What are the recommendations for skin testing with meropenem in an adult patient with normal renal function and a history of allergies to beta-lactam (β-lactam) antibiotics prior to treating a Serratia marcescens infection?

Skin Testing for Meropenem in Beta-Lactam Allergic Patients

Skin testing is not necessary before administering meropenem to patients with a history of penicillin or cephalosporin allergy, including those with prior anaphylaxis, and meropenem can be given directly without testing or graded challenge. 1

Direct Administration Without Testing

Carbapenems like meropenem can be administered directly to patients with any history of penicillin or cephalosporin allergy without skin testing or additional precautions. 1 This recommendation is based on the minimal cross-reactivity between penicillins/cephalosporins and carbapenems due to their different core ring structures. 1

• Multiple prospective studies support this approach, including a 12-month study of 110 patients with reported penicillin allergies (51 with anaphylactic reactions, 59 with non-anaphylactic reactions) who all tolerated prolonged meropenem therapy (1-4 weeks) without any allergic reactions. 2
• A retrospective analysis of 182 hospitalized patients labeled with penicillin allergy who underwent bedside meropenem allergy assessment showed that 189 of 196 diagnostic workups (96.4%) were tolerated, with only two patients experiencing non-severe cutaneous reactions. 3

Clinical Algorithm for Meropenem Use

Step 1: Obtain Detailed Allergy History

• Document the specific beta-lactam that caused the reaction, timing, type of reaction (immediate vs. delayed), and severity. 4
• Identify whether the reaction was anaphylactic (angioedema, bronchospasm, hypotension) or non-anaphylactic (rash, urticaria). 2

Step 2: Screen for Absolute Contraindications

Do NOT administer meropenem (or any beta-lactam) if the patient has a history of:

• Stevens-Johnson syndrome 1
• Toxic epidermal necrolysis 1
• DRESS syndrome 1
• Other severe cutaneous adverse reactions 1

Step 3: Proceed with Direct Administration

• For patients with immediate-type hypersensitivity (including anaphylaxis) to penicillins or cephalosporins: administer meropenem directly without skin testing. 1, 2
• For patients with non-severe delayed reactions (e.g., simple rash): administer meropenem directly without skin testing. 1

Evidence Supporting This Approach

The recommendation against routine skin testing is supported by both guideline evidence and clinical research:

• The American Academy of Allergy, Asthma, and Immunology explicitly states that carbapenems may be given without testing or additional precautions regardless of whether the prior reaction was anaphylactic. 1
• Clinical experience demonstrates that there is little to no potential cross-reactivity between meropenem and penicillins, even in patients with definite anaphylactic reactions to penicillins. 2
• The limited availability of standardized skin test reagents makes testing impractical in clinical practice. 4

Important Caveats

When Skin Testing Might Be Considered

While not routinely recommended, bedside allergy assessment including skin prick tests, intradermal tests, and drug challenge tests can be performed if there is institutional capacity and the clinical situation allows for it. 3 However, this is not necessary for safe administration and should not delay treatment in serious infections like Serratia marcescens bacteremia.

Monitoring During Administration

• Observe the patient during the first dose administration for any signs of immediate hypersensitivity. 3
• Have standard resuscitation equipment available, as with any antibiotic administration in patients with allergy histories. 2

Cross-Reactivity Considerations

The cross-reactivity rate between penicillins and carbapenems is extremely low (estimated <1%) due to structural differences in the core ring structures. 1 This is in contrast to the higher cross-reactivity between penicillins and cephalosporins, which share more similar side-chain structures. 1

Practical Implementation for Serratia marcescens Infection

For your specific clinical scenario of treating Serratia marcescens in a patient with beta-lactam allergy history:

• Proceed directly with meropenem at standard dosing (1g IV every 8 hours for normal renal function) without skin testing. 5, 6
• Document the specific nature of the prior beta-lactam reaction in the medical record. 4
• Ensure the reaction history does not include severe cutaneous adverse reactions (absolute contraindication). 1
• Monitor clinically during initial administration as standard practice. 3

The evidence strongly supports that delaying meropenem therapy to perform skin testing is unnecessary and potentially harmful, as it delays appropriate antimicrobial therapy for a serious infection. 2