Kate Johnson

September 20, 2015

SAN DIEGO — Staphylococcus lugdunensis is underestimated as a cause of hospital-acquired osteoarticular infection, and should be treated aggressively, researchers reported here at the Interscience Conference of Antimicrobial Agents and Chemotherapy 2015.

"Until now, there have been only 47 cases published in the literature, and they are microbiology reports with no clinical information about outcome of treatment," said Piseth Seng, MD, PhD, from Assistance Publique des Hôpitaux de Marseille in France.

When this virulent coagulase-negative bacteria is encountered, "you have to treat it rapidly and follow for 2 years because most relapse occurs after 1 year," he told Medscape Medical News.

Dr Seng and his team assessed 138 patients with bone and joint infections caused by S lugdunensis who were treated at nine hospitals and three private clinics in southern France from 1995 to 2014.

The majority — 82% — of infections were associated with orthopedic devices. There were 66 infections of the prosthetic joint, 42 of the orthopedic joint, three of a vertebral orthopedic device, and two that occurred after anterior cruciate ligament reconstruction.

Median age of the patients was 61 years, 68% of the cohort was male, and 88% of infections occurred more than 1 month after device implantation.

Most patients were treated with surgery. However, outcomes were not significantly different between patients treated with surgery alone and those treated with device removal or extended antibiotic treatment, Dr Seng reported.

Table. Characteristics of the Study Cohort

Presentation and Surgical Treatment Percent
Clinical and biologic presentation  
   Pain 78
   Purulent discharge 59
   Erysipelas 59
   Fever 36
   Elevated C-reactive protein levels 62
Treatment  
   Amputation 6
   Surgical debridement with retention of orthopedic device 41
   Removal of orthopedic device 23
   Prosthesis exchange 14
   Prosthesis removal 1

 

After treatment, 76% of patients recovered, 19% experienced remission, and 3% died.

"We had a high percentage of relapse," said Dr Seng. "We suspect that the capacity to relapse may be due to resistant strains."

Reduced susceptibility to antistaphylococcal agents was low, however, with only five strains resistant to oxacillin, four to fosfomycin, two to fusidic acid, two to co-trimoxazole, one to rifampicin, and one to clindamycin, he reported.

"Coagulase-negative Staphylococcus is usually considered normal skin flora," said Alexander Blackwood, MD, from the University of Michigan Medical School in Ann Arbor. "However, in the context of medical devices, catheters, and other foreign body instrumentation, colonizations might be pathogenic."

Although coagulase-negative Staphylococcus is typically associated with less-severe and subacute illnesses, S lugdunensis appears to be more virulent than other coagulase-negative staph infections. In fact, it presents more like the coagulase-positive S aureus, as evidenced by these findings, he told Medscape Medical News.

Dr Seng and Dr Blackwood have disclosed no relevant financial relationships.

Interscience Conference of Antimicrobial Agents and Chemotherapy (ICAAC) 2015: Abstract K308. Presented September 18, 2015.

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