Microbiology of Respiratory Tract Infection

Question 1

describe clinical presentation of influenza

Answer 1

fever - high, abrupt onset (up to 40 degree)
malaise
myalgia
headache
cough - initially dry and painful but becomes productive and painless
prostration

Question 2

describe different types of influenza

Answer 2

classical flu - influenza A (more than 1 subtype circulating) and B viruses
flu-like illnesses - parainfluenza virus
haemophilus influenzae - bacterium, not primary cause of flu, may be secondary invader

Question 3

describe transmission of influenza

Answer 3

droplets or through direct contact with respiratory secretions of someone with the infection
infection control precautions also include aerosol protection for aerosol generating procedures only;
intubation, extubation (and related procedures)
cardiopulmonary resuscitation
bronchoscopy
surgery and post mortem procedures (where high speed devices used)
dental procedures
non invasive ventilation
high frequency oscillatory ventilation
induction of sputum

Question 4

describe complications of influenza

Answer 4

primary influenzal pneumonia - disease of young adults, high mortality
secondary bacterial pneumonia - common in infants, elderly and debilitated, pre-existing disease, and pregnant woman, cause of mortality in all influenza patients
bronchitis
otitis media
influenza during pregnancy may also be associated with perinatal mortality, prematurity, smaller neonatal size and lower birth weight

Question 5

describe therapy for influenza

Answer 5

symptomatic - bed rest, fluids, paracetamol

antivirals - oseltamivir, zanamivir

Question 6

describe future threats of influenza

Answer 6

highly pathological avain flu

bird to human transmission - high mortality

Question 7

describe lab confirmation of influenza

Answer 7

direct detection of virus - PCR;
nasopharyngeal swabs in virus transport medium
throat swabs in virus transport medium
other respiratory samples 
laboratory based or point of care

Question 8

explain prevention of influenza

Answer 8

killed vaccine;
virus grown in hen’s eggs or cell culture then inactivated and combined with adjuvant. Currently contains 2 different influenza A viruses and 1 or 2 influenza B viruses. Given annually to adult patients at risk of complications (health care workers)
live attenuated vaccine - more effected than killed vaccine in children. Attenuated by cold adaption, contains multiple viruses, intra-nasal treatment
protective efficacy depends on match of vaccine to circulating virus and on patient group, but it never better than 70% effective in preventing clinical infection

Question 9

describe community acquired pneumonia

Answer 9

caused by microorganisms - mycoplasma pneumoniae (children and young adults),
coxiella burnetii (Q-fever - spread via sheep and goats, complication - culture negative endocarditis)
chlamydia - psittacosis (caught from pet birds)

therapy - antibiotics (tetracycline, macrolides e.g. clarithromycin)
mortality - varies with pathogen but generally lower than classical bacterial pneumonia
known as atypical pneumonia - relates to presentation and response to therapy in pre-antibiotic era

Question 10

describe lab confirmation of community acquired pneumonia

Answer 10

serology - send acute and convalescent bloods to lab, gold top vacutainer
virus detection - PCR on respiratory swabs/secretions (gradually increasing but only currently used for mycoplasma)

Question 11

describe bronchiolitis

Answer 11

clinical presentation;
1st or 2nd year of life
fever
coryza
cough
wheeze
severe cases - grunting, decreased PaO2, intercostal/sternal indrawing 

complications;
respiratory and cardiac failure - prematurity, pre-existing disease

aetiology - 80% cases due to respiratory syncytial virus

lab confirmation - PCR on throat or pernasal swabs

therapy - supportive, nebulised ribavirin no longer used

Question 12

describe epidemiology and control of bronchiolitis

Answer 12

epidemics every winter
common
no vaccine
nosocomial spread in hospital wards - cohort nursing, hand washing, gowns, gloves
passive immunisation - poor efficacy and cost-effectiveness

Question 13

describe epidemiology of metapneumovirus

Answer 13

contribution of ARTI
most children antibody positive by age 5
found in wade range of ages
virus is newly discovered (not new)
highest incidence in winter - world wide distribution 

association with disease;
second only to RSV in bronchiolitis
similar symptoms to RSV in both children and adults
range of severity from mild to requiring ventilation
2% of cases of influenza like illness

laboratory confirmation - PCR

Question 14

describe chlamydia trachomatis

Answer 14

STI which can cause infantile pneumonia

diagnosed by PCR on urine of mother or pernasal/throat swabs of child

Question 15

describe chlamydophila pneumoniae

Answer 15

person to person
mostly mild respiratory infections
may be picked up by test for psittacosis