Surveillance of Antimicrobial Susceptibility of Anaerobe Clinical Isolates in Southeast Austria: Bacteroides fragilis Group Is on the Fast Track to Resistance

Abstract

Anaerobic bacteria play an important role in human infections. Bacteroides spp. are some of the 15 most common pathogens causing nosocomial infections. We present antimicrobial susceptibility testing (AST) results of 114 Gram-positive anaerobic isolates and 110 Bacteroides-fragilis-group-isolates (BFGI). Resistance profiles were determined by MIC gradient testing. Furthermore, we performed disk diffusion testing of BFGI and compared the results of the two methods. Within Gram-positive anaerobes, the highest resistance rates were found for clindamycin and moxifloxacin (21.9% and 16.7%, respectively), and resistance for beta-lactams and metronidazole was low (<1%). For BFGI, the highest resistance rates were also detected for clindamycin and moxifloxacin (50.9% and 36.4%, respectively). Resistance rates for piperacillin/tazobactam and amoxicillin/clavulanic acid were 10% and 7.3%, respectively. Two B. fragilis isolates were classified as multi-drug-resistant (MDR), with resistance against all tested beta-lactam antibiotics. The comparative study of 109 BFGI resulted in 130 discrepancies in 763 readings (17%) with a high number of Very Major Errors (VME) and Major Errors (ME). In summary, resistance rates, with the exception of clindamycin and moxifloxacin, are still low, but we are facing increasing resistance rates for BFGI. Surveillance studies on a regular basis are still recommended.

Recent Trends in Antimicrobial Resistance among Anaerobic Clinical Isolates

“…A decrease in susceptibility to meropenem among the B. fragilis group was also reported in Japan between 2010 and 2018–2019 (98% to 90%) [ 16 ]. In recent studies, AMC resistance ranges from 2 to 9% in B. fragilis, except in Spain, where higher rates were reported (29%) [ 15 , 17 , 18 , 19 , 20 ]. PTZ resistance remains lower, with a resistance rate varying between 1 and 3%, while the resistance rate reaches 5% in Korea and Greece [ 17 , 21 , 22 , 23 ].…”

“…PTZ resistance remains lower, with a resistance rate varying between 1 and 3%, while the resistance rate reaches 5% in Korea and Greece [ 17 , 21 , 22 , 23 ]. Higher AMC and PTZ resistance rates were reported in the B. fragilis group excluding B. fragilis , especially in B. thetaiotaomicron and Phocaeicola vulgatus [ 17 , 18 , 23 ]. In B. fragilis , the rate of resistance to carbapenems ranges from 0 to 5% for imipenem and from 2 to 5% for meropenem [ 15 , 17 , 18 , 19 , 20 , 21 , 23 , 24 ].…”

“…Higher AMC and PTZ resistance rates were reported in the B. fragilis group excluding B. fragilis , especially in B. thetaiotaomicron and Phocaeicola vulgatus [ 17 , 18 , 23 ]. In B. fragilis , the rate of resistance to carbapenems ranges from 0 to 5% for imipenem and from 2 to 5% for meropenem [ 15 , 17 , 18 , 19 , 20 , 21 , 23 , 24 ].…”

Compositional Data Analysis of 16S rRNA Gene Sequencing Results from Hospital Airborne Microbiome Samples

“…It is also the most common anaerobe recovered from various infections, such as intra-abdominal infection, foot ulcer, and bloodstream infection (e.g., [ 70 ]). In more detail, the Bacteroides fragilis group represents one of the most important anaerobic clinical pathogens and ranges under the 15 most common pathogens causing nosocomial infections (e.g., [ 71 ]). Within the Streptococcus genus, the related species S. pneumoniae is a major cause of community-acquired pneumonia, bacteraemia, and meningitis, with asymptomatic nasopharyngeal colonization generally representing a predisposing factor for pneumococcal infections [ 72 ].…”

Detection of the antibiotic resistance gene content of normal microbiota Bacteroides, Parabacteroides and Phocaeicola isolates from European countries

“…Antibiotic treatment is also important in such cases, but these species are the most antibiotic resistant anaerobic bacteria in terms of the antibiotic resistance levels and the number of resistance mechanisms against the various antibiotic classes. Their empirical therapy is based on resistance surveys which were frequent for the USA [3] and Europe [4] and were conducted from time to time in several westernized country [5][6][7][8][9][10]; and the number of developing countries where such studies were conducted is high or at least increasing [11][12][13]. The general trend is that very high (> 70%) resistance rates were obtained for penicillins, cephalosporins and tetracyclines, for cephamycins, MLS B drugs as clindamycin, and for moxi oxacin and amoxicillin/clavulanic acid intermediate serious resistances (10-50%) were detected and carbapenems, 5nitroimidazoles, tigecycline and sometimes piperacillin/tazobactam are very effective with low (< 10 − 5%) resistance rates [2,4].…”