Micro 12 | Gram-Negative Bacteria IV

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32 Terms

1

What is Neisseria gonorrhoeae?

A kidney bean-shaped, Gram-negative diplococci, and does not have a capsule.

<p>A <strong>kidney bean-shaped, Gram-negative diplococci</strong>, and <strong>does not have a capsule</strong>.</p>
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2

How is Neisseria gonorrhoeae transmitted?

It is sexually transmitted and can also be passed from mother to baby at birth (perinatal transmission).

<p>It is <strong>sexually transmitted</strong> and can also be <strong>passed from mother to baby at birth (perinatal transmission)</strong>.</p>
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3

How can Neisseria gonorrhoeae be identified in the lab?

It is Gram-negative, oxidase-positive, and catalase-positive, ferments glucose (but not lactose or maltose), and is cultured on chocolate agar, Thayer-Martin, or Martin-Lewis agar in a CO₂ environment.

<p>It is <strong>Gram-negative, oxidase-positive, and catalase-positive</strong>, <strong>ferments <u>glucose</u></strong><u> </u>(but <strong>not lactose or maltose</strong>), and is cultured on <strong>chocolate agar, Thayer-Martin, or Martin-Lewis agar</strong> in a <strong>CO₂ environment</strong>.</p>
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4

How to diagnose Neisseria gonorrhoeae?

  • Thayer-Martin agar (selective media in CO₂) or Martin-Lewis Agar (enriched and selective media)

  • Nucleic acid amplification test (NAAT) is the best diagnostic method.

<ul><li><p><strong>Thayer-Martin agar</strong> (selective media in CO₂) or <strong>Martin-Lewis Agar </strong>(enriched and selective media)</p></li><li><p><strong>Nucleic acid amplification test (NAAT)</strong> is the best diagnostic method.</p></li></ul><p></p>
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5
<p>What are the <strong>virulence factors </strong>for <strong><em>N. gonorrhoeae?</em></strong></p>

What are the virulence factors for N. gonorrhoeae?

  • Intracellular infection in polymorphonuclear leukocytes (PMNs).

  • LOS (lipo-oligosaccharide) acts as an endotoxin.

  • Pilin proteins help with attachment but interfere with immune response.

  • IgA protease breaks down IgA, reducing mucosal immunity.

  • Antigenic variation in pili allows immune evasion.

<ul><li><p><strong>Intracellular infection</strong> in polymorphonuclear leukocytes (PMNs).</p></li><li><p><strong>LOS (lipo-oligosaccharide)</strong> acts as an endotoxin.</p></li><li><p><strong>Pilin proteins</strong> help with attachment but interfere with immune response.</p></li><li><p><strong>IgA protease</strong> breaks down IgA, reducing mucosal immunity.</p></li><li><p><strong>Antigenic variation</strong> in pili allows immune evasion.</p></li></ul><p></p>
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6

What is the main symptom of gonorrhea?

Creamy and purulent (pus-like) discharge from the urethra.

  • Primary site in women: cervix

  • Primary site in men: urethra

<p><strong>Creamy and purulent (pus-like) discharge from the urethra.</strong></p><ul><li><p>Primary site in women: cervix</p></li><li><p>Primary site in men: urethra</p></li></ul><p></p>
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7

What are other diseases that can arise from gonorrhea?

  • Disseminated gonococcal infection: Can cause arthritis and septicemia (bacteria in the blood).

  • Purulent conjunctivitis: Affects newborns, transmitted during birth or in utero.

  • Fitz-Hugh Curtis syndrome: Inflammation of the liver capsule (perihepatitis) with fibrosis and adhesions, often due to pelvic inflammatory disease

<ul><li><p><strong>Disseminated gonococcal infection</strong>: Can cause <strong>arthritis and septicemia</strong> (bacteria in the blood).</p></li><li><p><strong>Purulent conjunctivitis</strong>: Affects newborns, transmitted during birth or in utero.</p></li><li><p><strong>Fitz-Hugh Curtis syndrome</strong>: <strong>Inflammation of the liver capsule</strong> (perihepatitis) with <strong>fibrosis and adhesions</strong>, often due to pelvic inflammatory disease</p></li></ul><p></p>
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8

Why is there no vaccine for gonorrhea?

The pilus protein of the bacteria undergoes frequent antigenic variation, making it difficult for the immune system to develop lasting protection.

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9

What type of bacteria is Neisseria meningitidis?

An encapsulated, Gram-negative diplococcus, oxidase positive, and catalase positive.

<p>An <strong>encapsulated, Gram-negative diplococcus</strong>, <strong>oxidase positive</strong>, and <strong>catalase positive</strong>.</p>
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10

What is the second most common cause of bacterial meningitis in all age groups except neonates?

Neisseria meningitidis

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11

How is Neisseria meningitidis transmitted?

It spreads person-to-person through respiratory droplets and oral secretions, especially in crowded environments like dorms, military barracks, and family households.

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12

Who is at high risk for Neisseria meningitidis infection?

Travelers to the "meningitis belt" in sub-Saharan Africa.

<p> Travelers to the<strong> "meningitis belt"</strong> in sub-Saharan Africa.</p>
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13

What sugars does Neisseria meningitidis oxidize?

It oxidizes glucose and maltose, but not lactose. Oxidase-positive

<p>It <strong>oxidizes glucose and maltose</strong>, but <strong>not lactose</strong>. <em>Oxidase-positive</em></p>
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14

What culture media are used to grow Neisseria meningitidis?

It grows on chocolate agar (enriched, non-selective) and Martin-Lewis agar (selective).

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15

What is the preferred method for diagnosing Neisseria meningitidis?

NAAT (Nucleic Acid Amplification Test)

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16

Virulence factors for N. meningitidis?

  • Polysaccharide capsule – Prevents phagocytosis and is used for serotyping. Major role in disease causation.

  • Pili proteins – Aid in attachment, facilitating disease spread.

  • LOS (lipo-oligosaccharide) – Acts as an endotoxin, causing endotoxemia. LOS endotoxin increases vascular permeability

  • IgA protease – Degrades IgA, helping the bacteria evade mucosal immunity.

<ul><li><p><strong>Polysaccharide capsule</strong> – Prevents phagocytosis and is used for <strong>serotyping</strong>. <em>Major role in disease causation.</em></p></li><li><p><strong>Pili proteins</strong> – Aid in attachment, facilitating disease spread.</p></li><li><p><strong>LOS (lipo-oligosaccharide)</strong> – Acts as an endotoxin, causing endotoxemia. LOS endotoxin increases vascular permeability</p></li><li><p><strong>IgA protease</strong> – Degrades IgA, helping the bacteria evade mucosal immunity.</p></li></ul><p></p>
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17

How is Neisseria meningitidis prevented?

Prevention is through vaccination, which targets the polysaccharide capsule of the bacteria

<p>Prevention is through <strong>vaccination</strong>, which targets the <strong>polysaccharide capsule</strong> of the bacteria</p>
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18

How does LOS endotoxin act as a virulence factor?

LOS endotoxin damages blood vessels by making them more leaky, leading to inflammation, swelling, and severe complications like septic shock.

<p>LOS endotoxin <strong>damages blood vessels by making them more leaky</strong>, leading to inflammation, swelling, and severe complications like septic shock.</p>
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19

What are the main diseases caused by N. meningitidis?

Meningitis and meningococcemia

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20

Characteristics of meningitis caused by N. meningitidis?

Progresses rapidly with symptoms like headache, fever, and vomiting (especially in young children).

<p><strong>Progresses rapidly </strong>with symptoms like headache, fever, and vomiting (especially in young children).</p>
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21

Characteristics of Meningococcemia caused by N. meningitidis?

A severe bloodstream infection resulting from LOS endotoxin and cytokine release, leading to blood vessel damage, excessive clotting, and widespread inflammation.

<p>A severe bloodstream infection resulting from <strong>LOS endotoxin</strong> and <strong>cytokine release</strong>, leading to <strong>blood vessel damage, excessive clotting, and widespread inflammation</strong>.</p>
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22

What complications can arise from Meningococcemia?

Waterhouse-Friderichsen syndrome, which causes septic shock, acute hypotension, tachycardia, and disseminated intravascular coagulation.

<p><strong>Waterhouse-Friderichsen syndrome</strong>, which causes <strong>septic shock, acute hypotension, tachycardia, and disseminated intravascular coagulation.</strong></p>
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23
<p>What is <strong><em>Yersinia pestis?</em></strong></p>

What is Yersinia pestis?

a Gram-negative coccobacillus that is oxidase-negative and has a protein-containing capsule. It is a zoonotic pathogen, with humans as accidental hosts.

<p>a <strong>Gram-negative coccobacillus</strong> that is <strong>oxidase-negative</strong> and has a <strong>protein-containing capsule</strong>. It is a <strong>zoonotic pathogen</strong>, with humans as <strong>accidental hosts</strong>. </p>
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24

How is Yersinia pestis transmitted?

Primarily through flea bites.

<p>Primarily through <strong>flea bites</strong>.</p>
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25

What are Yersinia pestis-associated diseases?

  • Bubonic plague – Most common form; spreads via flea bites or cutaneous exposure. Causes fever, chills, headache, weakness, and painful swollen lymph nodes (buboes).

  • Pneumonic plagueMost severe form, the only type that spreads person-to-person via inhaled droplets. Leads to rapidly progressing pneumonia, fever, and weakness.

  • Septicemic plague – Can result from flea bites or infected tissue handling. Symptoms include fever, shock, abdominal pain, and tissue necrosis (blackened fingers, toes, nose).

<ul><li><p><strong>Bubonic plague</strong> – Most common form; spreads via <strong>flea bites</strong> or <strong>cutaneous exposure</strong>. Causes <strong>fever, chills, headache, weakness</strong>, and <strong>painful swollen lymph nodes (buboes)</strong>.</p></li><li><p><strong>Pneumonic plague</strong> – <strong>Most severe form</strong>, the only type that spreads <strong>person-to-person</strong> via <strong>inhaled droplets</strong>. Leads to <strong>rapidly progressing pneumonia, fever, and weakness</strong>.</p></li><li><p><strong>Septicemic plague</strong> – Can result from <strong>flea bites</strong> or <strong>infected tissue handling</strong>. Symptoms include <strong>fever, shock, abdominal pain, and tissue necrosis</strong> (blackened fingers, toes, nose).</p><p></p></li></ul><p></p>
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26

What are Bartonella species?

Bartonella species are Gram-negative coccobacilli that grow slowly (taking 2–6 weeks). They cause diseases like cat scratch disease (Bartonella henselae), trench fever (Bartonella quintana), and Carrion’s disease (Bartonella bacilliformis).

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27

Transmission of Bartonella species?

Zoonotic, spread through direct contact with infected animals or arthropod vectors.

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28

Which bacteria cause endothelial cell proliferation, leading to bacillary angiomatosis?

Bartonella henselae is the only bacteria known to cause this condition.

<p><strong>Bartonella henselae</strong> is the only bacteria known to cause this condition.</p>
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29

Bartonella henslae causes which two diseases?

  • Cat-scratch fever – Mild in healthy people, often in children, causing swollen lymph nodes near the scratch or bite. Can spread to organs in rare cases.

  • Bacillary angiomatosis – Affects immunocompromised patients, causing abnormal blood vessel growth in skin, lymph nodes, liver, and spleen.

<ul><li><p><strong>Cat-scratch fever</strong> – Mild in healthy people, often in children, causing swollen lymph nodes near the scratch or bite. Can spread to organs in rare cases.</p></li><li><p><strong>Bacillary angiomatosis</strong> – Affects <strong>immunocompromised</strong> patients, causing abnormal blood vessel growth in skin, lymph nodes, liver, and spleen.</p></li></ul><p></p>
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30

What is Brucella species?

Gram-negative bacteria that cause brucellosis, an infection that spreads from animals to humans. People get infected by eating contaminated dairy products, handling infected animals, or inhaling the bacteria.

<p><strong>Gram-negative bacteria</strong> that cause <strong>brucellosis</strong>, an infection that spreads from animals to humans. People get infected by <strong>eating contaminated dairy products, handling infected animals, or inhaling the bacteria</strong>.</p>
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31

Virulence factors of Brucella species?

  • Intracellular infection – Hides inside immune cells to spread and avoid immune detection.

  • LPS (O Ag component)– Helps protect against immune response.

  • Immunosuppressive effects – Reduces MHC II expression, blocks cytokine production, and prevents infected cells from undergoing apoptosis, weakening immune defenses.

<ul><li><p><strong>Intracellular infection</strong> – Hides inside immune cells to spread and avoid immune detection.</p></li><li><p><strong>LPS (O Ag component)</strong>– Helps protect against immune response.</p></li><li><p><strong>Immunosuppressive effects</strong> – Reduces <strong>MHC II expression</strong>, blocks <strong>cytokine production</strong>, and prevents infected cells from undergoing apoptosis, weakening immune defenses.</p></li></ul><p></p>
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32

How is Brucellosis transmitted?

  • Contaminated food (especially unpasteurized dairy).

  • Inhalation of infected animal tissues (e.g., slaughterhouse exposure).

  • Rarely, person-to-person transmission.

<ul><li><p><strong>Contaminated food</strong> (especially unpasteurized dairy).</p></li><li><p><strong>Inhalation of infected animal tissues</strong> (e.g., slaughterhouse exposure).</p></li><li><p><strong>Rarely, person-to-person transmission</strong>.</p></li></ul><p></p>
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