MICR5832 L13: LRT Infections 1/17/26

List all Gram Positive LRT bacteria

1) S. pneumoniae (diplococci)

2) H. influenzae (coccobacilli)

3) M. catarrhalis (diplococci)

List all Gram Negative LRT bacteria

1) Chlamydia pneumoniae (reticulate/elementary)

2) Legionella pneumophila (bacilli)

Is Bordetella pertussis Gram Positive or Gram Negative?

Gram Negative

Does Bordetella pertussis produce bacilli or cocci?

Coccobacilli

What is this?

-Small shiny "mercury drop" colonies

-Forms on charcoal agar or potato/glycerol

-Weakly stains Gram Negative coccobacilli

Bordetella pertussis

What are the symptoms of Bordetella pertussis/Whooping Cough?

-Dry cough, fever, runny nose, sneezing

-Coughing has characteristic "whoop" sound

True or False: Only humans can host Bordetella pertussis

True

How is Whooping Cough transmitted and controlled?

-Transmitted by aerosols

-Controlled by vaccination (DTaP)

What Adhesins does Bordetella pertussis use when it attaches to epithelial cells and colonizes the RT?

1) Pili (fimbriae)

2) Autotransporter proteins

3) Filamentous hemagglutinin

What types of Autotransporter proteins does Bordetella pertussis use on the bacterial surface?

1) Pertactin

2) Tracheal colonization factor

3) BrkA (inhibits complement)

What toxins does Bordetella pertussis produce?

1) Pertussis toxin

2) Adenylate cyclase toxin

3) Tracheal cytotoxin

4) Dermonecrotic toxin

What is the purpose of these toxins?

1) Pertussis toxin

2) Adenylate cyclase toxin

3) Tracheal cytotoxin

1) Toxic to cells in vitro, colonization, immune evasion

2) Immune evasion

3) Toxic to ciliated epithelia of trachea

What components of Bordetella pertussis are used in the Whooping Cough vaccine?

1) Pertactin autotransporter protein

2) Filamentous hemagglutinin

3) Pertussis toxin

How would you transport Bordetella pertussis swabs?

-Half strength Regan Lowe agar

-Contains starch, horse blood, charcoal agar and cephalexin

How do the charcoal agar and cephalexin in Regan Lowe agar support Bordetella pertussis?

-Charcoal enhances fastidious organisms

-Cephalexin suppresses normal flora growth

How can you lab diagnose Bordetella pertussis?

1) Immunofluorescence assays

2) PCR

3) MALDI-TOF

4) Microscopy

5) Culture

True or False: Culture has a higher sensitivity than every other testing method

True, second best is MALDI-TOF

What PCR targets would you use during Bordetella pertussis?

-Toxin promoter, porin gene (B. pertussis)

-IS1001 insertion element (B. parapertussis)

What culture would you use for Bordetella pertussis?

-Regan Lowe Agar (charcoal)

-Bordet-Gengou Agar (potato/glycerol)

How would you culture Bordetella pertussis?

-37C, humified and no CO2 for 12 days

-Regan-Lowe Agar or Bordet-Gengou Agar

You are trying to use agglutinating antiserum to differentiate between B. pertussis and B. parapertussis suspensions.

Which one is oxidase positive?

Bordetella pertussis

You are trying to use agglutinating antiserum to differentiate between B. pertussis and B. parapertussis suspensions.

Which one is oxidase negative?

Bordetella parapertussis

How would you treat Bordetella pertussis?

-Macrolides

-Erythromycin, clarithromycin, azithromycin

What are some Macrolides you could use to treat Bordetella pertussis/Whooping Cough?

Erythromycin, clarithromycin, azithromycin

When is it recommended to get DTaP vaccination for Bordetella pertussis?

15-17 yrs

List some examples of LRT infections

1) Acute bronchitis, Bronchiolitis

2) Pneumonia

List some common community-acquired bacterial pathogens

1) S. pneumoniae

2) H. influenzae

3) Mycoplasma pneumoniae

4) Chlamydophila pneumoniae

5) Mycobacterium tuberculosis

6) Moxarella catarrhalis

7) Legionella pneumophila

What are some hospital-acquired/nosocomial sources of bacterial LRT pathogens?

-Gram Neg: Enterobacteriacaeae, Acinetobacter, Klebsiella

-Gram Pos: Staph aureus, Staphylococci, Enterococci

True or False: Coagulase positive Staphylococcus tends to be harmful

False

True or False: Coagulase negative Staphylococcus tends to be harmful

True

True or False: Acute bronchitis/bronchiolitis are mainly caused by bacterial infections

False

True or False: Acute bronchitis/bronchiolitis are mainly caused by viral infections extending into the LRT

True

What bacteria occasionally cause Acute Bronchitis/Bronchiolitis?

-B. pertussis

-Mycoplasma pneumoniae

-Chlamydophila pneumoniae

What are some hospital-acquired/nosocomial sources of Pneumonia?

-Ventilation

-Nursing homes/facilities

-Invasive procedures

What are some LRT specimens to collect?

1) Sputum

2) Bronchial washings

3) Bronchial brushing

4) Broncho-alveolar lavage

5) Trans-tracheal aspirate

Why does Sputum need to be treated with a dithiotreitol like Sputasol?

Mucolytic agent releases bacteria from mucus

How do bronchial washings work?

-Small volume sterile saline introduced & then aspirated by bronchoscope

-Little/no normal flora contamination

How do bronchial brushings work?

-Brush attachment samples bronchial epithelium

-Recovered & material suspended in sterile saline

-Microscopy & culture

How do broncho-alveolar lavage work?

-Large volume of sterile saline (100-300ml)

-Infused into lung and aspirated

How do trans-tracheal aspirate work?

-Insertion of catheter into trachea through needle

-Uncomfortable; bleeding; non-compliant patients; rarely used

What bacteria require special media?

-Mycoplasma tuberculosis

-Mycoplasma pneumoniae

What media would you use for these Gram Positive pathogens?

-S. pneumoniae

-H. influenzae

-M. catarrhalis

BA or BCA

What media would you use for these Gram Negative bacilli?

-Enterobacteriaceae

-Pseudomonas

-Acinetobacter

MAC

What vaccines targeting the extracellular polysaccharide are there for Streptococcus pneumoniae?

-13 valent conjugate vax for children

-23 valent vaccine for older people

What is this?

-Gram Positive diplococci

-Alpha hemolytic, catalase negative

-Optochin sensitive

Streptococcus pneumoniae

Is Streptococcus pneumoniae Alpha or Beta hemolytic?

Alpha hemolytic

What antibiotics are effective against Streptococcus pneumoniae?

Optochin

How can you identify Streptococcus pneumoniae without any fancy kits?

1) Gram stain is Positive

2) Catalase test is Negative

3) Alpha hemolytic

4) Sensitive to Optochin

5) Soluble in bile

6) Latex agglutination test

How does Streptococcus pneumoniae react to bile salt solution?

-Lyses cells

-Dissolves colonies

What does it mean if you use bile salt solution on some alpha-hemolytic Streptococcus but it doesn't dissolve?

It is not Streptococcus pneumoniae but an oral strep

What does the Streptococcus pneumoniae latex agglutination test recognize?

Capsule polysaccharide

What antibiotic would you use to treat Streptococcus pneumoniae?

Penicillin

True or False: MIC tests are preferred over disc diffusion tests for determining Beta lactams sensitivity

True

What is this?

-Gram Negative coccobacilli

-Cannot grow on BA, requires BCA with X and V factors

-Found in low numbers in oropharynx of healthy humans

Hemophilus influenzae

When is Hemophilus influenzae considered pathogenic?

-Dominates all other Gram Negatives

-Leukocytes found in sputum

True or False: Having difficulty clearing airways increases the risk of endogenous opportunistic infections

True

What is this?

-Gram Negative cocci, oxidase positive

-Does not grow on MAC, friable colonies on BA

-Associated with COAD and COPD

-Leukocytes found in sputum

Moxarella cattarhalis

This Gram Negative cocci causes oitis media, sinusitis, bronchitis, and pneumonia.

How can you identify it as Moxarella?

1) Biochemical strip of RapID

2) Oxidase test positive result

True or False: Moxarella catarhalis is an opportunistic pathogen normally found in the respiratory tract

True

How would you treat Moxarella?

Non-beta lactams

Is this an LRT or URT caused by Mycoplasma pneumoniae?

-Mild, runny nose, inflammation of nasal epithelium, cough, no fever

URT

Is this an LRT or URT caused by Mycoplasma pneumoniae?

-Mild, non-productive cough, fever, mailaise, myalgia

-Walking pneumonia

-Insidious onset

LRT

True or False: Mycoplasma pneumoniae has no cell wall and is not visible via Gram stain

True

How would you culture Mycoplasma pneumoniae?

-SP4 Broth and Agar at 37C, 5% CO2 for 4 weeks

-Directly inoculate agar

-Inoculate biphasic medium (agar/broth)

-Subculture on agar if evidence of growth after 7 days

What medium would you use to culture Mycoplasma pneumoniae?

SP-4 Agar and Broth

What does SP-4 Agar contain to suppress normal flora and support Mycoplasma pneumoniae?

-Penicillin

-Amphotericin B

-Polymyxin

What is some evidence that Mycoplasma pneumoniae is successfully growing and can be subcultured onto agar?

pH changes orange colonies to yellow

How can you identify Mycoplasma pneumoniae?

1) Hemadsorption with guinea pig RBCs

2) Enzyme immunoassay

3) ELISA test for antibodies to cell extract

4) PCR

5) Rapid antigen test

What is a sign that the Mycoplasma pneumoniae in a plate of phosphate buffer has been correctly identified?

Guinea pig RBCs adhere to plate

What indicates a positive Serology test for M. pneumoniae?

4x rise in antibody

What Rapid Antigen Test can you use to identify Mycoplasma pneumoniae that is only slightly less sensitive than PCR?

Colloidal gold chromatographic strip

What antibiotics would you use to treat Mycoplasma pneumoniae?

-Macrolides (erythromycin, clarithromycin)

-Tetracycline

-Fluoroquinolones (ciprofloxacin)

True or False: Most labs conduct antibiotic susceptibility testing before treating Mycoplasma pneumoniae

False

True or False: Mycoplasma pneumoniae is mostly treated empirically

True

Why is it so difficult to get a reliable diagnosis for Mycoplasma pneumoniae?

-Culture is insensitive, takes too long (4 weeks)

-Not Gram stainable

-Requires special SP-4 broth and agar

What is this?

-Obligate intracellular, either reticulate or elementary body

-Can only be cultured in cell lines

-Associated with pneumonia, bronchitis, pharyngitis, sinusitis, flu-like illness

Chlamydophila pneumoniae

True or False: Most Chlamydophila pneumoniae infections are asymptomatic or mildly asymptomatic due to most adults having antibodies

True

True or False: The reticulate body of Chlamydia is intracellular and the elementary body is extracellular

True

True or False: Chlamydia can only be cultured using Hep-2 cell lines

True

True or False: Chlamydia is associated with coronary artery disease and can be found in atherosclerotic plaques

True

How would you diagnose Chlamydophila pneumoniae using Serology?

1) Microimmunofluorescence technique for antibodies to C. pneumonieae

2) Commercially available ELISAs to measure IgG & IgM antibodies to C. pneuтoniae

3) Rise in antibody titre in paired sera indicates recent infection

How would you culture Chlamydophila pneumophila?

-Hep-2 cell line

-Immunofluorescence with antibodies specific for C. pneumoniae

-Too laborious and time-consuming to do regularly

What antibiotics would you use to treat Chlamydophila pneumophila empirically?

-Tetracycline

-Erythromycin

What is this?

-Gram Negative, aerobic, catalase positive (+), oxidase negative (-)

-Flagellated bacteria found inside amoeba in warm water/moisture

-Fever, headache, myalgia and diarrhea, respiratory distress

Legionella pneumophila

How does Legionella pneumophila transmitted?

-Air conditioners cause water droplet inhalation

-Invades and replicates inside macrophages

True or False: Legionnaire's disease is not contagious

True, no person to person spread

How would you culture Legionella pneumophila?

-BCYE agar with charcoal, yeast extract, glycin, polymyxin, cycloheximide and vancomycin

-Needs cystine and iron, VERY slow growing

What medium would you use to culture Legionella pneumophila?

BCYE Agar

Why can't Legionella pneumophila grow on BA?

Needs cystine and iron

What is a disadvantage of using a Rapid Urinary Antigen Test for Legionella pneumophila?

Only detects one serogroup (LP1)

What antibiotics would you use to treat Legionella pneumophila?

-Macrolides: Azithromycin, erythromycin

-Fluroquinolones: Ciprofloxacin, Levofloxacin, Moxifloxacin

-Tetracyclines: Doxycycline

Why can't you use Penicillin to treat Legionnaire's Disease?

Legionella pneumophila has Beta lactamases

True or False: Pontiac's fever usually resolves without treatment

True

Why is epiglottitis so dangerous and what is the main causative organism?

-Very narrow, obstructs the airway when swollen

-Hemophilus influenzae type B (Hib)

What are the key tests for identifying Streptococcus pneumoniae?

-Must be Gram Positive, catalase negative

-Colonies must grow on BA and SSA Agar

-Alpha hemolysis, not beta

-No growth with optochin disc

-Soluble in bile

What chronic conditions is Moraxella cattarhalis associated with?

COAD or COPD

Which of these bacteria cannot be treated with Beta lactams like Penicillin?

1) Moxarella catarrhalis

2) Mycoplasma pneumoniae

3) Legionella pneumophila