Microbiology I Practical Guide

<p>Mannitol salt agar (B)</p> Signup and view all the answers

<p>Streptococcus pyogenes (B)</p> Signup and view all the answers

<p>Bacitracin sensitivity test (A)</p> Signup and view all the answers

<p>Rash with vesicles (D)</p> Signup and view all the answers

<p>Cocci in chains (D)</p> Signup and view all the answers

<p>To differentiate between streptococci and staphylococci (D)</p> Signup and view all the answers

<p>It produces yellow colonies on mannitol salt agar (C)</p> Signup and view all the answers

<p>Bubbles are produced (C)</p> Signup and view all the answers

<p>To convert fibrinogen to fibrin (D)</p> Signup and view all the answers

<p>Staphylococcus aureus (D)</p> Signup and view all the answers

<p>Bound coagulase (D)</p> Signup and view all the answers

<p>Using a metal loop to transfer the sample (C)</p> Signup and view all the answers

<p>As a reagent in the coagulase test (A)</p> Signup and view all the answers

<p>Quellung test (B)</p> Signup and view all the answers

<p>Negative (A)</p> Signup and view all the answers

<p>They appear as unstained halos in a gram-stained film. (B)</p> Signup and view all the answers

<p>Alpha hemolysis (D)</p> Signup and view all the answers

<p>Swollen capsule around the organism (A)</p> Signup and view all the answers

<p>Produces CAMP factor (D)</p> Signup and view all the answers

<p>Incubation in 5-10% CO2 at 35˚C (D)</p> Signup and view all the answers

<p>Quellung positivity (A)</p> Signup and view all the answers

<p>Latex agglutination test (A)</p> Signup and view all the answers

<p>Color change to purple within 10 seconds (D)</p> Signup and view all the answers

<p>Escherichia coli (A)</p> Signup and view all the answers

<p>CO2 incubator or candle jar (B)</p> Signup and view all the answers

<p>It shows no acid production from glucose (C)</p> Signup and view all the answers

<p>Pneumonia (B), Otitis media (D)</p> Signup and view all the answers

<p>Gram-negative kidney-shaped diplococci (B)</p> Signup and view all the answers

<p>Ear discharge (B)</p> Signup and view all the answers

<p>Non-haemolytic reaction with Medusa head colonies (B)</p> Signup and view all the answers

<p>Polychrome methylene blue stain (C)</p> Signup and view all the answers

<p>Gram positive bacilli with square ends (B)</p> Signup and view all the answers

<p>Both produce a β-haemolytic reaction on blood agar. (D)</p> Signup and view all the answers

<p>The formation of large white colonies with a rough surface (A)</p> Signup and view all the answers

<p>Inverted fire tree appearance (B)</p> Signup and view all the answers

<p>Sputum sample (B)</p> Signup and view all the answers

<p>Gram positive bacilli with square ends and central spores (D)</p> Signup and view all the answers

<p>Robertson cooked meat medium (C)</p> Signup and view all the answers

<p>Double zone of beta hemolysis (C)</p> Signup and view all the answers

<p>Gelatin liquefier (D)</p> Signup and view all the answers

<p>Opacity around the control streak (C)</p> Signup and view all the answers

<p>Gram stain (C)</p> Signup and view all the answers

<p>Anaerobic conditions (C)</p> Signup and view all the answers

<p>Coagulation of milk protein (A)</p> Signup and view all the answers

<p>Clostridium tetani (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

A test to differentiate between catalase-positive (staphylococci) and catalase-negative (streptococci) bacteria.

A bacterium that is catalase-positive, coagulase-positive and often forms yellow colonies on mannitol salt agar.

A test to detect the presence of coagulase, an enzyme that causes blood plasma to clot.

A method to identify the presence of free coagulase, which causes plasma to clot.

Bacteria that stain purple with Gram stain and have a spherical shape.

A selective and differential medium, often used to identify Staphylococcus aureus due to its ability to ferment mannitol and produce yellow colonies.

A type of coagulase found attached to the bacterial cell membrane.

An extracellular coagulase that causes plasma to clot in the tube coagulase test.

A bacterial cell type appearing as spherical-shaped cells, positive to Gram stain, found in clusters.

A test to determine if a bacteria produces the enzyme catalase. Involved in the breakdown of hydrogen peroxide.

A test to determine if a bacteria produces the enzyme coagulase which causes blood clotting

Staphylococcus aureus. A bacterium that causes a variety of diseases characterized by an arrangement of gram-positive cocci in clusters, beta-hemolytic.

Staphylococcus aureus. A bacterium causing skin infections and skin scalded syndrome is characterized by an arrangement of gram-positive cocci in clusters, coagulase positive.

An enzyme produced by certain bacteria that causes the coagulation (clotting) of blood plasma either from humans or rabbits.

Streptococcus pyogenes, a bacteria characterized by an arrangement in chains (streptococci) and causes beta hemolysis.

Coagulase test; distinguishes staphylococci (Coagulase positive) from streptococci (Coagulase negative).

S. pyogenes does not produce CAMP factor, a protein important in bacterial interactions.

S. agalactiae produces CAMP factor.

Gram-positive diplococci, often encapsulated, present in pus-like samples.

Displays alpha-hemolysis on blood agar.

Catalase-negative.

A test used to identify and type pneumococci based on capsule swelling.

Identifying and typing bacteria by observing swelling in bacterial capsules after introducing specific antiserum.

Differentiating pneumococci from other streptococci, often using tests like the Quellung reaction and biochemical characteristics.

Samples used to identify anthrax in the lab, such as sputum and skin exudates.

Anthrax bacteria appear as large, square-ended, Gram-positive rods arranged in chains. They also have a capsule that appears as an unstained halo.

A specific stain highlights the capsule of anthrax bacteria, appearing purple or pink, while the bacteria itself is blue.

On blood agar, anthrax bacteria form non-haemolytic colonies with a Medusa head appearance.

Anthrax bacteria grow on gelatin medium and create an “inverted fire tree” pattern.

Similar bacteria to anthrax, often found as contaminants in the lab. They are typically non-capsulated and can be motile.

Anthracoids grow as β-haemolytic colonies on blood agar.

Anthracoids on nutrient agar produce white, rough colonies with a fimbriated edge.

A serious bacterial infection caused by Clostridium perfringens, characterized by gas production, tissue death, and rapid spread.

A bacterium responsible for gas gangrene, produces a double zone of beta-hemolysis on blood agar and has characteristic subterminal spores.

A culture medium used for isolating Clostridium perfringens, it provides a rich environment for bacterial growth.

A sealed container used to cultivate anaerobic bacteria, such as Clostridium perfringens, by removing oxygen and creating an oxygen-free environment.

The complete destruction of red blood cells by bacteria, producing a clear zone around the bacterial colonies on blood agar.

A characteristic reaction of Clostridium perfringens in litmus milk medium, resulting in gas production and coagulation of milk protein.

A rapid diagnostic test for Clostridium perfringens, based on the inactivation of the alpha-toxin by an antibody.

A serious bacterial infection caused by Clostridium tetani, characterized by muscle spasms and rigidity.

Neisseria meningitidis grows best in a CO2 enriched environment, typically a 5-10% CO2 incubator or candle jar.

The oxidase test is used to identify Neisseria species by detecting the enzyme cytochrome c oxidase. A positive test results in a color change to purple within 10 seconds.

Neisseria meningitidis, a causative agent of meningitis, can be cultured on chocolate agar, which provides essential nutrients for its growth.

Direct microscopy of a Gram-stained smear can reveal Gram-negative kidney-shaped diplococci, characteristic of Neisseria meningitidis.

Moraxella catarrhalis can grow on nutrient agar at 37˚C and even at room temperature, making it a versatile bacterium.

Moraxella catarrhalis, a common cause of ear infections, can be cultured on chocolate agar, providing optimal growth conditions.

Moraxella catarrhalis does not ferment sugars like glucose, maltose, lactose, or sucrose, setting it apart from other bacteria.

Neisseria meningitidis ferments sugars like glucose and maltose, producing acid as a byproduct of this process.

Staphylococcus aureus appears as Gram-positive cocci arranged in clusters, often seen in pus.

Staph. aureus produces hemolytic reactions on blood agar, indicating the ability to breakdown red blood cells.

Staph. aureus grows on nutrient agar, where it can be observed for its characteristic golden yellow pigmentation.

Total magnification is calculated by multiplying the objective lens magnification by the ocular lens magnification: 100 x 10 = 1000x, 10 x 10 = 100x, 40 x 10 = 400x

A Gram stain is used to differentiate bacteria based on their cell wall structure, classifying them as either Gram-positive or Gram-negative bacteria

The catalase test helps differentiate bacteria by determining if they produce the enzyme catalase which breaks down hydrogen peroxide.

The coagulase test identifies if a bacterium produces the enzyme coagulase which causes the clotting of blood plasma.

Mannitol salt agar is a selective and differential medium used to identify Staph. aureus, as it ferments mannitol, producing a yellow color change in the medium.

Some streptococci produce CAMP factor, a protein that enhances the hemolytic activity of other bacteria. This is used to differentiate between streptococcal species.

Streptococcus pyogenes does not produce CAMP factor, which can be helpful in identifying it.

Streptococcus agalactiae (Group B Strep) produces CAMP factor, leading to an enhanced hemolytic zone on blood agar.

Pneumococcus (Streptococcus pneumoniae) is catalase-negative, meaning it does not produce the enzyme catalase to break down hydrogen peroxide.

Microscopy of a Gram-stained smear reveals gram-positive diplococci, often encapsulated, within pus samples. This is a valuable tool for identifying pneumococcal infections.

Alpha-hemolysis is a type of hemolysis where bacteria partially break down red blood cells, resulting in a greenish discoloration around colonies on blood agar.

Enterococcus faecalis grows on blood agar and produces non-hemolytic colonies, meaning they do not break down red blood cells.

Enterococcus faecalis grows on MacConkey agar and produces pinpoint rose pink colonies.

Enterococcus faecalis hydrolyzes esculin on bile esculin agar, producing black colonies.

The PYR hydrolysis test is a biochemical test used to identify bacteria that produce the enzyme pyrrolidonyl arylamidase (PYR). Enterococci and Group A streptococci are positive for this test. Adding a reagent produces a dark pink color in the area where the bacteria was rubbed.

Enterococcus faecalis is catalase-negative. This means it does not produce the enzyme catalase, which breaks down hydrogen peroxide.

Enterococcus faecalis is non-hemolytic. This means it does not produce any hemolysis (breakdown of red blood cells) on blood agar and forms white, round colonies.

The bile solubility test is used to differentiate Streptococcus pneumoniae from other alpha-hemolytic streptococci. It assesses the bacteria's sensitivity to bile salts (sodium deoxycholate). When Streptococcus pneumoniae is exposed to bile salts, its cell wall is disrupted, causing the bacteria to lyse (break apart).

Optochin sensitivity is a test that differentiates Streptococcus pneumoniae from other alpha-hemolytic streptococci. It assesses the bacteria's sensitivity to optochin, a chemical that inhibits the growth of Streptococcus pneumoniae. If a zone of inhibition surrounds the optochin disk, the bacteria is sensitive to this substance.

Mycobacteria are thin, straight or curved rods. They are acid-fast and alcohol-fast, meaning they resist decolorization by acids and alcohol, due to the presence of mycolic acids in their cell wall. This characteristic is revealed by the Ziehl-Neelsen stain. They appear as thin, pink rods, single or in small groups.

Mycobacterium tuberculosis grows only on selective media like Lowenstein-Jensen medium. It is an obligate aerobe, requiring oxygen for growth, and has a slow growth rate of 2-8 weeks.

Sputum, not saliva, is the preferred specimen for Mycobacterium tuberculosis culture. Collect 3 morning sputum samples on consecutive days for best results.

Direct smears from sputum stained with Ziehl-Neelsen stain are used to identify Mycobacterium tuberculosis under a microscope. Acid-fast bacteria will appear pink against a blue background.

Decontaminated and concentrated sputum is cultured on Lowenstein-Jensen (LJ) medium and incubated at 35-37°C. Colony growth can take up to 8 weeks.

PCR (polymerase chain reaction) can rapidly detect Mycobacterium tuberculosis DNA in patient specimens, providing a quick diagnosis.

Tuberculin skin test (PPD) and Interferon-Gamma Release Assays (IGRA) are indirect methods to assess exposure to or infection with Mycobacterium tuberculosis.

For intestinal TB, stool is examined like sputum. For urinary TB, 24-hour urine is collected and examined like sputum.

Clostridium perfringens is the bacterium responsible for gas gangrene, a severe infection characterized by tissue death and gas production.

Clostridium perfringens produces a double zone of beta-hemolysis (clear zone) around its colonies on blood agar, due to its toxin that destroys red blood cells.

Tetanus is a serious disease caused by the bacterium Clostridium tetani, which produces a toxin that affects the nervous system, leading to muscle spasms.

Clostridium tetani is characterized by its spores - thick, resistant structures that are located at the ends of the bacterial cells.

These are growth factors required by Haemophilus influenzae to grow. X factor is hemin (a precursor to heme) and V factor is NAD (nicotinamide adenine dinucleotide).

Haemophilus influenzae is a common cause of bacterial meningitis, particularly in children.

Haemophilus influenzae is a small, pleomorphic, gram-negative, coccobacillus bacterium.

Direct tests include the use of specific antisera for capsule typing and the use of specific biochemical tests like the oxidase test, which is positive for Haemophilus influenzae.

Haemophilus influenzae requires blood agar for growth. It forms small, translucent, pinpoint colonies.

Actinomyces israelii is an anaerobic, filamentous, gram-positive bacterium characterized by its "stormy clot reaction" in litmus milk medium.

Listeria monocytogenes is a small, short, gram-positive rod. Diphtheroids are often larger, gram-positive rods with club-shaped ends.

Listeria monocytogenes exhibits a narrow zone of beta-hemolysis, while diphtheroids can exhibit alpha-hemolysis or no hemolysis.