Question

A patient with diabetes has a history of foot ulcer progressing to infection. Specifically, this is recurrent diabetic foot infection (DFI). That is, despite apparent success of the treatment the infection continues to reappear.

The initial diagnosis by the pathology laboratory uses microbiological investigation that has identified Staphylococcus aureus in this infection. Further simple analysis by PCR has revealed the presence of common toxins associated with S. aureus infections in the blood, skin and soft tissue and bone.

Describe a research plan you would undertake to identify:

if the recurrence of infection is due to a new infection or the same bacteria remaining present,

the molecular mechanisms used by this specific S. aureus isolate for its colonization,

the molecular mechanisms for its persistence and recurrent cause of DFI disease.

Answer 1

Staphylococcus aureus is a member of the normal flora of the body and frequently found in the nose, respiratory tract, and on the skin.

Patient sample of diabetic foot, nose and skin swabs can be taken for microbiological analysis and DNA analysis, to check if the bacteria is pre-existing from the body or not. This will also indicate a new infection if present.

The bacterial colonies can be tested with different antibiotics sensitive to S. aureus like erythromycin and mupirocin. Any resistant species can also be detected.

Further, DNA sequencing of S. aureus present in the patient infection can be carried out to identify any new strain in the infection.

To analyse S. aureus colonization mechanism, Proteomic profiling can be conducted on taped stripped skin samples of lesional and non-lesional skin of patients.This will help in the identification of potential biomarkers associated with colonization.

Analysis of pateint history, carriage frequency at several body sites and the diversity of S. aureus strains from patients and normal individuals (as control) to examine the recurrence.