A landmark international clinical trial has identified the optimal antibiotics for golden staph bloodstream infections, a breakthrough that is set to reshape treatment for the life-threatening condition.
The SNAP Trial found that the standard antibiotic, flucloxacillin, should no longer be the drug of choice to treat the infection, revealing that cefazolin and benzylpenicillin offer safer and equally effective alternatives to patients.
The Staphylococcus aureus Network Adaptive Platform Trial (SNAP Trial), led by researchers at the Peter Doherty Institute for Infection and Immunity (Doherty Institute) and the University of Newcastle, is the largest international clinical trial ever conducted for golden staph (Staphylococcus aureus) infections involving more than 150 hospitals across more than 14 countries. The multi-centre trial rapidly evaluates different antibiotics and treatment strategies to reduce mortality and improve patient outcomes.
Professor Joshua Davis.
Golden staph infections cause over one million deaths per year. The most serious form of golden staph infections is when it enters the bloodstream, with a mortality rate of 15 to 25 per cent. While there are effective antibiotics to treat the bloodstream infections, uncertainty has remained over which treatments lead to the best patient outcomes.
Findings from the SNAP Trial, published today in the New England Journal of Medicine (NEJM) and The Lancet, challenge the long-held assumption that flucloxacillin should remain the default treatment and provide important new evidence to guide treatment strategy.
The NEJM study – Comparing cefazolin and flucloxacillin
In the study published in the NEJM, researchers compared antibiotics used to treat methicillin-susceptible Staphylococcus aureus (MSSA) infections. They found that cefazolin is at least as effective as flucloxacillin, but associated with fewer side effects and a lower risk of kidney injury.
The Royal Melbourne Hospital's Professor Steven Tong, an Infectious Diseases Physician at the Doherty Institute in Australia and global co-lead investigator of the SNAP Trial, said the results provide clear evidence that cefazolin should be considered the first-line option to treat MSSA bloodstream infections.
"In the treatment of MSSA bloodstream infections, there is an 89 per cent probability that cefazolin is associated with lower mortality," said Professor Tong.
"Patients treated with cefazolin fare better, with fewer deaths within 90 days (15 per cent compared to 17 per cent for those who received flucloxacillin). Cefazolin was also associated with fewer cases of acute kidney injury, at 14 per cent, compared to 20 per cent with flucloxacillin.
"The results are sufficiently compelling that I immediately made the switch in my own clinical practice."
The Lancet study – Comparing benzylpenicillin and flucloxacillin
In the paper published inThe Lancet, the study evaluated whether benzylpenicillin could be used to treat penicillin-susceptible Staphylococcus aureus (PSSA) infections where laboratory testing confirmed the susceptibility to penicillin.
Professor Todd Lee, a Scientist at the Research Institute of the McGill University Health Centre and Infectious Diseases and Internal Medicine Physician at the McGill University Health Centre in Canada and co-lead investigator of both studies, said benzylpenicillin was as effective as flucloxacillin and likely safer.
"Patients treated with benzylpenicillin experienced less kidney damage, with mortality also lower at 14 per cent compared with 22 per cent in the flucloxacillin group," said Professor Lee.
A shift away from flucloxacillin
Researchers said these results mark a turning point in the treatment of MSSA and PSSA bloodstream infections, signalling a shift in clinical practice.
Penicillin was once widely used to treat Staphylococcus aureus, but antibiotic resistance of golden staph led clinicians to adopt flucloxacillin as the standard treatment for MSSA and PSSA infections.
The findings support moving away from flucloxacillin as the default treatment for MSSA and PSSA infections, given safer and equally effective alternatives are available.
Professor Joshua Davis, an Infectious Diseases Physician at the University of Newcastle and the Hunter Medical Research Institute in Australia, and global co-lead investigator of the SNAP Trial, said some strains are once again susceptible to penicillin, renewing interest in carefully reintroducing older antibiotics.
"These findings show clinicians can confidently use penicillin susceptibility results to guide treatment where laboratory testing is available," said Professor Davis.
Lyn Whiteway, a sepsis survivor and consumer representative on both trials, welcomed the findings.
"The SNAP Trial shows what is possible when patients are truly at the centre of research. These findings will save lives and spare people from unnecessary harm," said Ms Whiteway.
Translating the findings
Researchers say the next challenge will be translating the findings into routine clinical practice.
While cefazolin availability may need to increase in some countries, researchers say implementation will ultimately depend on hospitals, laboratories and guideline groups incorporating the findings into clinical care.
"This is the largest trial ever conducted on staphylococcal bloodstream infections. It brought together countries from all over the world to answer important questions and improve care for millions of people," added Professor Lee.
"Trials generate the evidence, but the next step is making sure that evidence changes practice."
