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20 Cards in this Set
- Front
- Back
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UTIs
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• UTI’s can be acquired from urethra to bladder
(ascending) or from kidney to bladder (descending); ascending infections are much more common • Very few viruses or parasites cause UTI’s Viral causes: polyomaviruses (JC and BK), CMV in infants, adenovirus • Very few parasites cause UTI’s • Non-bacterial causes: Candida albicans (yeast), Trichomonas vaginalis (protozoan) |
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Risk Factors for UTIs
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• Females more susceptible than males;
increased incidence in sexually-active females and males • Uncircumcised males more susceptible than circumcised males, especially infants • Pregnancy, prostate hypertrophy, kidney stones, and tumors promote UTI’s Failure to empty bladder completely Can be loss of neural control to the bladder Anything that obstructs urine flow can increase incidence of UTI |
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Community acquired and
nosocomial infections |
• Community-acquired and nosocomial
infections are distinguished Indwelling urinary catheters put patient at risk for nosocomial Healthy urinary tract is resistant to bacterial colonization Nosocomial infections may have increased antibiotic resistance |
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Causes of Nosocomial Infections
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Over half are caused by Gram negative bacteria (mostly escherichia)
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Acute lower UTI
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• Dysuria: burning pain on passing urine
• Urgency: the urgent need to pass urine • Frequency: frequency of urine increases • Can be asymptomatic, especially in elderly, those with catheters • Urine is often cloudy due to pus, bacteria, and (possibly) blood • Recurrent UTI’s are common in some people (why?) |
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Bacterial Cystitis
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Symptoms: Abrupt onset, burning pain on urination, urgency, frequency, foul smell, red colored urine, pyelonephritis, fever, chills, back pain, vomiting
Causative agents: mostly E. coli Pathogenesis: Usually bacteria ascend the urethra, enter the bladder, and attach by pili to receptors on urinary tract epithelium. spread to the kidneys can occur |
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Upper UTI
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• Pyelonephritis (infection of the kidney) can
occur with lower UTI symptoms • Abscesses can form in kidneys • Sometimes associated with kidney stones (probably due to obstruction of the renal tract) • Hematuria (blood in urine), though seen in other, non-infectious diseases |
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Diagnosis of UTI
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• Quantitative culture: # of bacteria in midstream
urine sample UTI when > 100,000 organisms (CFU)/ml; usually only one species Possible UTI when 10,000 – 100,000; often several species May be due to contaminated sample (normal flora) • Urine sample can be obtained by catheter (if already present) or by suprapubic aspiration (used mostly in infants) |
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Lab Investigations
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• Presence of bacteria in gram-stained urine
sample not enough to diagnose UTI Red or white blood cells in urine also not enough to diagnose UTI (though rare) • May have another cause (autoimmune, trauma, stones, cancer, endocarditis) |
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Escherichia coli (p. 268-273)
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• GNR; motile; + capsule; facultative anaerobe
• Most common cause of UTI • Lactose-fermenter • Special fimbriae allow attachment to urethral cells • Other virulence factors: endotoxin, exotoxins • Rarely causes disease in neonates (passage through birth canal) • Most common normal flora of colon (humans and animals) • Drug resistance increasing |
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Coagulase-negative staphylococci (p. 213-214)
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• Staphylococcus saprophyticus: especially
common in young, sexually active women • Patients respond well to antibiotics and are rarely re-infected • Differentiated from S. aureus (coagulasepositive) but not from S. epidermidis • Can be endogenous spread • Virulence factors unknown • Urination after intercourse helps to wash organisms out of the bladder and prevent infection |
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Other gram-positives (Staphylococcus epidermidis)
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• S. epidermidis: less frequent than S.
saprophyticus (also coag-negative) Part of normal skin flora; may be contaminant (catheter) Mostly an opportunist; associated with catheters Produces slime layer; helps in colonizing catheters High degree of drug resistance |
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Other gram-positives (S. aureus)
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• S. aureus: coagulase-positive; can be
normal skin, URT flora – Much more virulent than other staph – Cause of toxic shock syndrome (due to exotoxin TSST-1) – Produces other exotoxins as well – Especially associated with indwelling catheters – High degree of drug resistance |
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Other gram-positives (Enterococcus faecalis)
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• E. faecalis: also known as fecal strep
– Used to be classified as group D strep – GPC in pairs or short chains; found in large intestines (humans and animals), UG tract (humans) – Few virulence factors, but can cause life-threatening infections • May be due to hemolysin (found on plasmid) • Responsible for ~10% of all nosocomial infections – Also common in people who have been treated with broad spectrum antibiotics – Several antibiotics have been designed specifically for enterococcus infections due to drug resistance |
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Candida albicans (p. 664-667)
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• Yeast; growth by budding; forms germ
tube in serum (lab test) • Treated with systemic anti-fungal drugs • Can be part of normal vaginal flora; also on skin in groin region (moist) • Grown on Sabouraud dextrose agar (SDA; sab dex) • Part of normal vaginal flora |
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Gram-negative rods (Proteus mirabilis) (p. 278)
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– GNR; non-lactose-fermenter
– Produces large amount of urease, which increases pH – Highly motile (swarmer); grown on chocolate agar; produces nasty smell – Diagnosed by indole test – Part of normal gut flora (humans); also in soil, water – Infection usually endogenous – Virulence factors: endotoxin, urease – Increased drug resistance |
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Other gram-negatives (Klebsiella pneumonia) (p. 278):
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• Klebsiella pneumonia (p. 278): prominent
capsule/slime layer – GNR; facultative anaerobe – Lactose-fermenter (KEE) – Produces urease – Can be part of normal flora; difficult to tell if colonization or infection – Virulence factors: endotoxin, fimbriae, capsule/slime layer – Can also cause pneumonia, especially in alcoholics |
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Other gram-negatives (Enterobacter)
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• Enterobacter (p. 278): lactose-fermenter
(KEE) – GNR; closely related to Klebsiella – + capsule/slime – mostly an opportunist – has endotoxin, fimbriae |
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Other gram-negatives (Serratia)
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• Serratia (p. 278)
– GNR; closely related to Klebsiella – Opportunist (rare) – Produces bright red pigment on agar |
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Other gram-negatives (Pseudomonas aeruginosa)
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????
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