Lemaire, Sandrine
[UCL]
Kosowska-Shick, Klaudia
Appelbaum, Peter C.
Glupczynski, Y.
[UCL]
Van Bambeke, Françoise
[UCL]
Tulkens, Paul M.
[UCL]
BACKGROUND: Co-trimoxazole, clindamycin and linezolid are used to treat community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, but little is known about intracellular activity. Moxifloxacin is active against intracellular methicillin-susceptible S. aureus (MSSA), but CA-MRSA has not been studied.
METHODS: We used 12 clinical CA-MRSA, 1 MSSA overexpressing norA and 2 hospital-acquired MRSA (moxifloxacin MICs: 0.03 to 4 mg/L). Activity was assessed in broth and after phagocytosis by THP-1 macrophages or keratinocytes {concentration-dependent experiments [24 h of incubation] to determine relative potencies [EC(50)], static concentrations [C(s)] and maximal relative efficacies [E(max) (change in log(10) cfu compared with initial inoculum)] and time-dependent experiments [0-72 h] at human C(max)}.
RESULTS: Concentration-dependent experiments: in broth, EC(50) and C(s) were correlated with the MIC for all antibiotics, but moxifloxacin achieved significantly (P < 0.01) greater killing (more negative E(max)) than the comparators; and in THP-1 cells and keratinocytes, moxifloxacin acted more slowly but still reached a near bactericidal effect (2 to 3 log(10) cfu decrease) at 24 h with unchanged EC(50) and C(s) as long as its MIC was ≤0.125 mg/L (recursive partitioning analysis). Clindamycin and linezolid were static, and co-trimoxazole was unable to suppress the intracellular growth of CA-MRSA. At human C(max) in broth, moxifloxacin killed more rapidly and more extensively (≥5 log(10) cfu decrease at 10 h) than clindamycin (4 log(10) cfu at 48 h) or co-trimoxazole and linezolid (1-2 log(10) cfu at 72 h).
CONCLUSIONS: Moxifloxacin is active against both extracellular and intracellular CA-MRSA if the MIC is low, and is more effective than clindamycin, co-trimoxazole and linezolid.
Bibliographic reference |
Lemaire, Sandrine ; Kosowska-Shick, Klaudia ; Appelbaum, Peter C. ; Glupczynski, Y. ; Van Bambeke, Françoise ; et. al. Activity of moxifloxacin against intracellular community-acquired methicillin-resistant Staphylococcus aureus : comparison with clindamycin, linezolid and co-trimoxazole and attempt at defining an intracellular susceptibility breakpoint.. In: Journal of Antimicrobial Chemotherapy, Vol. 66, no. 3, p. 596-607 (2011) |
Permanent URL |
http://hdl.handle.net/2078.1/105973 |