Susceptibility of clinical isolates of Campylobacter jejuni to sixteen antimicrobial agents.

The activities of 16 antimicrobial agents against 103 clinical isolates of Campylobacter jejuni were tested. All the strains were susceptible to kanamycin and gentamicin. Chloramphenicol, nalidixic acid, and clindamycin were active against most of the strains. More than one-third of the strains were resistant to the tetracyclines and 12.5% were resistant to erythromycin.     

Susceptibility of Campylobacter jejuni and Campylobacter coli to macrolides and related compounds.

The susceptibility of 105 thermophilic campylobacters from human and swine origins to eight macrolides and related compounds was tested. Erythromycin, josamycin, clindamycin, and ASE 136 BS (a new erythromycin derivative) were the most active against the human strains. The swine strains were highly resistant, except to pristinamycin. The human Campylobacter coli strains (except for two strains) behaved like the C. jejuni strains.     

In vitro activities of new oral beta-lactams and macrolides against Campylobacter pylori.

The in vitro activities of amoxicillin, cefuroxime, ceftetrame, cefetamet, cefixime, tigemonam, erythromycin, roxithromycin, and dirithromycin against 30 clinical isolates of Campylobacter pylori were determined by an agar dilution technique. Roxithromycin and amoxicillin (MICs for 90% of isolates tested, 0.01 and 0.06 micrograms/ml, respectively) were the most active antibiotics tested, but all strains were susceptible to all antimicrobial agents tested.     

Effect of clavulanic acid on susceptibility of Campylobacter jejuni and Campylobacter coli to eight beta-lactam antibiotics.

The effect of clavulanic acid on the susceptibility of 32 strains of Campylobacter jejuni and Campylobacter coli to eight beta-lactam agents was studied. Almost all strains tested became susceptible to amoxicillin and ticarcillin with 1 microgram of clavulanic acid per ml. This compound had little or no effect on susceptibility to penicillin G, cephalothin, cefamandole, and cefoxitin. Clavulanic acid had a marginal effect on cefotaxime and moxalactam susceptibility.     

Susceptibility of clinical isolates of Campylobacter jejuni to twenty-five antimicrobial agents

The in-vitro activity of 25 antimicrobial agents against 113 to 161 clinical isolates of Campylobacter jejuni was tested by an agar dilution method. All strains were susceptible to the four aminoglycosides tested, to imipenem, chloramphenicol and norfloxacin. One strain (0.6%) was resistant to each of the following antibiotics: nalidixic acid, erythromycin and clindamycin. The frequency of tetracycline, metronidazole and cotrimoxazole resistance among our isolates was 14.5%, 56.4% and 96% respectively. In general, the beta-lactam antibiotics (penicillins and cephalosporins) showed only moderate to poor activity against C. jejuni. Of 159 strains tested, 89.3% produced beta-lactamases.     

In vitro synergistic activity between bismuth subcitrate and various antimicrobial agents against Campylobacter pyloridis (C. pylori).

The in vitro interactions between bismuth subcitrate and a variety of antimicrobial agents against 12 Campylobacter pyloridis (C. pylori) isolates were studied by the agar dilution checkerboard technique. The combination of bismuth subcitrate with the older quinolone, oxolinic acid, produced synergistic activity against all strains. This observation, however, could not be extended to the (aryl) fluoroquinolones, norfloxacin, ofloxacin, and difloxacin, since synergy was rare or absent when bismuth subcitrate was combined with these antibiotics. Among the other antimicrobial agents tested, rifampin and the beta-lactams frequently showed showed MICs for C. pyloridis similar to those of bismuth subcitrate.     

Comparison of antimicrobial susceptibility patterns of Campylobacter jejuni and Campylobacter coli

To determine whether employing antibiograms is useful to separate Campylobacter jejuni and Campylobacter coli, we determined the MICs of 12 antibiotics for 104 human clinical strains and 74 swine strains. Of 74 swine strains, 5 (7%) were hippurate positive, as were 93 (89%) of 104 human strains. The 12 antimicrobial agents tested were ampicillin, amoxicillin, clindamycin, chloramphenicol, erythromycin, furazolidone, norfloxacin, nalidixic acid, rosoxacin, rosaramicin, tetracycline, and Sch 32063. Isolates from humans were significantly (P less than 0.001) more susceptible than swine strains to clindamycin, erythromycin, rosaramicin, and Sch 32063. Of 11 human hippurate-negative strains, 3 (27%) were resistant to clindamycin, erythromycin, rosaramicin, and Sch 32063, compared with 1 of 93 (1%) hippurate-positive strains. Nearly all human and swine strains were susceptible to furazolidone and nalidixic acid. Campylobacter isolates from humans and swine have different antibiograms, and the susceptibility to certain antibiotics, such as clindamycin, may be helpful for differentiation of C. jejuni from C. coli.     

Comparative in vitro activities of twelve antimicrobial agents against Campylobacter species.

The in vitro susceptibility of 27 Campylobacter jejuni, 31 Campylobacter coli, and 30 Campylobacter fetus subsp. fetus strains to 12 antimicrobial agents was determined. Ciprofloxacin, a new quinoline derivative, was the most active agent tested. Antimicrobial susceptibility differed among the three species tested.     

Susceptibility of Campylobacter fetus subsp. jejuni to Twenty-Nine Antimicrobial Agents

The activity of 29 antimicrobial agents was tested against 95 strains of Campylobacter fetus subsp. jejuni isolated from human stools. Furazolidone and gentamycin were the most active agents. The tetracyclines, erythromycin, and chloramphenicol were very active against most of the strains, but with each antibiotic a few resistant strains were found. The penicillins were relatively inactive, and the cephalosporins tested were only active against occasional strains.     

Susceptibilities of fluoroquinolone-resistant strains of Campylobacter jejuni to 11 oral antimicrobial agents.

The resistance of Campylobacter jejuni strains to the fluoroquinolones is increasingly frequent, and in our area it reaches nearly 50%. We studied the susceptibilities of 60 of these strains to 11 oral antibiotics. All strains except one were susceptible to the macrolides tested, with azithromycin being the most active agent tested. Of the rest of the antibiotics studied, amoxicillin-clavulanic acid, clindamycin, and fosfomycin displayed good in vitro activities. Knowledge of the susceptibilities of these microorganisms to a varied group of oral agents is necessary in view of the appearance of multiresistant strains, such as those included in our series.     

In vitro activities of 47 antimicrobial agents against three Campylobacter spp. from pigs.

The in vitro activities of 47 antimicrobial agents against 30 isolates of Campylobacter species from pigs were determined by the agar dilution technique. The isolates were obtained from pigs with proliferative enteritis and included 10 strains each of Campylobacter coli, Campylobacter sputorum subsp. mucosalis, and "Campylobacter hyointestinalis Gebhart et al." (this name is not on the Approved Lists). Carbadox, furazolidone, nitrofurantoin, gentamicin, and dimetridazole were the most active drugs, inhibiting all three Campylobacter species with a MIC for 50% of the isolates of 2 micrograms/ml or less. Trimethoprim-sulfamethoxazole, cefazolin, sulfachloropyridazine, novobiocin, vancomycin, sulfathiazole, cyclohexamide, bacitracin, p-arsanilic acid, and colistin were the least active, with MICs for 50% of the isolates ranging from 16 to greater than or equal to 128 micrograms/ml.     

In vitro susceptibilities of aerotolerant Campylobacter isolates to 22 antimicrobial agents.

We evaluated the in vitro activities of 22 antimicrobial agents against 78 human and animal isolates belonging to two aerotolerant Campylobacter species, C. cryaerophila and C. butzleri, using a broth microdilution technique. An additional 10 antimicrobial agents were included at concentrations found in selective Campylobacter media. Strains of C. cryaerophila belonged to two DNA hybridization groups: DNA hybridization group 1A, which includes the type strain of C. cryaerophila, and DNA hybridization group 1B. The aminoglycosides, fluoroquinolones, and one tetracycline (minocycline) demonstrated the most activity against all DNA hybridization groups (C. cryaerophila DNA groups 1A and 1B and C. butzleri). Most isolates were resistant to cephalosporin antibiotics, with the exception of cefotaxime, and were variably susceptible to trimethoprim-sulfamethoxazole. C. cryaerophila DNA hybridization group 1A isolates were generally susceptible to the tetracyclines, chloramphenicol, nalidixic acid, azithromycin, erythromycin, and roxithromycin and moderately susceptible to clindamycin, trimethoprim-sulfamethoxazole, ampicillin, and ampicillin-sulbactam. The MICs of tetracyclines were higher for C. butzleri and C. cryaerophila DNA hybridization group 1B isolates than for C. cryaerophila DNA hybridization group 1A isolates, but most strains were still susceptible to doxycycline and tetracycline; all isolates were susceptible to minocycline. C. butzleri and C. cryaerophila DNA hybridization group 1B isolates were generally resistant to the macrolide antibiotics (including erythromycin), chloramphenicol, clindamycin, nalidixic acid, ampicillin, and trimethoprim-sulfamethoxazole. Differences in antimicrobial susceptibility between aerotolerant Campylobacter species and more common Campylobacter species, e.g., C. jejuni, suggest that different treatment strategies may be necessary. Strains of all three DNA hybridization groups of aerotolerant Campylobacter isolates were susceptible to colistin, polymyxin B, and rifampin at concentrations commonly used in selective media. These results suggest that primary isolation methods for Campylobacter species may need to be modified to include aerotolerant Campylobacter strains.     

Susceptibility of clinical isolates of Campylobacter pyloridis to 11 antimicrobial agents.

The activities of 11 antimicrobial agents, including two bismuth salts, against 70 strains of Campylobacter pyloridis isolated from gastric biopsy specimens were tested. The isolates were very susceptible to penicillin (the MIC for 90% of the strains tested [MIC90] was 0.03 microgram/ml), erythromycin, cefoxitin (MIC90, 0.12 microgram/ml), gentamicin, and ciprofloxacin (MIC90, 0.25 microgram/ml). The bismuth salts and nalidixic acid had moderate activity (MIC90, 16 to 64 micrograms/ml). Twenty percent of the isolates were resistant to metronidazole (MIC, greater than 1 micrograms/ml), and all were resistant to sulfamethoxazole and trimethoprim (MIC90, greater than 256 micrograms/ml).     

Susceptibility of Campylobacter pylori isolated from pediatric and adult patients to seven new quinolone antibiotics and nalidixic acid

The susceptibility of 26 strains of Campylobacter pylori to 7 new quinolone antibiotics and nalidixic acid was determined. All strains were resistant to nalidixic acid. Difloxacin, A-56620, A-62254, and ciprofloxacin were equally effective against the test strains with MICs ranging from 0.06 to 2.0 micrograms/ml. Fleroxacin, amifloxacin, perfloxacin, and norfloxacin showed only moderate activity against C. pylori. The new quinolone agents, which are bactericidal, may prove useful in the eradication of C. pylori from the gastric mucosa.     

Comparative susceptibilities of Campylobacter pylori to norfloxacin and other agents.

Twenty-one strains of Campylobacter pylori (Campylobacter pyloridis) were tested for susceptibility to norfloxacin and other agents by the serial agar dilution method. Ampicillin (MIC for 90% of isolates [MIC90], 0.016 micrograms/ml) and famotidine (MIC90, greater than 1,024 micrograms/ml) were, respectively, the most and the least active of the agents tested. Norfloxacin (MIC90, 1 microgram/ml) and imipenem (MIC90, 0.125 micrograms/ml) were substantially active against this organism.     

Emergence of fluoroquinolone resistance in Campylobacter jejuni and Campylobacter coli in subjects from Finland.

The in vitro susceptibilities of 102 human campylobacter strains isolated between 1978 and 1980 and 100 strains isolated in 1990 to ciprofloxacin, norfloxacin, erythromycin, gentamicin, and doxycycline were examined. The biotypes and heat-stable serotypes of the strains as well as antimicrobial treatments and travel history of the campylobacter-positive patients were also studied. The results indicated that susceptibility to erythromycin, gentamicin, and doxycycline has remained the same during the past 10 years. No gentamicin-resistant strains were found. Resistance to erythromycin was 3% in both groups of strains. However, the number of norfloxacin-resistant strains increased from 4 to 11% in the follow-up period, and ciprofloxacin-resistant strains, which had not occurred 10 years ago, composed 9% of the strains isolated in 1990. Thus, the increase of fluoroquinolone resistance in Campylobacter jejuni and Campylobacter coli has been significant in Finland in the past 10 years.     

Bacteriostatic and bactericidal activities of 24 antimicrobial agents against Campylobacter fetus subsp. jejuni.

The bacteriostatic and bactericidal activities of 24 antimicrobial agents were tested with the Dynatech MIC 2000 system against 86 strains of Campylobacter fetus subsp. jejuni from human sources. The penicillins (penicillin G, ampicillin, amoxycillin, carbenicillin) had poor activity. Ampicillin and amoxycillin were equally active. Cefotaxime revealed a rather good activity. Erythromycin, gentamicin, tobramycin, amikacin, and furazolidone were the most active compounds. Two strains (2.3%) were resistant to erythromycin. One strain (1.2%) was completely resistant to tobramycin. The tetracyclines (tetracyline, doxycycline, minocycline) were generally effective, but 8% of the strains were totally resistant to them. Minocycline was the most active. Chloramphenicol, thiamphenicol, and clindamycin had good activity. The bacteriostatic and bactericidal distributions for colistin, nalidixic acid, and metronidazole were broad.     

Tetracycline resistance of Australian Campylobacter jejuni and Campylobacter coli isolates

OBJECTIVES: Tetracycline resistance in Campylobacter is encoded by the tet(O) gene and is usually associated with conjugative plasmids. Little was known about tetracycline resistance in Australian Campylobacter species, therefore we investigated this resistance in 41 Campylobacter jejuni and five Campylobacter coli strains from humans and healthy chickens. METHODS: Tetracycline MICs were determined for each isolate using an agar dilution method. The distribution and localization of tet(O) on plasmid and chromosomal DNA was determined by Southern-blot experiments. The ability to transfer resistance to recipient strains was examined through conjugation studies. Identity of transconjugants was confirmed by PCR and flaA-restriction fragment length polymorphism analysis. RESULTS: High-level tetracycline resistance was observed, ranging from 32 to >256 mg/L. Plasmids were detected in 74% of isolates with plasmids between 30 and 40 kb in size most frequently isolated. tet(O) was present in all tetracycline-resistant isolates. In the majority of strains under study the tet(O) gene was chromosomally encoded. Tetracycline resistance of six C. jejuni strains in which tet(O) was plasmid mediated was transferred by conjugation to a C. jejuni recipient strain. Transfer did not occur between tetracycline-resistant C. jejuni strains and a C. coli recipient. No difference in MICs, plasmid carriage and tet(O) localization was detected between human and chicken isolates. CONCLUSIONS: These data indicate that the tet(O) gene, previously reported in Campylobacter strains throughout the world, is present in Australian Campylobacter. This study will lead to a greater understanding of antibiotic resistance distribution in Campylobacter spp. in Australia.     

Antimicrobial resistance in Campylobacter jejuni and Campylobacter coli strains isolated in 1991 and 2001-2002 from poultry and humans in Berlin, Germany

The susceptibilities of 430 Campylobacter jejuni strains and 79 C. coli strains to six antimicrobial agents were tested and analyzed. The two sets of strains originated from retail market chicken and turkey samples and from humans, respectively, in Berlin, Germany. Two groups of isolates, one dating from 1991 and the other dating from 2001-2002, were tested. Of the Campylobacter sp. isolates recovered from humans in 2001-2002, 45.1% were resistant to ciprofloxacin, 37.8% were resistant to tetracycline, 12.8% were resistant to ampicillin, and 50.0% were resistant to trimethoprim-sulfamethoxazole. All isolates were susceptible to gentamicin, while the overall rate of resistance to erythromycin was 6.1%. During the 10 years between the two sampling times, the rates of resistance to ciprofloxacin (P<0.001), ampicillin (P=0.035), and tetracycline (P=0.01) increased significantly among strains isolated from humans. Furthermore, among human C. coli strains the rate of resistance to erythromycin rose from 7.1% in 1991 to 29.4% in 2001-2002. In comparison, Campylobacter sp. isolates from poultry already had high rates of resistance in 1991. Different rates of resistance to tetracycline among isolates from chickens and turkeys suggested the development of resistance during antimicrobial treatment in food animals. Thus, discrepancies in the antimicrobial resistance rates among Campylobacter isolates originating from poultry and humans support the hypothesis that at least some of the resistant Campylobacter strains causing infection in humans come from sources other than poultry products.     

Antibiotic resistance in Campylobacter strains isolated from animals, foods, and humans in Spain in 1997-1998

Colonization by Campylobacter strains was investigated in human, broiler, and pig fecal samples from 1997-1998, as well as in foods of animal origin, and antibiotic susceptibility testing was carried out for these strains. Campylobacter strains were isolated in the foods of animal origin (55 of 101 samples; 54.4%), intestinal samples from broilers (85 of 105; 81%), and pigs (40 of 45; 88.9%). A total of 641 Campylobacter strains were isolated from 8,636 human fecal samples of clinical origin (7.4%). Campylobacter jejuni was the most frequently isolated species from broilers (81%) and humans (84%), and Campylobacter coli was most frequently isolated from pigs (100%). An extremely high frequency of ciprofloxacin resistance was detected among Campylobacter strains, particularly those isolated from broilers and pigs (99%), with a slightly lower result for humans (72%); cross-resistance with nalidixic acid was almost always observed. A higher frequency of resistance to erythromycin (81.1%), ampicillin (65.7%), gentamicin (22.2%), and amikacin (21.6%) was detected in C. coli strains isolated from pigs compared to those isolated from humans (34.5, 29.3, 8.6, and 0%, respectively). A low frequency of erythromycin resistance was found in C. jejuni or C. coli isolated from broilers. A greater resistance to ampicillin and gentamicin (47.4 and 11.9%, respectively) was detected in C. jejuni isolated from broilers than in human strains (38 and 0.4%, respectively). Beta-lactamase production was found in 81% of the Campylobacter strains tested, although 44% of them were characterized as ampicillin susceptible. The increasing rates of Campylobacter resistance make advisable a more conservative policy for the use of antibiotics in farm animals.