Management of Infections

Introduction

• Patients fulfilling sepsis criteria should initially receive intravenous antimicrobial therapy.
• Ensure appropriate dosing and consider drug interactions. Factors such as age, body weight, renal and hepatic function may require dose adjustments. 
• Review allergy history and ascertain the nature of drug reactions. Many reported allergies are intolerances or expected side effects.
• Review antimicrobial prescriptions daily. Review clinical response and new culture results and adjust antimicrobial therapy accordingly. For further guidance, see de-escalation and escalation sections below.
• Adhere to suggested durations of treatment. The majority of uncomplicated infections require ≤7 days of antimicrobial treatment.
• Dosing within this guidance is as per BNF unless otherwise stated, adjusted for severity of infection.

The Empirical Antimicrobial Guidelines

For general information on the Empirical Antimicrobial Guidelines, see link below:

• Empirical Antimicrobial Guidelines General Information

De-escalation of antimicrobial therapy

Early appropriate de-escalation improves outcomes, reduces the risk of adverse effects, such as C. difficile infection, and preserves the utility of broad spectrum antimicrobials for resistant infections.

In uncomplicated infections without bacteraemia, switch to oral therapy after 48 hours of IV therapy. Complicated and bacteraemic infections usually require courses of IV treatment >48 hours.

CRP does not reflect the severity of infection and may remain elevated even when infection is resolving. It cannot be used in isolation to assess the severity of infection and hence the need for IV therapy.

Once culture results are available, antimicrobial therapy should be adjusted to the most narrow-spectrum effective agent.

In the absence of culture results, the IV-to-oral switch therapy (IVOST) section provides guidance on oral conversion of the most commonly used empirical intravenous regimens.

Stopping antimicrobial therapy

Uncomplicated, non-bacteraemic infections should be treated with the shortest possible effective course if the patient is showing clinical improvement on the chosen antimicrobial regimen; suggested durations for the most common infections are given in the Empirical Antimicrobial Guidelines.

Infections associated with bacteraemia usually require courses of intravenous antimicrobials >48 hours; the duration is organism-dependent. Clinical advice regarding the management of any significant bacteraemia is routinely provided by a consultant microbiologist when the result is communicated to the clinical team.

Complicated or deep seated infections often require several weeks of intravenous antimicrobial treatment, especially if associated with sources that are inaccessible to surgical or radiological intervention. Advice can be sought from an infection specialist.

Escalation of antimicrobial therapy

Request urgent senior review if the patient is deteriorating clinically with new onset of severe sepsis, septic shock, or rapidly spreading severe skin and soft tissue infection.

If the patient is not clinically improving after 72 hours of antimicrobial therapy, but does not have severe sepsis or septic shock, continue current antimicrobials initially and:

• review the clinical diagnosis
• review microbiology results
• review dosing of antimicrobials
• ensure appropriate samples have been obtained
• re-culture if clinically indicated
• ensure source control

Antimicrobial prescribing tips

• Raised inflammatory markers and Systemic Inflammatory Response Syndrome (SIRS) are not specific to infection.  If you suspect infection:  identify the clinical source, sample and treat accordingly. If no clinical source of infection can be identified, also consider non-infective causes of inflammation.

• Review previous microbiology results before prescribing antimicrobials. Empirical antimicrobial guidelines apply only in the absence of previous microbiology results indicating resistance to the empirical regimen.

• Patients fulfilling sepsis criteria should initially receive intravenous antimicrobial therapy.

• Ensure appropriate dosing and consider drug interactions. Factors such as age, body weight, renal and hepatic function may require dose adjustments.

• Review allergy history and ascertain the nature of drug reactions. Many reported allergies are intolerances or expected side effects.

• Review antimicrobial prescriptions daily. Review clinical response and new culture results and adjust antimicrobial therapy accordingly.

• Adhere to suggested duration of treatment. The majority of uncomplicated infections require ≤7 days of antimicrobial treatment.

Sampling

Sampling advice for all conditions covered by the NHS Ayrshire & Arran Empirical Antimicrobial Guidance can be found in the respective organ-system sections. 

Detailed information on sampling requirements and processing (including tests sent to other laboratories) is available in the NHS Ayrshire & Arran Laboratory Handbook (link only active if accessing via NHS network).

Empirical treatment relies on more broad spectrum, more toxic agents, or agents associated with a high risk of C. difficile infection, and should not be regarded as a definitive treatment regimen in most cases of infection.

Susceptibility information is only available after culture and allows de-escalation to narrow spectrum, effective alternatives. 

Empirical therapy should be reviewed and replaced with a culture-based regimen as soon as results become available.

Good Practice

• The empirical policy only applies in the absence of previous results. 
• Sampling of the suspected focus of infection before antimicrobials are started or changed should be undertaken wherever possible.
• Do not obtain blood cultures at insertion of a peripheral venous cannula - this practice is associated with high rates of contamination.  
• Samples from sterile sites should be sent to the laboratory in a sterile universal container (white top). If the sample is injected into a blood culture bottle, it is not possible to perform cell counts or microscopy on receipt. 
• Samples of pus or fluids in a universal container are preferable to swabs.

Bacterial isolates with "I" susceptibility

For information on bacterial isolates with "I" susceptibility, see link below:

• Bacterial isolates with "I" susceptibility

Accessing advice from a microbiologist

For information on how to access advice from a microbiologist, see link below:

• Accessing advice from a microbiologist