Diphtheroids/Propionibacterium Bacteraemia

Quick reference guide to the management of Diphtheroid/Propionibacterium bacteraemia

• Aim
• Background
• About Diphtheroids and Propionibacterium
• 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: Diphtheroids/Propionibacterium

Aim

The aim of this guideline is to:

• 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: Link (including Gram stain/Culture/MALDI/16S process):

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 Diphtheroids and Propionibacterium

Corynebacterium and propionibacterium species are both Gram positive bacilli (GPB).

Non-diphtheria corynebacterium, also known as coryneforms or diphtheroids, are environmental organisms found in water and soil, and commensals of the skin and mucous membranes of human and other animals. As a result, corynebacteria colonising the skin are able to contaminate blood culture samples. However, they may cause infection in some patient groups. Repeat negative blood cultures whilst off antibiotics may be required to confirm a diagnosis of contamination.

Propionibacterium species (e.g. Propionibacterium acnes) are part of the normal flora of human skin and mucosal surfaces. It is also a common environmental surface contaminant. Similar to corynebacteria, it is difficult to determine whether positive culture results for propionibacteria reflect contamination or true infection. Again repeat negative blood cultures whilst off antibiotics may be required to confirm a diagnosis of contamination.

Diphtheroids (Corynebacteria) and Propionibacterium species can cause infections. The most common type of infection they cause is an infection of prosthetic material, for example: Central venous catheters, prosthetic joints and central nervous system devices/catheters.

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Antimicrobial susceptibilities

The approach to antibiotic therapy should be guided by antimicrobial susceptibility. Treatment should be individualized depending on the clinical circumstances. The choice, duration, and route of antimicrobial therapy depend on the site of infection.
Corynebacteria are uniformly sensitive to vancomycin, teicoplanin and daptomycin.

Propionibacterium species are usually highly susceptible to penicillins, clindamycin, cephalosporins and vancomycin.

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Clinical differential diagnosis

Diphtheroids and propionibacterium species often represent contamination especially in the absence of any prosthetic devices. Where there is uncertainty blood cultures should be repeated. If multiple blood cultures are positive this increases the likelihood that this represents a significant result.

Diphtheroids and propionibacterium species are opportunistic pathogens that typically cause infection by colonising biomedical devices. They cause particular problems in:

• Prosthetic valve endocarditis
• CSF shunt infections
• Prosthetic joints
• Intravascular catheters, both temporary and permanent.

Identification of both diptheroids and propionibacterium species are identified in the laboratory by Gram film and colony morphology. Please refer to the GPB guideline for further details. If the clinical picture does not fit with the above, more uncommon GPB may be the cause (e.g. Listeria monocytogenes, Mycobacterium species, Actinomyces). Contact microbiology for further discussion if indicated.

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Antimicrobial treatment

The table below outlines some of the common infections associated with each of the clinical syndromes. Please be aware that these organisms can present in unusual ways, and that this list is by no means exhaustive.

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Supplementary Investigations

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

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References

• BNF
• EMC