Multicenter Survey of the Changing In Vitro Antimicrobial Susceptibilities of Clinical Isolates of Bacteroides fragilis Group, Prevotella, Fusobacterium, Porphyromonas , and Peptostreptococcus Species

Abstract

In vitro surveys of antimicrobial resistance among clinically important anaerobes are an important source of information that can be used for clinical decisions in the choice of empiric antimicrobial therapy. This study surveyed the susceptibilities of 556 clinical anaerobic isolates from four large medical centers using a broth microdilution method. Piperacillin-tazobactam was the only antimicrobial agent to which all the isolates were susceptible. Similarly, imipenem, meropenem, and metronidazole were highly active (resistance, <0.5%), whereas the lowest susceptibility rates were noted for penicillin G, ciprofloxacin, and clindamycin. For most antibiotics, blood isolates were less susceptible than isolates from intra-abdominal, obstetric-gynecologic, and other sources. All isolates of the Bacteroides fragilis group were susceptible to piperacillin-tazobactam and metronidazole, while resistance to imipenem and meropenem was low (<2%). For these same isolates, resistance rates (intermediate and resistant MICs) to ampicillin-sulbactam, cefoxitin, trovafloxacin, and clindamycin were 11, 8, 7, and 29%, respectively. Among the individual species of the B. fragilis group, the highest resistance rates were noted among the following organism-drug combinations: for clindamycin,Bacteroides distasonis and Bacteroides ovatus; for cefoxitin, Bacteroides thetaiotaomicron, B. distasonis, and Bacteroides uniformis; for ampicillin-sulbactam,B. distasonis, B. ovatus, and B. uniformis; and for trovafloxacin, Bacteroides vulgatus. For the carbapenens, imipenem resistance was noted among B. fragilis and meropenem resistance was seen among B. fragilis, B. vulgatus, and B. uniformis. With few exceptions all antimicrobial agents were highly active against isolates of Prevotella, Fusobacterium, Porphyromonas, andPeptostreptococcus. These data further establish and confirm that clinically important anaerobes can vary widely in their antimicrobial susceptibilities. Fortunately most antimicrobial agents were active against the test isolates. However, concern is warranted for what appears to be a significant increases in resistance to ampicillin-sulbactam and clindamycin.

Anaerobic bacteria colonizing the lower airways in lung cancer patients

“…Amoxicillin/ /clavulanate was the only antimicrobial agent active against all the tested isolates, which may be important in the choice of empiric therapy not only for anaerobic but also for mixed infections. Moreover, among the tested anaerobes, representing mainly Gram-positive bacteria, the lowest resistance rates were for imipenem and cefoxitin, while the highest were for metronidazole and penicillin G. Consistent with the results of previous studies [18,20,22], the rates of resistance may show clinically important variations among geographic areas and between countries.…”

“…However, antimicrobial resistance of anaerobes has become an increasing problem over the past two decades; beta-lactamase production is one of the commonest resistance mechanisms [20,21]. According to our data, the anaerobic bacteria isolated from bronchial secretions in lung cancer patients were susceptible to the majority of the tested antimicrobials.…”

High Incidence of Cefoxitin and Clindamycin Resistance among Anaerobes in Taiwan

“…However, over the past 20 years, there e Fusobacterium species included F. mortiferum (3), F. necrophorum (3), F. nucleatum (6), F. varium (6), and an unidentified Fusobacterium sp. (1). f Prevotella species included P. buccae (4), P. intermedia (3), P. melaninogenicus (2), P. oralis (2), and unidentified Prevotella spp.…”

“…Antimicrobial resistance is becoming less predictable and may fluctuate from one medical center to another, as well as from one geographic region to another (1)(2)(3)(4)(7)(8)(9). The increasing resistance among several species emphasizes the need to survey the susceptibility patterns of these organisms.…”

“…Over the past 10 years, there has been a significant problem with increasing resistance to antimicrobial agents among anaerobic bacteria (1)(2)(3)(7)(8)(9). Antimicrobial resistance is becoming less predictable and may fluctuate from one medical center to another, as well as from one geographic region to another (1)(2)(3)(4)(7)(8)(9).…”