Bacterial Pathogens 1

Question 1

Where does Haemophilus Influenzae colonise?

Answer 1

it colonises the upper respiratory/gastrointestinal/ genital tract

Question 2

what does Haemophilus Influenzae cause?

Answer 2

it causes respiratory infections, meningitis, blood stream infections

Question 3

what are the laboratory features of haemophilus species?

Answer 3

They are pleomorphic Gram-negative bacilli/coccobacilli

they are picky - need very particular growth requirements

require X factor (haemin) or V factor (NAD) to grow

*grow in chocolate agar

Question 4

what form of H. Influenzae is most virulent?

Answer 4

the capsulate version

Question 5

Non-capsulated strains of H. Influenzae is strongly associated with what type of infeciton?

Answer 5

it is associated with respiratory infections

• exacerbation of chronic bronchitis
• otitis media

Question 6

what is the most common serotype of H. Influenzae?

Answer 6

Tybe B (Hib)

(inhaled)

Question 7

what is the major virulence factor of capsulated H. Influenza?

Answer 7

anti-phagocytic polysaccharide capsule

“PRP (polyribosyl ribitol phosphate)”

Question 8

what type of clinical infections does the H. Influenzae Type B cause?

Answer 8

• early childhood: resp. tract infections (acute epiglotttis)
• meningitis
• sequelae of deafness, seizures, and intellectual impairment
• blood stream infections
• septic arthritis
• cellulitis (head and neck)

Question 9

Non-capsulated H. Influenzae are less virulent, but who do they commonly colonize?

Answer 9

patients with COPD, cystic fibrosis,

Question 10

Non-capsulatd H. influenzae can cause what?

Answer 10

• Respiratory infection
  
  • recurrent sinusitis
  • acute/chronic bronchitis
  • acute/chronic otitis media
  • community-acquired pneumonia

Question 11

what sort of antibiotic treatment should we use against H. Influenzae?

Answer 11

give a broad spectrum cephalosporin b/c only 20% are beta lactamase producers

Question 12

do we have a vaccine for H. Influenzae?

Answer 12

there is a vaccine for the capsulated form

there is NOT A vaccine for the non-encapsulated strain

Question 13

describe the laboratory characteristics of bordetella pertussis

Answer 13

• very small gram negative cocco-bacillus
• 3 serotypes
• strictly aerobic
• capsulated
• long term carriage thought not to occur, but can be carried asymptomatically
• highly infectious
• causes whooping cough
  *

Question 14

Describe the pathogenesis of B.Pertussis

Answer 14

Bronchioles become blocked with inflammatory cells, lymphocytes and mucous

obstruction leads to collapse of alveoli, resulting in diminished oxygenation of the blood

Question 15

what are the clinical stages of whooping cough?

Answer 15

100 day cough

catarrhal stage (1-2 weeks) - most infectious stage

• nonspecific symptoms: malaise, rhinorrhoea, and mild cough

paroxysmal stage (2-4 weeks)

• cough= severe, vigorous coughs and vigourous inhalation leading to ‘whooping’ sound
• post-cough vomit

covalescent stage (3-4 weeks)

• gradual reduction in the frequency and severity of cough
  *

Question 16

what is the CDCs estimate of percentage of cough illnesses in adults that are due to pertussis ?

Answer 16

• 10-20% of cough illnesses in adults lasting more than 14 days are due to pertussis

Question 17

what are the laboratory characteristics of B. Pertussis?

Answer 17

• culture - charcoal blood agar, antibiotics to inhibit normal flora, gram negative coccobacilli

Question 18

what is the quickest way to diagnose B. Pertussis?

Answer 18

do PCR on a swab or nasopharyngeal aspirate

Question 19

why is there a resurgence in adult pertussis infections?

Answer 19

b/c in the 70s there was hype about the pertussis vaccine causing encephalopathy… it was a whole cell suspention vaccine

they changed it to an acellular vaccine to reduce any symptoms after vaccintion

however this vaccine is significantly less local/systemic reactions than whole cell vaccine

Question 20

what does Leionella pneumophila cause?

Answer 20

causes pontiac fever and legionnaires disase (pneumonia)

Question 21

what are the characteristics of the legionella species?

Answer 21

non-capsulated gram-negative bacillus

possesses flagellae

strict aerobe

Question 22

what is the general source of L.Pneumophila in the environment?

Answer 22

water is the environmental reservoir -

isolated from water, air-conditioning units, shower heads, piped water supplies and taps

infection arises following inhalation of aerosols from contaminated water

Question 23

describe the pathogenesiss of legionella

Answer 23

1. inhalation of aerosol contaminated with legionella
2. attaches to resp. epithelial cells and alveolar macrophages
3. infects macrophages and monocytes - after phagocytosis survives by inhibiting phagosome lysosome fusion
4. person - to person transmission has not been documented

Question 24

what is the result of legionnaire’s disease?

Answer 24

• abrupt onset of fever, chills, dry cough, headache
• may get multi-ogan disease
  
  • GIT, CNS, liver, RENAL
• overall mortaility = 15-20%

Question 25

what is the most commonly used test to detect legionnaire’s disae?

Answer 25

Urinary antigen detection

• sensitivity serogroup 1 = does nOT detect other serogroups

rapid test

Question 26

what sort of treatment do we use in legionnaire’s disease?

Answer 26

• beta lactam agents are NOT effective
• need drugs with god intracellular penetration
• use respiratory fluoroguinolones or macrolides

Question 27

Describe the characteristics of mycoplasma species

Answer 27

they are the smallest known free-living microorganisms, non-motile, have no rigid cell wall (gram stain not useful)

Question 28

describe the characteristics of Mycoplasma pneumoniae

Answer 28

• person-person transmission by resp. droplets
• any age - infection rates highest in children/young adults
• more common during colder months
• may casue institutional outbreaks
• mainly cause upper resp. tract infections

Question 29

what clinical finding would you see on the hands of someone with mycoplasma pneumonia?

Answer 29

erythema multiforme

Question 30

what treatment would you use for mycoplasm pneumoniae?

Answer 30

sensitive to antibiotics which act on the ribosomes

ie) macrolides, tetracyclines, quinolones etc

Question 31

which of the organisms woudl you ocnsider in a 70 year old man with pneumonia after 2 week holiday in spain?

Answer 31

Legionella

water on holidays

Question 32

which of these organisms would you consider in a 50 year old patient with unresolving cough lasting 4 weeks?

Answer 32

Pertussis

Question 33

what is a common feature of these infectious agents?

Answer 33

they are all transmitted by inhalation

they are intracellular organisms

they have a high level of beta lactam

*think about which antibiotic you use before you start them*