The AmpC inhibitor, Syn2190, can be used to reveal extended-spectrum beta-lactamases in Escherichia coli.

AmpC beta-lactamases are not inhibited by clavulanic acid and could potentially mask detection of extended-spectrum beta-lactamases (ESBLs) using the Clinical and Laboratory Standards Institute confirmatory test. Syn2190 (1,5-dihydroxy-4-pyridone monobactam) selectively inhibits AmpC, but not ESBLs. Fifty-four MicroScan ESBL screen-positive strains of Escherichia coli and an unrelated group of 20 cefoxitin-nonsusceptible E. coli strains were tested with the confirmatory ceftazidime-cefotaxime-clavulanate disk method with or without 4 microg/mL of Syn2190 in the agar. Without Syn2190, 8 (14.8%) of 54 E. coli isolates and 0 of 20 cefoxitin-nonsusceptible E. coli isolates were confirmed. With Syn2190, an additional 9 (16.6%) of 54 of the MicroScan screen-positive E. coli isolates and 6 (30%) of 20 of the cefoxitin-nonsusceptible E. coli isolates were found. Multiplex polymerase chain reaction and sequence analysis confirmed the presence of the plasmid-associated beta-lactamase gene bla(CMY-2) in the 2 available MicroScan-screened E. coli isolates and in 5 of 6 of the cefoxitin-resistant group. These data suggest that in the presence of AmpC, ESBLs in E. coli may not be detected by the currently recommended confirmatory test.

Case of emphysematous pyelonephritis in a renal allograft.

Emphysematous pyelonephritis is a rare, but serious complication after renal transplantation. This is a case report of a 49-yr-old female who had a renal transplant for diabetic nephropathy. She presented to ER with about 1 wk history of right lower abdominal pain and fever 15 months after the transplant. She had gross hematuria and mental status changes just prior to presentation. A computed tomography (CT) scan of the abdomen showed extensive retroperitoneal and extraperitoneal air dissecting from the transplanted kidney in the right lower quadrant to the level of the mediastinum. There was air in the urinary bladder. These findings were highly suggestive of extensive emphysematous pyelonephritis. The patient was taken to the operating room emergently and underwent a transplant nephrectomy. Blood culture and urine culture were subsequently positive for Salmonella (serogroup O 6, 8 or C2). Initial blood culture also yielded Enterobacter cloacae. The patient was treated with imipenem, cefepime, flagyl, and diflucan empirically: this was later changed to complete a 6-wk course of ciprofloxacin upon discharge. Her hospital course was complicated by a urinary leak; she was discharged to home on day 21. This is the 12th reported case of emphysematous pyelonephritis occurred in a renal transplant recipient.