Microbiology Media Quiz: MSA, EMB, HE

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Questions and Answers

What color indicates a mannitol fermenter on MSA media?

Red

Pink

Green

Yellow (correct)

Which of the following best describes the purpose of EMB agar?

To culture anaerobic bacteria

To select for Gram positive bacteria

To differentiate between lactose fermenters (correct)

To stain bacterial cells

What is indicated by blue/green growth on HE media?

Lactose fermentation

Fermentation of sugar

Reduction of sulfur

Protein breakdown to alkaline products (correct)

Where do B cells originate and mature?

Bone marrow; bone marrow Signup and view all the answers

What is the name of the effector B cell and its main function?

Plasma cells; to release antibodies Signup and view all the answers

What distinguishes Gram-positive bacteria from Gram-negative bacteria?

Thick peptidoglycan layer Signup and view all the answers

What indicates a false negative result in Gram staining?

Over-decolorization Signup and view all the answers

What is an unusual side effect of one of the antibiotics used to treat TB?

Hearing loss Signup and view all the answers

What characteristic does Gram-positive bacteria exhibit after staining?

They appear purple. Signup and view all the answers

Which type of toxin is released during cell lysis in Gram-positive bacteria?

Exotoxin Signup and view all the answers

What is the primary difference in cell wall structure between Mycobacterium and Mycoplasma?

Mycobacterium has a waxy cell wall. Signup and view all the answers

What type of hemolysis is characterized by a complete destruction of red blood cells?

Beta Signup and view all the answers

Which two genera are known for their ability to sporulate?

Bacillus and Clostridium Signup and view all the answers

What does the presence of the K antigen indicate in bacteria?

The presence of a capsule. Signup and view all the answers

What type of culture media is used to assess the oxygen tolerance of bacteria?

Thioglycolate medium Signup and view all the answers

What is the primary action of the enzyme hyaluronidase?

Breaks down hyaluronic acid. Signup and view all the answers

Which bacteria is known to cause pseudomembranous colitis?

Clostridium difficile Signup and view all the answers

Which medication is effective against herpes infections by inhibiting nucleic acid synthesis?

Both A and C Signup and view all the answers

Which feature distinguishes MSA agar as selective for certain bacteria?

Addition of a high concentration of sodium chloride Signup and view all the answers

What does pink or lavender growth on EMB agar indicate about the bacteria?

It is a weak lactose fermenter Signup and view all the answers

How does the HE agar differentiate between bacteria?

By evaluating lactose fermentation and sulfur reduction Signup and view all the answers

What is a key difference between the activation of B cells and T cells?

T cells require interaction with MHC molecules to be activated Signup and view all the answers

Which of the following correctly describes primary tuberculosis infection?

Infection remains contained in the lungs Signup and view all the answers

What role does glycocalyx play in bacterial survival within a host?

It provides a mechanical barrier to antibiotics Signup and view all the answers

How does the structure of a Gram-negative cell wall differ from that of a Gram-positive cell wall?

It has an outer membrane with lipopolysaccharides Signup and view all the answers

Which scenario describes a true Gram-positive reaction in Gram staining?

Purple after primary stain and purple after decolorization Signup and view all the answers

Which type of transport requires ATP and moves against the concentration gradient?

Active transport Signup and view all the answers

What type of vaccine is created by using a killed version of the pathogen?

Inactivated vaccine Signup and view all the answers

Where do RNA viruses typically replicate within a host cell?

Cytoplasm Signup and view all the answers

In which type of solution would water move into the cell, indicating a state of overhydration?

Hypotonic solution Signup and view all the answers

Which bacteria is known to cause whooping cough?

Bordetella pertussis Signup and view all the answers

Which vector is primarily responsible for transmitting Zika virus?

Aedes (aegypti) Signup and view all the answers

What is a complication that can arise from mumps infection?

Permanent deafness Signup and view all the answers

What is the main method used to determine bacterial resistance to antibiotics?

Kirby-Bauer method Signup and view all the answers

Which of the following is a characteristic of an endemic disease?

Constantly present within a geographical area Signup and view all the answers

Which type of symbiotic relationship involves one organism benefiting at the expense of another?

Parasitism Signup and view all the answers

Which symptom is associated with Wuchereria bancrofti infection?

Elephantiasis Signup and view all the answers

What is the primary method of diagnosing infections caused by Schistosoma mansoni?

Examination of stool for eggs Signup and view all the answers

What mechanism is used by Ivermectin to treat nematode infections?

Causes paralysis Signup and view all the answers

Which of the following describes the reproduction of Fasciola hepatica?

Monoecious Signup and view all the answers

How are the symptoms of Taenia solium infection primarily characterized?

Seizures and headaches Signup and view all the answers

What is the common characteristic of the larval life stages of Dirofilaria immitis that are targeted by heartworm prevention medications?

L3 and L4 larval stages Signup and view all the answers

Which organism is known as the Guinea worm?

Dracunculus medinensis Signup and view all the answers

What is a distinguishing feature of Taenia solium compared to Taenia saginata?

Has hooks and suckers on the scolex Signup and view all the answers

What is the primary target of Praziquantel in treating helminth infections?

Parasite tegument Signup and view all the answers

Which type of helminths includes both flatworms and roundworms?

Platyhelminthes Signup and view all the answers

Which symptoms are indicative of an infection with Fasciola hepatica?

Fever and jaundice Signup and view all the answers

What is the lifecycle characteristic of filarial worms like Wuchereria bancrofti?

Nocturnal activity of microfilariae Signup and view all the answers

What is the main concern related to the consumption of undercooked pork in relation to Taenia solium?

Cysticercosis risk Signup and view all the answers

What distinguishes the yeast form of dimorphic fungi from the mold form?

The yeast form thrives at body temperature (37°C). Signup and view all the answers

Which type of asexual reproductive spores are borne on specialized structures in fungi?

Conidia Signup and view all the answers

What is the primary purpose of Sabouraud's agar in fungal culture?

To create an acidic environment that promotes fungal growth Signup and view all the answers

Which of the following fungal infections is primarily transmitted through direct or indirect contact?

Tinea corporis Signup and view all the answers

Which antifungal medication is known for causing nephrotoxicity as a side effect?

Amphotericin B Signup and view all the answers

What is the function of the kOH test in diagnosing fungal infections?

To make fungal elements visible under a microscope Signup and view all the answers

Which of the following describes the triggers for cyst formation in protozoa?

Harsh environmental conditions Signup and view all the answers

Which of the following bacteria is responsible for Lyme disease?

Borrelia burgdorferi Signup and view all the answers

What is the role of an intermediate host in the life cycle of protozoa?

To harbor juvenile stages and asexual reproduction Signup and view all the answers

What color will Gram-negative bacteria appear after decolorization in a Gram stain procedure?

Colorless Signup and view all the answers

Which antiprotozoal medication is primarily used to treat malaria?

Chloroquine Signup and view all the answers

What are exotoxins released from Gram-positive bacteria during?

Cell lysis Signup and view all the answers

Which of the following protozoal infections is characterized by the presence of trophozoites?

Amoebiasis Signup and view all the answers

What is the main function of coagulase in bacteria?

Triggers blood clotting Signup and view all the answers

What type of fungal infections is characterized by localized infections in the skin, hair, and nails?

Superficial infections Signup and view all the answers

Which fungus is commonly associated with histoplasmosis due to its association with bird and bat droppings?

Histoplasma capsulatum Signup and view all the answers

Which bacteria is known to grow well in cold enrichment conditions?

Listeria monocytogenes Signup and view all the answers

Which of the following statements about the mold phase of dimorphic fungi is accurate?

It requires oxygen for growth. Signup and view all the answers

Which type of antigen is associated with the K antigen in bacteria?

Capsular antigen Signup and view all the answers

Which bacteria is responsible for pseudomembranous colitis?

Clostridium difficile Signup and view all the answers

What is the key distinguishing feature of Mycoplasma regarding its cell structure?

Lacks a cell wall Signup and view all the answers

What type of medium is used to measure the oxygen tolerance of bacteria?

Thioglycolate media Signup and view all the answers

What defines an alpha hemolytic bacteria in terms of red blood cell destruction?

Partial destruction resulting in a greenish zone Signup and view all the answers

What type of growth media would you use to confirm the presence of capsulated bacteria?

Charcoal enriched media Signup and view all the answers

Which of the following statements is true about the action of ergosterol in fungi?

It is analogous to cholesterol in animal cells Signup and view all the answers

What does the process of margination in inflammation refer to?

WBC adhering to blood vessel walls Signup and view all the answers

Which of the following protozoa is transmitted primarily through the fecal-oral route?

Giardia lamblia Signup and view all the answers

What is the definitive host for Toxoplasma gondii?

Cats Signup and view all the answers

Which phase of Plasmodium malariae occurs within the mosquito?

Sexual stage Signup and view all the answers

Which of the following symptoms is associated with Entamoeba histolytica infection?

Bloody diarrhea and abdominal pain Signup and view all the answers

How is Trypanosoma cruzi primarily transmitted?

Bite from triatomine bugs Signup and view all the answers

What is the transmission route for Naegleria fowleri?

Nasal passage exposure to contaminated water Signup and view all the answers

Which nematode is most commonly associated with perianal itching among children?

Enterobius vermicularis Signup and view all the answers

What role do antacids play in increasing infection risk for Balantidium coli?

They neutralize stomach acid, allowing more cysts to survive. Signup and view all the answers

What is a common symptom of Trichomonas vaginalis infection?

Vaginal discharge Signup and view all the answers

Which organism is responsible for causing Chagas disease?

Trypanosoma cruzi Signup and view all the answers

What type of modules do the trophozoites of Balantidium coli typically undergo upon excystation?

They invade the mucosal lining of the intestines. Signup and view all the answers

Which of the following correctly describes the symptoms of Acanthamoeba keratitis?

Eye pain and blurred vision Signup and view all the answers

What is a characteristic symptom of necator americanus infection?

Abdominal discomfort Signup and view all the answers

Which protozoan is known to survive in contaminated water and cause gastrointestinal distress?

Giardia lamblia Signup and view all the answers

Study Notes

MSA (Mannitol Salt Agar)

Selective: High salt concentration (7.5% NaCl) inhibits the growth of most bacteria except for Staphylococcus.
Differential: Differentiates mannitol fermenters (yellow) from non-fermenters (pink). Yellow colonies indicate mannitol fermentation, producing acid; pink colonies show no mannitol fermentation.
Differentiates pathogenic Staphylococcus aureus from non-pathogenic Staphylococcus species.
Yellow growth: Mannitol fermenter.
Pink growth: Non-mannitol fermenter.

EMB (Eosin Methylene Blue Agar)

Differential: Differentiates based on lactose fermentation ability.
Pink/Lavender Growth: Gram-negative bacteria that are weak lactose fermenters.
Red Growth: Gram-negative bacteria that are non-lactose fermenters.
Metallic Green Growth: Gram-negative bacteria that are rapid lactose fermenters. Used to identify fecal coliforms.

HE (Hektoen Enteric Agar)

Differential: Differentiates based on lactose fermentation and sulfur reduction.
Yellow: Fermentation of sugar (e.g., E. coli).
Blue/Green: Breakdown of protein to alkali products (e.g., Salmonella and Shigella).
Black: Sulfur reduction (e.g., Salmonella).
Differentiates Salmonella and Shigella from E. coli.
Differentiates by the addition of thiosulfate and ferric ammonium citrate, and lactose fermentation.

B vs. T Cells

B Cells: Originate and mature in the bone marrow. Activated by the MHC complex.
T Cells: Originate in the bone marrow and mature in the thymus; produces regulatory cells. Activation involves an antigen-presenting cell.
Not all self-reactive cells undergo apoptosis (programmed cell death).

Tuberculosis (TB)

Bacteria: Mycobacterium tuberculosis
Primary TB: Infection contained in the lungs.
Secondary TB: Tubercle breaks open, spreading the infection.
Tertiary/Disseminated TB: Mycobacterium spread throughout the body.
Antibiotics: Isoniazid and rifampin.
Unusual Side Effect (Rifampin): Turns bodily fluids (urine, tears, sweat) an orange-red color.

Effector B Cell

Effector B Cell: Plasma cell.
Job: Releases antibodies.

Glycocalyx

Examples: Endothelial cells and digestive system cells.
Role in bacterial survival: Provides a mechanical barrier against antibiotics and evades host defense systems.
Biofilm contribution: Allows bacteria to invade host defense systems.

Cell Wall Makeup

Gram-Positive: Thick peptidoglycan layer.
Gram-Negative: Thin peptidoglycan layer.
Acid-Fast: Used for Mycobacterium bacteria (e.g., TB).

Gram Stain

Gram-Positive: Retain crystal violet (purple).
Gram-Negative: Lose crystal violet, stain pink with safranin.
Primary Stain: Crystal violet.
Decolorizer: Ethyl alcohol.
Counterstain: Safranin.
False Positive: Gram-negative bacteria appearing purple due to insufficient decolorization.
False Negative: Gram-positive bacteria appearing pink due to excessive decolorization.
Counterstain Purpose: To visualize Gram-negative bacteria.
Gram-Positive Appearance After Decolorization: Purple.
Gram-Negative Appearance After Decolorization: Clear/Colorless.

Endotoxin vs. Exotoxin

Endotoxin (Gram-Negative): Released upon bacterial death. Also known as lipopolysaccharide (LPS).
Exotoxin (Gram-Positive/Gram-Negative): Released during cell lysis or by active secretion; Lipoteichoic acid (LTA).
Types of Exotoxins: Various, including cytotoxins and neurotoxins.

Lyme Disease

Disease: Lyme disease.
Bacteria: Borrelia burgdorferi.
Classification: Spirochete.

Cell Wall Differences (Mycobacterium vs. Mycoplasma)

Mycobacterium: Thick, protective, waxy cell wall.
Mycoplasma: Lacks a cell wall.

Hemolysis

Alpha: Greenish/brownish zone around colonies. Partial RBC destruction.
Beta: Clear zone. Complete RBC destruction.
Gamma: No visible change. No RBC destruction.

Sporulation

Genera: Bacillus and Clostridium.
Definition: Formation of spores.
Trigger: Unfavorable growth conditions.
Oxygen's Role: Bacillus (aerobic or facultative anaerobe) sporulates as a result of oxygen concentration; Clostridium (anaerobe) doesn't sporulate in oxygen.
Germination: The process of a spore returning to a vegetative state.

Anti-retroviral Medications

Examples: Medications used for COVID-19, Herpes, Hepatitis B & C, and HIV.

Breath Test

Diagnosis: Helicobacter pylori.
Causes: Pain, inflammation, and ulcers in the upper digestive tract.

Antigens

H Antigen: Flagellar antigen (variable). Example: Salmonella.
K Antigen: Capsular antigen (protective). Example: Escherichia coli.

Th vs. Tc Cells

Tc (Cytotoxic T Cells): CD8; Binds MHC I; Kills infected cells. Memory cells provide future immunity.
Th (Helper T Cells): CD4; Binds MHC II; Regulates immune response. Memory cells provide future immunity.
Treg (Regulatory T Cells): Suppresses immune response.
MHC I: Present on all nucleated cells.
MHC II: Present on antigen-presenting cells (APCs).
Not all self-reactive cells undergo apoptosis.

Tc Effector Cell and Innate Cell Comparison

Innate Cell: Similar to natural killer (NK) cells.
Substances secreted: Perforin and granzymes.

Oxygen Tolerance

Media: Thioglycolate broth.
Interpretation: Growth position in media indicates oxygen tolerance.

Coliforms vs. Non-coliforms

Coliforms: Gram-negative, facultative anaerobes, ferment lactose.
Non-coliforms: Do not ferment lactose.

Enzymes

Hyaluronidase: Breaks down hyaluronic acid.
Kinase: Adds phosphate groups to molecules.
Coagulase: Converts fibrinogen to fibrin (blood clotting).
Collagenase: Breaks down collagen.

Antibiotic MOA (Mechanism of Action)

Sulfonamides (e.g., Bactrim, Gantrisin): Competitive inhibitors of PABA, preventing folic acid production.

Syphilis

Bacteria: Treponema pallidum.
Stages:
- Incubation (3-6 weeks): Ulcers at infection site.
- Onset (3-6 weeks): Skin rashes.
- Severe Organ Damage.

WBC Response to Injury

Margination: White blood cells migrate to the injury site and adhere to the site.
Diapedesis: White blood cells squeeze between endothelial cells into the interstitial fluid.
Chemotaxis: White blood cells migrate to the injury site.

Pseudomembranous Conditions

Pseudomembranous Colitis: Clostridium difficile; Watery diarrhea, abdominal pain, fever, pseudomembrane in colon.
Pseudomembranous Pharyngitis: Corynebacterium diphtheriae; Sore throat, fever, grayish-white pseudomembrane, swollen neck.
Strep Throat: Streptococcus pyogenes; Severe sore throat, fever, swollen tonsils, white exudates.

Bacteria Growth in Specific Media

Charcoal-Enriched: Supports Legionella pneumophila and Bordetella pertussis.
Cold Enrichment: Favors Listeria monocytogenes, Yersinia enterocolitica, Campylobacter jejuni, and Salmonella enterica.
Heat Enrichment: Promotes Thermophilic Bacillus species, Clostridium species, thermotolerant Enterococcus faecalis.

Antimicrobial for Herpes

Antiviral: Acyclovir and Ganciclovir
Mechanism: Nucleic acid synthesis inhibitors.

Mycology

Mycology: The study of fungi and their properties.
Mycoses: Fungal infections in humans or animals.
Characteristics: Eukaryotic, cell wall made of chitin, unicellular (yeasts) or multicellular (molds).
- Obtain nutrients as saprobes or parasites.
Ergosterol: A component of fungal cell membranes.
Fungistatic: Inhibit ergosterol synthesis (e.g., azoles).
Fungicidal: Bind to ergosterol, causing membrane damage (e.g., polyenes).
Morphological Forms: Hyphae (thread-like structures), septate (divided by cross walls), nonseptate (continuous), yeasts (single-celled), pseudohyphae (chains of elongated yeasts).
Dimorphic Fungi: Alternate between yeast and mold forms based on environmental temperature.
Reproductive Spores: Asexual (conidia, sporangiospores) and sexual (zygospores, ascospores, basidiospores).
Fungal Culture: Sabouraud's agar (Sab agar) is slightly acidic, inhibiting bacterial growth and facilitating fungal growth. Most fungal infections are not contagious, some exceptions like dermatophytes are contagious.
Diagnosis: KOH test, GMS stain, colony morphology.
Antifungal Medications: Fungistatic (azoles, side effects: hepatotoxicity), Fungicidal (polyenes, side effects: nephrotoxicity), other drugs (flucytosine, griseofulvin).
Special Fungi: Histoplasma capsulatum (histoplasmosis), Coccidioides immitis (cocci), Candida albicans (thrush), Cryptococcus neoformans, Penicillium chrysogenum, Malassezia furfur (tinea versicolor).
Superficial Fungal Infections: Tinea infections (capitis, corporis, pedis, cruris, barbae, manuum, unguium).
Subcutaneous Fungi: Sporothrix schenckii (rose gardener's disease).

Protozoa

General Characteristics: Unicellular, eukaryotic, diverse motility.
Modes of Motility: Flagella, cilia, pseudopodia, non-motile.
Trophozoite vs. Cyst: Active vs. dormant stages.
Definitive Host vs. Intermediate Host: Host with sexual vs. asexual reproduction.
Prevention for Insect-Transmitted or Food/Water-Borne Diseases: Insect-borne (insect repellents, vector control) and water/food-borne (safe water, food preparation).
Antiprotozoal Medications: Metronidazole (GI upset, potential neurotoxicity), chloroquine (GI upset, potential retinal damage), Artemisin-based Combination Therapy (fever, chills, headache), Nitazoxanide (nausea, abdominal pain), Pentamidine (hypoglycemia, kidney damage, low blood pressure), Suramin and Melarsoprol (severe), Paromomycin (GI upset, nephrotoxicity).
Plasmodium malariae: Symptoms, vector (Anopheles mosquito), asexual and sexual stages, parts of erythrocytic stage, definitive vs. intermediate host.
Toxoplasma gondii: Definitive and intermediate hosts, transmission, vertical transmission, congenital toxoplasmosis.
Balantidium coli: Only pathogenic ciliate to humans, transmission, zoonotic source, excystation trigger, antacid implications, symptoms.
Giardia lamblia: Nickname, zoonotic, transmission, symptoms, lactose intolerance implication.
Trichomonas vaginalis: Transmission, cyst stage, symptoms.
Trypanosoma cruzi: Disease, vector (triatomine bug), symptoms, complications.
Leishmania donovani: Nickname, vector (sandfly), forms and symptoms.
Entamoeba histolytica: Transmission, life cycle, symptoms, complications.
Acanthamoeba keratitis: Transmission, symptoms, route to brain (GAE).
Naegleria fowleri: Transmission, symptoms, route to brain (PAM).

Nematodes and Platyhelminthes

Nematodes (Roundworms):
- Ascaris lumbricoides: Nickname, transmission, migration, symptoms, egg resistance.
- Enterobius vermicularis: Nickname, transmission, diagnosis, symptoms, commonality.
- Necator americanus: Nickname, transmission, symptoms.
- Trichinella spiralis: Nickname, transmission, symptoms, diagnosis.
- Wuchereria bancrofti: Nickname, transmission, symptoms, testing timing.
- Dracunculus medinensis: Nickname, transmission, symptoms.
Platyhelminthes (Flatworms):
- Schistosoma mansoni: Nickname, appearance, transmission, acute/chronic symptoms, dioecious, egg effects.
- Fasciola hepatica: Nickname, appearance, transmission, feeds on, acute/chronic symptoms, monoecious.
- Taenia solium vs. Taenia saginata: Nicknames, scolex differences, proglottid differences, transmission, symptoms (intestinal vs. cysticercosis).
General Characteristics of Helminths: Multicellular eukaryotes, life cycles involving intermediate and definitive hosts, egg/larval reproduction.
Dioecious vs. Monoecious: Separate vs. single-sex organism reproduction.
Antihelminthic Drugs: Albendazole/mebendazole, praziquantel, ivermectin, pyrantel pamoate - mechanisms and common targets.
Heartworm Prevention: Ivermectin or Milbemycin oxime - targeting larval stages, monthly administration importance.
How Antibiotics Kill Helminths Indirectly: Doxycycline or other antibiotics disrupting symbiotic bacteria within filarial worms.

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Test your knowledge on selective and differential media used in microbiology, including Mannitol Salt Agar, Eosin Methylene Blue Agar, and Hektoen Enteric Agar. This quiz will help you understand how to differentiate between various bacterial species based on their growth characteristics. Perfect for students studying microbiology or preparing for exams.