathogen, commonly isolated from nasal passages.

Staphylococcus epidermidis

less pathogenic, capable of causing disease in humans and frequently the cause of nosocomial infections.

Nosocomial infections

infections resulting from hospital stays and were not present at the time of admission

hemolysis test

uses sheep blood agar plates (BAP) as the test medium and pure cultures are streaked across the surface. allows for the differentiation of different types of hemolysis.

hemolysins

hemolysis results from the presence of bacterial exotoxins

beta hemolysis

the complete destruction of erythrocytes and hemoglobin. If bacteria exhibit beta hemolysis, the normally opaque agar appears clear in the area immediately surrounding the growth.

Gamma hemolysis

non hemolysis, no change to the color of the blood agar.

coagulase test

differentiates Staphylococcus aureus (positive) from less pathogenic coagulase-negative staphylococci (CONS) by detecting the enzyme coagulase, which clots plasma. incubate at 35C

Selective agar

enhance growth for target organisms while inhibiting others using antibiotics, dyes, or salts

Differential agar

distinguish between microorganisms by causing visible changes (e.g., color) in colonies based on metabolic activity.

MSA test (mannitol salt agar)- selective

salt, concentration 7.5% NaCl which inhibits some bacteria. The agar is first examined for the presence or absence of growth. If growth is present, the test bacterium is tolerant

MSA test - differential

Mannitol, fermentable sugar and the pH indicator phenol red. Mannitol fermenters yellow - postive. red negative