Antimicrobial Susceptibility Profile of Rare Anaerobic Bacteria

Abstract

Anaerobes play an important role in clinically relevant infections and resistance is increasing worldwide. We tested 120 rare anaerobic isolates belonging to 16 genera for antimicrobial resistance using the agar dilution method and compared those results to the time-saving E-test method. The susceptibility data for 12 antimicrobial substances (benzylpenicillin, ampicillin/sulbactam, piperacillin/tazobactam, imipenem, meropenem, cefoxitin, metronidazole, moxifloxacin, clindamycin, doxycycline, tigecycline, eravacycline) were collected. Susceptibility testing showed low resistance to β-lactam/β-lactamase inhibitor combinations and no resistance to carbapenems and tigecycline. We observed moderate to high rates of resistance to moxifloxacin and clindamycin which differed depending on the methodology used. The essential and categorical agreement was over 90% for ampicillin/sulbactam, meropenem, moxifloxacin, and tigecycline. For metronidazole and clindamycin, the essential agreement was below 90% but the categorical agreement was near or above 90%. Penicillin presented with the lowest categorical agreement of 86.7% and a very high very major error rate of 13.3%. The resistance rates reported in this study are concerning and show the importance of routine susceptibility testing. Further investigations are necessary to determine the reason for high error rates and how to improve susceptibility testing of fastidious anaerobes.

Recent Trends in Antimicrobial Resistance among Anaerobic Clinical Isolates

“…and Alistipes spp. have also been reported [26]. Grampositive bacteria such as Actinomyces spp., Cutibacterium spp., and Propionibacterium spp.…”

“…Among Prevotella spp., a slight increase in penicillin-resistant isolates was described in Belgium between 1993–1994 (52%) and 2011–2012 (65%), while a higher increase was observed in Bulgaria between 2003–2004 (15%) and 2007–2009 (61%) [ 13 , 25 ]. In recent studies, most isolates are resistant to penicillin, with a prevalence of 60–80% in European countries, except for Germany, where Wolf et al noted a lower rate (36%) [ 13 , 19 , 26 , 27 ]. Over the world, resistance rates were similar in the US (65%) and Canada (63.5%), while a higher resistance rate was noted in Korea (91%) [ 21 , 22 , 28 ].…”

Antimicrobial resistance pattern of anaerobic bacteria causing lower respiratory tract infections

“…They have a broad spectrum of activity with low toxicity and are efficacious across anaerobic genera. However, recent resistance to this has been observed with a prevalence of 60–80% in European countries [ 11 , 12 , 28 ], USA (65%), Canada 63.5% and as high as 91% in Korea [ 8 – 10 ]. In our study, the resistant rates ranged from 58 to 65% in Gram-negative anaerobes and as high as 100% in Gram-positives.…”

“…[ 8 – 10 ]. Furthermore, the Gram-positive anaerobes showed sensitivity to imipenem and cefoxitin, while the highest resistance was seen for metronidazole and penicillin G [ 5 , 9 , 11 – 14 ]. The rates of resistance may show variations among geographic areas and between countries and hence need to be tested for deciding on empirical therapy.…”

Editorial for the Special Issue: “Current Technique for Antibiotic Susceptibility Test: Advantages and Limitations; Need for Next-Generation Test”

“…Their study aimed to provide susceptibility data for rare anaerobes and compare the gold-standard agar dilution method to the time-saving E-test methodology. Consequently, even though the species that were tested in this study are rare, it was unclear whether E-tests provided reliable results [ 10 ].…”