Case10-Ecoli - Case 10 Lydyard, Peter; Cole, Michael;...

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1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person? Causative agent Uropathogenic E. coli (UPEC) is the major cause of urinary tract infec- tions (UTIs) in anatomically normal, unobstructed urinary tracts. Escherichia coli is a motile nonsporing gram-negative bacillus approximately 0.6–1 m m wide and 2–3 m m long (Figure 2). It has a typical gram-negative cell wall with an outer hydrophobic membrane containing lipopolysaccha- ride (LPS). It has peritrichous flagella and possesses fimbriae , which are important in adhesion (Figure 3). Eighty percent of all urinary tract infec- tions are caused by E. coli in the community and about 60% in hospital. The LPS is composed of lipid A, an inner core of polysaccharide linked to the lipid A by ketodeoxyoctonate (KDO) and an outer variable polysac- charide (Figure 4). The general arrangement of LPS is similar in most Case 10 Escherichia coli A 50-year-old worker at a school cafeteria went to her primary care physician complaining of tiredness, shaking chills, a pain in her loin, and a burning sensation on passing urine, which she was doing more frequently than normal. On examination, her doctor noted that she seemed a bit pale and that she had some suprapubic tenderness. He tested her urine with a dipstick and found she had a positive result for nitrite, pus cells, and protein. The doctor took a blood and urine sample for confirmation and sent them to the local hospital laboratory. A diagnosis of pyelonephritis was made and she was started on antibiotics. The following day the laboratory results were available. The full blood count showed a neutrophilia and a pure culture of Escherichia coli was grown from the urine (Figure 1). Figure 1. E. coli cultured from the urine. This shows the growth of lactose-fermenting (yellow colonies) E. coli on a medium containing lactose and a pH indicator. In routine practice urine is cultured on cystine lactose electrolyte-deficient (CLED) medium. Cystine is a growth factor for some organisms; lactose is incorporated to differentiate utilization of lactose from nonutilization (e.g. Pseudomonas ); and the electrolyte deficiency inhibits the swarming of Proteus , which may obscure bacterial colonies. Figure 2. E. coli organisms. This is a Gram stain of E. coli showing the red (gram-negative) appearance. © Lydyard, Peter; Cole, Michael; Holton, John; Irving, Will; Porakishvili, Nino; Venkatesan, Pradhib; Ward, Kate, Jan 01, 201 Garland Science, Hoboken, ISBN: 9780203856871
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gram-negative bacteria, with the highest variability appearing in the outer ‘O’ antigen component. The inner lipid A component comprises different fatty acids (such as hexanoic (6:0), dodecanoic (12:0), tetradecanoic (14:0), hexadecanoic (16:0), and octadecanoic (18:0), with their monoenoic equiv- alents) linked by ester amide bonds to KDO via N -acetylglucosamine. This part of LPS is the
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This note was uploaded on 09/14/2011 for the course PHARM mb taught by Professor Staff during the Spring '11 term at UCSD.

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Case10-Ecoli - Case 10 Lydyard, Peter; Cole, Michael;...

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