Intracellular Staph and abx resistance: implications for osteomyelitis

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J Orthop Res. 2006 Jan;24(1):87-93. Related Articles, Links

Intracellular Staphylococcus aureus and antibiotic resistance:

implications for treatment of staphylococcal osteomyelitis.

Ellington JK, M, Hudson MC, Vishin S, Webb LX, Sherertz R.

Department of Orthopaedic Surgery, Carolinas Medical Center, 1000

Blythe Boulevard, Charlotte, North Carolina 28223, USA.

Staphylococcus aureus is responsible for 80% of human osteomyelitis.

It can invade and persist within osteoblasts. Antibiotic resistant

strains of S. aureus make successful treatment of osteomyelitis

difficult. Null Hypothesis: antibiotic sensitivities of S. aureus do

not change after exposure to the osteoblast intracellular

environment. Human and mouse osteoblast cultures were infected and

S. aureus cells were allowed to invade. Following times 0, 12, 24,

and 48 h ( +/- the addition of erythromycin, clindamycin, and

rifampin at times 0 or 12 h), the osteoblasts were lysed and

intracellular bacteria enumerated. Transmission electron microscopy

was performed on extracellular and intracellular S. aureus cells. In

mouse osteoblasts, administration of bacteriostatic antibiotics at

time 0 prevented the increase in intracellular S. aureus. If the

antibiotics were delayed 12 h, this did not occur. When rifampin

(bactericidal) was introduced at time 0 to human and mouse

osteoblasts, there was a significant decrease in number of

intracellular S. aureus within osteoblasts compared to control. If

rifampin was delayed 12 h, this did not occur. Significant time-

dependent S. aureus structural changes were observed after exposure

to the osteoblast intracellular environment. These studies

demonstrate that once S. aureus is established intracellularly for

12 h, the bacteria are less sensitive to antibiotics capable of

eukaryotic cell penetration (statistically significant). These

antibiotic sensitivity changes could be due in part to the observed

structural changes. This leads to the rejection of our null

hypotheses that the antibiotic sensitivities of S. aureus are

unaltered by their location.

PMID: 16419973 [PubMed - indexed for MEDLINE]