Increasing Trends in Antimicrobial Resistance among Clinically Important Anaerobes and Bacteroides fragilis Isolates Causing Nosocomial Infections: Emerging Resistance to Carbapenems

Abstract

This study reports data on the susceptibilities to five commonly used antianaerobic agents of five clinically frequently encountered anaerobes from 2000 to 2007 and to Bacteroides fragilis isolates causing nosocomial infections from 1990 to 2006. There was a trend of decreasing susceptibilities of these anaerobes to ampicillinsulbactam, cefmetazole, chloramphenicol, and clindamycin with time during the study period. The rates of susceptibility to clindamycin and cefmetazole for all clinical isolates of Bacteroides fragilis isolates were higher than those of isolates associated with nosocomial infections. The MICs of 207 anaerobic blood isolates collected in 2006 to 14 antimicrobial agents were determined by the agar dilution method. The rates of nonsusceptibility to imipenem and meropenem were 7% and 12% for B. fragilis isolates (n ‫؍‬ 60), 7% and 3% for Bacteroides thetaiotamicron isolates (n ‫؍‬ 30), 4% and 4% for Fusobacterium species (n ‫؍‬ 27), 6% and 0% for Prevotella species (n ‫؍‬ 16), 15% and 0% for Clostridium species (n ‫؍‬ 28), and 0% and 0% for Peptostreptococcus species (n ‫؍‬ 32). The rates of susceptibility to moxifloxacin were 90% for B. fragilis isolates, 87% for B. thetaiotaomicron isolates, 81% for Fusobacterium species, 75% for Prevotella species, 93% for Clostridium species, and 78% for Peptostreptococcus species. Thirty-six percent of Clostridium species and 12% of Peptostreptococcus species were not susceptible to metronidazole. Comparison of the data with the data from a previous survey from the same institute in 2002 revealed higher rates of nonsusceptibility to carbapenems, especially for B. fragilis, Fusobacterium species, and Prevotella species isolates. The high rates of nonsusceptibility to commonly used antianaerobic agents mandate our attention, and periodic monitoring of the trend of the resistance is crucial.

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.…”

Antianaerobic Antimicrobials: Spectrum and Susceptibility Testing

“…Consequently, they are employed in more serious anaerobic infections, such as intra-abdominal and skin and soft tissue infections (89)(90)(91). Two recent reports have noted the development of some carbapenem resistance among anaerobes (22), ranging from 1.1 to 2.5% in a multicenter U.S. survey but with a higher rate for a small number of isolates from Taiwan (33).…”

“…Surveillance tests have been conducted for years by groups worldwide and reflect sweeping general trends (18,24,27,33,34,147) However, these results will not necessarily reflect the patterns of specific patients or hospitals. Because of this, the CLSI strongly recommends that hospitals conduct at least annual surveillance antimicrobial susceptibility testing to elucidate their local patterns.…”

“…These findings suggest that some isolates possessed novel inactivation mechanisms, suggesting that more than one mechanism of inactivation exists. A recent report from Taiwan noted increased carbapenem resistance in B. fragilis and other B. fragilis group species as well as some Prevotella species strains (33).…”

The antimicrobial peptide Ci-MAM-A24 is highly active against multidrug-resistant and anaerobic bacteria pathogenic for humans

“…Antibiotic treatment of these bacteria is often complicated by their slow growth, the low pH of the abscess environment and the increasing spread of resistance genes among these organisms [9]. Although the emergence of microbes posing severe therapeutic problems is constantly increasing, very few antibacterial therapeutic compounds of novel classes have been allowed admission to the market over the past 40 years [8,10].…”