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Flashcards in Intro to infection Deck (10)
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What are the 3 types of host-microbial infections?

Commensal - symbiotic relationship between two different species where one derives some benefit and; the other is unaffected
Colonisation - when a microbe grows on or in another organism without causing any disease
Infection - the invasion and multiplication of microbes in an area of the body where they are not normally present, which usually leads to disease


What is a symbiotic relationship?

close and often long-term interaction between two different species (mutualistic / commensal / parasitic)


What are normal flora/microbiota what do they do?

Normal commensal bacteria - occupy skin, mouth, upper airways, lower airways, gastro-intestinal tract & genital tract. They are at least commensal & probably mutualistic in preventing more pathogenic bacteria from occupying those areas.
Ab use can eliminate these flora


What are the host risk factors for infection?

Extremes of age
Stress and starvation
compromised barriers to infection
Immunocomprimised host


What are the 2 types of barriers to infection? (give examples of each)

Physical barrier (skin, mucus, respiratory cilia, comensal organisms)
Biochemical barrier ( Sebaceous secretions in skin, Lysozyme in tears, Spermine in sperm, Gastric acidity)


List investigations which can be carried out for diagnosing infecions.

Markers of inflammation - blood/bodily fluids
Microscopy, culture & sensitivity (m, c & s) testing for bacteria
Nucleic acid (DNA / RNA) detection (usually PCR) for viruses
Antibody detection (serology) for viruses & unusual pathogens
Antigen detection (of a microbial component) for unusual pathogens
Imaging studies (X-rays / US / CT / MR) to look for a focus


Why are females more likely to get UTIs?

Urethra is shorter
Urethra closer to anus


What are the host risk factors for UTIs?

Younger children and older adults (post-menopause)
Shorter urethra (sexually active/post-menopause)
Internal obstructions (stones. tumours)
Bladder outflow obstructions (pregnancy, prostate enlargement)
Iatrogenic (catheters, ops, post-ops)
Immunocomprimised host (diabetes)


How do bacteria cause pathogenesis in UTIs? (hint: access, adherence, invasion, multiplication, evasion, resistance, damage, transmission)

Access : most bacteria causing UTI are found in colon (eg. commensals)
Adherence : pili (fimbriae) & adhesin molecules
Invasion : haemolysin increases invasive potential
Multiplication : colonisation of urinary tract may precede infection
Evasion : relatively few immune cells in urinary tract
Resistance : many bacteria causing UTI have multi-drug resistance
Damage : causes urethritis, cystitis, pyelonephritis, nephritis & septicaemia
Transmission : easily passed out in urine (limited infection risk)


How can you diagnose UTIs? (symptoms, risk factors, signs and investigations)

S: Dysuria, frequency or urgency of micturition, Haematuria, opaque or malodorous urine, Lower abdominal or loin pain
RF: age, diabetes
S: Lower abdominal or loin tenderness, Fever or septic shock
I: Describe earlier