Recent Trends in Antimicrobial Resistance among Anaerobic Clinical Isolates

Abstract

Anaerobic bacteria are normal inhabitants of the human commensal microbiota and play an important role in various human infections. Tedious and time-consuming, antibiotic susceptibility testing is not routinely performed in all clinical microbiology laboratories, despite the increase in antibiotic resistance among clinically relevant anaerobes since the 1990s. β-lactam and metronidazole are the key molecules in the management of anaerobic infections, to the detriment of clindamycin. β-lactam resistance is usually mediated by the production of β-lactamases. Metronidazole resistance remains uncommon, complex, and not fully elucidated, while metronidazole inactivation appears to be a key mechanism. The use of clindamycin, a broad-spectrum anti-anaerobic agent, is becoming problematic due to the increase in resistance rate in all anaerobic bacteria, mainly mediated by Erm-type rRNA methylases. Second-line anti-anaerobes are fluoroquinolones, tetracyclines, chloramphenicol, and linezolid. This review aims to describe the up-to-date evolution of antibiotic resistance, give an overview, and understand the main mechanisms of resistance in a wide range of anaerobes.

Emergence of Antibiotic-Resistant Porphyromonas gingivalis in United States Periodontitis Patients

“…Meanwhile, clindamycin resistance in P. gingivalis is reported to be absent or low in the Netherlands, Germany, Switzerland, Japan, Spain, Italy, Turkey, Iran, and Brazil [5,6,73]. Consistent with our findings in the United States, anaerobic bacteria residing in non-oral body sites have also recently exhibited large increases in clindamycin resistance linked to the spread of rRNA-methylase-encoding erm antibiotic resistance genes [74].…”

Gastrointestinal Variant of Lemierre Syndrome due to <i>Fusobacterium nucleatum</i>: A Case Report

“…Blood cultures obtained during hospitalization did not reveal any growth for our patient; therefore, antibiotic susceptibility could not be ascertained. However, metronidazole, ampicillin-sulbactam, cephalosporins, and carbapenems generally demonstrate high susceptibility (95–100%) against Fusobacterium species, while resistance to penicillin within this group ranges from 5 to 17% [ 25 – 27 ]. Clindamycin resistance rates vary regionally, ranging from 6.7% to 25% [ 25 , 27 ].…”

“…However, metronidazole, ampicillin-sulbactam, cephalosporins, and carbapenems generally demonstrate high susceptibility (95–100%) against Fusobacterium species, while resistance to penicillin within this group ranges from 5 to 17% [ 25 – 27 ]. Clindamycin resistance rates vary regionally, ranging from 6.7% to 25% [ 25 , 27 ]. The patient was initially treated with IV cefepime and oral metronidazole but switched to IV ampicillin-sulbactam and oral trimethoprim-sulfamethoxazole for broader coverage.…”

“…Some studies report similar mortality in patients who were treated with therapeutic anticoagulation therapy and antibiotics versus antibiotics only [ 29 ]. However, a recent retrospective study by Naymagon et al [ 30 ] examined a cohort of 67 pylephlebitis patients, with those treated with anticoagulation demonstrating significantly higher rates of PVT resolution compared to non-anticoagulated patients (58% vs. 21%, p = 0.0201) [ 27 ]. This also led to lower rates of future chronic portal hypertensive symptoms in anticoagulated patients (11% vs. 47%, p = 0.0034).…”