Mircobiology Final Med Lab

A sputum specimen is received in the laboratory for orders to culture and stain for the bacteria that causes tuberculosis. Which of the following stains would be used?

Gram stain

Acid-fast stain

Supravital stain

Wright stain

Acid-fast stain

A patient is seen by their physician for a wound that has not been healing properly for the past week. The patient states that they are in the garden quite frequently and when pruning their rose bushes, the thorns sliced their finger. The physician examines the wound and wants to rule out the possibility of a fungal infection. What protocol may the laboratory need to follow to culture the specimen to assure if fungal elements are present, that they will grow?

The media used to culture the wound specimen should contain antibiotics to inhibit normal flora organisms.

The laboratory must put the specimen in the freezer until the supervisor arrives.

The laboratory needs to culture the specimen to regular media used for wound cultures.

The laboratory needs to place the swab in the incubator and then culture in the morning when more staff are available.

The media used to culture the wound specimen should contain antibiotics to inhibit normal flora organisms.

A technologist removes a culture plate from the incubator and notices that the colonies of the bacteria seem to have swarmed all over the plate indicating motility. Which of the following bacteria may be presumptively identified by this feature?

Escherchia coli

Staphylococcus aureus

Proteus vulgaris

Streptococcus pyogenes

Proteus vulgaris

A culture plate contains a colony of bacteria that the technologist has identified as either Stapylococcus sp. or Streptococcus sp. Which of the following is a quick enzyme test that will differentiate the two organisms?

Bile esculin agar

Bile solubility test

Catalase test

atalaCoagulase test

Catalase test

A group of college students are seen in the nurse's office for what appears to be a wound infection. The group of students state that over the weekend they stayed with friends that had a hot tub that may have not been cleaned recently before they got in. What may be the most likely bacteria identified in their wound cultures?

Pseudomonas aeruginosa

Klebsiella pneumoniae

Streptococcus pneumonia

Enterococcus sp.

Pseudomonas aeruginosa

A technologist needs to perform antibiotic susceptibility testing on a urine culture containing E. coli. Which of the following media needs to be used for antibiotic testing using the disk diffusion procedure?

Blood agar

Mueller-Hinton agar

Trypticase soy agar

MacConkey agar

Mueller-Hinton agar

A 5-year-old male is seen in the emergency room for abdominal pain and diarrhea over the past week. He has recently immigrated with his family from Africa and the physician wants to rule out a parasitic infection. Which of the following specimens would need to be collected?

Wound

Stool

Synovial fluid

Cerebral spinal fluid

Stool

A technologist pulls a respiratory culture from the incubator. When looking at the plates, there is no growth on the blood agar plate but small tan colonies on the chocolate agar plate. The colonies are suspicious for which type of bacteria:

Streptococcus pneumoniae

Streptococcus pyogenes

Haemophilus sp.

Staphylococcus aureus

Haemophilus sp.

A technologist is working on a stool culture and observes green colonies with a black center on the Hektoen Enteric agar plate. This would indicate which type of pathogen found in the stool:

Shigella sp.

Salmonella sp.

E. coli

Campylobacter sp.

Salmonella sp.

A technologist is working on a blood culture that is suspected of containing Candida albicans. Which of the following would be a rapid test to identify this yeast?

India ink

Gram stain

KOH preparation

Germ tube

Germ tube

What is meant by the term normal flora?

Normal flora – The helpful bacteria that live in our body and protect us from harmful germs.

What is a pathogen? What is an opportunistic pathogen?

Pathogen – A germ that causes disease. Opportunistic pathogen – A germ that usually doesn’t cause disease but can if the body is weak.

How does infection occur?

When harmful germs enter the body, grow, and cause illness.

Describe the 3 morphological types of bacteria

Three shapes of bacteria – Round (cocci), rod-shaped (bacilli), and spiral (spirilla).

What is a gram stain?

A test that colors bacteria to tell if they are Gram-positive (purple) or Gram-negative (pink).

What is the difference between aerobic and anaerobic bacteria?

Aerobic bacteria need oxygen to grow, anaerobic bacteria don’t.

How are viruses different from microorganisms? Name three viral diseases

Microorganisms are living organisms that are too small to be seen with the naked eye, encompassing bacteria, fungi, and protozoa, while viruses are non-living entities, much smaller than microorganisms, that require a host cell to replicate.

Examples – Flu, HIV, COVID-19.

Facultative anaerobe

A germ that can live with or without oxygen.

What are the purposes of primary, selective and differential (indicator) media?

Purpose of media –Primary – Grows all bacteria.
Selective – Grows only certain bacteria.
Differential – Helps tell bacteria apart.

What hemolytic reactions of bacteria can be used to identify the organism?

Show how bacteria break down red blood cells to help identify them.

Why is the media inoculated with a swab before the smear is made?

To spread bacteria evenly and get a good sample.

Why must the smear for Gram stain be heat-fixed?

Sticking bacteria to the slide so they don’t wash away.

Why are some bacteria gram positive and others gram negative?

Due to differences in their cell walls, which hold or lose the purple stain.

The technique of killing or destroying all microorganisms including bacterial spores is called?

Killing all microorganisms (including spores) – Called sterilization.

Describe what Staphylococcus sp. would appear to be on a gram stain

Staphylococcus on Gram stain – Round, in clusters, and purple (Gram-positive).

Describe what Streptococcus sp. would appear to be on a gram stain

Streptococcus on Gram stain – Round, in chains, and purple (Gram-positive).

What is the biosafety level of most clinical microbiology labs?

Usually Level 2 (BSL-2).

What are 2 effective disinfectants to use in the clinical microbiology lab? Why should the surfaces be allowed to remain wet as long as possible with the disinfectant?

Bleach and alcohol. Surfaces stay wet so the disinfectant can kill all germs.

Which specimen type can be collected in a clean non-sterile container?

Non-sterile sample – Stool (poop).

Which of the following requests for a bacterial culture can be refrigerated?

CSF, genital, urine or blood?

Urine.

A growth of bacteria that eventually becomes visible on an agar plate is called?

Colony

An acid-fast stain is typically used with which bacteria?

Acid-fast stain – Used for Mycobacterium (like TB).

The lowest concentration of an antimicrobial agent that will visibly inhibit the growth of the organism being tested is called.

Lowest concentration of antibiotic that stops bacteria – Called Minimum Inhibitory Concentration (MIC).

What is the differences between sepsis, transient bacteremia and intermittent bacteremia?

Sepsis – A dangerous infection in the blood.
Transient bacteremia – Bacteria in blood for a short time.
Intermittent bacteremia – Bacteria that come and go in the blood.

Define:

a. Subculture

b. Primary culture

c. Mixed culture

d. Pure culture

Subculture – Taking bacteria from one plate to another to study it better.

Primary culture – The first time bacteria are grown in a lab.

Mixed culture – More than one type of bacteria in a sample.

Pure culture – Only one type of bacteria in a sample.

Common types of microbiology media:

a. MacConkey (MAC)

b. Sheep blood agar (SBA)

c. Columbia -colistin Nalidixic Acid with sheep blood (CNA)

d. Chocolate (CHOC)

e. Modified Thayer Martin (MTM)

MacConkey (MAC) – Grows Gram-negative bacteria.

Sheep blood agar (SBA) – Shows how bacteria break red blood cells.

Columbia CNA – Grows Gram-positive bacteria.

Chocolate (CHOC) – Grows picky bacteria like Haemophilus and Neisseria.

Modified Thayer Martin (MTM) – Grows Neisseria gonorrhoeae.

What is the Kirby Bauer Method?

Kirby-Bauer Method – A test to see which antibiotics kill bacteria.

Indi Ink test and Germ tube – what organisms can be identified using these tests?

India Ink – Identifies Cryptococcus.
Germ Tube – Identifies Candida albicans.

The following tests are used to differentiate which organisms?

a. Catalase

b. Coagulase

c. Indole

d. Oxidase

Catalase – Distinguishes Staphylococcus (+) from Streptococcus (-).
Coagulase – Identifies Staphylococcus aureus.
Indole – Identifies E. coli.
Oxidase – Identifies Pseudomonas.

What two tests on a urinalysis strip can indicate that a patient has a UTI?

Nitrites & Leukocyte esterase