Lab Exam 2

1. What is the goal of diagnostic immunology testing?

The goal of dignostic immunology testing is to identify diseases by analyzing the immune system’s response or detecting specific immune-related substances in the body

1. How do bacterial, viral, and fungal cultures differ in terms of growth requirements and time to results?

Bacterial: we are able to do testing on the isoloated organism to identify it and also do antibiotic susceptibility testing. This is usually cost effective and results of culture can often be completed within 48 hours. 

Viral: These cultures require living cells and often take 7-10 days or longer. Are usually performed at reference specialty labs 

Fungal: The growth rate for these cultures varies depending on the fungal agent causing the infection

1. What is serologic testing, and what is its purpose in diagnosing infectious diseases?

an immunologic test in which antibodies are detected in serum by visualizing an Ag-Ab complex

1. What is the difference between qualitative and quantitative serologic tests?

• Qualitative: presence or absence of antibodies 

• Quantitative: how much antibody is persent

1. Describe how serial dilutions are prepared in quantitative serologic testing

A row of tubes containing equal amounts of saline diluent is set up: a measured amount of the patient’s serum is placed in the first tube and mexed well. Then a measured portion of this first tube is placed in the second tube and mixed. This process is repeated down the line of tubes to obtain a graded series of dilutions

1. What is a serum titer, and how is it determined?

the last dilution of serum that shows reactivity is reported as the serum titer

1. Why are both acute and convalescent serum samples tested in serologic diagnoses?

Acute and convalescent serum titers are often performed to show at least a fourfold increase in titer between this acute and convalescent stage. This fourfold in titer is considered serologic evidence of a current active response to the microorganism

1. How can changes in IgM and IgG levels help determine the stage of infection?

Appropritate test for IgM and IgG help determine if the patient is in the acute stage of infection or whether active infection has subsided.

1. How does antigen testing work, and what types of results indicate a positive reaction?

 In antigen testing the organisms or speciment is mized witha solution that extracts the antigen from the organisms’ cell wall. This solution is then tested with antibodies unique to the specific orgamism. If the test incorporates antibody-coated latex particles, a positive reaction will produce agglutination. If the test incorporates enzyme-linked antibodies (ELA), a positive test will produce a colored end product. 

1. Compare the sensitivity of antigen testing to that of culture methods

100% sensitive. The sensitivity of the test is directly related to the amount of the orgamism present in the collected specimen. 

1. Why might a culture be recommended even if an antigen test is negative?

Culture is more sensitive that antigen testing and is often recommended if the antigen test is negative

1. Define natural and acquired immunity

Natural immunity is the immunity that people are born with that provides general protection against microorganisms. Acquired immunity is immunity that develops after exposure to a microorganism, like a vaccine.

Differentiate between active and passive immunity

Active immunity is your own immune system making antibodies after infections or vaccines. Passive is from another source to help provide protection, like an antibody shot that is supposed to help temporarily

1. Toxin, toxoid, and antitoxin, and explain their relevance in immunology

A toxin is a poisonous substance produced by microorganisms that can damage our bodies. Toxoids are toxins that have been inactivated so they will not cause damage to our bodies, but will help our immune system to identify the toxin. It is used in vaccines. Antitoxins are antibodies that will neutralize a specific toxin

1. Why is immunity to tuberculosis detected by a skin test rather than a serum test?

Immunity to tuberculosis is detected by a skin test because it involves T cells rather than antibodies

1. What are the advantages of serologic tests for diagnosing infections compared to other diagnostic methods?

• Rapid results compared to culture

• Can detect infections when the microorganism is difficult or impossible to culture 

• Can identify  current or past exposure by detecting antibodies 

• Often require only a blood sample, making collection relatively easy 

• Useful for monitoring a patient’s immune response or response to vaccination

1. What factors can affect the sensitivity of antigen testing?

• Low levels of antigens in the specimen, especially early or late in infection 

• Poor specimen collection or handling, resulting in to little antigen 

• Testing after treatmnet has reduced the amount of the pathogen 

• Improper storage or delays in processing the specimen 

• Variations in the quality or performance of the test kit

1. What might cause discrepancies between antigen detection results and culture results?

• False-negative antigen test due to low antigen levels or porr specimen collection 

• False-positive antigen test casued by cross-reactivity with similar antigens or testing errors 

• Culture-negative results if the organism is no longer alive because of prior antibiotic treatment, even though antigens remain 

• Culture-positive but anitgen-negative if antigen levels are below the test’s detection limit 

• Differences in the sensitivity and specificity of the two testing methods 

1. What is the primary purpose of susceptibility testing?

Susceptibility testing is usually done when clinically significant bacteria are isolated from a patient specimen

1. How does in vitro testing predict in vivo effectiveness of antibiotics?

By determining which antibmicrobial agents inhibit the growth of the organism in vitro, it is possible to predict which agents will be effective un vivo.

1. Define MIC and explain its role in susceptibility testing.

MIC (minimum inhibitory concentration) are determined by diluting an antimicrobial agent over a range of concentrations that are achievable in patient’s bloodstream and then determining at which concentration the growth of the infectious agent if inhibited.

1. How does MIC determine whether an organism is susceptible, intermediate, or resistant?

• If the infectious agent is inhibited by readily achievable drug levels, the organism is called S (susceptible)

• If readily achievable levels do not inhibit an organism, it is called R (resistant)

• Some organisms may be reported as I (intermediate), meaning that they may be be sensitive to the drug if higher levels are achieved by either changing the doasge or concentrating the drugs (as in the urine). 

1. Why are drug concentrations used in MIC testing based on achievable levels in the bloodstream?

Use drug concetrations that can be safely achieved in the bloodstream so the results help healthcare providers cjoose an antibiotic that will be effective in treating the infection

1. What is the Kirby-Bauer method, and how is it performed?

An agar plate is incoculated with a standard amount of organism. This agar must be appropriately enriched to support growth of the organism being tested. Filter paprer disks impreganted with a define concetration of antimicrobial agents are placed on the surface of the agar. The agar is the incubated at 35°C for 18-24 hours.

1. Describe the significance of zones of inhibition.

Bacterial growth (clear rings) around the antimicrobial disks. The diameter of the zone is measured in millimeters. 

1. How do factors like diffusion rate, organism growth, and inoculum size affect zone sizes?

• Faster antibiotic diffusion-> larger zone 

• Faster bacterial growth -> smaller zone 

• Larger inoculum (more bacteria)-> smaller zone 

• Smaller inoculum (fewer bacteria) -> larger zone

1. Why must the Kirby-Bauer test be standardized?

Determines the interpretatuon of the zone sizes for each antimicrobial agent 

1. What do the terms susceptible, intermediate, and resistant indicate about an organism’s response to an antibiotic?

• Susceptible: indicates the organism may be appropriately treated with the antimicrobial agent using the recommended dosage 

• Resistant: indicated the organism is not inhibited with the usual dosage of antimicrobial 

• Intermediate: indicates the organism may be inhibited by the antimicrobial provided that either higher doses of the drug are given or the infection is at a body site where the drug is concentrated 

1. Explain why an intermediate result may still be clinically effective in certain conditions

The antibiotic may concentrate at the site of infection (such as in the urine), reaching levels higher than those in the bloodstream

1. Why is a McFarland turbidity standard used in susceptibility testing?

It can adjust the turbidity of bacterial suspensions so that the number of bacteria will be within a given range to standardize testing

1. Why is it important to avoid using a mixed culture when performing susceptibility testing?

A mixed culture contains more than one type of bacterium. Different bacteria may respond differently to antibiotics, leading to inaccurate or misleading results.

1. Outline the steps for preparing and inoculating a Mueller-Hinton plate

• Prepare a standardized bacterial suspension 

• Dip sterile swab into the suspension and remove excess liquid 

• Swab the entire surface of the Mueller-Hinton agar in three directions to create an even bacterial lawn 

• Allow the plate to dry for about 3-5minutes. 

• Place antibiotics disks on the agar using sterile forceps or a disk dispenser 

• Gently press each disk to ensure full contact with agar 

• Incubate the plate 

• Measure the zones of inhibition and interpret the results using standard guidelines 

1. What is the purpose of pressing antibiotic disks gently onto the agar surface without denting it?

Pressing teh disks gently ensures good contact between the disk and the agar so the antibiotic diffuses evenly. Avoiding dents prevents uneven diffusion and inaccurate zone sizes 

1. Define broad-spectrum antibiotics and explain their significance.

Broad-spectrum antibiotics are effective against a wide variety of Gram-positive and Gram-negative bacteria. They are useful when the specific cause of an infection is unknown or when multiple types of bacteria may be involved.

1. Provide examples of appropriate uses for broad-spectrum antibiotics.

• Treating serious infection before culture results are available 

• Treating mixed bacterial infections 

• Treating infections caused by multiple possible pathogens, such as sepsis or pneumonia

1. What factors should be considered when selecting an antibiotic for therapy?

• Results of susceptibility testing 

• Type of infecting organism 

• Site of infection 

• Ability of the drug to reach the infected tissue 

• Patient allergies 

• Potential side effects and drug interacts 

• Cost and ease of administration

1. How do body site concentrations (e.g., urinary tract) influence antibiotic selection?

Some antibiotics become highly concentrated in certain body sites, such as the urine. An antibiotic that reaches high levels in the urinary tract may successfully treat a urinary tract infection even if laboratory results indicate only intermediate susceptibility

1. What role does quality control play in susceptibility testing?

Ensures that the testing methods, media, antibiotic disks, and equipment are working properly so that the susceptibility results are accurate, reliable, and reproducible 

1. How are zone size ranges used to ensure accuracy during testing?

The measured zone sizes must fall within the accepted reference ranges. If they do, the test is considered valid. If not, there maybe a problem with the procedure or materials

1. Why might a specific antibiotic disk fail, and what steps should be taken if this occurs?

• do not report the test results 

• Replace the disk with a new one

• Repeat susceptibility test 

• Verify the media, incubation conditions, and quality control procedures are correct before reporting patient’s results

1. Define direct transmission and provide an example

  is direct contant, direct contact is when the host comes into physical contact with a pathogen

1. Define indirect transmission and provide an example

is where the pathogen spreads without direct physical contact with the source. Some examples include airborne transmissionn, vehicle transmission, and vector transmission 

1. What is a fomite, and how does it facilitate indirect transmission?

is a nonliving object or surface that can carry and spread infectious microorganism from one person to another

1. What is a reservoir, and what role does it play in infection spread?

refers to sources or locations where infectious agents can persist and potentially infect new hosts

1. Explain how the hand-shaking activity modeled indirect transmission.

Demonstrating how microorganisms can spread from one person to another though contaminated hands or objects (fomites) rather than by direct contact with an infected person 

1. What prediction was made about the number of colonies formed by tube passers versus hand shakers?

The “tube passers” should have more colonies growing than “hand shakers” because they have more direct contact with the contamination

1. Were the predictions about colony growth correct? Why or why not?

Yes! The tube passers had more growth because they had direct contact with Staphylococcus aureus than the handshakers did

1. How did the procedure simulate real-world transmission patterns?

it stimulate real-world tranmission patterns because it showed how quickly microorganisms can spread through everyday contact

1. Define airborne transmission and droplet transmission

• Airtborne: the spread of infectious microorganisms through very small particles that remained suspended in the air for long periods and can be inhaled by people over long distances 

• Droplet: the spread of infectious microorganisms through larger respiratory droplets produced by coughing, sneezing, or talking. Short distances

1. What differences exist between airborne and droplet transmission regarding

1. Distance traveled by particles? Airborne: long distances Droplet: Short distances
   b) Size of particles involved?Airborne: Small particles Droplet: large particles
   c) Contact versus vehicle transmission?Airborne: vehicle transmission Droplet: contact 

1. What type of transmission occurs during a cough or sneeze? Explain the mechanisms involved

Droplet transmission because it releases large respiratory droplets that can land on another person.

1. Analyze the recorded data for colony growth using the 1+ to 4+ scale. What trends are observed?

Colony growth increased among individuals with more contact

1. Based on your results, what recommendations would you make to minimize transmission risks in real-life scenarios?

• Wash hands 

• Disinfect frequently used touched surfaces and equipment 

• Avoid touching your face 

• Cover coughs and sneezes 

• Wear PPE 

• Stay home when sick 

• Follow proper infection-control procedures in healthcare and community settings 

1. What is the goal of the handwashing lab?

Demonstrate how proper handwashing reduces the number of microorganisms on the hands and helps prevent the spread of infection

1. What are some types of handwashing procedures you can choose for this experiment?

(hot water/ soap, cold water, hand sanitizer, surgical scrub)

1. What predictions might you make about the effect of handwashing on normal skin flora?

Handwashing will reduce the number of microorganisms on the skin, but it will not completely elminate normal skin flora

1. Why is it important to culture your hands both before and after washing?

It is import to culture your hands before and after so you can see the effects of handwashing

1. What steps should you follow to properly collect a hand culture sample?

• Use a sterile swab 

• Moisten the swab with sterile saline if instructed 

• Rub the swab firmly over the surface of the hand 

• Aboid touching any other surfaces 

• Immediately inoculate the culture plate with swab

1. How is the culture plate inoculated with the swab?

• gently streak the swab across the surface of the agar in a zigzag pattern while rotating the swab to transfer the collected microorganisms evenly

1. What are the possible results for colony counts on the culture plates, and how are they categorized?

Colony growth is categorized a 1+ to 4+ scale

1. How do you determine if your experimental data supported your initial prediction?

If the number of colonies decreased after handwashing, your data suppurt the prediction that handwashing reduces microogranisms on the hands

1. Handwashing and Hygiene Practices

• wash hands throughly for at least 20 seconds 

• Use alcohol-based hand sanitizer 

• Wash hands when preparing food, going to the bathroom, between patients, when they are dirty 

1. Why aren't antibacterial soaps recommended for everyday use at home?

 Using antibacterial soaps is not recommended for everyday at home use because it will strip away more than is needed and make your hands dry and irritated. It stripes away your normal flora. Also, overuse can lead to promoting antibiotic-resistant bacteria

1. Why is handwashing critical in patient care settings?

 It is important because it helps prevent the spread of diseases among patients and between healthcare workers. It keeps the evironment cleaner as well 

1. How can healthcare providers avoid spreading microorganisms among patients?

• wash or sanitize hands between patient’s 

• Wear PPE

• Change gloves and wash hands inbetween 

• Clean and disinfect 

• Use sterile techniques 

• Follow isolation precautions 

• Dispose of contaminated materials properly 

• Practice proper respiratory hygiene

1. Besides hand scrubbing, what other precautions must healthcare personnel take to prevent infection in an operating room?

Healthcare workers have to wear sterile gloves in the operating room. The sterile gloves are a barrier between any mciroorganisms that may still remain on the hands and the patient’s surgical site

1. How might long or artificial fingernails interfere with hand scrub effectiveness, and why?

I think the long or artifical fingernails would interfere with the effectiveness of hand scrub because they can hide so many microorgisms underneath them. It would be difficult to effectively remove them with a hand scrub. 

1. Why is wearing rings with stones unsuitable in hospital settings?

Because the stones have little grooves where it would be a great place for microorganisms to sit and grow, and it would be hard to remove 

1. Why should hands be washed both before and after dressing changes, even when gloves are worn?

Hands need to be washed before dressing changes to make sure gloves are not contamined for the procedure. The hands need to be washed after the dressing changes because the gloves may have tiny tears, or your hands could get contaminated during the glove removal process

1. Why is proper specimen collection critical for culture results?

culture results are only as accurate as the specimen collected

1. What factors must be considered to ensure proper specimen transport and storage?

• the from the right patient

• At the proper time 

• Using the appropriate technqiue 

• Stored at the rigth temperature 

1. Define septicemia, bacteremia, fungemia, and viremia

• Septicemia: infection in the blood 

• Bacteremia: bacterial infection in the blood 

• Fungemia: fungal infection in the blood 

• Viremia: viral infection in the blood

1. What are common indications of bacteremia?

• Increased pulse rate 

• Fever

• Chills 

• Hypotension

• Physical or mental exhaustion 

• Prolonged, mild, or intermittent fever

1. How does transient bacteremia differ from continuous and intermittent bacteremia?

• Transient bacteremia: bacteria enter the bloodstream for a short period, often after activities such as brushing teeth, dental procedures, or minor injuries. 

• Continuous bacteremia: bacteria are continuously present in the blood stream due to a persistent source of infection, such as infective endocarditis 

• Intermittent bacteremia: bacteria enter the bloodstream at irregular intervals from an infection that periodically releases bactera, such as an absces or localized infection

1. Why is it recommended to collect blood cultures at different time intervals for suspected infective endocarditis?

Blood cultures are collected at different time intervals to increase the likelihood of detecting the bacteria causing infective endocarditis. Multiple cultures help confirm continuous bacteremia and reduce the chance of false-negative or contaminated results

1. How should blood cultures be collected during acute febrile episodes?

Blood cultures shoudl be collected as soon as possible at the onset of fever or chills and before antbiotics are started, because bacteria are most likely to be present in the bloodstream during these episodes

1. What is the rationale for obtaining blood cultures from separate sites during intermittent bacteremia?

• increase the chance of detecting bacteria that are only intermittently present 

• Distinguish true bloodstream infections from contamination caused by normal skin flora 

• Improve the accuracy and reliability of the diagnosis 

1. What is the recommended blood-to-broth ratio for blood cultures, and why is it important

The recommended blood-to-broth ratio approximately 1:10. It is important because it dilutes substances in the blood that can inhibit bacterial growth, such as antibodies and complement proteins. Provides enough nutrients for microorganisms to grow. Increases the likelihood of recovering bacteria from the blood stream, improving the accuracy of the culture results

1. What are the guidelines for collecting blood cultures from adults versus infants?

• Adults: Collect 20-30mL of blood per culture set

• Infacts: 1-5mL

1. Why is it generally discouraged to draw blood through indwelling vascular catheters?

Is more likely to become contaminated with bacteria that colonize the catheter, whcih can lead to false positive culture results

1. How should the site be prepared for blood culture specimen collection?

• Wash hands and wear gloves 

• Clean site with 70% alcohol to remove dirt and oils 

• Apply an appropriate antiseptic(chlorhexidine or iodine) 

• Allow antiseptic to air dry completely 

• Do not touch the cleaned site before collecting the specimen

1. Why must the disinfectant be allowed to dry completely before obtaining a specimen?

• Maximizes its ability to kill skin microorganisms 

• Reduces contamination of the blood culture 

• Prevents the antiseptic from entering the blood sample and interfering with culture results

1. What is the purpose of inoculating blood into aerobic and anaerobic culture bottles?

• Aerobic bacteria: which require oxygen to grow 

• Anaerobic bacteria: which grow only in the absence of oxygen

1. Describe how the BacT/Alert system detects microbial growth in blood cultures.

Continously monitors blood culture bottles for carbon dioxide produced by growing microorganisms. When CO2 is released it causes a color change in a sensor at the bottome of the bottle. Which means a positive culture

1. After a positive result is detected by the BacT/Alert system, what are the next steps in processing the blood culture?

• Remove positive culture from the instrument 

• Perform Gram Stain 

• Report Gram stain results 

• Subculture the specimen into appropriate media to isolate the organism 

• Identify the microorganisms 

• Perform antibiotic susceptiblility testing

1. What does a gram-positive (purple) result indicate for a patient?

Gram-positive bacteria is present in their blood

1. What does a gram-negative (red) result indicate for a patient?

Gram-negative bacteria is present in their blood