1 Final Lab Exam Review Ames Test Prototroph Bacterial reversed mutation assay evaluates mutagenic properties and detects mutation using bacteria that synthesize biochemical molecules for growth own growth Auxotroph Amino acid dependent strain of S typhimurium is used and will not grow when bacteria that are able to synthesize all biochemical needed for their bacteria unable to synthesize biochemical needed for growth an external source of histidine is absent o Colony will return to grow if reversion of the mutation occurs thus allowing histidine to be available o Spontaneous mutation reversions occur with each strain o Mutagenic compounds increase in the number of mutants returning to their original genotype relative to the background level Zone of inhibition around the disk indicates that the bacteria is unable to grow and unable to mutate in the presence of the compounds Staphylococcus Staph aureus G cocci clusters o Present in 1 3 of people nose o Opportunist pathogen resistant to harsh environmental conditions Methicillin resistant staph aureus MRSA o Nosocomial infections o S epidermidis and S aureus Blood agar detects lysing of red blood cells by bacterial toxins alpha toxin in SA allows RBCs to be lysed Mannitol Salt Agar NaCl is selective for staph fermentation of mannitol allows the pH to be acidic and agar will turn red to yellow Coagulase test if the liquid doesn t move then it is SA tests for coagulase enzyme Streptococcus G cocci chains Strep throat S pyogenes B hemolytic lyse RBCs and leaves a clear zone A hemolytic reduce iron in hemoglobin giving a green yellow tint around colonies Optochin Sensitivity Pneumococci are sensitive to this antibiotic Viridans are resistant zone of inhibition Bile Esculin Hydrolysis All Group D strep Enterococci can hydrolyze esculin and are positive reacts with iron changes the agar brown Salt Tolerance Group D Enterococci are salt tolerant Group D Strep S bovis are not growth in the salt broth CAMP Test Tests for synergistic hemolysis between the unknown 2 strep and S aureus A positive result indicates S agalactiae SXT Sensitivity Sensitivity to SXT with hemolysis and resistance to bacitracin indicates group C strep Simulated Epidemic Epidemiology study of frequency distribution and transmission of a disease Epidemics widespread prevalence of a disease through a population Common source epidemic when individuals pick up a disease through a common through a population source Propagated transmission epidemic disease passed one from one person to another Index case first case of a disease outbreak Incidence amount of new cases that occur within a specific population Prevalence total number of cases in a population Morbidity total number of infections from a disease Mortality total number of deaths due to a disease Oxygen Tolerance Obligate aerobe requires oxygen found at top of tube Obligate Anaerobe do not require oxygen found at bottom of tube Facultative aerobe uses oxygen when in aerobic conditions throughout tube Aerotolerant do not require oxygen always anaerobic Microaerophile live in low conc of oxygen just below top Fluid Thioglycollate Media used to test tolerance of oxygen provides oxygen gradient