Antibiotic escalation, culture results, and a prescription audit
A 70-year-old man with type 2 diabetes is admitted with 3 days of fever, dysuria, and right flank pain. Temperature 38.6 C, blood pressure 118/72 mmHg, pulse 104/min, respiratory rate 20/min. Urinalysis shows nitrites, leukocyte esterase, and many white cells. Blood and urine cultures are taken, and he is started on intravenous ceftriaxone 2 g once daily plus gentamicin 5 mg/kg once daily. On day 3 he is afebrile and clinically improved, but the laboratory reports that the urine culture grew an extended-spectrum beta-lactamase-producing Escherichia coli susceptible only to meropenem, amikacin, and fosfomycin, and that the blood culture is sterile. His creatinine has risen from 88 to 156 micromol/L since admission. The pharmacy log shows that gentamicin was continued for 3 days without a level being checked, and that the ceftriaxone order was never reviewed after the culture result.
1. Interpret the culture result and renal trend, and decide the antibiotic plan for the next 24 hours.
Read the worked answer
The patient has improved clinically and is afebrile, but the organism is an ESBL-producing E. coli resistant to ceftriaxone, so continued ceftriaxone is not treating the pathogen even though the patient looks better; the improvement may reflect source control and the gentamicin, or partial response. The rising creatinine from 88 to 156 micromol/L while on once-daily gentamicin is a warning of nephrotoxicity, and no level was measured, so the exposure is unquantified. The plan: stop ceftriaxone and stop gentamicin, because the pathogen is resistant to the former and the latter is the likely cause of the renal injury with no monitoring. Choose a targeted agent from the susceptibility list. Meropenem is appropriate for a confirmed ESBL uropathogen with systemic infection, and amikacin is a reserve alternative but carries the same renal risk. Fosfomycin is generally reserved for uncomplicated cystitis and is not the right choice for a febrile upper urinary tract infection with bacteraemia risk. Reassess renal function, adjust the meropenem dose to renal clearance, obtain repeat cultures if fever recurs, and review fluid status, diabetes control, and any obstruction that could impair drainage.
2. Identify the prescription-standard and monitoring failures in this admission and explain how each should have been prevented.
Read the worked answer
Failures: (1) Gentamicin was started without a documented baseline creatinine, weight-based dose justification, or a plan for levels and renal monitoring; aminoglycosides require a documented indication, dose, duration limit, and monitoring plan. (2) The antibiotic order was not reviewed when the culture result returned, so the patient remained on an inactive agent; there should be a scheduled review at 48 to 72 hours with de-escalation or escalation documented. (3) The combination of ceftriaxone plus gentamicin was not justified in the record, and empirical choice should be matched to local resistance patterns and to the severity of the infection. (4) No note explains why the patient's renal function was not rechecked earlier despite a nephrotoxic drug. Prevention: use a structured prescription with indication, dose, route, frequency, planned duration, and monitoring parameters; require a documented antibiotic review at 48 hours; use the local antibiogram to choose empirical therapy; and flag aminoglycoside orders automatically for level monitoring. The case is a rational-drug-use problem, not a knowledge gap.
3. Explain how you would communicate this problem to the prescriber and the family without damaging trust, and what you would record.
Read the worked answer
Speak to the prescriber privately and specifically: describe the culture result, the renal trend, and the absence of a gentamicin level, and ask what the plan was, rather than announcing a mistake. Frame it as a shared review of the antibiotic plan and offer the concrete correction: stop the two agents, start targeted therapy, and set monitoring. With the family, explain that the infection is caused by a resistant organism, that the treatment is being changed to match the organism, and that kidney function is being watched closely and has been affected, which is why one drug is being stopped. Avoid blaming language and avoid speculation about fault before review. Record the culture result and its date, the decision and its rationale, the discontinuation of each drug with the time, the new drug with dose and renal adjustment, the monitoring plan, and the content of the conversation with the family. Then refer the event to the clinical governance or quality committee as a medication-safety review, because the pattern, not just this patient, is the problem.