Clinical Case Studies Urine and Stool Cultures

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

Group work- Isolation streaks Urine culture plates EMB MAC TSA MSA Blood Stool culture plates EMB MAC TSA Blood MSA

Urine cultures Please handle the specimens carefully Use aseptic technique to avoid contamination

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.

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. urinary tract infection

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.

Urinary Tract Infection (greater than 10,000 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 10,000 CFU/ml usually indicates that there is no infection.

Causative agents of urinary tract infections E. coli Proteus vulgaris Other gram – enteric pathogens Klebsiella Chlamydia

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.trimethoprim- sulfamethoxamolenitrofurantoin penicillins 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;

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.

Stool cultures Make sure that you use aseptic technique for your cultures

Gastrointestinal infections Bacteria Viruses Parasites Fungi Invasive Gastroenteritis(click on organisms for more detail)Shigella sp.Entamoeba histolyticaSalmonella sp.Campylobacter jejuniEnteroinvasive E. coli (EIEC)Enterohemorrhagic E. coli (EHEC)Vibrio vulnificusYersinia sp.Francisella tularensis,Helicobacter pylori Invasive GastroenteritisShigella sp.Entamoeba histolyticaSalmonella sp.Campylobacter jejuniEnteroinvasive E. coli (EIEC)Enterohemorrhagic E. coli (EHEC)Vibrio vulnificusYersinia sp.Francisella tularensisHelicobacter pylori

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

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

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

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

Symptoms Type 1: starchy food= vomiting; little diarrhea; no fever Type 2: meats and cream sauces= diarrhea; little vomiting; no fever