Opportunistic Infections Flashcards
What are the frequently encountered opportunistic pathogens?
E coli Staph aureus Klebsiella pneumoniae Enterococcus spp Pseudomonas aeruginosa Enterobacter spp Serratia spp Proteus spp C. difficile
Which frequently encountered opportunistic pathogens cause nosocomial epidemics?
Staph aureus Klebs pneumo Enterococcus spp Pseduomonas aeruginosa Enterobacter spp Serratia spp
What local host factors contribute to opportunistic infection?
Anatomical defects Surgical and other wounds Burns Catheterisation (bladder, IV) foreign bodies (sutures etc.)
Opportunistic infections are especially important to recognize because
They are a sign that something else is wrong with the patient - always ask WHY the patient has this infection
T/F Sutures reduce the chance of infection
False; the presence of a foreign body including sutures increases the chance of infection
Why do foreign bodies predispose to opportunistic infection?
They can provide a haven from the immune system for bacteria eg injecting medical students with S aureus and talc - the ability to hide in the talc made the S aureus more pathogenic
T/F Burns are commonly associated with Pseudomonas infection
False; previously Pseudomonas infections were more common; now we see more Staph and other bacteria
Catheters are a source of opportunistic infection because
they bypass normal host defenses
What systemic host factors contribute to opportunistic infection?
Extremes of age Leucopenia Malignancy Malnutrition Diabetes Liver disease Certain infections (HIV, measles) Tx with antimicrobials (C. diff) 1' congenital immunodeficiency
Leucopenia as a predisposing factor for opportunistic infection is commonly seen in
Patients undergoing treatment for malignancy which itself is immunocompromising
Candidiasis (Candida albicans infection) can be an indication of
Diabetes
Someone who is treated with antimicrobials is susceptible to infection by
C difficile
Fungi (eg post UTI tx co-amoxyclav, then they get thrush)
Why does antimicrobial treatment predispose to fungal infection eg candidiasis post UTI Tx?
It alters the normal microbiota that protects against fungal overgrowth
Common types of opportunistic infections seen include
wound infection UTI intra-abdo infection pneumonia septicaemia/sepsis meningitis (esp neonates)
Why are exogenous sources of OI important to recognize?
something has gone wrong with infection control procedures
Sources of OI pathogens can be __________ or __________
Endogenous - own microbiota OR own microbiota as acquired in hospital
Exogenous - other people
Why are bactericidal agents required in some OIs?
If the patient is immunocompromised they not have the necessary immune response to deal with microbes that are alive but not growing (bacteriostatic) and can relapse
What is used for epidemiological classification of Pseudomonas?
RFLP or multilocus sequence typing
What makes Pseudomonas resistant to many ABs?
chromosomal encoded beta lactamase that degrades many penicillins (eg amoxycilin) and is not inhibited by clavulanic acid
Psuedomonas colonises
skin, mucous membranes, gut
T/F Pseudomonas colonization is permanent
False; transient colonization UNLESS they have CF or other disorder that allows permanent colonization
Pseudomonas infections are mostly acquired
from the environment
Pseudomonas is spread in hospital on
hands and fomites (inanimate objects)
What is unique about Pseudomonas isolation techniques in the lab?
Weak disinfectant agents are used - centrimide agar - that stop other bacteria from growing ie acts as a selective media; allows pseudomonas to flourish
