Untitled Flashcards Set

Bacteria are named by genus and species. Genus begins with a capital letter, species begins with a lower case letter and both are underlined.
i.e. Streptococcus pyogenes
1. cell wall - gives bacteria its shape, and site of action for many
antibiotics - determines gram reaction (purple positive; pink negative)
2. cell membrane - just inside the cell wall - thin, permeable membrane
of lipids - proteins embedded in it - regulates exchange of materials
into and out of the cell
3. chromosome- closed circle of double stranded DNA which contains
the genetic information of the cell
4. nuclei- area in the cytoplasm where the chromosome is located
5. cytoplasm- liquid matrix of the cell, made mostly of water, dissolved
nutrients and wastes
6. plasmid- a small piece of extra chromosomal DNA. It is much
smaller than the chromosome, and is double
stranded. It may be transferred from one cell to another
7. pili- hair-like structure extending from the surface of the cell
a. for attachment to other cells (human/bacteria) or to other surfaces.
e.g.: intestinal bacteria
b. to exchange plasmids: sex pili used in a process called conjugation
8. lribosome- site of protein synthesis bacteria. Humans have 80s
ribosome’s (40s + 60s)
9. flagella- responsible for bacterial motility
a. polar or monotrichous - one flagella at one pole
b. tuft or lophotrichous - group of flagella at one pole
c. peritrichous - flagella over the entire surface of bacteria
d. amphitrichous - single or tuft at one or both poles
e. atrichous - without flagella
10. Endospores- some bacteria have them, some don't. They are a
resistant form of the microorganism and form when the
environmental conditions are unfavorable. e.g.: Clostridium botulinum
and Clostridium tetani
Media
Media is any substance that contains all the necessary components for growth and reproduction of bacteria
Basic Media Types
Liquid (broth) test tube , solid- contains 1.5% agar ( the gelling agent) , petri plates or test tubes semi- solid-contains 0.7% agar, test tubes
Media Definitions and Examples
Enrichment Media- Basic media containing additives such as blood or serum which enhance the growth of many fastidious and non-fastidious organisms.
TSA (nutrient agar) with 5% Sheep Blood (Blood Agar Plate- BAP)- 1. Common enrichment media 2. grows many organisms 3. shows hemolysis
Hemolytic Patterns: Alpha (  )- green zone due to partial destruction of RBC surrounding colony Beta ( )- clear zone due to total destruction of RBC
surrounding colony Gamma ( )- no Hemolysis
Chocolate Agar (Choc) - An enrichment medium of many organisms especially Heamophilus sp. and Neisseria gonorrhea which will only grow on Choc. Agar
Mueller Hinton Agar (MH) - An enrichment medium for many kinds of organisms. It is used for the Kirby- Bauer sensitivity test.
Nutrient Broth (N Broth) - Grows many organisms including anaerobes and can recover small amounts of organisms in cultures.
Selective Media- Media that contains chemicals or dyes that prevent or retard growth of certain organisms and select or allow growth of other organisms without
necessarily differentiating them. Example: Colistin Nalidixic Acid (CNA) - Enhance the growth of most gram positive organisms. Colistin and nalidixic acid is the
inhibitor agent that inhibits the growth of gram negative organisms. Sabourad Dextrose Agar- an enrichment medium for the isolation of fungi (yeast and molds)
Differential Media- Media that allows the growth of groups of organisms and demonstrates certain characteristics. Most differential media is also selective. Example:
Mannitol Salt Agar (MSA) - 1. used to isolate staphylococcus species, 2. The high salt concentration (7.5%) allows the medium to be selective for Staphylococcus
since most organisms cannot tolerate that high salt content, 3. Staph. aureus appears yellow, 4. Staph. epidermidis appears pink MacConkey Agar (MAC)) - 1. A
selective, differential medium for the isolation of gram negative rods (bacilli), 2. Gram positive organisms and coliform organisms are inhibited by the bile salts
mixture, 3. Lactose fermenters are hot pink to red, non-lactose fermenters form colorless or very light pink colonies. Salmonella Shigella Agar (SS) 1. A selective,
differential medium for the isolation of Salmonella and Shigella which is a gram negative rods from feces or rectal swabs, 2. Gram positive organisms and coliform
organisms are inhibited by the bile salts mixture, 3. Lactose fermenters are hot pink to red, 4. non-lactose fermenters form colorless or very light pink colonies.
SS Agar shows H2S production, MAC Agar does not. Examples: Salmonella- clear colonies with black center, non-lactose fermenter (H2S). Shigella- Clear colonies
without black non-lactose fermenter. Hektoen Enteric Agar (HE) 1. A selective, differential medium for the isolation of Salmonella and Shigella which is a gram
negative rods from feces or rectal swabs, 2. Gram positive organisms and coliform organisms are inhibited by the bile salts mixture, 3. Lactose fermenters are yellow
4. non-lactose fermenters green colonies.
HE Agar shows H2S production, MAC Agar does not.
Biochemical Media - Media used to identify microorganisms. Examples SIM, MRVP, Simmons Citriate, and TSI
Temperature and technique employed in the incubation of primary culture
Most organisms multiply best at temperatures similar to those in the host:
350- normal human body temperature 300- temperature of the surface of the body. ( most fungi are incubated at 300)
42o- most organisms will not grow 42o except for Pseudomonas aeruginosa
Factors Affecting Microbial Growth
1. Oxygen Requirements: a. aerobic organism (aerobe) = require O2 for growth b. anaerobic organism (anaerobe) = can't survive in presence of O2
c. microaerophilic organism = require small amounts of O2 d. facultative = can grow in the presence or absence of O2
2. pH requirements Practical Application of pH and growth of bacteria: Use of weak acids to preserve foods
All bacteria have a pH optimum a pH at which they grow best and have the shortest generation time.
a. acidophile= grow best at 5.0 or less; some bacteria, yeast and molds
b. neutrophiles= grow best at near neutral pH of 6.0- 8.0, but most at 7.0
c. alkylophiles= grow best in an alkaline environment of 9.0 or more
3. Temperature requirements ( refrigeration; 4oC slows bacterial growth, freezing slows growth even more)
All bacteria have a To at which they grow best and have their shortest generation time = T optimum.
a. psychrophiles= cold lovers; grow best at -50C through 200C b. thermophiles= hot lovers; like ToC 45oC and above
c. mesophiles= like mild temperatures; grow best at To between 20oC- 45oC
4. Osmotic Pressure Requirements Practical applications: ( use of salts to pressure foods, use of sugars to preserve foods)
Osmotic Pressure is the concentration of dissolved sugars or salts in a solution. Growth of most microorganisms in inhibited by solutions whose osmotic
pressure is more than 1%. Exception: halophiles: require high salt concentration to grow and reproduce
Control of Microbes
1. Sterilization - 100% killing of microbes in or on a surface 2.Disinfecting - reduces microbial population, but not a 100% kill.
3. Antiseptics - reduce microbial growth, but not a 100% kill. 4. Bactericidal 100% killing of microbes 5.Bacteriostatic- reduces growth
Control of Microbes with Heat
1. Dry Heat-( cooking food) must cook food throughout to kill microbes, not just the surface. Moist Heat- (boiling, 100oC)
3. Steam under pressure- (autoclave) kills vegetative forms and spores achieves 100% kill, sterilization at 121oC, 15 lbs psi, 15 minutes

Interpretation of Cultures
1. Inoculate plates, and streak plate to get good isolation by flaming loop between each quadrant
2. After incubation observe colonies for growth, gross colony morphology, (see picture in book), and look closely for mixed organisms.
3. Hold Blood Agar Plate up to the light to look for hemolysis.
4. Culture quantity should be done
5. Gram stain examinations should be done to determine: a. gram stain reaction - positive (purple) vs. Negative (pink) b. morphology (shape of bacterial cell)
Principle of GRAM STAIN
STAINS USED TO MAKE THE BACTERIA CELLS VISIBLE
a. Heat fix slide to make bacteria adhere to the slide.
b. Crystal Violet- stains organisms purple
c. Iodine- enhances purple stain
d. Decolorizer- decolorize (remove purple stain from certain organisms)
****DO NOT LEAVE ON TOO LONG OR ALL ORGANISMS WILL LOSE PURPLE STAIN AND END UP STAINING RED****
e. Safranin- stains organisms that did not retain the purple stain red/pink
GRAM POSITIVE ORGANISMS-- stains purple. They retain purple dye.
GRAM NEGATIVE ORGANISMS-- stains red/pink. They did not retain purple dye but took up the red counterstain.
5. Colonies should be examined for characteristics such as:
a. elevation - mucoid vs. flat colonies on MAC Agar b. swarming colonies on blood or choc. agar
c. color of colony d. margins, form and elevations of colony
6. Set up biochemical test - Common biochemical test:
Catalase -to distinguish staphylococcus species from streptococcus species.
Coagulase -to distinguish staphylococcus aureus from staphs epidermidis and other staphylococcus species.
Optochin (“P” disc) -to detect Streptococcus pneumoniae.
Bactitracin (“A” disc) -to detect Group AB Streptococci.
Bile Esculin only -to detect Group D Streptococcus (not Enterococcus).
Bile Esculin and Salt -to detect Group D Enterococcus.
Oxidase -to distinguish Enterobacteracae species (E. coli., Klebsiella, and Enterobacter) from Pseudomonas species.
Lactose Fermentation -Determine which biochemical test to be done or setup on gram negative rods.
SIM, Citrate, MR-VP, TSI -To identify various gram negative rods.
X & V Differential -To identify Haemophilus species.
7. Perform antibiotic sensitivity test (see picture 25) to determine if organisms are sensitive or resistant to various antibiotics: (A) MH Agar plates are
completely covered with a .5 Macfarland concentration of bacteria. (B) Antibiotic discs are dropped on agar plates and
incubated for 24 hours. (C ) Plates are read as follows:
Sensitive = organisms will not grow up to the antibiotic disc because the antibiotics inhibited the organisms from growing around the disc which means that the
doctor could use this drug to treat the patient infected with that bacteria.
Resistant = organisms will grow up to the antibiotic disc because the antibiotics did not inhibit the organisms from growing around the disc which means that
the doctor could not use this drug to treat the patient infected with that bacteria.
PATHOGENS DISEASE
Streptococci pyogens strep throat, scarlet fever, rheumatic fever,
(group A strep) and septicemia (bacteria in the blood which causes high fever)
Streptococcus pneumoniae pneumonia
Staphalococcus aureus boils, carbuncles,pneumonia, and septicemia
Escherichia coli urinary infections
rotius mirabilis urinary tract infection
Pseudomonas aeruginosa respiratory & urogenital infections
Salmonella enteritis typhoid fever
Neisseria gonorrhea gonorrhea
Clostridium botulinum botulism (food poisoning)
Klebsiella pneumoniae pneumonia
Fungi ring worm , vaginal infections, and athlete’s foot
Haemophilis influenza meningitis ear infections
Enterococcus faecalis wound infections and urinary tract infection
(group D strep)
Corynebacteium diptheriae causes diptheria, infection forming a false membrane on any mucus surface