Microbiology Lab 8 Exam Questions and Answers

Microbiology Lab 8 Exam Questions and Answers antimicrobials -Answer-any compounds that kill or inhibit microorganisms antibiotics -Answer-antimicrobials, usually of low molecular weight, naturally produced by microorganisms to inhibit or kill other microorganisms ex. penicillin and streptomycin semi-synthetics -Answer-antimicrobials that are chemically synthesized in the laboratory and are not produced by microbial biosynthesis at all ex. sulfa drugs healthcare acquired infections (HAIs) -Answer-formerly nosocomial infections; acquired in hospitals; MRSA is responsible for many hospital infections Kirby-Bauer method -Answer-used to determine the sensitivity or resistance of a bacterium to an antimicrobial performed by streaking a standardized inoculum of the test organism on Mueller-Hinton medium, and then paper disks containing specific concentrations of an antimicrobial are deposited on the agar surface. The antimicrobial diffuses out from the disk into the agar, forming a concentration gradient. If the agent inhibits or kills the test organism, there will be a zone around the disk where no growth occurs, called the zone of inhibition. Mueller-Hinton II agar is the recommended medium with pH between 7.2 and 7.4 zone of inhibition -Answer-the zone around the disk where no growth occurs if an agents inhibits the microorganism; affected by diffusibility of the agent, size of the inoculum, the type of medium, and other factors antiseptics -Answer-substances such as alcohol or betadine that inhibit microbial growth or kill microorganisms but they are gentle enough to be applied to living tissue; do not destroy endospores disinfectants -Answer-chemical agents that are applied to inanimate objects such as floors, walls, and tabletops to kill microorganisms; damaging to living tissue sterilants; sporocides -Answer-destroy all microbial life, including endospores ex. ethylene oxide sanitizers -Answer-agents that reduce microbial numbers to a safe level but do not completely eliminate all microbes bacteriostatic -Answer-if a particular agent only inhibits the growth of bacterial cells but does not kill them bacteriocidal -Answer-agents that kill bacterial cells Heat affects... -Answer-proteins (enzymes) nucleic acids (DNA and RNA structure) other small molecules thermal death point -Answer-the lowest temperature at which a population of the target organism is killed in 10 minutes thermal death time -Answer-the shortest time required to kill a suspension of cells or spores under defined conditions at a given temperature