Multiple resistance to betalactam antibiotics, azithromycin or moxifloxacin in implant associated bacteria.

ABSTRACT

BACKGROUND: Antibiotics are more and more frequently prescribed in dentistry for prevention and treatment of oral diseases. Bacterial resistance to these agents is clearly increasing, including even previously susceptible micro-organisms and true pathogens. The aim of the present investigation was to examine resistant bacterial strains with respect to possible multiple antibiotic resistance. METHODS: In a previous investigation, implant-associated bacteria were tested first as mixed cultures and again as pure isolates (n = 138) for resistance to one of five antibiotics (ampicillin/AM, ampicillin + sulbactam/AB, azithromycin/AZ, penicillin/PG, moxifloxacin/MX) using the Etest. The resistance of most of the pure isolates was lower than in mixed culture, but 31.2% had retained their original resistance. Subsequently, all 138 isolates were tested for resistance or susceptibility to the other four antibiotics, again using the Etest. RESULTS: 27.6% (38/138) of the isolates retained their original antibiotic resistance and were resistant to at least one other antibiotic (MIC > or = 128 microg/mL for AB, AM or AZ, > or = 32 microg/mL PG, > or = 24 microg/mL MX). 2.2% (3/138) strains had lost their original antibiotic resistance, but were resistant to at least one other antibiotic (MIC > 128 microg/mL for AB, AM, or AZ, > or = 32 microg/mL PG, > or = 24 microg/mL MX). CONCLUSIONS: Some of the isolates belonging to the implant-associated microflora were multi-resistant, even though the patients had not received any antibiotics six weeks prior to the sampling. The exact mechanisms that lead to multiple resistance need to be examined in further studies.