Association between double mutation in gyrA gene of ciprofloxacin-resistant clinical isolates of Escherichia coli and MICs.

The mutations in the quinolone resistance-determining region of the gyrA and gyrB genes from 27 clinical isolates of Escherichia coli with a range of MICs of ciprofloxacin from 0.007 to 128 micrograms/ml and of nalidixic acid from 2 to > 2,000 micrograms/ml were determined by DNA sequencing. All 15 isolates with ciprofloxacin MICs of > or = 1 micrograms/ml showed a change in Ser-83 to Leu of GyrA protein, whereas in clinical isolates with a MIC of > or = 8 micrograms/ml (11 strains), a double change in Ser-83 and Asp-87 was found. All isolates with a MIC of nalidixic acid of > or = 128 micrograms/ml showed a mutation at amino acid codon Ser-83. Only 1 of the 27 clinical isolates of E. coli analyzed showed a change in Lys-447 of the B subunit of DNA gyrase. A change in Ser-83 is sufficient to generate a high level of resistance to nalidixic acid, whereas a second mutation at Asp-87 in the A subunit of DNA gyrase may play a complementary role in developing the strain's high levels of ciprofloxacin resistance.     

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.     

Comparison of the Etest and agar dilution for in vitro antimicrobial susceptibility testing of Campylobacter

The performance of the Etest and agar dilution for in vitro antimicrobial susceptibility of Campylobacter spp. was evaluated using a quality control strain Campylobactor jejuni ATCC 33560, and 81 C. jejuni and 54 Campylobacter coli isolates recovered from retail raw meats. Seven antimicrobial agents: chloramphenicol, ciprofloxacin, doxycycline, erythromycin, gentamicin, nalidixic acid and tetracycline, were tested using the two methods, whereas azithromycin was tested using the Etest only. The correlation between the Etest and agar dilution MICs varied greatly depending on the antimicrobial agents tested. The overall agreement of MICs (+/-1 log(2) dilution) between the two methods was 61.9%, ranging from 21.4% for nalidixic acid to 92.6% for gentamicin. MICs obtained using the Etest were generally lower than those by agar dilution regardless of the species of organism tested. MIC(50) and/or MIC(90) values were at least one dilution lower for the Etest than for agar dilution when testing chloramphenicol, ciprofloxacin, doxycycline, erythromycin and nalidixic acid. Based on the agar dilution MICs, the resistant rate of the 135 Campylobacter isolates was highest for tetracycline (82.2%), followed by doxycycline (78.5%), nalidixic acid (21.5%), ciprofloxacin (20.7%) and erythromycin (17.0%). None of the isolates demonstrated resistance to chloramphenicol or gentamicin. The study indicated that the Etest results were not in complete agreement with the agar dilution test. Although the Etest has been proven to be a satisfactory testing method, its use for Campylobacter susceptibility testing requires further standardization. The study also showed that C. jejuni and C. coli isolates resistant to antimicrobials used for treating campylobacteriosis were common in retail raw meats.     

Comparative susceptibilities of 173 aerobic and anaerobic bite wound isolates to sparfloxacin, temafloxacin, clarithromycin, and older agents.

The in vitro activities of sparfloxacin, temafloxacin, ciprofloxacin, ofloxacin, clarithromycin, erythromycin, tetracycline, cephalothin, penicillin G, and amoxicillin-clavulanic acid against 173 recent clinical bite wound isolates were determined by agar dilution. Sparfloxacin was active against all strains (MIC for 90% of strains tested, < or = 1 micrograms/ml) except for most fusobacteria and one-third of the Prevotella spp. The other fluoroquinolones had similar activities but higher MICs, especially for streptococci. Clarithromycin was more active against many isolates including Pasteurella multocida than erythromycin, with MICs of < or = 2 micrograms/ml (versus 4 micrograms/ml for erythromycin).     

Proposed criteria for interpretation of susceptibilities of strains of Neisseria gonorrhoeae to ciprofloxacin, ofloxacin, enoxacin, lomefloxacin, and norfloxacin.

The susceptibilities of 45 strains of Neisseria gonorrhoeae, including 25 strains susceptible to ciprofloxacin (MICs, < or = 0.06 microgram/ml) and 20 strains exhibiting decreased susceptibilities to ciprofloxacin (MICs, > or = 0.125 microgram/ml), to ciprofloxacin, ofloxacin, enoxacin, lomefloxacin, norfloxacin, and nalidixic acid were determined by agar dilution and disk diffusion. On the basis of theoretical calculations of predicted susceptibilities at which infections may fail therapy (supported by observed failures of infections to respond to the therapeutic doses of enoxacin and ciprofloxacin), the Centers for Disease Control and Prevention has adopted the following agar dilution breakpoints for interpretation of resistance to these agents: MICs of > or = 1.0 microgram of ciprofloxacin, enoxacin, and norfloxacin per ml and MICs of > or = 2.0 micrograms of ofloxacin and lomefloxacin per ml. The corresponding disk diffusion breakpoints for these agents were as follows: ciprofloxacin, < or = 29 mm; ofloxacin, < or = 24 mm; enoxacin, < or = 31 mm; lomefloxacin, < or = 26 mm; and norfloxacin, < or = 32 mm. The Centers for Disease Control and Prevention recommends two strains as interim quality control strains for susceptibility testing of ciprofloxacin and ofloxacin. These are N. gonorrhoeae CDC-10,328 (MIC of ciprofloxacin, 0.125 to 0.25 microgram/ml [inhibition zone diameter range, 30 to 34 mm]; MIC of ofloxacin, 0.5 microgram/ml [inhibition zone diameter range, 27 to 32 mm]) and N. gonorrhoeae CDC-10,329 (MIC of ciprofloxacin, 1.0 to 2.0 micrograms/ml [zone inhibition diameter range, 21 to 26 mm]; MIC of ofloxacin 2.0 micrograms/ml [inhibition zone diameter range, 18 to 21 mm]).     

Prevalence of multiple antibiotic resistance in 443 Campylobacter spp. isolated from humans and animals

AIMS: In view of recent findings that a multidrug efflux pump CmeABC exists in Campylobacter jejuni, 391 C. jejuni and 52 Campylobacter coli of human and animal origin were examined for a multidrug resistance phenotype. MATERIALS AND METHODS: The MICs of ampicillin, chloramphenicol, ciprofloxacin, erythromycin, kanamycin, tetracycline, cetrimide, triclosan, acridine orange, paraquat and ethidium bromide were determined. Resistance to organic solvents and the effect of salicylate (known inducer of the marRAB operon in Escherichia coli and Salmonella) were also examined. RESULTS: Two C. coli and 13 C. jejuni isolates, mainly from pigs or poultry, were resistant to three or more antibiotics and 12 of these strains had reduced susceptibility to acridine orange and/or ethidium bromide. Strains (n = 20) that were less susceptible to acridine orange, ethidium bromide and triclosan were significantly more resistant (P < 0.05) to ampicillin, chloramphenicol, ciprofloxacin, erythromycin, nalidixic acid and tetracycline, with two- to four-fold increases in MIC values compared with strains (n = 20) most susceptible to acridine orange, ethidium bromide and triclosan. Growth of strains with 1 mM salicylate caused a small (up to two-fold) but statistically significant (P < or = 0.005) increase in the MICs of chloramphenicol, ciprofloxacin, erythromycin and tetracycline. CONCLUSIONS: These data indicate that multiple antibiotic resistant (MAR)-like Campylobacter strains occur and it may be postulated that these may overexpress cmeABC or another efflux system.     

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).     

In vitro susceptibilities of isolates of Haemophilus ducreyi from Thailand and the United States to currently recommended and newer agents for treatment of chancroid.

We determined the in vitro susceptibilities of 54 isolates of Haemophilus ducreyi from Thailand (29 isolates) and San Francisco (25 isolates) to penicillin G, tetracycline, amoxicillin-clavulanic acid, ceftriaxone, cefixime, erythromycin, azithromycin, ciprofloxacin, ofloxacin, and trimethoprim-sulfamethoxazole. Isolates were susceptible to < or = 0.25 microgram of ceftriaxone per ml, < or less 0.5 microgram of cefixime per ml, < or = 0.125 microgram of ciprofloxacin per ml, and < or = 0.06 microgram of ofloxacin per ml. Erythromycin was active against all isolates (MIC for 90% of isolates tested, 0.25 microgram/ml), as was azithromycin (MIC, < or = micrograms/ml). In contrast, all but one isolate were resistant to > or = 8.0 micrograms of tetracycline per ml, 11.1% of the isolates were resistant to and 40.9% of the isolates were resistant to trimethoprim-sulfamethoxazole (MIC, > or = 4/76 microgram/ml.)     

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.     

In vitro activities of new fluoroquinolones against Campylobacter jejuni and Campylobacter coli isolates obtained from humans in 1980 to 1982 and 1997 to 2001

The antibacterial activities of three newly developed fluoroquinolones (gatifloxacin, levofloxacin, and moxifloxacin) against a total of 307 gastrointestinal human isolates of Campylobacter jejuni and Campylobacter coli collected during 1980 to 1982 and 1997 to 2001 were examined and compared to those of ciprofloxacin and the unrelated antibacterial agents, clarithromycin, erythromycin, and tetracycline by using the agar plate dilution method. All of the fluoroquinolones exhibited a good activity against Campylobacter, and some of them were more active than ciprofloxacin, the macrolides, and tetracycline. Among the fluoroquinolones, gatifloxacin and moxifloxacin showed the highest anticampylobacter activity, with MICs at which 50% of the isolates tested are inhibited (MIC(50)s) and MIC(90)s of 0.125 and 4 microg/ml, respectively; the MIC(50) for both levofloxacin and ciprofloxacin was 0.25, and the MIC(90)s were 16 and 32 microg/ml, respectively. About 30% of the strains were found to be resistant to at least one fluoroquinolone. Resistance to gatifloxacin occurred in 9.8% of the isolates tested, and resistance to the other fluoroquinolones occurred in 19.9 to 27.4% of the isolates tested; the frequency of cross-resistance was 35.7 to 100%. An increase in fluoroquinolone resistance from 0% in 1980 to 1982 to 11.8 to 29% in 1997 and 1998, 8.2 to 31.8% in 1999 and 2000, and 12.1 to 30.3% in 2001 was found. A total of 61.4 to 73.2% of the C. jenuni strains resistant to erythromycin, clarithromycin, and/or tetracycline were susceptible to fluoroquinolones; gatifloxacin showed the highest percentage of inhibition. These results show that the newer fluoroquinolones with their potent activity could be used to treat infections with C. jejuni and C. coli. However, when these drugs are used, one must consider the increase in resistance and the high cross-resistance to these antimicrobial agents.     

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.     

Characterization of erythromycin resistance in Campylobacter jejuni and Campylobacter coli.

The mechanism of resistance to erythromycin, the drug of choice in the treatment of campylobacter gastroenteritis, was investigated. Erythromycin resistance (MICs, greater than 1,024 micrograms/ml) in three clinical isolates of Campylobacter jejuni and one C. coli isolate was determined to be constitutive and chromosomally mediated. In vivo protein synthesis in erythromycin-susceptible C. jejuni and C. coli strains was completely inhibited by low levels of erythromycin (5 micrograms/ml), whereas a high concentration of the antibiotic (100 micrograms/ml) had no effect on protein synthesis in erythromycin-resistant strains. Biological assays showed that extracellular degradation of erythromycin was not responsible for erythromycin resistance in strains of Campylobacter species. The rates and amounts of uptake of [14C]erythromycin by resistant and susceptible campylobacter cells were determined to be similar. Binding assays with purified campylobacter 70S ribosomes as well as 50S ribosomal subunits showed that those from erythromycin-resistant strans bound much less [14C]erythromycin than did those from susceptible strains. Genomic DNA from C. coli UA585 was used to transform erythromycin resistance to C. coli UA417. The erythromycin resistance marker was associated with a 240-kb SmaI fragment of the C. coli UA585 genome. Our results rule out erythromycin inactivation or efflux and are not consistent with the production of an RNA methylase, although they are consistent with a mutational mechanism of resistance due to a change in a ribosomal protein gene. This study constitutes a detailed biochemical and genetic characterization of erythromycin resistance in Campylobacter species.     

Genetic evidence for a role of parC mutations in development of high-level fluoroquinolone resistance in Escherichia coli.

Fifteen strains of Escherichia coli with MICs of ciprofloxacin (CIP) between 0.015 and 256 micrograms/ml were examined for the presence of mutations in the quinolone resistance-determining region of the gyrA gene and in an analogous region of the parC gene. No mutation was found in a susceptible isolate (MIC of CIP, 0.015 microgram/ml). Four moderately resistant strains (MIC of CIP 0.06 to 4 micrograms/ml) carried one gyrA mutation affecting serine 83, but in only one strain was an additional parC mutation (Gly-78 to Asp) detected. All ten highly resistant strains examined (MIC of CIP, > 4 micrograms/ml) carried two gyrA mutations affecting residues serine 83 and aspartate 87, and at least one parC mutation. These parC mutations included alterations of serine 80 to arginine or isoleucine and glutamate 84 to glycine or lysine. The parC+ and two mutant alleles (parCI-80 and parCI-80,G-84) were inserted into the mobilizable vector pBP507. Transfer of a plasmid-coded parC+ allele into parC+ strains did not alter the susceptibilities towards ciprofloxacin or nalidixic acid, while a significant increase in susceptibility was detectable for parC mutants. This increase, however, did not restore wild-type susceptibility, whereas transfer of a plasmid-coded gyrA+ allele alone or in combination with parC+ did. These data are in agreement with the view that topoisomerase IV is a secondary, less sensitive target for quinolone action in Escherichia coli and that the development of high-level fluoroquinolone resistance in E. coli requires at least one parC mutation in addition to the gyrA mutation(s).     

Resistance to fluoroquinolones in Escherichia coli isolated from poultry.

Quinolone-resistant Escherichia coli strains were isolated from poultry clinical samples in Saudi Arabia. The poultry flocks had been treated with oxolinic acid or flumequine prophylaxis. The measure of the uptake of fluoroquinolones showed that none of the strains had a reduced accumulation of quinolones. The result of complementation with the wild-type E. coli gyrA gene, which restored fluoroquinolone susceptibility, and the isolation of DNA gyrase from six isolates indicated that the resistant strains had an altered DNA gyrase. The minimum effective dose of ciprofloxacin for inhibition of supercoiling catalyzed by the isolated gyrases varied from 0.085 microgram/ml for a susceptible isolate (MIC < 4 micrograms/ml) up to 96 micrograms/ml for the more resistant one (strain 215, MIC > 64 micrograms/ml). For the same two isolates, the minimum effective doses of sparfloxacin varied from 0.17 up to 380 micrograms/ml. The in vitro selection of spontaneous single-step fluoroquinolone-resistant mutants using ciprofloxacin suggested that the more resistant mutants are likely the result of several mutations. These results also show that, as in human medicine, cross-resistance between older quinolones and fluoroquinolones can exist in veterinary isolates and reiterate the need for the prudent use of these drugs.     

In vitro activities of 12 orally administered antimicrobial agents against four species of bacterial respiratory pathogens from U.S. Medical Centers in 1992 and 1993.

Clinical isolates of Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes, and Moraxella catarrhalis were gathered from 19 different clinical laboratories throughout the continental United States. The in vitro activities of 12 orally administered antimicrobial agents were compared by broth microdilution tests with 3,151 bacterial isolates. Among 890 H. influenzae isolates, 30% were capable of producing beta-lactamase enzymes (12 to 41% in different medical centers). Most of the 619 beta-lactamase-negative H. influenzae strains were susceptible to ampicillicin (MIC, < or = 1.0 micrograms/ml): 5 strains were intermediate in susceptibility (MIC, 2.0 micrograms/ml) and 1 strain was ampilicillin resistant (MIC, 4.0 micrograms/ml). Ninety-two percent of 698 M. catarrhalis strains were beta-lactamase positive. Of 799 S. pneumoniae isolates, 15% were intermediate in susceptibility to penicillin and 7% were resistant to penicillin. The prevalence of penicillin-susceptible pneumococci in different institutions ranged from 63 to 95%. Only 1% of 764 S. pyogenes isolates were resistant to the macrolides, but 5% of S. pneumoniae isolates were macrolide resistant. Only 71% of 58 penicillin-resistant S. pneumoniae isolates were erythromycin susceptible, whereas 97% of the 622 penicillin-susceptible strains were erythromycin susceptible. Penicillin-resistant pneumococci were also relatively resistant to the cephalosporins and amoxicillin. Penicillin-susceptible pneumococci were susceptible to amoxicillin-clavulanic acid (MIC for 90% of isolates tested [MIC90], < or = 0.12/0.06 microgram/ml), cefixime (MIC90, 0.25 microgram/ml), cefuroxime axetil (MIC90, < or = 0.5 microgram/ml), cefprozil (MIC90, < or = 0.5 micrograms/ml), cefaclor (MIC90, 0.5 microgram/ml), and loracarbef (MIC90, 1.0 microgram/ml). Most strains of the other species remained susceptible to the study drugs other than amoxicillin.     

In vitro activities of sparfloxacin, tosufloxacin, ciprofloxacin, and fleroxacin.

The in vitro activity of sparfloxacin was compared with those of tosufloxacin, ciprofloxacin, and fleroxacin against 730 bacterial isolates representing 49 different species. Sparfloxacin and ciprofloxacin had similar spectra of activity, but sparfloxacin was less active against Pseudomonas aeruginosa and more active against many gram-positive cocci and anaerobic bacteria. Tosufloxacin MICs were generally 8- to 16-fold lower than those for sparfloxacin or ciprofloxacin. All four fluoroquinolones were active against nalidixic acid-susceptible strains of the family Enterobacteriaceae (MIC for 90% of the isolates [MIC90], less than or equal to 0.25 micrograms/ml) but nalidixic acid-resistant strains were less susceptible (MIC90, greater than or equal to 4.0 micrograms/ml). Against Pseudomonas aeruginosa isolates, MIC90s were 1.0 micrograms/ml for tosufloxacin, 2.0 micrograms/ml for ciprofloxacin, and 4.0 micrograms/ml for sparfloxacin. Against Enterococcus faecalis, sparfloxacin and ciprofloxacin MIC90s were 1.0 and 2.0 micrograms/ml, respectively. MIC90s for ciprofloxacin-susceptible Staphylococcus aureus were 0.016 micrograms/ml for tosufloxacin, 0.06 micrograms/ml for sparfloxacin, and 0.5 micrograms/ml for both ciprofloxacin and fleroxacin. With four species of gram-negative bacilli, mutants resistant to two to four times the sparfloxacin MIC occurred spontaneously at frequencies of 10(-7) to 10(-9): single-step high-level resistance was not observed. In vitro-selected sparfloxacin-resistant mutants displayed cross-resistance to other quinolones, as did clinical isolates of ciprofloxacin-resistant S. aureus. Tosufloxacin MICs with broth microdilution methods were four- to eightfold greater than those obtained with agar dilution methods. The two procedures gave comparable results when sparfloxacin or ciprofloxacin was being tested.     

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。     

Antimicrobial susceptibilities of enterococci isolated from hospitalized patients.

One hundred and one isolates of Enterococcus species isolated recently from hospitalized patients were evaluated in vitro for antibiotic susceptibility. Teicoplanin and mideplanin were the most active agents, followed by ramoplanin, vancomycin, ciprofloxacin, ampicillin, and imipenem. High-level resistance to gentamicin (MIC > 500 micrograms/ml) and/or streptomycin (MIC > 2,000 micrograms/ml) was found in 60 isolates. High-level resistance to ampicillin (MIC > or = 16 micrograms/ml) was found in 17 isolates. MBC studies revealed that ramoplanin possesses significant bactericidal activity.     

Emergence of quinolone resistance among clinical isolates of methicillin-resistant Staphylococcus aureus in Ontario, Canada.

One hundred two isolates of methicillin-resistant Staphylococcus aureus (MRSA) randomly selected from across the Canadian province of Ontario were tested for their susceptibility to ciprofloxacin, norfloxacin, and nalidixic acid by the agar dilution method. Forty-nine percent (50 of 102) had high levels of resistance to these quinolone compounds. For the 50 resistant isolates, ciprofloxacin and norfloxacin had high MICs for 90% of isolates (MIC90s) of 128 micrograms/ml and greater than 128 microgram/ml, respectively; for these isolates, the nalidixic acid MIC90 was greater than 640 micrograms/ml. The majority (98%) of the 50 isolates were also resistant to tobramycin (MIC90, greater than 128 micrograms/ml), while 42% of the isolates were resistant to gentamicin (MIC90, 64 micrograms/ml). Quinolone-resistant MRSA isolates were susceptible to bacteriophages from several groups, indicating independent selection of resistant strains. These results suggest that a reappraisal of the use of fluoroquinolones against MRSA in Canada is necessary.     

Erythromycin-resistant Campylobacter infections in Thailand.

Erythromycin therapy was compared with no treatment in a prospective trial of acute diarrheal disease among 100 infants in an orphanage in Bangkok. Within 24 h of the onset of diarrhea, 50 children received erythromycin ethylsuccinate (40 mg/kg per day) in four divided doses for 5 days. Campylobacter jejuni isolated from 31, Campylobacter coli isolated from 21, and Shigella spp. isolated from 21 of 100 children were the most commonly recognized pathogens; use of a sensitive, nonselective method substantially increased Campylobacter isolation. Treatment with erythromycin had no effect on the duration of diarrhea caused by Campylobacter spp., Shigella spp., or other agents; 37% of the treatment group and 35% of the control group had diarrhea for 1 week. Of 23 Campylobacter strains isolated from the treatment group before treatment, 15 (65%) were resistant (MIC, greater than or equal to 8 micrograms/ml) to erythromycin. Among orphanage-acquired strains, 53% of 43 C. jejuni strains and 91% of 23 C. coli strains were resistant to erythromycin compared with 11% of 114 C. jejuni strains and 46% of 35 C. coli strains that were community acquired. Erythromycin resistance is common among Campylobacter strains in Bangkok, especially in an institutional setting, which may account for the lack of efficacy of erythromycin for treatment of acute diarrheal illnesses.