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1.
The minimal inhibitory concentrations (MIC) of five tetracyclines and ten other antimicrobial agents were determined for four porcine bacterial respiratory tract pathogens by the agar dilution method. For the following oxytetracycline-susceptible strains, the MIC50 ranges of the tetracyclines were: P. multocida (n = 17) 0.25-0.5 micrograms/ml; B. bronchiseptica (n = 20) 0.25-1.0 micrograms/ml; H. pleuropneumoniae (n = 20) 0.25-0.5 micrograms/ml; S. suis Type 2 (n = 20) 0.06-0.25 micrograms/ml. For 19 oxytetracycline-resistant P. multocida strains the MIC50 of the tetracyclines varied from 64 micrograms/ml for oxytetracycline to 0.5 micrograms/ml for minocycline. Strikingly, minocycline showed no cross-resistance with oxytetracycline, tetracycline, chlortetracycline and doxycycline in P. multocida and in H. pleuropneumoniae. Moreover, in susceptible strains minocycline showed the highest in vitro activity followed by doxycycline. Low MIC50 values were observed for chloramphenicol, ampicillin, flumequine, ofloxacin and ciprofloxacin against P. multocida and H. pleuropneumoniae. B. bronchiseptica was moderately susceptible or resistant to these compounds. As expected tiamulin, lincomycin, tylosin and spiramycin were not active against H. pleuropneumoniae. Except for flumequine, the MIC50 values of nine antimicrobial agents were low for S. suis Type 2. Six strains of this species showed resistance to the macrolides and lincomycin.  相似文献   

2.
M Y Lin 《Avian diseases》1987,31(4):705-712
Twenty-nine antibiotics or drugs were incorporated individually into mycoplasma agar to evaluate their inhibitory activity against avian mycoplasmas: 100 recent Taiwan isolates of 7 serotypes and 10 standard strains of 7 serotypes were tested. All of the standard strains were very sensitive to erythromycin, chlorotetracycline, doxycycline, minocycline, and tetracycline, but the local isolates were highly resistant to these antibiotics. The drugs or antibiotics that possessed an MIC90 of 50 micrograms/ml or less against the local isolates were tiamulin (less than 0.4 micrograms/ml), lincospectin (2.7), josamycin (2.7), lincomycin (3.0), spectinomycin (4.8), tylosin (6.0), kanamycin (6.0), chloramphenicol (6.0), gentamicin (7.5), apramycin (24.5), doxycycline (27.4), minocycline (29.0), spiramycin (30.0), colistin (44.3), leucomycin (45.0), and streptomycin (50.0). The MIC90 of the other antibiotics or drugs was greater than 50 micrograms/ml. None of the isolates or strains were sensitive to nalidixic acid, ronidazole, penicillin, ampicillin, cephalexin, carbadox, or four sulfa drugs at a concentration about 5 times the therapeutic level.  相似文献   

3.
The in vitro activity of flumequine in comparison with several other drugs was tested against 17 P. multocida, 16 P. haemolytica, 21 S. dublin, 21 S. typhimurium and 21 E. coli strains, isolated in (veal) calves in the Netherlands. The MIC50 of flumequine for the respective pasteurellas was 0.25 and 1 microgram/ml, for the salmonellas and E. coli 0.5 micrograms/ml. In comparison with flumequine, enrofloxacin and ciprofloxacin showed higher in vitro activity, with MIC50 less than or equal to 0.008 micrograms/ml for ciprofloxacin. Decreased susceptibility of the pasteurellas was found for kanamycin, neomycin, streptomycin, gentamicin, oxytetracycline and doxycycline. The MIC50 of minocycline for P. multocida was 0.5 micrograms/ml and there was no cross resistance with the other tetracyclines. P. multocida was very susceptible to ampicillin (MIC50 less than or equal to 0.03 micrograms/ml), P. haemolytica, however, was 100% resistant to this drug. Both pasteurellas were susceptible to cephalothin and approximately 50% of the strains of both bacteria were resistant to chloramphenicol. The MIC50 of either spiramycin or tylosin was greater than or equal to their respective breakpoint-MIC values. Both pasteurellas were susceptible to the combination of trimethoprim and sulphamethoxazole. However, for P. multocida, the addition of sulphamethoxazole to trimethoprim had no synergistic effect on its MIC. In comparison with trimethorpim, aditoprim was less potent. Therefore only P. multocida was susceptible to aditoprim.  相似文献   

4.
The minimum inhibitory concentrations (MICs) of tetracycline, enrofloxacin, tylosin, spiramycin and a lincomycin:spectinomycin 1:2 combination, against 24 Sicilian isolates of Mycoplasma agalactiae, the causative organism of contagious agalactia were determined in vitro by a broth dilution method. Enrofloxacin was the most effective antimicrobial in vitro with a range of MIC values from 0.125 to 0.500 microg/ml and an MIC(50) of 0.203 and MIC(90) of 0.365 microg/ml. Using the MIC(50) and MIC(90) values the remaining four antimicrobials are ranked in order of in vitro effectiveness as follows: tylosin (MIC(50)0.292; MIC(90)0.525 microg/ml) was slightly more effective than tetracycline (MIC(50)0.296; MIC(90)0.533 microg/ml), followed by lincomycin:spectinomycin (MIC(50)0.521; MIC(90)0.938 microg/ml) and spiramycin (MIC(50)1.583; MIC(90)2.850 microg/ml). MIC values above 1.000 microg/ml were obtained using tetracycline, tylosin and spiramycin for some M. agalactiae isolates.  相似文献   

5.
The minimum inhibitory concentrations (MICs) of 18 antimicrobial agents were determined for 49 Arcanobacterium pyogenes isolates (42 bovine isolates and 7 porcine isolates). Benzylpenicillin and ampicillin were the most active antibiotics, with MIC ranges of < or = 0.0125-0.05 microgram/ml for both bovine and porcine isolates. All isolates were susceptible to penicillins and cephems. MICs for 90% of the isolates of dihydrostreptomycin, gentamicin and oxytetracycline for bovine isolates were > 100 micrograms/ml, 1.56 micrograms/ml and 25 micrograms/ml, respectively. More resistance to dihydrostreptomycin appeared among porcine isolates (85.7%) than among bovine isolates (52.4%). Resistance to gentamicin occurred in only 3 (7.1%) of the bovine isolates. Resistance to oxytetracycline also appeared more frequent among porcine isolates (85.7%) than among bovine isolates (57.1%). All bovine isolates were susceptible to erythromycin, tilmocosin and lincomycin, but two porcine isolates (28.6%) were simultaneously resistant to these antibiotics. Tiamulin was as active as tilmicosin, with an MIC for 50% of the isolates (MIC50) of 0.05 microgram/ml for both bovine and porcine isolates. The MIC50s of chloramphenicol and its derivatives florfenicol and thiamphenicol were all 1.56 micrograms/ml. The fluoroquinolones enrofloxacin and ofloxacin were not so active as penicillins and macrolides, with MIC50s of 0.78 microgram/ml and 1.56 micrograms/ml, respectively, for both bovine and porcine isolates.  相似文献   

6.
This study was conducted to compare the applicability of three different media in sensitivity testing of Actinobacillus pleuropneumoniae by means of MIC and tablet diffusion tests. The media used were: modified PPLO agar, chocolatized Mueller-Hinton-II and Columbia agar supplemented with NAD. Seven antimicrobial agents were tested: ceftiofur, enrofloxacin, penicillin, spectinomycin, tiamulin, trimethoprim + sulfadiazine and tylosin, against 40 randomly selected A. pleuropneumoniae isolates. In general, good agreement was found between results obtained with all combinations of media, most antimicrobials tested and the two-test systems. Some variations between media were observed for spectinomycin, tiamulin and tylosin. For ceftiofur and trimethoprim + sulfadiazine some isolates with low MIC-values were classified as resistant using tablet diffusion, indicating that the break points of resistance for these antimicrobials using the tablet diffusion tests need adjustment. Using current break points for resistance with MIC-determinations, all isolates tested susceptible to ceftiofur, enrofloxacin, penicillin, tiamulin and trimethoprim + sulfadiazine. A larger number of isolates tested resistant to spectinomycin and tylosin on all three media using both MIC determinations and tablet diffusion.  相似文献   

7.
猪链球菌Ⅱ型四川分离株对抗菌药的敏感性分析   总被引：6，自引：1，他引：6  
对四川省不同地区链球菌病病死猪体内分离的7株链球菌Ⅱ型进行抗菌药敏感性试验,用链球菌兰氏D群C55914作为对照,比对菌为肺炎链球菌质控菌株ATCC49619.在32种抗菌药中,选择29种药物进行纸片法药敏试验.试验结果表明:7株链球菌耐药谱非常相似,对青霉素、氨苄西林、阿莫西林、奥格门丁、卡那霉素、红霉素、壮观霉素、氯霉素、氟苯尼考、头孢氨苄、头孢拉定、头孢他定、头孢呋辛、头孢曲松、环丙沙星、氧氟沙星、二氟沙星、沙拉沙星、达氟沙星、恩诺沙星、复方新诺明、万古霉素、亚安培南均敏感;对阿米卡星、新霉素、庆大霉素3株敏感,4株中敏;对四环素和多西环素2株中敏,5株耐药;对链霉素1株中敏,6株耐药.用21种药物进行最小抑菌浓度(MIC)测定,结果7株均对青霉素、氨苄西林、卡那霉素、红霉素、头孢他定、头孢呋辛、头孢曲松、头孢噻呋、环丙沙星、达氟沙星、氧氟沙星、二氟沙星、沙拉沙星、恩诺沙星、磺胺六甲氧嘧啶敏感,1株对新霉素和阿米卡星中敏,2株耐药;所有菌株对四环素、土霉素、多西环素、链霉素均耐药.两种方法总体结果一致.  相似文献   

8.
Results of susceptibility tests of clinical isolates of animal pathogens are periodically summarized and reported by the Animal Health Service. However, these results are based upon qualitative test methods. In the present paper results of quantitative susceptibility tests of twelve antibacterial agents against Mannheimia haemolytica (MHA) and Pasteurella multocida (PMU) isolated from Dutch calves in 1996 and 1997 are presented. Minimum inhibitory concentrations of amoxicillin, ceftiofur, tetracycline, trimethoprim-sulphamethoxazole, tilmicosin, neomycin, gentamicin, spectinomycin, flumequine, enrofloxacin, chloramphenicol and florfenicol were determined. No resistance was detected for ceftiofur and florfenicol. Three strains had an intermediate susceptibility to tilmicosin. The resistance percentages of MHA and PMU for neomycin, gentamicin, spectinomycin, flumequine, enrofloxacin, and chloramphenicol varied from 2% to 16%. Higher resistance percentages (16%-53%) were observed for amoxicillin, tetracycline, and trimethoprim-sulphamethoxazole. The MIC breakpoints used to determine whether a strain is susceptible, intermediate, or resistant are arbitrary and discussed in this paper.  相似文献   

9.
The in vitro susceptibilities of 50 field isolates of Riemerella anatipestifer from ducks to ceftiofur and 16 other commonly used antimicrobials were determined. The MIC90 values (MIC refers to minimum inhibitory concentrations) for the antimicrobials used in this study are as follows: penicillin was 16 microg/ml; ceftiofur was 32 microg/ml; cephalothin, chloramphenicol, flumequine, and kanamycin were 64 microg/ml; nalidixic acid, nitrofurantoin, and sulfamethoxazole were 128 microg/ml; amikacin, ampicillin, gentamicin, lincomycin, spectinomycin, streptomycin, tetracycline, and trimethoprim were > or = 256 microg/ml. The therapeutic efficacy of ceftiofur against a highly lethal experimental R. anatipestifer infection in ducks was also evaluated. All experimental ducks were infected through the infraorbital sinus with 1 ml of 9 x 10(9) CFU of R. anatipestifer. Ceftiofur (0, 0.25, 0.5, 1, and 2 mg/kg) was injected subcutaneously 5 hours after infection. A single dose of 2 mg/kg resulted in 73% survival as compared with 10% survival in the infected, but untreated controls.  相似文献   

10.
Minimum inhibitory concentrations (MICs) were determined for 1570 bacteria from eight geographic locations (1204 Escherichia coli, 231 other enteric gram-negative bacilli [including Citrobacter spp., Enterobacter spp., Klebsiella spp., Proteus spp., and Salmonella spp.], 31 Pseudomonas spp., 18 coagulase-positive staphylococci, 26 coagulase-negative staphylococci, and 55 streptococci and enterococci) by the National Committee for Clinical Laboratory Standards broth microdilution procedure. Antimicrobial agents tested included ampicillin, ceftiofur, enrofloxacin, erythromycin, florfenicol, gentamicin, neomycin, spectinomycin, sulfamethazine, tetracycline, and trimethoprim/sulfadiazine. Against the E. coli strains tested, ceftiofur, enrofloxacin, gentamicin, and trimethoprim/sulfadiazine were the most active compounds with MIC at which 50% of the strains are at or below (MIC50) = 0.5, < or = 0.03, 0.5, and 0.13 microg/ml, respectively, and MIC at which 90% of the strains are at or below (MIC90) = 1.0, 0.13, 32.0, and 2.0 microg/ml, respectively. Ampicillin, florfenicol, neomycin, and spectinomycin were the next most active compounds against the E. coli strains, with MIC50 = 4.0, 4.0, 16.0, and 16.0 microg/ml, respectively. MIC90 values for these compounds against E. coli strains were > 32.0, 8.0, 512.0, and > 128.0 microg/ml, respectively. The remaining compounds exhibited limited, strain-dependent activity against the E. coli strains tested. As with the E. coli, enrofloxacin, ceftiofur, and trimethoprim/sulfadiazine were also the most active compounds against the 231 other enteric organisms tested, with MIC50 < or = 1.0 microg/ml for all of these genera. The remaining compounds exhibited limited activity against these genera. Against the gram-positive cocci tested, ampicillin, enrofloxacin, ceftiofur, and trimethoprim/sulfadiazine were most active, whereas the remaining compounds exhibited strain-dependent activity. When MIC data for E. coli were summarized separately, differences were observed between the geographic locations for the various antimicrobial agents. In conclusion, ceftiofur, enrofloxacin, and trimethoprim/sulfadiazine were the most active of the compounds tested against all of the bacterial strains.  相似文献   

11.
OBJECTIVE: To determine the susceptibility of strains of Pasteurella multocida subsp multocida isolated from lung specimens of pigs with pneumonia to 20 antimicrobials and to evaluate the emergence of resistance to those antimicrobials in Spain during the past 2 decades. SAMPLE POPULATION: 63 isolates recovered from 1987 to 1988 and 132 isolates recovered from 2003 to 2004. PROCEDURE: A broth microdilution method was used to determine minimal inhibitory concentration (MIC) range and values for MIC50 and MIC90. Resistance of a strain to an antimicrobial agent was determined by use of the breakpoint value when available. RESULTS: Isolates were generally susceptible to penicillin, ampicillin, ceftiofur, gentamicin, apramycin, neomycin, spectinomycin, chlortetracycline, erythromycin, tilmicosin, enrofloxacin, and florfenicol, and most isolates were resistant to clindamycin, tylosin tartrate, and tiamulin regardless of the time period. A substantial increase in resistance to sulfa-chlorpiridazine, sulfadimethoxine, sulfathiazole, and trimethoprim-sulfamethoxazole was observed, and a minor increase in resistance to oxytetracycline was also detected. Several multiresistance patterns were observed, most frequently among isolates recovered in the 2003 to 2004 interval. CONCLUSIONS AND CLINICAL RELEVANCE: Ceftiofur, florfenicol, and enrofloxacin are recommended for treatment of infections caused by P multocida subsp multocida in Spain. Increased frequency of resistance to oxytetracycline and sulfonamide drugs may be a contraindication for their use.  相似文献   

12.
Minimum inhibition concentrations (MICs) were determined for ampicillin, ceftiofur, cephalothin, chloramphenicol, enrofloxacin, gentamicin, lincomycin, lincospectin (lincomycin/spectinomycin), neomycin, premafloxacin, spectinomycin, sulfamethoxazole/trimethoprim, and tetracycline against a total of 180 isolates of Actinobacillus pleuropneumoniae, Escherichia coli, and Salmonella choleraesuis (60 each) clinically isolated from pigs on farms in Taiwan from 1994 to 1996. No more than 3 isolates per farm were used. Ceftiofur had the highest activity in vitro against isolates of A. pleuropneumoniae, E. coli, and S. choleraesuis, with MIC90 values of 0.03, 2, and 1 microg/ml, respectively. Premafloxacin was highly active against isolates of A. pleuropneumoniae, E. coli, and S. choleraesuis, with MIC90 values of 2, 8, and 0.5 microg/ml, respectively, which were lower than those with enrofloxacin (MIC90 8, 32, and 2 microg/ml, respectively). Neomycin was moderately active against A. pleuropneumoniae and E. coli, with MIC90 values of 8 and 64 microg/ml, respectively, but was inactive with S. choleraesuis. Gentamicin showed high activity against A. pleuropneumoniae (MIC90 of 2 microg/ml) but was only moderately active with E. coli and S. choleraesuis (MIC90 of 64 and 32 microg/ml). Cephalothin was highly active against isolates of A. pleuropneumoniae (MIC90 of 1 microg/ml) but was inactive with E. coli (MIC90 of 128 microg/ml). Lincomycin had moderate activity (MIC90 of 32 microg/ml) against A. pleuropneumoniae. Chloramphenicol, lincomycin, and tetracycline were inactive with E. coli and S. choleraesuis (MIC90 > 128 microg/ml). In conclusion, ceftiofur and premafloxacin were highly active against isolates of A. pleuropneumoniae, E. coli, and S. choleraesuis, enrofloxacin and gentamicin were highly to moderately active; cephalothin was highly active against A. pleuropneumoniae and moderately active against S. cholearesuis; chloramphenicol, lincomycin, and tetracycline were active only with A. pleuropneumoniae; neomycin was moderately active against A. pleuropneumoniae and E. coli. The other antimicrobials tested were inactive.  相似文献   

13.
The purpose of the present study was to determine the prevalence of antibiotic resistance, with special attention to vancomycin, in 104 strains of Enterococcus, which is the sentinel bacterium isolated from dog and cat faeces samples. The phenotypic characterization of the isolates classified them as E. faecium (58%), E. avium (41%) and E. faecalis (1%). Sensitivity testing used the diffusion method according to the recommendations of CASFM (Comite de l'Antibiogramme de la Société Fran?aise de Microbiogie), to oxacillin, amoxycillin, amoxycilin + clavulanic acid, ampicillin, piperacillin, cefoperazone, imipenem, enrofloxacin, ciprofloxacin, ofloxacin, nalidixic acid, tetracycline, lincomycin, erythromicin and vancomycin. Minimum inhibitory concentration (MIC) determination by E test revealed a MIC to vancomycin of between 0.5 microg/ml and 3 microg/ml. All the strains were resistant to nalidixic acid, erythromycin, cefoperazone and oxacillin. We detected resistance to amoxycillin + clavulanic acid in 1.9% of isolates, to amoxycillin in 4.8%, to piperacillin in 13.5%, and to ampicillin in 21.2% of strains. A high prevalence of antibiotic resistance to lincomycin, tetracycline, enrofloxacin, ciprofloxacin and ofloxacin was found in 98.1%, 95.2%, 76.9%, 73.1% and 64.4% of strains, respectively. Resistance to vancomycin was not found, which indicates that there is no transmission risk of vancomycin-resistant enterococcal strains to man or transfer of their resistance genes to other bacteria belonging to the endogenous flora of humans.  相似文献   

14.
The susceptibilities of 40 recent Belgian field isolates of Mycoplasma bovis to 10 antimicrobial agents were assessed. Tiamulin was the most active antimicrobial agent against M bovis, with an initial inhibitory concentration (IIC50) of 0.06 microg/ml, but it is not licensed for the treatment of cattle. All three fluoroquinolones tested (danofloxacin, enrofloxacin and marbofloxacin) were effective against strains of M bovis, and had a minimum mycoplasmacidal concentration (MMC50) less than or equal to 1 microg/ml. Gentamicin was poorly effective, having an IIC50 of 8 microg/ml. Many strains of M bovis were resistant to tylosin, spectinomycin, lincomycin, tetracycline and oxytetracycline.  相似文献   

15.
Using an agar dilution method we measured the minimum inhibitory concentration (MIC) of 12 antimicrobial agents against 11 strains of iota-toxigenic strains of Clostridium spiroforme. Each strain was isolated from a separate outbreak of toxic diarrhoea of rabbits. Vancomycin and bacitracin, both agents used to treat intestinal clostridioses of humans and other animals, had a relatively high MIC (8 micrograms/ml or more). Metronidazole was uniformly active against C. spiroforme. With MIC of 8 micrograms/ml or more, both lincomycin (11 strains) and erythromycin (9 strains) were relatively inactive against C. spiroforme, conversely, penicillin G was active (MIC for 8 strains was 0.5 micrograms/ml or less). Exposure to any one of these drugs has been implicated as a predisposing factor for C. spiroforme mediated diarrhoea of rabbits. The greatest variation in MIC was seen for erythromycin (8-fold), penicillin G (8-fold) and tetracycline (16-fold).  相似文献   

16.
采用2倍稀释法测定了恩诺沙星及其他8种抗菌药对鸡毒支原体BG44T株的最小抑菌浓度（MIC）,再以棋盘法测定恩诺沙星分别与其他8种抗菌药不同联合对鸡毒支原体BG44T株的敏感性。结果显示：恩诺沙星、替米考星、泰乐菌素、吉他霉素、林可霉素、沃尼妙林、泰妙菌素、氯霉素及氟苯尼考对鸡毒支原体BG44T株的MIC分别为0．063、0．004、0．016、0．063、16、〈0．004、0．008、8、8μg／mL。在8种不同联合用药对鸡毒支原体BG44T株的药敏试验中,恩诺沙星＋替米考星、恩诺沙星＋泰乐菌素、恩诺沙星＋吉他霉素、恩诺沙星＋林可霉素、恩诺沙星＋沃尼妙林、恩诺沙星＋泰妙菌素联合表现出相加作用,恩诺沙星＋氯霉素、恩诺沙星＋氟苯尼考表现出拮抗作用。  相似文献   

17.
Minimum inhibitory concentrations (MIC) and minimum mycoplasmacidal concentrations (MMC) of the antimicrobials danofloxacin, florfenicol, oxytetracycline, spectinomycin and tilmicosin were determined in vitro for 20 isolates of Mycoplasma mycoides subspecies mycoides small colony type (MmmSC), the causative agent of contagious bovine pleuropneumonia (CBPP). The majority of strains were most susceptible to tilmicosin, followed by danofloxacin, oxytetracycline, florfenicol and spectinomycin with MIC50 values of 0.015, 0.25, 0.5, 1 and 8 microg/ml, and MMC50 values of 0.06, 0.5, 8, 8 and 16 microg/ml, respectively. However, tilmicosin had poor mycoplasmacidal activity against two recent strains from Portugal. There was no evidence of resistance to danofloxacin in any of the strains.  相似文献   

18.
部分鸡场大肠杆菌对抗菌药物的耐药性   总被引：12，自引：0，他引：12  
从江西、辽宁、广东3个省的鸡场分离到204株大肠杆菌，按NCCLs推荐的纸片扩散法测定了其对24种抗菌药物的敏感性。结果表明，分离菌对四环素的耐药性最高，为92．2％．余下依次为二氟沙星、萘啶酸、磺胺、复方新诺明、氨苄西林、阿莫西林、恩诺沙星、沙拉沙星、洛美沙星、链霉素、达氟沙星、培氟沙星、环丙沙星、诺氟沙星、氧氟沙星、氯霉素、庆大霉素、卡那霉素、头孢噻吩、奥格门丁(阿莫西林和克拉维酸钾)、阿米卡星、氟苯尼考．头孢曲松无1例耐药。  相似文献   

19.
The purpose of the present study was to determine the prevalence of antibiotic resistance, with special attention to vancomycin, in 104 strains of Enterococcus, which is the sentinel bacterium isolated from dog and cat faeces samples. The phenotypic characterization of the isolates classified them as E. faecium (58%), E. avium (41%) and E. faecalis (1%). Sensitivity testing used the diffusion method according to the recommendations of CASFM (Comité de l'Antibiogramme de la Société Française de Microbiogie), to oxacillin, amoxycillin, amoxycilin + clavulanic acid, ampicillin, piperacillin, cefoperazone, imipenem, enrofloxacin, ciprofloxacin, οfloxacin, nalidixic acid, tetracycline, lincomycin, erythromicin and vancomycin. Minimum inhibitory concentration (MIC) determination by E test revealed a MIC to vancomycin of between 0.5 μg/ml and 3 μg/ml. All the strains were resistant to nalidixic acid, erythromycin, cefoperazone and oxacillin. We detected resistance to amoxycillin + clavulanic acid in 1.9% of isolates, to amoxycillin in 4.8%, to piperacillin in 13.5%, and to ampicillin in 21.2% of strains. A high prevalence of antibiotic resistance to lincomycin, tetracycline, enrofloxacin, ciprofloxacin and ofloxacin was found in 98.1%, 95.2%, 76.9%, 73.1% and 64.4% of strains, respectively. Resistance to vancomycin was not found, which indicates that there is no transmission risk of vancomycin‐resistant enterococcal strains to man or transfer of their resistance genes to other bacteria belonging to the endogenous flora of humans.  相似文献   

20.
A total of 522 strains belonging to streptococci, enterococci and staphylococci isolated from sub-clinical and clinical cases of bovine mastitis from the west littoral region of Uruguay were analysed for their susceptibility to several antimicrobial agents. The susceptibility patterns were studied by agar disk diffusion methods (ADDM) and broth micro-dilution to determine the minimum inhibitory concentration (MIC). The concentration that inhibits 90% (MIC90) of the analysed strains reported in micrograms per millilitre, for Staphylococcus aureus were > 8, 8, < or = 0.5, < or = 4, < or = 1, < or = 0.5, > 64, < or = 0.25, 0.5, < or = 1 and < or = 1 to penicillin, ampicillin, oxacillin, cephalotin, gentamicin, erythromycin, oxitetracycline, enrofloxacin, trimethoprim/sulfamethoxazole, neomycin, and clindamycin, respectively. Coagulase-negative staphylococci (CNS) had different values for penicillin (4) and ampicillin (2), while the other antimicrobial agents had the same MIC90 values as reported for S. aureus. The MIC90 values for streptococci were 0.12, 0.25, < or = 4, 16, < or = 0.25, 0.5, 0.25 for penicillin, ampicillin, cephalotin, gentamicin, erythromycin, oxytetracycline and trimethoprim-sulfamethoxazole, whereas MIC90 for enterococci were 4, 4, 4, < or = 0.5, 2, > 8 for penicillin, ampicillin, gentamicin, erythromycin, oxytetracycline and trimethoprim-sulfamethoxazole, respectively. Of 336 strains of S. aureus, 160 (47.6%) were resistant to penicillin. For 41 CNS strains, 10 (27%) presented penicillin-resistance. All the streptococcal strains were susceptible to penicillin, while 3 (7%) of the 43 enteroccocal strains were resistant. Non significant statistical differences were found between the results obtained by ADDM and broth micro-dilution for classifying bacterial isolates as susceptible or resistant according to the National Committee of Clinical Laboratory Standards.  相似文献   

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