Department of Microbiology Bacteraemia Guidelines

Coagulase negative staphylococci bacteraemia

• Aim
• Background
• About coagulase negative staphlococci
• Antimicrobial susceptibilities
• Clinical differential diagnosis
• Antimicrobial treatment
• Supplementary Investigations

This document provides guidelines for doctors on the management of patients with confirmed bacteraemias (blood cultures). This document is supplementary to, and should be used in conjunction with, the antimicrobial guidelines. Species: Coagulase negative staphylococci

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Aim

The aim of this guideline is to:

• Provide education to junior microbiology registrars
• Support communication of blood culture results from microbiologists to ward doctors
• Support ward doctors in treating and investigating bacteraemic patients

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Background

The blood culture process: Timings of culture, identification, susceptibility tests and clinical liaison.
How to use this guideline: This guideline should be used to help in the management of patients with a confirmed bacteraemia. The guideline should be used to support interaction with specialist advice e.g. Microbiology.

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About coagulase negative staphylococci

Coagulase negative staphylococci (CNS) comprise a large group of related species which are commonly found as part of normal skin flora e.g. Staphylococcus epidermidis. More than 40 species are recognised. As normal skin flora CNS are frequently encountered as blood culture contaminants. CNS are able to cause infections. They most commonly cause infections in the presence of prosthetic material. Due to the increased use of implants such as intravascular lines, cardiac valves, artificial joints they account for approximately 30% of health care associated bloodstream infections. Repeat negative blood cultures whilst off antibiotics may be required to confirm a diagnosis of contamination.

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Antimicrobial susceptibilities

Antibiotic treatment of CNS infections is complicated because susceptibility is generally unpredictable. Strains resistant to penicillin and penicillinase-stable penicillins (e.g. flucloxacillin and piperacillin/tazobactam) are common.

CNS are most reliably sensitive to Glycopeptides (e.g. vancomycin and teicoplanin) and are used empirically when CNS infection is suspected.

Vancomycin should be used to treat systemic CNS infections.

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Clinical differential diagnosis

CNS are opportunistic pathogens that typically cause infection by colonising biomedical devices. They cause particularly problems in:

• Prosthetic valve endocarditis
• CSF shunt infections
• Peritonitis (continuous and automated peritoneal dialysis)
• Prosthetic joints
• Intravascular catheters, both temporary and permanent.

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Antimicrobial treatment

Choice of antimicrobial and duration of treatment depends on clinical diagnosis. Please see table below.

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Supplementary Investigations

Consider further investigations as appropriate to source of infection, please see relevant guidelines.