Lecture 13 Haemophilus, Bordetella, Mycoplasma, Legionella

Question 1

What is Haemophilus influenzae?

Answer 1

Gram-negative coccobacillus, oxidase positive, facultative anaerobe, and non-motile. Frequently encapsulated (types a-f).

Question 2

What are some susceptible hosts of H influenzae?

Answer 2

-High rate of healthy pediatric and adult carriers
-primarily pediatric pathogen,
initial protection by maternal antibody,
-peak incidence of infection 6 mo-18 mo of age

Question 3

What are some virulence factors of H influenzae?

Answer 3

• pili and fimbriae for attachment
• capsule is antiphagocytic (Type b)
• IgA proteases
• can cross epithelial barrier, giving it capcity for vascular invasion.

Question 4

How is H influenzae transmitted?

Answer 4

-transmission from person to person by respiratory droplets and direct contact with resp. secretions

Question 5

How is H influenzae treated in pediatrics?

Answer 5

-vaccine: protein-linked PRP (invoke T cells!), very effective (given @ 2 months old)

Question 6

What are some risk factors of H influenzae infection?

Answer 6

• complement deficiency, hypogammaglobulinemia, sickle cell anemia, functional asplenia, malignancy, HIV
• In adults, chronic pulmonary disease, smoking, HIV alcoholism, pregnancy, malignancy
• Socioeconomic factors: crowding, poor immunization, daycare attendance

Question 7

What is non-typeable H influenzae?

Answer 7

• non-capsulated strains that are common constituents of nasopharyngeal microbiota
• cause localized disease: upper and lower respiratory tract infection, otitis media more
• severe disease in immunocompromised

Question 8

How does H influenzae cause Otitis Media/sinusitis?

Answer 8

-likely displacement of normal microbiota by pathogen, strains involved are frequently non-typeable

Question 9

What is Epiglottitis (H influenzae)?

Answer 9

• fever, sore throat, barking cough
• Rapid progression (24 h)
• dx by lateral neck X-ray or blood cx

Question 10

How can H Influenzae cause Meningitis?

Answer 10

• previous respiratory infection or various vague symptoms prior to onset
• likely route = respiratory tract, gets into blood, gets into CNS
• significant mortality even with antibiotic therapy, 1/3 survivors have neurological problems

Question 11

What diseases can also occur with URI by H influenzae?

Answer 11

Cellulitis/arthritis

Question 12

How is H Influenzae diagnosed?

Answer 12

culture and identify organism:

• Requires X factor (hemin)
• V factor (NAD) for growth
• CO2 –enriched atmosphere
• can grow on chocolate agar

Question 13

What is Haemophilus ducreyii?

Answer 13

• coccobacillus, often irregularly shaped with central indentation
• Common sexually STD in developing countries
• Enhances HIV transmission.

Question 14

What are effect of Haemophilus ducreyii?

Answer 14

Chancroid - soft chancre, painful

• satellite lesions
• painful, unilateral lymphadenopathy common

Question 15

How is H ducreyii diagnosed?

Answer 15

• gram stain from
• culture possible on chocolate + vancomycin (33°C, 5% CO2)
• Must rule out syphilis by dark field and serology

Question 16

What is Bordetella perussis?

Answer 16

• Gram-negative coccobacillus

- specifically colonizes and destroys ciliated respiratory epithelium of large airways

Question 17

What are some virulence factors of Bordetella perussis?

Answer 17

• Filamentous hemagluttinin (FHA) and pili for attachment
• Tracheal Cytotoxin (TCT)
• Pertussis toxin (PT)
• Adenylate cyclase toxin (ACT)
• FHA, PT, ACT expression controlled by two-component regulatory system
• spread via aerosolized droplets

Question 18

What is TCT?

Answer 18

toxic PG-fragment destroys ciliated cells via NO and IL-1 pathway

Question 19

What is PT?

Answer 19

AB subunit toxin, ADP-ribosylates G protein leading to increased host cell cAMP -> alters lymphocyte homing and function -> lymphocytosis (high lymphocyte counts)

Question 20

What is ACT?

Answer 20

catalyzes ATP->cAMP also hemolysin

Question 21

What is whopping cough or pertussis?

Answer 21

• Disease of Bordetella pertussis
• severe disease for children (95%)
• asymptomatic carriage by adolescents and adults
• frequent cause of persistent (>2 wks) cough among adults

Question 22

What are ways to treat Whooping cough?

Answer 22

• immunization: “P” part of DTaP (aP=acellular pertussis); administered at 2, 4, 6, 15-18 months; 4-6 yrs old)

Question 23

What are some complication to whooping cough?

Answer 23

• pneumonia,
• death secondary to dehydration, -malnourishment,
• brain damage secondary to anoxia

Question 24

What is the dx of Bordetella pertussis?

Answer 24

• clinical symptoms,
• lymphocytosis
• culture is optimal in 5% CO2, on selective media
• PCR: nasal swab

Question 25

What is mycoplasma pneumoniae?

Answer 25

- smallest free-living bacterium - pleomorphic filaments - no cell wall, cell membrane contains sterols -strict aerobe

Question 26

What diseases can M. pneumoniae cause?

Answer 26

Tracheobronchitis and pneumonia

Question 27

What group is susceptible to Tracheobronchitis and pneumonia?

Answer 27

- predominantly children/adolescents - military recruits - college students

Question 28

What is the mechanism of infection for M. pneuomoniae in causing tracheobronchitis and pneumonia?

Answer 28

- adhesin protein P1, necessary for attachment to ciliated respiratory epithelium - attaches to host glycolipid or glycoprotein on respiratory epithelial cells - destruction of ciliated respiratory epithelium, mucociliary escalator

Question 29

How large is M. pneumonaie genome?

Answer 29

- Just know small compared to H. influenza and E. Coli | - small genome: 689 encoded proteins

Question 30

What is the attack rate of M. pneumonaie in the respiratory tract?

Answer 30

- 90% cases upper respiratory tract: low fever, headache, malaise, non-productive cough - 10% cases lower respiratory tract: - tracheobronchitis - atypical pneumonia - secondary infection/superinfection

Question 31

How do you dx M. pneumonaie?

Answer 31

- culture (slow and insensitive) - PCR (rapid and sensitive) - Serology: lack of specificity

Question 32

What is Legionella pneumophila?

Answer 32

- pleomorphic GNR stains poorly with Gram stain - Environmental bacterium - facultative - intracellular pathogen (amoeba) - interaction with macrophage essential - virulence gene expression -> macrophage death - transmitted via contaminated aerosols - no documented human to human spread

Question 33

What is legionnaires disease?

Answer 33

- headache, myalgia, rising fever, cough without much sputum, severe necrotizing pneumonia, high mortality

Question 34

What is Legionnaires disease incidences dependent on?

Answer 34

depends on water contamination; exposure to contaminated water; susceptibility of host

Question 35

What are some risk factors to Legionnaires disease?

Answer 35

smoking and chronic lung disease; increasing age, hematopoietic transplantation, other forms of immunosuppression [glucocorticoid administration] but not patients with neutropenia, acute leukemia or HIV.

Question 36

What is pontiac fever?

Answer 36

- (Legionnella) acute febrile illness without pneumonia | - attack rate 90% (healthy and immunocompromised)

Question 37

How is legionella pneumonia diagnosed?

Answer 37

- direct fluorescent antibody staining (DFA) - Gram stain (often fails - culture: often negative

Question 38

How is legionella treated?

Answer 38

erythromycin .