Bacterial Pathogens 1 Flashcards
Where does Haemophilus Influenzae colonise?
it colonises the upper respiratory/gastrointestinal/ genital tract
what does Haemophilus Influenzae cause?
it causes respiratory infections, meningitis, blood stream infections
what are the laboratory features of haemophilus species?
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
what form of H. Influenzae is most virulent?
the capsulate version
Non-capsulated strains of H. Influenzae is strongly associated with what type of infeciton?
it is associated with respiratory infections
- exacerbation of chronic bronchitis
- otitis media
what is the most common serotype of H. Influenzae?
Tybe B (Hib)
(inhaled)
what is the major virulence factor of capsulated H. Influenza?
anti-phagocytic polysaccharide capsule
“PRP (polyribosyl ribitol phosphate)”
what type of clinical infections does the H. Influenzae Type B cause?
- early childhood: resp. tract infections (acute epiglotttis)
- meningitis
- sequelae of deafness, seizures, and intellectual impairment
- blood stream infections
- septic arthritis
- cellulitis (head and neck)
Non-capsulated H. Influenzae are less virulent, but who do they commonly colonize?
patients with COPD, cystic fibrosis,
Non-capsulatd H. influenzae can cause what?
- Respiratory infection
- recurrent sinusitis
- acute/chronic bronchitis
- acute/chronic otitis media
- community-acquired pneumonia
what sort of antibiotic treatment should we use against H. Influenzae?
give a broad spectrum cephalosporin b/c only 20% are beta lactamase producers
do we have a vaccine for H. Influenzae?
there is a vaccine for the capsulated form
there is NOT A vaccine for the non-encapsulated strain
describe the laboratory characteristics of bordetella pertussis
- 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
*
Describe the pathogenesis of B.Pertussis
Bronchioles become blocked with inflammatory cells, lymphocytes and mucous
obstruction leads to collapse of alveoli, resulting in diminished oxygenation of the blood
what are the clinical stages of whooping cough?
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
*
what is the CDCs estimate of percentage of cough illnesses in adults that are due to pertussis ?
- 10-20% of cough illnesses in adults lasting more than 14 days are due to pertussis
what are the laboratory characteristics of B. Pertussis?
- culture - charcoal blood agar, antibiotics to inhibit normal flora, gram negative coccobacilli
what is the quickest way to diagnose B. Pertussis?
do PCR on a swab or nasopharyngeal aspirate
why is there a resurgence in adult pertussis infections?
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
what does Leionella pneumophila cause?
causes pontiac fever and legionnaires disase (pneumonia)
what are the characteristics of the legionella species?
non-capsulated gram-negative bacillus
possesses flagellae
strict aerobe
what is the general source of L.Pneumophila in the environment?
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
describe the pathogenesiss of legionella
- inhalation of aerosol contaminated with legionella
- attaches to resp. epithelial cells and alveolar macrophages
- infects macrophages and monocytes - after phagocytosis survives by inhibiting phagosome lysosome fusion
- person - to person transmission has not been documented
what is the result of legionnaire’s disease?
- abrupt onset of fever, chills, dry cough, headache
- may get multi-ogan disease
- GIT, CNS, liver, RENAL
- overall mortaility = 15-20%
what is the most commonly used test to detect legionnaire’s disae?
Urinary antigen detection
- sensitivity serogroup 1 = does nOT detect other serogroups
rapid test
what sort of treatment do we use in legionnaire’s disease?
- beta lactam agents are NOT effective
- need drugs with god intracellular penetration
- use respiratory fluoroguinolones or macrolides
Describe the characteristics of mycoplasma species
they are the smallest known free-living microorganisms, non-motile, have no rigid cell wall (gram stain not useful)
describe the characteristics of Mycoplasma pneumoniae
- 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
what clinical finding would you see on the hands of someone with mycoplasma pneumonia?
erythema multiforme
what treatment would you use for mycoplasm pneumoniae?
sensitive to antibiotics which act on the ribosomes
ie) macrolides, tetracyclines, quinolones etc
which of the organisms woudl you ocnsider in a 70 year old man with pneumonia after 2 week holiday in spain?
Legionella
water on holidays
which of these organisms would you consider in a 50 year old patient with unresolving cough lasting 4 weeks?
Pertussis
what is a common feature of these infectious agents?
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*
