Gram negative coccobacilli Flashcards
Bordetella: gram stain, optimum growing temp, best agar:
Gram negative coccobacilli, occuring singly or in pairs, bipolar staining, 35-37c, charcoal blood agar with cefalexin, bordet-gengou,
Bordetella pertussis: laboratory findings
Strict aerobic, should be incubated aerobically without CO2, colonies are smooth, convex, glistening, surrounded by a zone of haemolysis.
B. pertussis does NOT grow on nutrient agar or MacConkey agar. It grows poorly on BA.
Hazard group 2
B. pertussis is weakly oxidase positive and non-motile, and urease negative.
*B parapertussis is oxidase negative,
Treatment of B. pertussis
Antibiotic mechanism of action
Different treatments for different patient cohorts
Macrolides
Macrolide resistance is almost never seen in UK
However macrolide resistance is more common in China/Iran
<1 month = clarithromycin
>1 year = azithromycin or clarithromycin
non-preg adults = azithromycin or clarithromycin
pregnant = erythromycin
If macrolides are contraindicated, give CoT,
do NOT give CoT in pregnancy or <6 weeks age.
Mechanism of action macrolides = bind and inhibit 50s ribosomal subunit, inhibit protein synthesis
Pathogenesis of B. pertussis
Toxin mediated disease
Bacteria attach to cilia of respiratory epithelial cells, produce toxins that paralyse cilia, cause inflammation of resp tract which interferes with the clearing of pulmonary secretions
Isolation of patients with Bordetella
Children and HCW should be excluded from school/work until 48 hours post antibiotic treatment,
or for 21 days post symptom onset
Bordetella in pregnancy:
When should you offer the vaccine?
The whooping cough vaccination programme for pregnant women offer vaccination to pregnant women, between 16-32 weeks (but up to 38 weeks) of pregnancy.
If a pregnant woman is diagnosed with whooping cough in pregnancy, she should still wait until 16 weeks gestation to have the vaccine.
Bordetella vaccine schedule (routine UK schedule):
part of the 6 in 1 vaccine (8, 12, 16 weeks)
part of the 4 in 1 preschool booster (3yrs 4 months)
How to define and deal with close contacts of Bordetella pertussis:
Define ‘close contact’
Offer abx prophylaxis to close contacts of the ‘index case’ if symptoms in the ‘index case’ occur within the previous 21 days AND the close contact is in one of the two priority groups:
Group 1 (people at increased risk of developing severe complications from whooping cough aka they are vunerable)
- unimmunised infants (born after 32 weeks gestation) aged younger than 2 months old, whose mum didnt have the vaccine after 16 weeks gestation or before 2 weeks of delivery.
- unimmunised infants (born BEFORE 32 weeks gestation) regardless of maternal vaccine status
- unimmunised and partially immunised infants (less than 3 doses of vaccine) aged 2 months or older, regardless of mums vaccine status
Group 2 (people at risk of transmitting infection to vulnerable people in group 1, who have not received a vaccine more than 1 week ago and less than 5 years ago)
- pregnant women 32+ weeks gestation
- healthcare workers who work with infants and pregnant women
- people who regularly work with infants that are too young to be fully vaccinated
- people who share a household with an infant too young to be fully vaccinated.
Close contact: family members or people living in the same household, and those in institutional settings with an overnight stay in the same room during the infectious period
Antibiotic prophylaxis choices are the same as treatment choices.
Vaccine should be offered to all people who have been offered antibiotic prophylaxis
Post exposure vaccination in pregnancy is important and specifically recommended for those who have not had a pertussis vaccine in the last 5 years:
- women exposed to whooping cough after 32 weeks
or - woman exposed at any stage of pregnancy if they are at risk of transmitting to people in group 1 (for example if they were a healthcare worker)
