Poster Presentation 20th Lancefield International Symposium on Streptococci and Streptococcal Diseases 2017

Streptococcus is still a common cause of diabetic foot infection, a retrospective observational study in a multidisciplinary diabetic foot unit (MDFU) inpatient cohort (#212)

Robert M Hand 1 2 , Paul Ingram 3 , Lydia Lamb 4 , Dipen Sankhesara 2 , Tina Dilevska 5 , Erica Ryan 6 , Carsten Ritter 5 , Paul Norman 5 , Laurens Manning 3 7 , Emma Hamilton 4
  1. Telethon Kids Institute, University of Western Australia, Subiaco, Western Australia, Australia
  2. Department of General Medicine, Fiona Stanely Hospital, Murdoch, Western Australia, Australia
  3. Infectious Diseases Department, Fiona Stanely Hospital, Murdoch, Western Australia, Australia
  4. Department of Endocrinology and Diabetes, Fiona Stanely Hospital, Murdoch, Western Australia, Australia
  5. Department of Vascular Surgery, Fiona Stanely Hospital, Murdoch, Western Australia, Australia
  6. Podiatry Department, Fiona Stanely Hospital, Murdoch, Western Australia, Australia
  7. School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia, Australia

Background

Empiric antimicrobial regimes for diabetic foot infections (DFI) vary according to local epidemiology and prior colonisation/infection with resistant pathogens.  The utility of using results from culture of superficial swabs to guide empiric antibiotic therapy is not well established in Australia, particularly in the context of rising prevalence of drug resistant organisms. 

Aims

To assess the utility of DFI microbiology results and their relationship to empiric antibiotic prescribing.

Methods

Retrospective observational study of 151 admissions in 128 patients admitted to Fiona Stanley Hospital MDFU from 1st February 2015 to January 30th 2016.

Results

The mean age of patients was 60.4±14.9 years, 11.7% were Indigenous Australians.  Ninety-two percent of admissions were moderate or severe DFI.  The DFI's culturing Streptococcus, 97% were moderate or severe.  Of those with positive cultures, 85% were polymicrobial. Dominant pathogens included: S. aureus (48%), beta-hemolytic streptococci (24%), Enterobacteriaceae (15%), enterococci (8%) and Pseudomonas (6%). Excluding cultures of known skin commensals, the proportion of superficial cultures concordant with deep tissue or blood cultures for Streptococcal species ranged from 0-41% compared with 21% for S. Aureus.  Streptococcal bacteraemia occurred on 3 admissions.  Despite following antibiotic prescribing guidelines, overprescribing with anti-MRSA and/or anti-pseudomonal agents occurred commonly (76%), however empiric prescribing provided insufficient antimicrobial activity in 12%.

Conclusion

Streptococcus remain a common cause of diabetic foot infections.  Superficial swabs results correlated poorly with deep tissue or blood cultures.  Local knowledge regarding causative organisms may allow for reduction in broad spectrum empiric antibiotic therapy, minimizing the development of resistant organisms.