KPC-Producing Klebsiella pneumoniae in a Critically Ill Surgical Patient
A 67-year-old man in the intensive care unit develops fever, leukocytosis, and purulent tracheal secretions on day 12 after abdominal surgery. He has received meropenem for 10 days for a pancreatic abscess. A tracheal aspirate culture grows Klebsiella pneumoniae. The laboratory reports the isolate as resistant to meropenem (MIC 16 mg/L), resistant to ceftazidime, and susceptible to ceftazidime-avibactam (MIC 2 mg/L) and colistin. The infection prevention team asks whether this is a carbapenemase-producing organism, whether the susceptibility result can be trusted, and what to do about contacts. The microbiology laboratory performs a lateral-flow carbapenemase assay that is positive for KPC and negative for NDM, IMP, VIM, and OXA-48.
1. Interpret the susceptibility pattern and the lateral-flow result. What is the most likely resistance mechanism, and what confirmatory testing is appropriate?
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The meropenem MIC of 16 mg/L is resistant for Enterobacterales, and resistance to ceftazidime with susceptibility to ceftazidime-avibactam is consistent with a serine carbapenemase that is inhibited by avibactam. The positive lateral-flow assay for KPC identifies a Klebsiella pneumoniae carbapenemase. This is a KPC-producing carbapenem-resistant Enterobacterales isolate. The susceptibility result is plausible because avibactam inhibits KPC; however, the laboratory should confirm with a molecular method such as PCR for blaKPC and ensure that the lateral-flow assay is performing properly with controls. Repeat testing and send the isolate to a reference laboratory if needed. The negative results for NDM, IMP, VIM, and OXA-48 argue against those mechanisms but do not replace confirmatory molecular testing.
2. What infection prevention and control actions are indicated, and what contact screening should be considered?
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Place the patient in contact precautions in a private room or cohort with other CRE patients. Notify infection prevention and the clinical team, perform hand hygiene, and ensure dedicated equipment and environmental cleaning. For high-risk units, consider rectal or perirectal surveillance cultures for contacts, especially if the patient was in a shared room or if there is evidence of transmission. Screen contacts according to local policy and report the organism as required by public health regulations. Review antibiotic use and stop unnecessary broad-spectrum therapy. Do not use the susceptibility result alone as evidence that the organism is nonvirulent; KPC-producing Klebsiella can cause severe pneumonia and bacteremia.
3. How should the susceptibility result guide antimicrobial selection, and what pitfalls should the laboratory and clinician avoid?
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Ceftazidime-avibactam is active in vitro against this KPC-producing isolate and is a reasonable targeted option, with dose adjustment for renal function and source control of the pancreatic abscess. Colistin susceptibility does not make it a preferred first-line agent because of nephrotoxicity and poor pulmonary penetration. Avoid meropenem monotherapy despite the carbapenem MIC being only moderately elevated, because carbapenemase production can lead to treatment failure. The laboratory should report the carbapenemase mechanism clearly, ensure that susceptibility testing for ceftazidime-avibactam is validated, and avoid interpreting a single MIC without confirming the mechanism. Clinicians should reassess response and consider combination therapy or source control in severe infection.