What is the best antibiotic for an elderly patient with multiple comorbidities and asthma, with sputum positive for Acinetobacter, who is not responding to Tazocin (piperacillin/tazobactam)?

Best Antibiotic Treatment for Elderly Patient with Asthma and Acinetobacter in Sputum Not Responding to Tazocin

For an elderly patient with multiple comorbidities and asthma who has sputum positive for Acinetobacter that is not responding to piperacillin/tazobactam (Tazocin), intravenous polymyxin (colistin) with adjunctive inhaled colistin is the recommended treatment option.

First-line Treatment Options

• For Acinetobacter species that is not responding to piperacillin/tazobactam, treatment should be guided by antimicrobial susceptibility testing results 1
• If the Acinetobacter isolate is susceptible to carbapenems, treatment with either a carbapenem (imipenem 500 mg IV q6h or meropenem 1 g IV q8h) or ampicillin/sulbactam (3 g IV q6h) is recommended 1
• For elderly patients, consider renal function when dosing as meropenem is substantially excreted by the kidney, and dose adjustment may be necessary 2

Treatment for Resistant Acinetobacter

• If the Acinetobacter is sensitive only to polymyxins (which may be the case given failure of piperacillin/tazobactam), intravenous polymyxin (colistin) is strongly recommended 1
• The recommended dosing for colistin is 5 mg/kg IV as a loading dose, then 2.5 mg (1.5 CrCl + 30) IV q12h 1
• Adjunctive inhaled colistin should be added to improve clinical outcomes, with a daily dose of 1.25-15 MIU divided in q8-12h, each dose diluted in 5 mL sterile normal saline 1

Alternative Treatment Options

• If susceptibility testing shows sensitivity to aminoglycosides, consider gentamicin (5-7 mg/kg IV qd) or amikacin (15-20 mg/kg IV qd), but be cautious with aminoglycosides in elderly patients due to risk of nephrotoxicity 1
• Tigecycline is not recommended for Acinetobacter infections due to increased mortality compared to other agents 1
• The FDA has issued a boxed warning for tigecycline, and its use should be avoided in this elderly patient with multiple comorbidities 1, 3

Treatment Duration and Monitoring

• For respiratory infections like pneumonia, a 14-day course of antibiotics is standard for Acinetobacter infections 1
• Monitor renal function closely, especially in elderly patients receiving nephrotoxic agents like colistin 1
• Consider obtaining follow-up sputum cultures to document clearance of infection 1

Important Considerations for Elderly Patients with Asthma

• Be vigilant for potential drug interactions and adverse effects, particularly in elderly patients with multiple comorbidities 1
• Colistin therapy has shown clinical cure in 57% of patients with Acinetobacter VAP with acceptable toxicity 1
• For elderly patients, the risk of adverse reactions may be greater due to decreased renal function; careful dose selection and renal function monitoring are essential 2

Common Pitfalls to Avoid

• Avoid aminoglycoside monotherapy for Acinetobacter infections as it is not recommended due to poor outcomes 1
• Do not use third-generation cephalosporins as they typically have poor activity against Acinetobacter species 1
• Avoid tigecycline due to increased mortality risk and FDA boxed warning 1
• Be aware that multidrug resistance is common in Acinetobacter isolates, with studies showing resistance rates of 73.3% to imipenem and 93.3% to piperacillin/tazobactam in some settings 4