Antibiotic Resistance in Centipeda periodontii Clinical Isolates

Objectives:  Centipeda periodontii may be isolated from severe periodontitis lesions and dental implants failing due to infectious complications (peri-implantitis), but its susceptibility to various antimicrobial agents remains unreported.  This study determined the occurrence of in vitro resistance to therapeutic levels of doxycycline, amoxicillin and metronidazole among fresh clinical C. periodontii subgingival isolates.  

Methods:  52 C. periodontii clinical isolates in subgingival specimens from severe periodontitis (51) and peri-implantitis (1) adult subjects were identified from flat, transparent, rapidly-spreading, non-corroding, colonies with irregular borders on anaerobically-incubated enriched Brucella blood agar as large, gram-negative, non-spore forming, obligately anaerobic, catalase-negative, multi-flagellated, serpentine motile rods with a centipede-like appearance in wet-mount darkfield microscopic preparations (Lai et al. 1983).  Species identification was confirmed with whole chromosomal C. periodontii-specific DNA probe dot-blot testing on a subset of isolates.  The organisms were tested in vitro for susceptibility to doxycycline at 2 µg/ml, amoxicillin at 2 µg/ml, and metronidazole at 4 µg/ml, with C. periodontii drug resistance noted when clinical isolate growth occurred on both antibiotic-supplemented and non-antibiotic supplemented enriched Brucella blood agar plates (van Winkelhoff et al. 2000; Rams et al. 2011).

Results:  C. periodontii in subjects averaged 1.2 ± 0.2 (SE) % (range 0.01-9.1%) of total cultivable subgingival anaerobic counts on non-antibiotic supplemented plates.  In vitro C. periodontii resistance to doxycycline at 2 µg/ml was detected in 2 (3.9%) clinical isolates.  No in vitro resistance to amoxicillin at 2 mg/ml or metronidazole at 4 mg/ml was found among any of the 52 C. periodontii clinical isolates studied.

Conclusions:  C. periodontii clinical isolates appear to be highly susceptible in vitro to therapeutic concentrations of antibiotics frequently used in the treatment of severe human periodontitis and peri-implantitis lesions.