Antimicrobial susceptibility of clinical isolates of non-jejuni/coli campylobacters and arcobacters from Belgium

OBJECTIVES: To determine the susceptibility of non-jejuni/coli campylobacters and arcobacters isolated from diarrhoeal stool specimens in Belgium. METHODS: The MICs were determined using Etest for six antimicrobial agents including ampicillin, erythromycin, nalidixic acid, ciprofloxacin, gentamicin and tetracycline for the most frequently isolated non-jejuni/coli campylobacter and arcobacter strains in two University Hospital laboratories between 1995 and 2005. RESULTS: In total, 85 Campylobacter upsaliensis, 20 Campylobacter concisus, 11 Campylobacter fetus, 61 Arcobacter butzleri and 10 Arcobacter cryaerophilus isolates were tested. Most C. upsaliensis strains were susceptible to ampicillin (100%), gentamicin (100%), ciprofloxacin (94.1%) and tetracycline (100%), whereas 11.8 and 12.9% were resistant to nalidixic acid and erythromycin, respectively. For A. butzleri, 78.7% of isolates were susceptible to ampicillin and erythromycin. Most A. butzleri isolates were susceptible to ciprofloxacin (96.7%), nalidixic acid (82.0%), gentamicin (100%) and tetracycline (100%). All C. concisus strains were fully susceptible to ampicillin and tetracycline, but 5% of them were resistant to gentamicin, ciprofloxacin and erythromycin. Nearly all C. fetus and A. cryaerophilus strains were susceptible to erythromycin but the results should be interpreted with caution since only a small number of strains were tested. CONCLUSIONS: Fluoroquinolones should be considered in the treatment of severe C. upsaliensis and A. butzleri infection. When clinically indicated, erythromycin remains the first choice for the treatment of intestinal campylobacteriosis caused by C. concisus and C. fetus.     

Antimicrobial resistance in Campylobacter strains isolated from French broilers before and after antimicrobial growth promoter bans

OBJECTIVES: The antimicrobial susceptibility of Campylobacter strains isolated from standard and free-range broilers in 1992-1996 and 2001-2002 was studied. METHODS: Strains were isolated from caeca or skin samples collected from standard or free-range broilers arriving in slaughterhouses. The MICs of ampicillin, nalidixic acid, enrofloxacin, tetracycline, erythromycin and gentamicin were determined by agar dilution and compared according to species (Campylobacter jejuni or Campylobacter coli), production system and sampling period. RESULTS: Results showed that all chickens harboured Campylobacter. An increase over time of the C. coli/C. jejuni ratio for standard chickens occurred. A wide range of MICs was observed among isolates from the same broiler or from the same farm. Strains collected on entry to the slaughterhouse and after storage showed no significant difference in their antibiotic resistance. C. coli was more resistant than C. jejuni to tetracycline and erythromycin during the first period and to all tested molecules (except gentamicin) during the second period. Strains isolated from standard chickens were also more often resistant than those isolated from free-range broilers. The percentage of C. jejuni strains resistant to ampicillin decreased from 1992-1996 to 2001-2002, whereas no change could be observed for the other antimicrobial agents. However, for C. coli the resistance to ampicillin, nalidixic acid, enrofloxacin, tetracycline and erythromycin significantly increased. CONCLUSION: There was an increase in the incidence of antibiotic resistance of C. coli between 1992-1996 and 2001-2002.     

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.     

Role of efflux pumps and topoisomerase mutations in fluoroquinolone resistance in Campylobacter jejuni and Campylobacter coli

Point mutations in the topoisomerase (DNA gyrase A) gene are known to be associated with fluoroquinolone resistance in Campylobacter. Recent studies have shown that an efflux pump encoded by cmeABC is also involved in decreased susceptibilities to fluoroquinolones, as well as other antimicrobials. Genome analysis suggests that Campylobacter jejuni contains at least nine other putative efflux pumps. Using insertional inactivation and site-directed mutagenesis, we investigated the potential contributions of these pumps to susceptibilities to chloramphenicol, ciprofloxacin, erythromycin, and tetracycline in C. jejuni and Campylobacter coli. Insertional inactivation of cmeB resulted in 4- to 256-fold decreases in the MICs of chloramphenicol, ciprofloxacin, erythromycin, and tetracycline, with erythromycin being the most significantly affected. In contrast, inactivation of all other putative efflux pumps had no effect on susceptibility to any of the four antimicrobials tested. Mutation of gyrA at codon 86 (Thr-Ile) caused 128- and 64-fold increases in the MICs of ciprofloxacin and nalidixic acid, respectively. The replacement of the mutated gyrA with a wild-type gyrA allele resulted in a 32-fold decrease in the ciprofloxacin MIC and no change in the nalidixic acid MIC. Our findings indicate that CmeABC is the only efflux pump among those tested that influences antimicrobial resistance in Campylobacter and that a point mutation (Thr-86-Ile) in gyrA directly causes fluoroquinolone resistance in Campylobacter. These two mechanisms work synergistically in acquiring and maintaining fluoroquinolone resistance in Campylobacter species.     

A European survey of antimicrobial susceptibility among zoonotic and commensal bacteria isolated from food-producing animals

OBJECTIVE: To study antimicrobial resistance in zoonotic bacteria isolated from food animals in different countries using uniform methodology. METHODS: Samples were taken at slaughter from chickens, pigs and cattle in four EU countries per host. Escherichia coli (indicator organism; n = 2118), Salmonella spp. (n = 271) and Campylobacter spp. (n = 1325) were isolated in national laboratories and MICs tested in a central laboratory against, where appropriate, ampicillin, cefepime, cefotaxime, ciprofloxacin, chloramphenicol, erythromycin, gentamicin, nalidixic acid, streptomycin, tetracycline and trimethoprim/sulfamethoxazole. RESULTS: Isolation rates were high for E. coli, low for Salmonella and intermediate for Campylobacter. MIC results showed resistance prevalence varied among compounds, hosts and countries. For E. coli and Salmonella, resistance to newer compounds (cefepime, cefotaxime, ciprofloxacin) was absent or low, but to older compounds (except gentamicin), resistance was variable and higher. E. coli isolates from Sweden showed low resistance, whereas among isolates from Spain (pigs), resistance to ampicillin, chloramphenicol, streptomycin, tetracycline and trimethoprim/sulfamethoxazole was higher; the UK, France, the Netherlands, Germany, Italy and Denmark were intermediate. For Campylobacter spp. isolates from chickens, nalidixic acid and ciprofloxacin resistance was >30% in France and the Netherlands, >6% in the UK and zero in Sweden. Nalidixic acid resistance was high in cattle (20%-64%), whereas ciprofloxacin resistance was markedly lower in cattle, variable in pigs (3%-21%) and highest in Sweden. Generally, Campylobacter coli was more resistant than Campylobacter jejuni. CONCLUSION: Antimicrobial resistance among enteric organisms in food animals varied among countries, particularly for older antimicrobials, but resistance to newer compounds used to treat disease in humans was generally low.     

In vitro susceptibilities of Campylobacter-like organisms to twenty antimicrobial agents.

We determined MICs of 20 antimicrobial agents for 50 representative strains of four subgroups of Campylobacter-like organisms (CLOs) by agar dilution. Ampicillin, gentamicin, doxycycline, tetracycline, ceftriaxone, rifampin, spectinomycin, nalidixic acid, and chloramphenicol were active against all strains of CLOs. Most CLO strains (83%) were inhibited by 4 micrograms of sulfamethoxazole per ml and by 8 micrograms of trimethoprim-sulfamethoxazole per ml. Of type 1 strains, 28% were resistant to 8 micrograms of erythromycin per ml. In addition, cross resistance between erythromycin and clindamycin was always present. Type 1 strains exhibited a broad distribution of MICs of metronidazole and streptomycin, whereas all type 2 strains were uniformly susceptible to metronidazole and resistant to streptomycin. Unlike type 1 and 3 strains, type 2 CLOs were susceptible to cephalothin and penicillin G and highly resistant to streptomycin. The type 3 strain was uniquely resistant to cefazolin. The majority of strains were not inhibited by cefoperazone; and all were resistant to trimethoprim. In contrast to Campylobacter jejuni and Campylobacter fetus subsp. fetus, all CLOs tested were susceptible to 0.5 microgram of rifampin per ml.     

Cost analysis and antimicrobial susceptibility testing comparing the E test and the agar dilution method in Campylobacter jejuni and Campylobacter coli

Although numerous reports have compared the antimicrobial susceptibility of Campylobacter spp., controversy still exists about the use of the E test as an alternative to the agar dilution method suggested by the Clinical and Laboratory Standards Institute. MICs of 8 antimicrobials were determined using the E test and agar dilution methods for 103 Campylobacter jejuni and Campylobacter coli isolates from fresh chicken randomly purchased from stores in 3 southern Ontario counties. Overall, 72.6% of E test MIC values were within 1 log₂ dilution and 95.7% within 2 log₂ dilutions of the corresponding agar dilution MICs. For individual antimicrobials, agreement within 1 log₂ dilution and 2 log₂ dilutions was as follows: ampicillin (n = 103), 90.3% and 98.1%, respectively; chloramphenicol (n = 104), 85.6% and 99%; ciprofloxacin (n = 99), 51.5% and 97.0%; clindamycin (n = 99), 26.3% and 78.8%; erythromycin (n = 99), 52.5% and 96.0%; gentamicin (n = 99), 100% and 100%; nalidixic acid (n = 98), 91.8% and 99.0%; and tetracycline (n = 86), 82.6% and 97.7%. Relative to agar dilution, the E test underestimated the MIC value by a mean of 0.74 (ampicillin), 0.82 (chloramphenicol), 1.44 (ciprofloxacin), 1.94 (clindamycin), 1.40 (erythromycin), 0.21 (gentamicin), 0.94 (nalidixic acid), and 0.20 (tetracycline) log₂ dilutions and by a median of 1 log₂ dilution for all antimicrobials except clindamycin (2), gentamicin (0), and tetracycline (0). Cost analysis, including materials and labor, showed a 39.0% higher cost per analyte for the agar dilution method as compared with the E test. The most relevant advantage of the E test over the agar dilution method is the turnaround time because testing 99 strains by the agar dilution method takes 3.6 times longer compared with the E test using the same number of strains. The E test is an acceptable alternative for antimicrobial susceptibility testing in Campylobacter because it corresponds well with the agar dilution method although being considerably less expensive, is less labor intensive, and is more rapid. However, the relationship between E test and agar dilution MICs must be considered when interpreting E test results.     

Comparison of automated microbroth dilution and agar dilution for antimicrobial susceptibility of Campylobacter jejuni isolated from dairy sources

OBJECTIVES: To compare the agreement between microbroth dilution and agar dilution for antimicrobial susceptibility testing of Campylobacter jejuni. METHODS: Utilizing commercially prepared antimicrobial panels, microbroth dilution was compared with agar dilution for determining antimicrobial susceptibility in C. jejuni isolates. To assess the performance of both techniques for ampicillin, 190 C. jejuni isolates from dairy cattle were utilized. A group of 172 C. jejuni isolates from dairy sources were used to compare the susceptibility to ciprofloxacin, erythromycin, nalidixic acid and tetracycline. RESULTS: Our results indicate that microbroth dilution and agar dilution agree within +/-1 log2 dilution for 86.7% of the isolates tested. Ciprofloxacin had the highest level of agreement for isolates tested by both techniques, resulting in a kappa of 0.886 and 97.1% agreement +/-1 log2 dilution. The least agreement was observed in determining the susceptibility of isolates to ampicillin and erythromycin (82.1 and 79.7% agreement +/-1 log2 dilution). However, kappa statistics were considered to have good agreement for these antimicrobials. There were no significant differences in the summary statistics for any of the five antimicrobials evaluated for the isolates analysed by the percentage of resistant isolates, MIC50, MIC75 or MIC90 beyond +/-1 log2 dilution. There was no association in the classification of resistance by the testing methods employed. We also demonstrated that the quality control strain of C. jejuni ATCC 33650 performed in a consistent manner for both agar dilution and microbroth dilution. CONCLUSIONS: Microbroth dilution may be an acceptable alternative to agar dilution for determining susceptibility of C. jejuni in research or surveillance where flow of samples, labour efficiency and cost may restrict the use of agar dilution.     

Susceptibilities of Campylobacter jejuni isolates from Germany to ciprofloxacin,moxifloxacin, erythromycin,clindamycin, and tetracycline

To elucidate Campylobacter jejuni resistance to antibiotics in Germany, MICs of ciprofloxacin, moxifloxacin, erythromycin, clindamycin, and tetracycline were determined (using agar dilution) for 144 clinical isolates. The data indicate a considerable ciprofloxacin resistance (45.1%) without a clonal relationship of the strains and a greater in vitro activity of moxifloxacin, erythromycin, and clindamycin.     

空肠弯曲菌耐药谱特征分析

目的 分析十几年间我国空肠弯曲菌临床分离株对10种抗生素耐药谱特征,了解我国空肠弯曲菌耐药的变迁趋势。 方法 采用世界卫生组织(WHO)全球食源性病原菌感染网络(GFN)推荐的弯曲菌琼脂稀释法,测定1995年至今分离的116株空肠弯曲菌对6类10种抗生素的最小抑菌浓度(MIC)。 结果 经对实验结果整体分析,甲硝唑的总体耐药率最高为97.4%(113/116),四环素为82.8%(96/116),环丙沙星为80.2%(93/116),萘啶酸为79.3%(92/116),左氧氟沙星和氨苄西林耐药率相同,为40.5%(47/116),氯霉素为18.1%(21/116),庆大霉素为8.6%(10/116),链霉素为4.3%(5/116),最低为红霉素0(0/116)。随着时间的推进,萘啶酸、环丙沙星、左氧氟沙星和氨苄西林的MIC有明显增高趋势;四环素、红霉素、庆大霉素、氯霉素和甲硝唑的MIC值变化不明显;链霉素的MIC值变化有下降的趋势。6.1%的菌株出现了8种抗生素多重耐药的结果,且菌株均出现在2010年后。经统计学分析,萘啶酸、环丙沙星、链霉素、庆大霉素、氯霉素和氨苄西林6种抗生素在2001年前、2001-2005年、2006-2010年和2010年后4个时间段中耐药率差异有统计学意义。 结论 空肠弯曲菌对红霉素、庆大霉素以及链霉素3种抗生素依旧保持了较高的敏感性,对萘啶酸、环丙沙星、左氧氟沙星、四环素、甲硝唑以及氨苄西林6种抗生素产生了较大程度的耐药。     

Comparison of antimicrobial susceptibility patterns of fifty-seven strains of Haemophilus ducreyi isolated in Amsterdam from 1978 to 1985

The in-vitro activities of 16 antimicrobial agents were tested against 57 strains of Haemophilus ducreyi isolated in Amsterdam during an eight year period. The susceptibility patterns of the isolates from different years were compared. In the first four years more than 30% were beta-lactamase negative and showed MICs for tetracycline of 2 mg/l or less. From 1982 to 1985 all strains, except one, produced beta-lactamase and were tetracycline resistant. Furthermore, MICs for cefotaxime, sulphamethoxazole and trimethoprim increased. No changes were seen with cephradine, erythromycin, kanamycin, gentamicin, chloramphenicol, nalidixic acid, pipemidic acid, norfloxacin, pefloxacin or ciprofloxacin.     

Antibiotic resistance in Campylobacter jejuni and Campylobacter coli isolated from poultry in the South-East Queensland region

OBJECTIVES: The aim of this study was to determine the antimicrobial resistance patterns of 125 Campylobacter jejuni and 27 Campylobacter coli isolates from 39 Queensland broiler farms. METHODS: Two methods, a disc diffusion assay and an agar-based MIC assay, were used. The disc diffusion was performed and interpreted as previously described (Huysmans MB, Turnidge JD. Disc susceptibility testing for thermophilic campylobacters. Pathology 1997; 29: 209-16), whereas the MIC assay was performed according to CLSI (formerly NCCLS) methods and interpreted using DANMAP criteria. RESULTS: In both assays, no C. jejuni or C. coli isolates were resistant to ciprofloxacin or chloramphenicol, no C. coli were resistant to nalidixic acid, and no C. jejuni were resistant to erythromycin. In the MIC assay, no C. jejuni isolate was resistant to nalidixic acid, whereas three isolates (2.4%) were resistant in the disc assay. The highest levels of resistance of the C. jejuni isolates were recorded for tetracycline (19.2% by MIC and 18.4% by disc) and ampicillin (19.2% by MIC and 17.6% by disc). The C. coli isolates gave very similar results (tetracycline resistance 14.8% by both MIC and disc; ampicillin resistance 7.4% by MIC and 14.8% by disc). CONCLUSIONS: This work has shown that the majority of C. jejuni and C. coli isolates were susceptible to the six antibiotics tested by both disc diffusion and MIC methods. Disc diffusion represents a suitable alternative methodology to agar-based MIC methods for poultry Campylobacter isolates.     

Antimicrobial susceptibility testing of Campylobacter jejuni: a comparison between Etest and agar dilution method

The susceptibility of Campylobacter jejuni strains (n = 50) against nine antimicrobials were determined in comparison with Etest (AB BIODISK, Solna, Sweden) and agar dilution method to further investigate the correlation between the two methods. All the strains were isolated from stool samples of patients with diarrhea in 1998 and found to be highly susceptible (>84%) to ampicillin, tetracycline, gentamicin, chloramphenicol, ciprofloxacin and erythromycin. The essential agreement between two methods was 66.6% (+/-1 log(2) dilution) and 85.5% (+/-2 log(2) dilution). The agreement of susceptibility categories was higher at 94.4%.     

Susceptibilities to 10 antimicrobial agents of 1,220 Campylobacter strains isolated from 1987 to 1993 from feces of pediatric patients.

We report the in vitro antibiotic susceptibility of 1,220 strains belonging to the thermotolerant Campylobacter species, isolated from the feces of pediatric patients with diarrhea in the period from 1987 to 1993. The strains were identified as 1,148 C. jejuni isolates and 72 C. coli isolates. The overall results show that the strains showed drug resistance as follows: 51.8% to ampicillin, 4.4% to clindamycin, 2.6% to chloramphenicol, 21.2% to tetracycline, and 1% to gentamicin. Twenty-one strains (1.7%) displayed resistance to the combination of amoxicillin-clavulanic acid, and 3.2% of the strains were resistant to erythromycin (MIC of > or = 4 micrograms/ml), with a notable difference according to the species under consideration. While C. jejuni remained stable at 0.9 to 4% resistance to erythromycin, for C. coli the percentages detected ranged from 0 to 33%, with overall rates of 2.5 and 15.2% for the two species, respectively. Resistance to nalidixic acid (MIC of > or = 32 micrograms/ml) was found in 27.2% of the strains (27.8% for C. jejuni and 18% for C. coli), and resistance to ciprofloxacin (MIC of > or = 4 micrograms/ml) was found in 24.2% of the strains for C. jejuni and 15.2% for C. coli). Cross-resistance between nalidixic acid and ciprofloxacin was found in 89.1% of the strains (type 1 mutants), while 10.9% were resistant to nalidixic acid but susceptible to ciprofloxacin (type 2 mutants).     

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.     

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.     

Susceptibility of Campylobacter fetus subsp. jejuni to Twenty Antimicrobial Agents

One hundred recent clinical isolates of Campylobacter fetus subsp. jejuni were tested by an agar dilution technique for susceptibility to each of 20 antimicrobial agents. Doxycycline and gentamicin were the most active of the drugs examined, inhibiting all strains at concentrations achievable in serum. Although the median minimal inhibitory concentration of erythromycin was low, 8% of the isolates were highly resistant. All isolates of Campylobacter fetus subsp. jejuni were relatively resistant to the beta-lactam antibiotics. Some strains were highly resistant to metronidazole and tinidazole.     

In vitro antibiotic susceptibility testing of clinical isolates of Mycoplasma penetrans from patients with AIDS.

In vitro susceptibilities of Mycoplasma penetrans were determined. MICs and MBCs were determined. The MICs at which 50% of the isolates are inhibited (micrograms per milliliter) for broth dilution testing were as follows: azithromycin, 0.039; chloramphenicol, 0.625; ciprofloxacin, 0.156; clindamycin, 0.078; doxycycline, 0.312; erythromycin, 0.312; gentamicin. > 10; levofloxacin, 0.078; lincomycin, 0.625; streptomycin, > 10; and tetracycline, 1.25. Bactericidal activity was significant only for ciprofloxacin (MBC at which 50% of the isolates are killed, 0.312 microgram/ml) and levofloxacin (MBC at which 50% of the isolates are killed, 0.312 microgram/ml).     

In vitro susceptibility of isolates of Francisella tularensis types A and B from North America

Due to concern that Francisella tularensis, the causative agent of tularemia, may be used as a bioterrorist weapon, the Clinical and Laboratory Standards Institute recently provided a susceptibility testing method with breakpoints. Here, 169 isolates (92 type A and 77 type B) from North America were tested against seven antimicrobial agents (streptomycin, gentamicin, tetracycline, doxycycline, ciprofloxacin, levofloxacin, and chloramphenicol) used for the treatment of tularemia. The MICs for all of the isolates fell within the susceptible range. In addition, all isolates had MICs for erythromycin of 0.5 to 4 microg/ml, in contrast to an MIC of >256 microg/ml for the common laboratory strain LVS (live vaccine strain).     

Antimicrobial susceptibilities of Campylobacter strains isolated from Finnish subjects infected domestically or from those infected abroad

The in vitro susceptibilities of 678 Campylobacter jejuni and Campylobacter coli strains isolated from stool samples of the same number of Finnish subjects were studied. A total of 523 patients, representing inhabitants from throughout Finland, had not traveled abroad within the 2 weeks prior to becoming ill, whereas 155 persons had presumably acquired their infections abroad. The antimicrobial agents studied were erythromycin, ciprofloxacin, levofloxacin, trovafloxacin, and moxifloxacin. The MICs of these antimicrobial agents were determined by the agar dilution method. The growth of all domestic isolates was inhibited by erythromycin at concentrations of 4 microg/ml, and for these isolates the fluoroquinolone MICs at which 90% of isolates are inhibited (MIC(90)s) ranged from 0.06 to 0.5 microg/ml. For the foreign isolates, the erythromycin MIC(90) was still low (4 microg/ml), but their susceptibilities to fluoroquinolones were clearly reduced (MIC(90)s, 8 to 64 microg/ml). Of the four different fluoroquinolones studied, ciprofloxacin was the least active (MIC(90), 64 micro g/ml).