Sensitivity of human strains of Oxalobacter formigenes to commonly prescribed antibiotics.
OBJECTIVE
To determine the sensitivity of 4 strains of Oxalobacter formigenes (Oxf) found in humans--HC1, Va3, CC13, and OxK--to varying concentrations of commonly prescribed antibiotics. Oxf gut colonization has been associated with a decreased risk of forming recurrent calcium oxalate kidney stones.


METHODS
For each strain and each antibiotic concentration, 100 μL of an overnight culture and 100 μL of the appropriate antibiotic were added to a 7-mL vial of oxalate culture medium containing 20 mM oxalate. On the fourth day, vials were visually examined for growth, and a calcium oxalate precipitation test was performed to determine whether Oxf grew in the presence of the antibiotic.


RESULTS
All 4 Oxf strains were resistant to amoxicillin, amoxicillin/clavulanate, ceftriaxone, cephalexin, and vancomycin, and they were all sensitive to azithromycin, ciprofloxacin, clarithromycin, clindamycin, doxycycline, gentamicin, levofloxacin, metronidazole, and tetracycline. One strain, CC13, was resistant to nitrofurantoin, and the others were sensitive. Differences in minimum inhibitory concentration between strains were demonstrated.


CONCLUSIONS
Four human strains of Oxf are sensitive to a number of antibiotics commonly used in clinical practice; however, minimum inhibitory concentrations differ between strains.
Department of Urology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
Jessica N
JN
Lange
Kyle D
KD
Wood
Hayes
H
Wong
Richard
R
Otto
Patrick W
PW
Mufarrij
John
J
Knight
Haluk
H
Akpinar
Ross P
RP
Holmes
Dean G
DG
Assimos
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D005243:Feces / Q000382:microbiology; D006801:Humans; D007422:Intestines / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D020624:Oxalobacter formigenes / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D014545:Urinary Calculi
D000900:Anti-Bacterial Agents