Microbiology Tech Info

  Introduction Bacitracin susceptibility test and SXT susceptibility test are two different types of tests used to determine the susceptibility of bacteria to certain antibiotics. The Bacitracin susceptibility test is used to determine if a bacterium is susceptible to the antibiotic bacitracin. It involves streaking a pure culture of the bacterium on an agar plate containing bacitracin. If the bacterium is susceptible to bacitracin, there will be a clear zone around the streaked area where the antibiotic has inhibited bacterial growth. The SXT susceptibility test, also known as the co-trimoxazole susceptibility test, is used to determine if a bacterium is susceptible to the antibiotics trimethoprim and sulfamethoxazole (SXT). It involves testing the bacteria's ability to grow in the presence of various concentrations of the antibiotic combination. The minimum inhibitory concentration (MIC) is determined by observing the lowest concentration of the antibiotic that prevents bac...

  Scope The presumptive identification of group B Streptococci can be done with the CAMP test. Principle The hemolytic phenomenon was first described in 1944 by Christie, Atkins, and Munch–Petersen, and it is their names that provide the acronym (CAMP) for the test. The hemolytic activity of the β-hemolysin produced by most strains of Staphylococcus aureus is enhanced by an extracellular protein produced by group B streptococci. Interaction of the β-hemolysin with this factor causes “synergistic hemolysis,” which is easily observed on a blood agar plate. This phenomenon is seen with both hemolytic and nonhemolytic isolates of group B streptococci. Other bacteria, such as Listeria monocytogenes, Rhodococcus equi, and certain strains of Vibrio cholera, are also CAMP-positive. Materials β-hemolysin-producing strain of Staphylococcus aureus Sheep Blood agar plate Quality Control Positive control: Group B Streptococcus Negative control: Group A Streptococcus Test ...