An 84-year-old woman is sent to the hospital from a nursing home due to 3 days of fever, abdominal pain, and progressive lethargy. The patient has a history of recurrent hospitalizations with multiple antibiotic courses for urinary tract infection, infected decubitus ulcer, and pneumonia. Her temperature is 38.2 C (101 F), blood pressure is 100/60 mm Hg, and pulse is 110/min. She has mild suprapubic and right costovertebral angle tenderness. Urine and blood cultures are obtained, and the patient is started on intravenous fluids and empiric ceftriaxone. Her urine culture shows extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli. Which of the following features is most likely to be found in this organism?

Question

An 84-year-old woman is sent to the hospital from a nursing home due to 3 days of fever, abdominal pain, and progressive lethargy.  The patient has a history of recurrent hospitalizations with multiple antibiotic courses for urinary tract infection, infected decubitus ulcer, and pneumonia.  Her temperature is 38.2 C (101 F), blood pressure is 100/60 mm Hg, and pulse is 110/min.  She has mild suprapubic and right costovertebral angle tenderness.  Urine and blood cultures are obtained, and the patient is started on intravenous fluids and empiric ceftriaxone.  Her urine culture shows extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli.  Which of the following features is most likely to be found in this organism?

Quizplus · Accepted Answer

11ec160b_3bf1_3ec2_9249_91881e6b2df2_MD0001_00 This patient has a urinary tract infection caused by an extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli. ESBL enzymes can inactivate extended-spectrum penicillins and cephalosporins (including third- and fourth-generation cephalosporins) and monobactams (aztreonam). Genes encoding these enzymes are often located on plasmids and therefore can be transferred between organisms and between different species through conjugation. Some have been incorporated into bacterial chromosomes. Carbapenems (eg, imipenem) are the treatment of choice for ESBL-producing organisms (although unfortunately, organisms with carbapenem resistance have emerged). (Choice A) Mutations in DNA gyrase can lead to fluoroquinolone resistance and generally do not impact beta-lactam antibiotic activity. (Choice B) Porin mutations can confer penicillin and aminoglycoside resistance and are particularly important in gram-negative organisms such as Pseudomonas. (Choice C) Penicillin-binding protein alterations are the mechanism that leads to methicillin resistance in Staphylococcus aureus. (Choice D) Vancomycin inhibits glycopeptide polymerization through binding to D-alanyl-D-alanine in the cell wall precursor; peptidoglycan changes (eg, D-alanine-D-lactate) can develop as a resistance mechanism. (Choice F) Ribosome mutations can confer resistance to ribosome-targeting antibiotics such as aminoglycosides and macrolides. Educational objective: Extended-spectrum beta-lactamases can be produced by gram-negative bacteria, rendering cephalosporins and other beta-lactam antibiotics inactive. These genes can be transmitted between organisms through plasmid conjugation. __________ References: Extended-spectrum beta-lactamase-producing organisms. (http://www.ncbi.nlm.nih.gov/pubmed/19596491) Resistance in gram-negative bacteria: enterobacteriaceae. (http://www.ncbi.nlm.nih.gov/pubmed/16735147)

An 84-Year-Old Woman Is Sent to the Hospital from a Nursing