Cultures/Sensitivity Testing

original sample diluted to thin out population, isolated cells grow into colonies and are used to establish pure cultures

only works if the spreading took is re-sterilized after each of the steps, streaking patterns

small volume of dilute microbial suspension spread evenly over agar plate, dispersed cells develop into isolated colonies which can be counted

possible purulent fluid- to grow colonies of bacteria to identify the pathogen and to determine its sensitivity to various antibiotics

blood agar- 5% sheep blood, most aerobic and facultative anaerobic organisms will grow on blood agar

contains heated (lysed) blood with or without supplement, will grow some bacteria that doesn't grow well on blood agar

selective for enteric gram negative rods, like e. coli

obligate anaerobes must be cultures on media specific for anaerobes

measures the ability of the isolated bacteria to grow in the presence of different antibiotics

susceptibility patters of isolates in that lab, type of infection, suspected source of infection

measures the organisms ability to grow in broth culture with various dilutions of antibiotics, the lowest conc of a drug that remains free from microbial growth, best estimate of drug conc needed to inhibit growth

results of susceptibility testing performed in that lab for particular organism-drug combinations in the recent past

acid fast bacteria, mycobacterium tuberculosis (gram+rod), selective media is used for culture, contains abx to prevent overgrowth of contaminating bacteria and fungi, AFB more resistant to penicillin

semisynthetic agar, inpissated egg media, broth media

18 hours, 10-14 days

more sensitive than KOH exam, use sabouraud's dextrose agar, commonly done in paired sets, identified by physiological and morphological phenotypes

has mostly been replaced by NAAT, may not establish the infectious agent due to latent phases. specimen should be obtained from location of infection. cell culture is fluid or tissue material. definitive identity made by administering type-specific antiserum