Module 3 – Respiratory infections SAQ annotated

Remember to be systematic about the key syndromes, pathogens and antimicrobials- read/revise the relevant chapters of Bailey and Scott and make notes for later! 

Respiratory infections PNG overview Ferguson Jan 2015

  1. Describe the Gram stain appearance and how a lab identifies pneumoniae.  TEXT BOOK STUDY!   What antibiotics are useful for treating pneumococcal pneumonia?  Benzylpenicillin/amoxycillin are the mainstays – very little resistance that is relevant to treatment of pneumonia;  erythromycin, tetracycline, cotrimoxazole (low levels of resistance in PNG). What about pneumococcal meningitis?     Important PNG CSF isolate data recently published (do read it!) :       Meningitis isolates.PNG                            Ceftriaxone susceptibility maintained and that is the mainstay for treatment of acute bacterial meningitis. Remember that although chloramphenicol susceptibility appears high (95%), the penicillin non-susceptible isolates will be tolerant to chloramphenicol and treatment failure then expected in a larger number of cases (reference available).        
  2. Describe what vaccines are available world-wide for pneumococcus in children and adults.  Distinguish conjugate (e.g. 13-PCV) from polysaccharide vaccines and how they differ in immune response.  Some famous PNG trials of the polysaccharide vaccine in Adults . Pneumonia in PNG review.     Australian childhood rates dropped in 2011 coindident with implementation of the 7vPCV – currently around 250-300 childhood events per annum. Contrast this to an estimate from PNG that approximately 826,000 children, mostly young infants, die annually from invasive pneumococcal disease  provided in this important recent 7vPCV RCT in PNG which examined safety and immunogenicity of neonatal pneumococcal conjugate vaccination in children.                                                             
  3. How does influenza evade the immune response?  Antigenic shift and drift – need to know what these mean!  What drugs are available to treat influenza? PRIMARILY the NEURAMIDIDASE inhibitors.  How well do they work?  NOT VERY WELL- if oseltamivir given within 48 hrs of symptom onset, then reduction in symptoms by average of 17 hours only. No change to need for hospital admission.         
  4. What is the natural history of whooping cough (pertussis) in children and adults? IN PNG AND MOST DEVELOPING WORLD COUNTRIES, recognise by clinical diagnosis – see text book- three stages- the cough of a 100 days!   Adult – persistent nocturnal cough without whoop; largely well during day. Children – paroxysmal cough, +/- whoop, pneumonia, secondary phenomena; monocytosis sometimes on blood film.   How is whooping cough diagnosed by the lab?  Used to be DFA and culture – now PCR from nasopharyngeal swab (optimal) or throat swab (less sensitive); positive results expected up to 3 weeks following onset of cough. Serology not a great deal of help.   N.B. pertussis vaccine and its effectiveness. See subsequent pertussis posting.                                                                                                                                               
  5. What are potential side effects or toxicity of doxycycline? What is its mechanism of action and spectrum?           TEXT BOOK!                                                  
  6. What are some of the unusual causes of bacterial or fungal pneumonia in PNG?  Pneumocystis (childhood respiratory infection and adults with advanced HIV),  Cryptococcus neoformans (mostly presents with meningitis but can cause pneumonia or mass lesion),  Melliodosis  (Important for part 2- see references by Dr B Currie from NT),  Disemminated strongyloidiasis, eosinophilic pneumonia from helminthic infection. ADD to the list! 

Remember this is a good place to look at Gram stains and culture pics.

About mdjkf

Microbiologist and Infectious Diseases Physician
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