Clinical Case Studies

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Clinical Case Studies

• Urine and Stool Cultures

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Project- Clinical diagnostics

• Each group of two are a team.
• You will try to culture and identify the
  causative agents in a simulated urine culture and
  stool culture

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Group work- Isolation streaks

• Urine culture plates
• EMB
• MAC
• TSA
• MSA
• Blood

• Stool culture plates
• EMB
• MAC
• TSA
• Blood
• MSA

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Urine cultures

• Please handle the specimens carefully
• Use aseptic technique to avoid contamination

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Origin of UTI

• In many cases bacteria first travel to the
  urethra. When bacteria multiply an infection can
  occur. An infection limited to the urethra is
  called urethritis. If bacteria move to the
  bladder and multiply a bladder infection called
  cystitis results. If the infection is not
  treated promptly bacteria may then travel
  further up the ureters to multiply and infect the
  kidneys. A kidney infection is called
  pyelonephritis.

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When should a urine culture be ordered

• urinary tract infection such as pain and burning
  when urinating and frequent urge to urinate.
  Antibiotic therapy may be prescribed without
  requiring a urine culture for symptomatic young
  women who have an uncomplicated lower urinary
  tract infection. If there is suspicion of a
  complicated infection or symptoms do not respond
  to initial therapy then a culture of the urine
  is recommended. Pregnant women without any
  symptoms may be screened for bacteria in their
  urine which could affect the health and
  development of the fetus.

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Clean catch specimen

• Cleanse with a disposable wipe.
• Urinate a few drops into the toilet and catch the
  stream of urine in the culture container(
  Midstream)
• Place the lid on the container.

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Urinary Tract Infection

• (greater than 10000 colony forming units
  (CFU)/ml) is considered a positive urine culture.
  A culture that is reported as no growth in 24 or
  48 hours or less than 10000 CFU/ml usually
  indicates that there is no infection.

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Causative agents of urinary tract infections

• E. coli
• Proteus vulgaris
• Other gram enteric pathogens
• Klebsiella
• Chlamydia

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• Once we have diagnosed a UTI we treat the patient
  with antibiotics. Typical antibiotics used for
  UTIs include trimethoprim-sulfamethoxamole
  nitrofurantoin and certain penicillins such as
  amoxicillin.
• In some cases when we are pretty sure from the
  symptoms that you actually have a UTI we will
  start antibiotics right after we get the urine
  culture

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Repeat the culture after treatment

• If the culture result shows that we need a
  different antibiotic we can always change.
• We repeat the culture 3-5 days after starting
  antibiotics to make sure that we are actually
  killing all the bacteria and again soon after
  the antibiotics are finished to make sure we
  killed everything that needed killing.

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Stool cultures

• Make sure that you use aseptic technique for your
  cultures

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Gastrointestinal infections

• Bacteria
• Viruses
• Parasites
• Fungi
• Invasive Gastroenteritis(click on organisms for
  more detail)Shigella sp.Entamoeba
  histolyticaSalmonella sp.Campylobacter
  jejuniEnteroinvasive E. coli (EIEC)Enterohemorrhag
  ic E. coli (EHEC)Vibrio vulnificusYersinia
  sp.Francisella tularensisHelicobacter pylori

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Salmonella

• Undercooked chicken
• Poor food handling
• Infected eggs( raw eggs)

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C. difficile

• C. difficile infection is usually acquired in
  hospital and almost all patients who develop C.
  difficile diarrhea are taking or have recently
  been given antibiotic therapy.
• Diarrhoea is the most common symptom but
  abdominal pain and fever may also occur. In the
  majority of patients the illness is mild and
  full recovery is usual although elderly patients
  may become seriously ill with dehydration as a
  consequence of the diarrhea.
• Occasionally patients may develop a severe form
  of the disease called pseudomembranous colitis
  or antibiotic-associated colitis which is
  characterised by significant damage to the large
  bowel

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Staphylococcus aureus

• Staphylococcus aureus-gram positive
  coccusIngestion
• Food poisoning mayonnaise containing and/or
  dairy products
• Heat stable enterotoxins 5 types labelled A B
  C D E
• Vomiting little or no diarrhea no fever

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Food Poisoning

• Bacillus cereus-gram positive rod
• Ingestion
• Food poisoningType 1 emetic form heat-stable
  enterotoxin. mechanism unknown Type 2 diarrheal
  form heat-labile enterotoxin stimulates
  adenylate cyclase (increases

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Symptoms

• Type 1 starchy food vomiting little diarrhea
  no fever Type 2 meats and cream sauces
  diarrhea little vomiting no fever