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IUPUI MICR J210 - Gram Negative Enterics

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MICR J210 1st Edition Lecture 16 Outline of Last Lecture I. PneumoniaII. Streptococcus pneumoniaeIII. Legionella pneumophilaIV. Mycoplamsa pneumoniaeV. Chlamydia pneumoniaeVI. Klebsiella pneumoniaeOutline of Current Lecture I. Meningitis II. Enterobacteriaceae III. Escherichia coliIV. Salmonella typhiV. Shigella dysenteriaeVI. Vibrio choleraVII. Campylobacter jejuniVIII. Clostridium difficile IX. Strep. pneumoniae X. Neisseria meningitidis XI. Haemophilus influenzaXII. Strep. AgalactiaeXIII. E. coli.Current Lecture- Meningitiso Enteric bacteria Commensal bacteria crowd out the pathogenic bacteriaThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Most enteric bacteria is commensal and therefore don’t typically cause disease Diarrhea Loose, watery stools more than three times in one day which might be associated with cramps, bloating, nausea and an urgent need to have a bowel movement. Corresponds with Types 6 & 7 on the Bristol Stool Chart. Acute diarrhea- Bacterial, parasitic infection, viral or food intolerance. o Staphylococcal food poisoning- Sudden onset- Comes and goes in a few days Chronic diarrhea - Associated with functional disorders, eg. irritable bowel syndrome(IBS).- Long onset and long duration Types of Diarrhea- Osmotico Too much water is drawn into the bowels. Due to malabsorbtion (eg. lactose intolerance) or laxative overuse.o Intestinal wall isn’t functioning properly - Secretory (watery)o Active secretion of fluid from plasma into bowel. Diarrhea has ion composition of plasma, and continues even when fasting. Often caused by bacterial toxins (eg. Cholera, ETEC)o Severe dehydration and electrolyte imbalance Plasma enters into the bowel The diarrhea then has the same composition as theplasma- Exudativeo Presence of blood and pus in the stool. This occurs with inflammatory bowel diseases, such as Crohn's disease or ulcerative colitis, and several infections.  Inflammation draws in the neutrophils and breakage in the gut allows the blood to enter the lumeno Dysentery is bloody diarrhea. Blood is caused by invasion of bowel tissue by pathogen (eg, EHEC, Salmonella, Shigella, Entamoeba histologica and others) Caused by pathogenso Enterics-gut associated bacteria Rod-shaped Gram-negative bacteria- Can also be gram +o Most are commensals or pathogens in intestines of humans and other animals Their nicheo There are 7 common Gram-negative enterics o All are rods (bacilli) except Vibrio which is a short helically- shaped rodo All are motile except Klebsiella and Shigella. Motility of enterics is often a distinguishing feature- Enterobacteriaceae o A family of Gram-negative bacilli that contains more than 100 species of bacteria which inhabit the intestines of humans and animals. Examples,  Escherichia coli  Klebsiella pneumoniae: normally present in the gut NOT the airways- Pneumonia results from emesis and aspiration Salmonella typhi  Shigella dysenteriaeo Coliforms Enterobacteriaceae that are commonly part of the normal intestinal tract flora (commensals). Examples,- Escherichia coli - Klebsiella pneumoniae - Grow on E and B plateso Characteristics of Gram-negative enterics Endotoxin- Part of lipopolysaccharide found in all Gram-negatives (Lipid A part)- Lipid Part A Catalase-positive- Just like Staph Surface antigens (useful in serology, can determine virulence)- H antigen (flagella)- K antigen (capsule or fimbrae)- O antigen (LPS, carbohydrate part)o O antigen differs between strainso The core remains the same between strains R-factors (antibiotic resistance & virulence)- Enterics are very efficient in exchanging genetic material by either conjugation or transduction by phage.- Resistant strains result—especially in the Klebsiella strain Coliforms grow as dark colonies on EMB agar- Use pilus to transfer plasma DNA across specieso Epidemiology Transmission is fecal-oral. The majority of fecal mass is bacteriao In the USA Mostly through mass processing of food- Cruise ships,- Meat packing plants,- Restaurant chains, etc Outbreaks monitored by the CDC  Source needs to be identified and recall of contaminated product issuedo In third-world countries Poor quality of water supply- Much higher incidence- Sewage contaminates water supply- Escherichia colio Named for Escherich (Germany) and inhabiting the colon o Biology Coliform  Normal microflora of 100% of human colon and live in the intestine of all warm blooded animals - Most is actually benign—helps us absorb vitamins- Symbiotic organisms Special strains are highly virulent due to possession of virulence factors- Only a few are reason for concerno Highly motileo Pathology Virulent strains of E. coli can cause- Gastroenteritis o Diarrheal type of diseases which are transmitted by fecal-oral routes are caused by several strains of E. coli, each having unique virulence factorso Enterotoxigenic E. coli (ETEC) Strains that produce a plasmid-encoded heat-stabletoxin which causes watery diarrhea.- Bacteria secrete toxin, then gut hypersecretes fluid and electrolytes into thelumen- NO blood is present Toxin stimulates hypersectretion of fluids and electrolytes from the gut epithelial cells. Significant cause of infant death (especially in 3rd world) Common cause for Travellers diarrhea- Because you aren’t used to the bacteria in that regiono Enterohemorrhagic E. coli (EHEC) Plasmid-encoded toxin causes bloody diarrhea (dysentery).- Blood IS present Toxin disrupts protein synthesis causing destructionof intestinal microvilli- Blood cells then migrate into the lumen Strain E. coli O157: H7 is the major cause of food associated diarrheal disease in US- Can also cause fatalitieso O antigen: lipopolysaccharideo H antigen: flagella Hemolytic Uremic Syndrome (HUS)- Complication of EHEC infection in 5%-10% children (<10y). Characterized by hemolytic anemia and damage tothe kidneys (leading to possible kidney failure) Bacteria enter blood stream and destroy red blood cells  Hemoglobin enters into the kidney and blocks off passageway---can result in kidney failure- Neonatal meningitis o E. coli is major cause of neonatal meningitiso Group E strep in the most common Caused by strains which have the K-1 capsuleo Have the K-1 antigen- Urinary


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IUPUI MICR J210 - Gram Negative Enterics

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