POUL 3000 Clinical Microbiology and Antimicrobials

what are characteristics of bacteria

• lack nucleus and other membrane bound organelles

• “naked” circular DNA (plasmid) in nucleoid region

• cell wall’

• generally smaller than eukaryotic cells

what are the two shapes of bacteria

cocci and bacilli

what are the two types of cell composition for bacteria

gram-negative and gram-positive

what does gram-positive mean

thick peptidoglycan layer stains blue/purple

what does gram-negative mean

outer lipopolysaccharide layer does not retain dye

what gram reaction does gram positive bacteria have

retain crystal violet dye

what gram reaction does gram negative bacteria have

does not retain dye and can be decolorized to counterstain with safranin (pink/red)

what kind of susceptibility does gram positive bacteria have to penicillin and sulfonamides

high

what kind of susceptibility does gram negative bacteria have to penicillin and sulfonamides

low

what kind of susceptibility does gram positive bacteria have to streptomycin, chloramphenicol, and tetracycline

low

what kind of susceptibility does gram negative bacteria have to streptomycin, chloramphenicol, and tetracycline

high

what kind of susceptibility does gram positive bacteria have to anionic detergents

high

what kind of susceptibility does gram negative bacteria have to anionic detergents

low

what kind of resistance to drying does gram positive bacteria have

high

what kind of resistance to drying does gram negative bacteria have

low

what are the 4 gaseous requirements of bacterial classification

• aerobe

• facultative anaerobe

• anaerobe

• strict anaerobe

what is an aerobe

requires O2

what is a facultative anaerobe

grow/replicate in presence or absence of O2

what is an anaerobe

grow in absence of O2 but not necessarily killed by O2

what is a strict anaerobe

killed by O2

what are the two nutritional patterns of bacterial classification

autotrophic and heterotrophic

what is autotrophic

produces own food - photo or chemosynthetic

what is heterotrophic

requires external food source

what are the three host/microbe interactions of bacterial classification

• commensal

• opportunistic pathogen

• pathogen

what is commensal

does not injure host

what is opportunistic pathogen

commensal that can become pathogenic

pathogen

injures host

which host/microbe interaction will we see most often in this class

opportunistic pathogen

what is general growth media

allows most organisms to grow

• undefined, defined

what is an example of a bacteria that grows in general growth media

Luria-Bertani (LB)

what is selective media

allows certain organisms to grow while inhibiting others

what are the two types of selective media

positive selection and negative selection

what are examples of positive selection

preferential carbon source

what are examples of negative selection

antibiotics, inhibitory dyes, salts

what is differential media

allows multiple organisms to grow and exhibit a different appearance

what are characteristics are looked at for differential media

• dyes, chemicals

• color

• growth pattern

what kind of media is used for gram positive bacteria and why

selective due to high salt concentration - staphylococcus, micrococcaceae

what kind of media is used for mannitol fermenting organisms and what is an example of that organism

differential - staphylococci

mannitol (____) and phenol red (_____)

sugar, pH indicator

what does S. aureus produce

yellow colonies with yellow zones (acidic)

what does S. epidermis produce

small pink/red colonies with no color change (no pH change)

what kind of media is used for gram negative bacteria and why

selective because it contains dye toxic to gram-positive - coliforms, E.coli, salmonella, shigella

what kind of media is used for lactose-fermenting organisms

differential - E. coli

what does lactose fermentation color look like

purple/black, sometimes with metallic green sheen

what does no fermentation look like

colorless

what color are gram positive cocci under a microscope

blue

what color are gram negative bacilli under a microscope

pink

what is an antimicrobial

any substance that kills or inhibits growth of microbes with little or no damage to the host

what are the three types of antimicrobials

natural, semisynthetic, synthetic

what is an antibiotic

a natural substance produced by one microbe that kills or inhibits growth of another - molds or bacteria

what is are the two kinds of antimicrobial classification

according to microorganisms they act against and according to spectrum of activity

what is microbicidal vs microbiostatic

microbiocidal agents actively kill microorganisms and microbiostatic agents inhibit their growth and reproduction

what are the four different types of antimicrobials

• antibacterial

• antifungal

• antiviral

• antiparasitic

what are the two types of spectrum antimicrobials

broad spectrum and narrow spectrum

what are broad spectrum antimicrobials

they go for a wide range of microbes

includes gram positive AND gram negative, aerobic AND anaerobic