Evaluation of linezolid, vancomycin, gentamicin and ciprofloxacin in a rabbit model of antibiotic-lock technique for Staphylococcus aureus catheter-related infection.
BACKGROUND
The effectiveness of linezolid, vancomycin, ciprofloxacin and gentamicin for treating experimental Staphylococcus aureus catheter-related infection by the antibiotic-lock technique was assessed.


METHODS
Two methicillin-susceptible (MSSA) ATCC strains and two methicillin-resistant (MRSA) clinical strains were used. New Zealand white rabbits were surgically implanted with a silicone intravenous catheter. Infection was induced by filling and locking the catheter with 0.3 mL of broth culture containing S. aureus, with turbidity equivalent to that of a 0.5 McFarland standard. Eighteen hours later the antibiotic-lock technique was started and continued for 24 h. Treatment groups were: control without treatment; 2000 mg/L linezolid; 2000 mg/L vancomycin; 2000 mg/L ciprofloxacin; and 40,000 mg/L gentamicin.


RESULTS
Linezolid and vancomycin showed equivalent activity, achieving significant reductions in log(10) cfu recovered from catheter tips in one MSSA strain (>1.12) and one MRSA strain (>0.77) as compared with controls (P < 0.05). Ciprofloxacin achieved significant log(10) cfu reductions in MSSA strains relative to controls (>2.51, P < 0.01). In one MSSA strain, ciprofloxacin showed a larger reduction in log(10) cfu than linezolid or vancomycin (P < 0.01). Gentamicin was the only antibiotic achieving negative catheter tip cultures (up to 87.5% in MSSA and up to 40% in MRSA, P < 0.01), and showed the greatest log(10) cfu reduction compared with controls (>4.25 in MSSA and >2.93 in MRSA, P < 0.05) and significant differences relative to the remaining treatment groups (P < 0.05 in both MSSA and MRSA).


CONCLUSIONS
Gentamicin showed the highest activity against both MSSA and MRSA biofilms.
Fernández-Hidalgo
Nuria
N
Infectious Diseases Department, Hospital Universitari Vall d'Hebron, Barcelona, Spain. nufernan@gmail.com
Gavaldà
Joan
J
Almirante
Benito
B
Martín
María-Teresa
MT
Onrubia
Pedro López
PL
Gomis
Xavier
X
Pahissa
Albert
A
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D018441:Biofilms / Q000187:drug effects; D055499:Catheter-Related Infections / Q000188:drug therapy*; D002404:Catheterization; D015169:Colony Count, Microbial; D004195:Disease Models, Animal; D004203:Disinfection / Q000379:methods*; D004864:Equipment and Supplies / Q000382:microbiology*; D006801:Humans; D011817:Rabbits; D013203:Staphylococcal Infections / Q000188:drug therapy*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents