Bio211 Quiz #5 Exercises 18, 19, 20, 29
What infections can be transmitted to humans from milk?
-Bacillus cereus -E coli -Salmonella
Various enteric bacteria, especially E. coli, are the cause of most urinary tract infections (UTI) in humans. A quick test for the presence of these bacteria in urine is to detect nitrite in the urine. Why?
Nitrite in the urine is an indication of a UTI
What is normal flora?
Bacteria found in our bodies on a semi-permanent basis without causing disease
What type of fermentation is involved in yogurt production?
Lactose fermentation is involved as it creates lactic acid and many of the characteristic flavors of yogurt
Significant bacteria in a clean-catch urine specimen is >10^5mL. Lower numbers are considered significant in urine collection by catheter or by suprapubic aspiration of the bladder. Why?
Lower numbers are considered significant because they are within the valid number for plate counts (30-300). There's less bacteria concentration
Why is milk a more suitable vector of disease than water?
Milk contains nutrients that benefit the bacteria, allowing them to live longer than they could in water
What are the normal microbial flora of the mouth and respiratory tract?
Mouth -S. Salivarius Respiratory Tract -Corynebacterium -Hemophilus -Neisseria -Staphylococcus -Streptococcus (found the most)
Staphylococcus aureus contains virulence factors that can be demonstrated in the laboratory. List two and describe the effects displayed by the testing procedure
-coagulase: combines with prothrombin to form staphylothrombin, which then causes blood plasma to clot (fribrinogen—> fibrin) -hemolysin/Staphylococcus alpha toxin: toxin that causes the complete lysis of red blood cells
What is the catalase test?
-The catalase test is used to differentiate staphylococci (catalase-positive) from streptococci (catalase-negative) - Interpretation Positive: bubbles produced, catalase is present Negative: no bubbles produced, catalase is not present Reaction 2H2O2—catalase—> 2H2O + O2
What universal precautions should be used to when handling body fluids?
-Wash your hands before and after handling -Disinfect before and after working -Wear gloves (latex or vinyl) -Wear a lab coat and closed toe shoes -Use protective barrier (Plexiglas shield) -Dispose of samples properly
Know the parameters measured with the dipstick. Understand the biological significance of a positive test
-Compare the color of the glucose pad 30 seconds after dipping. Positive means they might have diabetes-Compare the color of bilirubin pad 30 seconds after dipping. Positive means hemoglobin is degraded which leads to liver of gall bladder problems -Compare the color of ketone pad 40 seconds after dipping. Positive means excessive fatty acid breakdown which leads to uncontrolled diabetes, anorexia, high protein or low car diet, protracted vomiting -Compare the color of specific gravity pad after 45 seconds. Less than 1.002 means the patient can be diabetic, more than 1.028 means the patient is dehydrated -Compare the color of blood pad after 60 seconds. Positive means hemoglobin or erythrocytes aren't intact which leads to early signs of kidney or urinary tract disease -Compare the color of the pH pad after 60 seconds. Alkaline pH means UTI, renal failure, or vomiting. Acidic means emphysema, diabetic ketoacidosis, or diarrhea -Compare the color of the urine protein pad after 60 seconds. Positive means high concentrations of protein which leads to congestive heart failure, kidney infection -Compare the color of urobilinogen after 60 seconds. Positive means liver disease and hemolytic disorders -Compare the color of nitrite pad after 60 seconds. Positive means the presence of nitrite in urine is occurring and there's a UTI -Compare the color of the leukocytes pad after 2 minutes. Positive means UTI or kidney infection
What is the DNAse test?
-DNase agar is a differential medium that tests the ability of an organism to produce an exo-enzyme, called deoxyribonuclease -evasion of immune response (neutrophil extra cellular traps, or NETs) -Staphylococcus aureus is positive DNAse, pink halo -Staphylococcus epidermidis is negative DNAse, clear halo Interpretation Positive: A clear zone around the colony with the addition of the reagent, pink Negative: Whitening of the agar surrounding the colony, blue
What are the most common species of bacteria that cause a UTI?
-E. coli -Proteus spp. -Enterobacter spp. -Klebsiella spp. -Pseudomonas spp. -Lactobacilli
What is EMB agar and why is it used?
-Eosin methylene blue agar (EMB) is a selective and differential medium used to isolate fecal coliforms, gram negative rods -It is Selective because it encourages some bacteria to grow while inhibiting others. Eosin Y and Methylene Blue generally inhibits Gram positive bacteria from growing and generally allow Gram negative organism to grow -this agar slightly inhibits the growth of Gram-positive bacteria and provides a color indicator distinguishing between organisms that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella) -it contains lactose, so if the bacteria ferment this sugar and make acid, the colonies turn purple. If the bacteria cannot ferment lactose, the colonies are colorless
What Streptococci are responsible for dental plaque and dextran or levan production?
-S. salivarius
How are media SM 110 and mannitol salt agar used in this exercise?
-SM 110 is a differential medium for the isolation of Staphylococci -differentiates on the basis of pigment production -S. aureus produces a yellow pigment on SM 110 -S. epidermidis is negative for pigment production and appears white -mannitol salt agar is a selective type of medium that selects for the isolation of Staphylococci since they can grow at high salt concentrations -medium contains a color pH indicator that turns from red to yellow -if bacteria can ferment mannitol, acids are produced -S. aureus produces colonies with a yellow zone that is due to production of acod from mannitol -S. epidermidis colonies produce no color change of the medium, therefore the mediua surrounding them appears red
Name some of the normal flora of the skin and their characteristics
-Staphylococcus epidermidis Staphylococcus aureus -resident of skin and nasal cavity -pathogenic due to presence of certain virulence factors -coagulase: combines with prothrombin to form staphylothrombin, which then causes blood plasma to clot (fribrinogen—> fibrin) -hemolysin/Staphylococcus alpha toxin: toxin that causes the complete lysis of red blood cells -M-Staphylococcus selective medium contains soduim chloride, which restricts the growth of many different types of bacteria. Staphylococcus can withstand salt concentrations and grow on the medium -they dont normally cause disease -they are opportunistic pathogens -they can be acquired nosocomially
List 3 diseases that group A Streptococci cause in humans
-Strep throat -Scarlet fever -necrotizing fasciitis
What two tests can be used to distinguish Streptococcus pyogenes from other members of the Streptococci?
-hemolytic properties -Lancefield serotyping: based on specific carbohydrates in the bacterial cell wall (detected with antibodies)
What are nosocomial infections in relation to the staphylococci?
-nosocomial are acquired during the process of receiving healthcare and werent present beforehand -Staphylococci are mostly spread by skin-to-skin contact (touching). A doctor, nurse, other health care provider, or even visitors may have staph germs on their body and then spread them to a patient.
Although human pathogens may not be present in high plate counts what conditions might the high plate counts indicate about the improper handling of milk?
-sick cows -unsanitary handling -inadequate storage
Characteristics of Staphylococci
-spherical (coccus) -arranged in clusters -gram positive -catalase positive: contains an enzyme called catalase that breaks down hydrogen peroxide -colonies: opaque, ranging from white to cream-colored to yellowish
What is the coagulase test?
-the coagulase test identifies whether an organism produces the exoenzyme coagulase, which causes the fibrin of blood plasma to clot -used to differentiate Staphylococcus aureus from coagulase-negative staphylococci Interpretation Positive test: will clot, coagulase positive, bacteria tested produces coagulase Negative test: no clot, coagulase negative, bacteria tested does not produce coagulase
How does hemolysis look on sheep blood agar?
Alpha Hemolysis -partial destruction of red blood cells, greenish-gray -zone of the blood surrounding the colony -ex: Streptococcus pneumoniae Beta Hemolysis -complete destruction of the red blood cells forming a zone of clearing around the colony Ex: -Streptococcus pyogenes -Staphylococcus aureus Gamma Hemolysis -no hemolysis -no change in blood agar Ex: -Staphylococcus epidermidis -Enterococcus faecalis
How do you obtain a throat culture?
1. Use a sterile cotton swab to swab your own throat. Us a mirror and tongue depressor if necessary 2. Swab the area on both sides of the uvula 3. Label the bottom of a blood agar plate (BAP) and divide into sections for the T-streak technique 4. After obtaining the inoculum from the throat, swab approximately one-third to one-half of a blood agar plate for the area of primary isolation 5. Streak the remaining sections of the plate with a sterile loop. Streak for isolation as described in the T-streak technique 6. Invert the BAP plate and place it in a candle jar 7. Incubate the candle jars for 24 hours at 35C 8. After 24 hours, move the candle jars to refrigerator until the next lab period
How do you clean catch a urine sample?
1. Wash hands with soap 2. Remove towelette 3. Females: separate the folds of the labia with the thumb and forefinger and clean inside with the towelette, using downward strokes only. Keep folds separate during urination into the container 4. Males: clean the head of the penis with the towelette. Remove the container and DO NOT touch the inside of the container 5. Begin urination into the toilet. As urination continues, bring the container into the stream of urine. -fill the specimen container only halfway -remove the cap from the package, do not touch the inside of the cap -screw the cap on the container 6. Wash your hands and outside of the container 7. Place container in plastic wrap and carry to the lab
How do you determine the amount of bacteria in high and low quality milks using the reductase test for milk?
1. resazurin is added to the milk 2. the test tube is covered, mixed, and placed in a water bath at 35 degrees celsius. 3.the tube is examined at intervals up to 6 hours. 4. the time is takes for the resazurin to change from pink to colorless is the basis of the reductase test. Interpretation Lower quality milk = shorter reductase time, 30 mins is poor, reduced, loses color Higher quality milk = longer reductase time, 6 hours is good
What are five clinical syndromes caused by Staphylococcus aureus?
1.) Necrotizing fasciitis 2.) MRSA 3.) VRSA 4.) Toxic shock syndrome 5.) Pneumonia
How does the fermentation process work for making yogurt?
A bacteria called Lactobacillus that ferments lactose (sugar in milk) to form lactic acid which helps preserve the milk and denatures milk proteins, which gives the yoghurt its sharp taste -Streptococcus thermophilus and lactobacillus bulgaricus are added to pasteurized milk
What is a carrier?
A carrier (colonized individual) is a person in whom organisms are present and may be multiplying, but who shows no clinical response to their presence.
What test can be used to identify Streptococcus pneumoniae from other members of the Streptococci?
A optochin (P disc) can be used because S. pneumoniae is sensitive to optochin
Discuss how the coagulase test is a characteristic for pathogenicity
Coagulase solidifies blood plasma making a tough layer around Staph cells to sheild them from the host immune system The coagulase test identifies whether an organism produces this exoenzyme. This enzyme clots the plasma component of blood creating blood clots to protect themselves from the immune system. It is used to differentiate between S. aureus and S. epidermidis
How can you determine whether there's a absence or presence of a UTI?
Count how many bacteria is present in the sample. A count between 10,000-100,000 is evidence of a UTI Positive Tests for UTI on Urine Dipstick -blood pad color -nitrite pad -leukocytes pad -pH pad, alkaline means UTI
What are some gram negative and positive bacteria that cause UTI?
Gram negative -Escherichia coli -Proteus spp. -Enterobacter spp. -Klebsiella spp. Gram positive -Staphylococcus saprophyticus -Enterococcus faecalis -Streptococcus agalactiae
Why were mostly gram-positive cocci isolated from the fomite and nose cultures when a variety of organisms could have been present at these sites?
Gram positive cocci where isolated as the media used for the experiment selected for gram positive bacteria
After evaluating the standard plate count and reductase results on the two samples of milk, determine which milk is acceptable to drink
High quality milk is acceptable to drink because it contains less bacteria
What are nosocomial infections?
Immunocompromised patients can acquire a secondary infection of an opportunistic pathogen at the hospital
What's the difference between a opportunistic pathogen and a pathogen?
Pathogen A primary pathogen is a microbe that is able to cause disease in an otherwise healthy individual Opportunistic Pathogen A microbe that causes disease only when introduced into an unusual location or into an immunocompromised host Ex: Staph aureus, staph epidermidis
What's raw milk and pasteurized milk?
Raw Milk Milk that still contains harmful bacteria, straight from the cow Pasteurized Milk Milk that has been heated and cooled which makes it safe to drink
What's the most common source of bacteria in milk?
The air or the fluids it touched Bacilli, Staphyloccoci, Lactobacilli, Pseudomonas, and coliforms.
What advantage do you think reductase has over direct plate counts?
The reductase has a shorter turn around time than direct plate counts
Explain the connection between a diet rich in sucrose and tooth decay
The sucrose can react with the acids in your mouth used to break down sucrose, which can dissolve the tooth surface
How do you calculate the number of CFU/ml in an original sample based on a given number of CFUs on a dilution plate (same idea as Exercise 15)?
Use the formula: [Number of colonies counted] × 10 × [how many times the sample must be multiplied to get to the original concentration: for example, 105] = Number of colony forming units (CFU) per milliliter of starting cultureExample: If 2 colonies grow on the plate inoculated with a 10 microliter loop plate, thenNumber of bacteria per mL= 2 colonies/ 0.01 mL = 200 bacteria/mL of urine
How do you determine the amount of bacteria in high and low quality milks using the standard plate count method?
Used to differentiate between different qualities of milk 1. Mix milk with the liquid tryptone glucose extract agar then pour into a sterile Petri plate 2. Let agar solidify, then incubate at 35C
What is the use for identification discs?
Used to identify streptococci bacitracin susceptibility, Optochin susceptibility, bile esculin hydrolysis, 6.5% salt tolerance, and immuno serological identification
How does the pasteurization process work?
Used to preserve milk and other dairy products -heat milk to a temp below the boiling point (usually 60C) for 20 minutes, bring down to 10C -flash pasteurization: 72C for 15 seconds, rapid cooling to 10C Pasteurization doesn't kill all microbes but instead reduces their numbers
Does yogurt have any nutritional value? Why?
Yogurt has nutritional value because it contains probiotics that are added for health benefits
What would you report to the attending physician after the Dipstick of the "infected" urine?
You would report that there was a UTI
What would you report to the attending physician after the Dipstick analysis of the clean-catch urine?
You would report whether or not there was a presence of UTI