C Hernandez, N Antony, S Antony
C Hernandez, N Antony, S Antony. An Observational Study using Daptomycin to treat Osteomyelitis. A Pilot Study.. The Internet Journal of Infectious Diseases. 2008 Volume 7 Number 2.
Daptomycin is a novel new antibiotic that has been approved for the use of skin and soft
tissue infections, right sided endocarditis, and gram positive bacteremia (1,2,3). There
has been some data published on the use of this drug in prosthetic joint infections and on
bone infections like osteomyelitis (4,5,6), but there has been no prospective published
data on the treatment of osteomyelitis as yet.
Material and Methods
We summarize our observational data over a 2 year period wherein daptomycin was used
as a primary drug in the treatment of osteomyelitis in a variety of sites. There were 36
patients in the study. The sites of osteomyelitis included knee (3), femur (2), foot (13),
sternum (9), vertebral (3), skull (1), ankle/joint (1), elbow (1). Cure was defined as no
evidence of active infection after treatment as evidenced by imaging studies and lab
studies and follow up in 6 months and 12 months.
The diagnosis was based on the clinical presentation and or bone/deep cultures. The
pathogens isolated included 28 patients with gram positive infections, MRSA (21),
MSSA (5), polymicrobial infections (MRSA and gram negative organisms) (2), and
enterococcus (1)) and culture negative (8).Twenty two of the 32 patients (61%) had been
treated with previous antibiotics for standard periods of time and had failed therapy.
Previous drugs included vancomycin (9), quinolones (6), trimethoprim-
sulphamethaxazole (2), nafcillan (1), cephalexin (1), aminogylcosides (1), carbapenem
(1), and linezolid (1).
No obvious risk factors were noted in the patients who failed antibiotic therapy.
MIC’s were < 0.5ug/ml in 12 patients in whom MIC’s were obtained. Eighteen patients
had no surgical debridement with the remaining undergoing debridement (92%) had
removal of hardware (11%) if needed. Mean duration of treatment with daptomycin was
37 days, with a range between 17 and 42 days. Dosage of daptomycin used was 4- 6
mg/kg/24h. All these patients were followed for an average of 6 months to 12 months.
Two patients (6%) expired of non-drug related causes; four patients (11%) failed
daptomycin therapy and had to be retreated with daptomycin- with clinical success.
MRSA patients comprised 21 (58%) of the study; which despite being treated with
daptomycin only 5% failed. Two patients were lost to follow up, and 28 patients (78%)
were presumed cured/improved. Among the 22 patients (61%) who received antibiotics
prior to the study, nine patients (25%) were treated with vancomycin, of which two of
these patients failed daptomycin the first time. No patients were terminated in this study
due to side effects of the drug. The overall failure rate of this study was 11% (4 patients).
The cure/improvement rate (78%) seen in this study is encouraging and seems to be in
keeping with other studies published (3) but will need to be substantiated in larger
multicentered prospective studies. This study also adds to the data available regarding the
safety of the drug. It appears that the 4 to 6 weeks of therapy at dosages ranging between
4- 6 mg/kg are safe and well tolerated. Repeat use of the drug was also well tolerated. In
addition, use of a higher dose (>6 mg/kg) may be necessary to see higher rates of clinical
success as suggested by other studies (3,5,6). Further study is needed to study patients
who fail therapy with daptomycin in osteomyelitis. Failure in this group of patients may
be due to a variety of reasons such as the site of infection, organism causing the
infections (MRSA), presence of hardware, underlying host factors, and other factors that
have not been well delineated (7-10). This data is additive to the data published
previously and suggest that daptomycin is a useful drug to treat osteomyelitis but
additional study is warranted to define whether surgical intervention in addition to
daptomycin plays a role in the outcome.