Microbiology of mandibular third molar pericoronitis: incidence of beta-lactamase-producing bacteria.
OBJECTIVE
The purpose of this study was to evaluate the predominant flora associated with pericoronitis in third molars and to investigate the presence of beta-lactamase-producing strains.


METHODS
The third molars in 26 adults were evaluated by cultures with nonselective media and with selective media containing amoxicillin, pristinamycin, spiramycin, metronidazole, and spiramycin plus metronidazole.


RESULTS
In the majority of cases (19/26), the flora found in an anaerobic atmosphere predominated. Obligate anaerobes were present in 21 of the 26 samples. The bacteria most commonly detected were alpha-hemolytic streptococci (26/26) and the genera Prevotella (15/26), Veillonella (15/26), Bacteroides (9/26), and Capnocytophaga (9/26). Amoxicillin and pristinamycin were the most active in reducing the anaerobic cultivable counts. beta-Lactamase-producing strains were detected in 9 samples and were mostly bacteria of the genera Prevotella, Staphylococcus, and Bacteroides.


CONCLUSIONS
These results highlight (1) the diversity of the microflora associated with pericoronitis and the importance of the anaerobic flora and (2) the existence of selection pressure related to the use of beta-lactams that may culminate in failure of prescribed penicillins.
Sixou
Jean-Louis
JL
University of Rennes 1, Rannes, France. jean-sixou@univ-rennes1.fr
Magaud
Christophe
C
Jolivet-Gougeon
Anne
A
Cormier
Michel
M
Bonnaure-Mallet
Martine
M
D000293:Adolescent; D000328:Adult; D000658:Amoxicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001421:Bacteria, Anaerobic / Q000145:classification* / Q000201:enzymology; D001439:Bacteroides / Q000145:classification / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008795:Metronidazole / Q000494:pharmacology; D008964:Molar, Third / Q000382:microbiology*; D010406:Penicillins / Q000494:pharmacology; D010497:Pericoronitis / Q000382:microbiology*; D018720:Prevotella / Q000145:classification / Q000187:drug effects; D025762:Pristinamycin / Q000494:pharmacology; D015572:Spiramycin / Q000494:pharmacology; D013291:Streptococcus / Q000145:classification / Q000187:drug effects; D014678:Veillonella / Q000145:classification / Q000187:drug effects; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D010406:Penicillins; D025762:Pristinamycin; D008795:Metronidazole; D015572:Spiramycin; D000658:Amoxicillin; D001618:beta-Lactamases