Identifying when to instruct a microbiologist in post-operative infection claims

The role of the microbiologist in clinical negligence litigation

In claims involving post-operative infection, the identification of the appropriate expert discipline is essential to the structure of the evidence. An instructing solicitor must determine whether the claim concerns the clinical management of a suspected infection, such as the timing and choice of antimicrobial therapy, or the surgical standard of care, such as intra-operative prophylaxis and theatre practice. Where the focus is on the clinical decision-making surrounding the diagnosis and treatment of a pathogen, a microbiologist expert report may be an appropriate instrument for establishing breach of duty.

Under CPR Part 35, the expert’s duty is to the court, and evidence must be limited to what is reasonably required to resolve the proceedings. A microbiologist provides specialist opinion on the interpretation of laboratory results, sensitivity patterns of organisms, and the appropriateness of an antimicrobial management plan. Conversely, when the disputed question is whether a surgeon adhered to aseptic technique, or whether a wound closure was adequate, the required evidence is surgical.

Establishing breach of duty

The standard for breach is defined by the Bolam test as qualified by Bolitho. A microbiologist may be instructed to establish whether the antimicrobial strategy adopted by the treating clinicians fell below a responsible body of professional opinion. This involves an assessment of the records against the clinical picture available at the time, without the benefit of hindsight. The report must demonstrate whether the selection of an antibiotic, the duration of treatment, or the decision to escalate therapy met the standards expected of a competent consultant microbiologist or infectious diseases physician.

If the evidence suggests that the infection was a recognised risk of the procedure, the microbiologist provides the necessary analysis to determine if the clinical response was compliant. Where an expert report fails to distinguish between an unavoidable complication and a failure to diagnose or treat, it risks conflating clinical outcome with a breach of duty. Professional legal guidance for clinical negligence claims can assist in navigating these complex distinctions during the early stages of litigation.

The evidential base for expert opinion

An expert opinion on microbiological management rests upon a complete clinical record. This includes:

• Microbiology laboratory reports, including sensitivity and resistance profiles.
• The full drug administration chart to verify the timing and dosage of antimicrobial agents.
• The patient’s pre-operative clinical history, including any documented history of colonisation with resistant organisms.
• Daily progress notes, which provide the chronological record of the patient’s physiological response to treatment.

Where the medical records are incomplete, the expert should state these limitations clearly. An opinion delivered in the absence of a comprehensive records review may be subject to challenge during cross-examination, as the expert cannot account for the evolving clinical evidence that informed the treating clinician’s decisions.

Causation and the boundaries of discipline

In post-operative infection claims, a microbiologist can address the causation aspect of the ‘but-for’ analysis. The expert must address whether, but for the alleged breach—such as a delay in initiating effective therapy—the outcome would have been different. This requires a granular assessment of the progression of the infection and the timing of clinical interventions.

The boundary between a microbiologist and a surgeon is particularly relevant when assessing the source of infection. A microbiologist can opine on whether the organism was likely introduced at the time of surgery or acquired as a nosocomial infection. However, the surgeon’s opinion is required to address whether the surgical field was appropriately prepared and maintained. Under CPR 35.12, the court may direct that two experts provide a joint statement, allowing the microbiologist and the surgeon to identify the areas of consensus and disagreement. This procedural step ensures that evidence on infection control is unified for the court.

Jurisdictional considerations

The instructions outlined here relate to civil litigation in England and Wales under the Civil Procedure Rules. In Scotland, the instruction of a skilled witness is governed by Chapter 43 procedure, with the admissibility of evidence guided by the principles in Kennedy v Cordia (Services) LLP [2016]. In Northern Ireland, similar principles of independent expert testimony apply. Where an expert has been instructed and further documents emerge, it may be necessary to request an addendum report. The expert’s overriding duty to the court under CPR 35.3 requires them to notify the instructing party if new evidence significantly alters their original opinion.