What is the recommended antimicrobial therapy and management for a patient with a Raoultella planticola infection?

Management of Raoultella planticola Infection

For Raoultella planticola infections, empiric therapy should consist of a carbapenem (meropenem or imipenem-cilastatin) or ceftazidime-avibactam, with definitive therapy guided by antimicrobial susceptibility testing, as this emerging pathogen demonstrates increasing carbapenem resistance and requires treatment similar to carbapenem-resistant Enterobacterales.

Initial Empiric Antibiotic Selection

First-Line Options Based on Infection Severity

For serious infections (bacteremia, pneumonia, necrotizing soft tissue infections):

• Carbapenems remain the most reliable empiric choice, with meropenem 4g IV q8h or imipenem-cilastatin 1.25g IV q6h recommended for suspected carbapenem-susceptible isolates 1
• Aminoglycosides (amikacin) show consistent activity and should be considered, particularly as monotherapy has demonstrated efficacy in neonatal cases 2, 3
• Ceftazidime-avibactam 2.5g IV q8h infused over 3 hours is the preferred agent for carbapenem-resistant isolates, as it has proven efficacy against carbapenemase-producing R. planticola 1, 4

For less severe soft tissue infections:

• Fluoroquinolones (levofloxacin) may be appropriate for outpatient management of wound infections when susceptibility is confirmed 5
• Piperacillin-tazobactam can be considered in settings without high local prevalence of ESBL-producing organisms 1

Critical Resistance Patterns to Consider

R. planticola demonstrates alarming resistance patterns that directly impact treatment decisions:

• Carbapenem resistance is increasingly reported, with OXA-48 and KPC carbapenemases documented 4, 3
• ESBL production occurs in approximately 17% of isolates 3
• Intrinsic resistance to ampicillin-sulbactam and many cephalosporins is common 2
• Amikacin maintains the highest susceptibility rates across reported cases 2, 3

Combination Therapy Considerations

For critically ill patients or confirmed carbapenem-resistant isolates:

• Polymyxin-based combination therapy (polymyxin B or colistin) combined with ceftazidime-avibactam is recommended 1, 4
• A loading dose of 9 MU colistin followed by maintenance dosing of 4.5 MU twice daily should be used if polymyxin is selected 1
• Renal function must be monitored closely during colistin treatment as acute kidney injury significantly impacts mortality 1

For bloodstream infections with carbapenem resistance, combination therapy should be based on susceptibility results, typically pairing ceftazidime-avibactam with an aminoglycoside or polymyxin 1

Site-Specific Treatment Modifications

Pneumonia

• Treat as healthcare-associated pneumonia with antipseudomonal coverage 6
• Duration of 7-8 days is adequate for uncomplicated cases, though immunocompromised patients may require extended therapy 1

Bacteremia/Sepsis

• Minimum 14 days of therapy for uncomplicated bacteremia 3
• Blood cultures should be repeated to document clearance 7
• Consider endocarditis evaluation if persistent bacteremia occurs, as Gram-negative endocarditis requires 6 weeks of combination therapy 1, 7

Soft Tissue Infections

• Urgent surgical debridement is mandatory for necrotizing infections 1
• Antimicrobial therapy should continue until debridement is no longer necessary and fever has resolved for 48-72 hours 1
• Broad-spectrum coverage with carbapenems is appropriate in settings with high ESBL prevalence 1

Antimicrobial Susceptibility Testing Requirements

Susceptibility testing is absolutely essential as R. planticola resistance patterns are unpredictable:

• Request specific testing for carbapenems, aminoglycosides, and newer beta-lactam/beta-lactamase inhibitors 1
• Phenotypic carbapenemase detection should be performed for all carbapenem-resistant isolates 4, 3
• Genotypic testing (PCR for blaKPC, blaOXA-48, blaNDM) guides optimal therapy selection 4, 3

De-escalation Strategy

Once susceptibility results are available:

• Narrow to the most targeted agent with the narrowest spectrum 1
• Amikacin monotherapy is appropriate for susceptible isolates in neonates and less severe infections 2
• Fluoroquinolones can serve as oral step-down therapy for susceptible isolates 5
• Clinical improvement should be evident within 48-72 hours; lack of response mandates reassessment 8

Special Population Considerations

Neonates and Pediatric Patients

• R. planticola sepsis in neonates typically occurs after prolonged broad-spectrum antibiotic exposure (7-27 days) 2
• Amikacin demonstrates the most consistent activity in neonatal cases 2
• Infections cluster in hot, humid months (May-June), suggesting environmental transmission 2

Immunocompromised Patients

• Higher risk for severe infections including pneumonia and bacteremia 6
• Empiric coverage should include antipseudomonal agents pending culture results 1
• Consider combination therapy even for susceptible isolates given severity of infection 6, 4

Critical Pitfalls to Avoid

Do not assume susceptibility based on related organisms: R. planticola resistance patterns differ significantly from Klebsiella species despite phenotypic similarities 3

Do not delay carbapenemase testing: Carbapenem-resistant R. planticola has been associated with the only reported mortalities from this organism 6, 4

Do not overlook environmental sources: Prior broad-spectrum antibiotic use and proton pump inhibitors may select for R. planticola 2, 5

Do not use colistin monotherapy: Combination therapy is preferred for carbapenem-resistant isolates to prevent treatment failure 1, 4

Infection Control Measures

Active isolation and early detection are essential to prevent nosocomial outbreaks, as 80.9% of R. planticola infections are healthcare-associated 2, 3. Indwelling catheters and ICU stays are the most significant risk factors 3.