Multicentre survey of the in-vitro activity of seven antimicrobial agents, including ertapenem, against recently isolated Gram-negative anaerobic bacteria in Greece

145

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.

Section: Discussionmentioning

confidence: 50%

Section: Discussionmentioning

confidence: 78%

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

Liu¹,

Huang

Liao

et al. 2008

145

“…Rates of resistance to clindamycin remained stable in the 33% to 35% range until 1998 and increased to 42.5% in 1999. In 2006, we found a clindamycin resistance rate of 47.9%, higher than the rates recently detected by other groups, that is, between 23% and 39% (8,13,16,19). Resistance to cefoxitin decreased from 12.8% in 1997 to 3.4% in 1999 (P Ͻ 0.04); this rate increased to 27% in 2006 (P Ͻ 0.0001).…”

mentioning

confidence: 47%

Resistance Trends of the Bacteroides fragilis Group over a 10-Year Period, 1997 to 2006, in Madrid, Spain

Betriú

Culebras

Gómez

et al. 2008

The changes in susceptibilities of Bacteroides fragilis group strains isolated in our hospital from 1997 to 2006 were studied. A total of 1,343 clinical strains were included. The study showed differences in the resistance rates in the different species of the group. Increasing resistance to clindamycin and moxifloxacin was observed. Susceptibility to imipenem, piperacillin-tazobactam, and metronidazole remained unchanged.Members of the Bacteroides fragilis group can cause infections as serious as intra-abdominal infection, postoperative wound infection, and bacteremia. An increase in the mean incidence of anaerobic bacteremia has recently been noted by Lassmann et al. (9), with the most commonly isolated organisms being those of the B. fragilis group. Over the past 20 years, geographic variations and increasing resistance of this group to several of the traditionally used antimicrobial agents and some of the newer ␤-lactam agents have been reported (1,2,6,14,17,18). Periodic monitoring of the susceptibility patterns of these organisms is now recommended. We studied the susceptibilities of B. fragilis group strains isolated in our hospital from 1997 to 2006 to determine changes and to detect resistance trends.(This study was presented at the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, IL, 17 to 20 September 2007).The study included a total of 1,343 B. fragilis group clinical strains isolated in our hospital from 1997 to 2006. Only one isolate per patient was studied to avoid duplication. The isolates were recovered from the following sources: abdomen (45.6%), skin and soft tissue (40.1%), blood (10.3%), genital tract (2.1%), respiratory tract (0.9%), and other sites (0.9%). Species were identified using the Rapid ID 32A system (bioMérieux, Marcy l'Etoile, France). Reference strains B. fragilis ATCC 25285 and B. thetaiotaomicron ATCC 29741 were used as controls. The MICs obtained by testing the quality control strains in parallel with test strains were within the acceptable range indicated by CLSI (formerly the NCCLS) for each antimicrobial agent tested.Susceptibilities were determined by the agar dilution method according to CLSI criteria (10). The following agents were studied: metronidazole, chloramphenicol, clindamycin, cefoxitin, imipenem, amoxicillin-clavulanate, piperacillin-tazobactam, moxifloxacin, and tigecycline (tested since 2000). To calculate antibiotic resistance rates, the CLSI-approved breakpoints (4) were used. The breakpoint for tigecycline resistance used was that established by the U.S. Food and Drug Administration.The most frequent species isolated within the group was B. fragilis (62%), followed by B. thetaiotaomicron (13.5%), B. uniformis (7.8%), B. vulgatus (3.5%), B. caccae (3.3%), B. distasonis (3.2%), B. ovatus (3.1%), B. eggerthii (0.6%), B. stercoris (0.5%), B. merdae (0.5%), and Bacteroides spp. (1.8%). There were no significant differences in the distribution of the various species during the study period.MIC ranges, MICs at which 50% and 90% of ...

“…(20,23,27), nim-positive Prevotella strains have rarely been found. Lubbe et al (23) detected one nimA-positive strain (Prevotella bivia) among seven strains screened, while Katsandri et al (20) recovered one nimC-positive strain (Prevotella oralis) and two nimE-positive isolates (P. oralis, Prevotella buccalis) from among 57 isolates tested.…”

Section: Discussionmentioning

confidence: 99%

“…have only rarely been investigated for the presence of nim genes in studies concerning metronidazole susceptibility (20,23,27). This led us to investigate a large panel of clinical Prevotella strains that belong to different species and that were isolated from patients hospitalized in two French tertiary-care teaching hospitals for the presence of nim genes and for the type of nim genes that they carry.…”

mentioning

confidence: 99%

Metronidazole Resistance in Prevotella spp. and Description of a New nim Gene in Prevotella baroniae

Alauzet

Mory

Teyssier

et al. 2010

Nonduplicate clinical isolates of Prevotella spp. recovered from patients hospitalized between 2003 and 2006in two French tertiary-care teaching hospitals were investigated for their susceptibility to metronidazole and the presence of nim genes. Of the 188 strains tested, 3 isolates displayed reduced susceptibility to metronidazole after 48 h of incubation, while 27 additional isolates exhibited heterogeneous resistance after prolonged incubation; all 30 of the isolates were nim negative. Among the remaining 158 isolates, 7 nim-positive isolates were detected. All of these strains were identified as Prevotella baroniae by 16S rRNA gene sequence analysis and contained a new nim gene, named nimI, as determined by DNA sequence analysis. Chromosomal localization of this single-copy gene was demonstrated in all clinical isolates as well as in type strain P. baroniae DSM 16972 by using Southern hybridization. No known associated insertion sequence elements were detected upstream of the nimI gene in any of the nim-positive strains by PCR mapping. After prolonged exposure to metronidazole, stable resistant subpopulations could be selected in nimI-positive Prevotella isolates (n ‫؍‬ 6) as well as in nim-negative Prevotella isolates (n ‫؍‬ 6), irrespective of their initial susceptibility to this antibiotic. This study is the first description of a new nitroimidazole resistance gene in P. baroniae which seems to be silent and which might be intrinsic in this species. Moreover, our findings highlight the fact that high-level resistance to metronidazole may be easily induced in both nim-positive and nim-negative Prevotella sp. strains.