Analysis of parameters and validation of method for normalized interpretation of antimicrobial resistance

The method of normalized resistance interpretation (NRI), uses the high-zone side of the susceptible peak in a zone diameter histogram as an internal calibrator to construct the real standard distribution of susceptible isolates even in the presence of resistant isolates. NRI parameters were optimized using control strain histograms from microbiology laboratories in Stockholm, Argentina, and the Philippines. A moving average based on four-zone values was slightly better than based on two-zone average values. The optimal peak adjustment from the switch position of the moving average was 1.0 for two-zone averages and 2.5 for four-zone averages. A comparison between true means and NRI-calculated means showed a highly significant correlation (R²=0.963). Coefficients of variation (CV), comparing the CV of the true distribution of control strain test results with the NRI calculated distribution, identified two types of aberrant histograms. NRI calculations on clinical isolates of Escherichia coli and Staphylococcus aureus from selected laboratories showed a good agreement between the local resistance interpretations with the NRI calculated levels. One type of deviation was most marked with cephalothin histograms for E. coli isolates where the regular zone breakpoints used cut through the population of susceptible strains. With proper markers for required quality of disc test results, the NRI method might be a valuable tool for both resistance surveillance and for quality control of the disc diffusion method.     

Setting interpretive breakpoints for antimicrobial susceptibility testing using disk diffusion

Antimicrobial susceptibility testing plays a key role in clinical microbiology. The disk diffusion test dates back to the 1940s and became standardised from the 1950s, with the International Collaborative Study (ICS) and National Committee for Clinical Laboratory Standards (NCCLS) as the two major standards. Interlaboratory variation of disk test results was recognised early but has never been dealt with in a satisfactory manner. The error-rate bounded method was described in 1974 and its role is discussed. Species-specific susceptibility interpretation was coined in 1980 for Proteus mirabilis and chloramphenicol. In the late 1970s, more extensive use of species-specific breakpoints was introduced in Lund (Sweden). At the same time, P. Mouton constructed species-specific regression lines and pointed out the difficulties with narrow ranges of minimal inhibitory concentration (MIC) values. A more general use of species-specific regression lines was made possible with single-strain regression analysis, using one well-defined strain tested in disk diffusion with a range of disk contents. This method made it possible to calibrate the disk test in an individual laboratory. Other methods to achieve such calibration are also described. A recent method, ‘MIC-coloured zone diameter histogram-technique’, has proven useful for the validation of species-specific interpretive breakpoints. The microbiological breakpoint proposed by Williams in 1990 has experienced a renaissance with the European Committee on Antimicrobial Susceptibility Testing (EUCAST) epidemiological cut-off value (ECOFF). MIC and zone diameter distributions with accompanying ECOFFs for species-antimicrobial combinations are published on the EUCAST website. A method for the reconstruction of wild-type zone diameter populations, namely normalised resistance interpretation, is described. This method can produce resistance figures that are truly comparable between laboratories.     

Extended antimicrobial resistance screening of the dominant faecal Escherichia coli and of rare resistant clones

Fifty faecal samples from healthy adults were grown on MacConkey agar and three pink colonies were subcultured, identified to species level and their antimicrobial susceptibility determined. Forty-seven samples yielded 141 isolates of Escherichia coli that were susceptible to most antimicrobials. Resistance was noted for ampicillin (30.5%), chloramphenicol (12.1%), tetracycline (23.4%), trimethoprim (24.8%) and co-trimoxazole (22.7%). A direct faecal plating method was used for extended resistance screening with E. coli as the indicator organism. Zone breakpoints were determined using normalised resistance interpretation and gave similar susceptibility results. Eighty-eight isolates of E. coli from within the zones of inhibition revealed four times more antimicrobial resistance. Extended antimicrobial resistance screening both provides the susceptibility profile of the dominant E. coli isolate and detects greater resistance in rare isolates.     

安妥沙星纸片扩散法外抗菌活性测定折点初步研究

目的：确定安妥沙星对葡萄球菌属、肠杆菌科、非发酵菌及嗜血杆菌属的纸片扩散法体外抗菌活性测定折点。方法：采用标准琼脂二倍稀释法与纸片扩散法（5μg和10μg）测定安妥沙星对临床常见致病菌的敏感性,并与临床常用的氟喹诺酮类药物相比较分析,结合人体药代动力学参数,利用MIC与抑菌圈直径散点图,初步确定安妥沙星纸片扩散法对常见细菌的折点。结果：安妥沙星的体外抗菌作用与左氧氟沙星接近且相关性最好,根据安妥沙星琼脂稀释法体外抗菌活性测定的临界浓度（嗜血杆菌敏感临界浓度为≤1mg／L,其他细菌敏感、中介与耐药临界浓度分别为≤2、4、≥8mg／L）,利用MIC与抑菌圈直径散点图初步确定安妥沙星（10扯g）纸片对嗜血杆菌抑菌圈直径≥21mm为敏感,其它菌种耐药、中介与敏感的抑菌圈直径分别为≤14mm、15～17mm和≥18mm。标准菌株质控范围分别为大肠埃希菌ATCC2592224～31mm,铜绿假单胞菌ATCC2785322～26mm,金黄色葡萄球菌ATCC2592322～28mm。结论：通过体外抗菌活性比较,利用MIC与抑菌圈直径散点图,初步确定了安妥沙星纸片扩散法体外抗菌活性测定对常见细菌的折点,供临床应用参考与验证。     

Antimicrobial susceptibility testing for Helicobacter pylori: sensitivity test results and their clinical relevance

There are multiple test methodologies to determine the antibiogram of an organism. Standardized susceptibility test methods are based upon rapidly growing, aerobic microorganisms in which overnight incubation results in definitive endpoints. In vitro susceptibility testing for fastidious organisms that require complex media for growth, require incubation in atmospheres other than ambient air, or are slow-growing (anaerobes, mycobacteria, filamentous fungi) are problematic and in general are not standardized. H. pylori falls into this category of troublesome organisms. For the microaerobic organism H. pylori, testing is challenging because the organism grows slowly even under optimal culture conditions. Recently the National Committee for Clinical Laboratory Standards (NCCLS) approved the agar dilution method as the test of choice for testing H. pylori. While not entirely reliable in predicting the outcome of treatment for metronidazole resistant organisms, the resistance determined for clarithromycin by this method generally predicts treatment failure. Quality control breakpoints for H. pylori ATCC 43504 were established and breakpoints for clarithromycin were approved by the NCCLS in 1999. Breakpoints are minimum inhibitory concentrations (MIC) of a drug at which an organism is deemed either susceptible or resistant to the antibiotic using standard dosing regimens containing that drug. Significant progress has been made with respect to development of tests to detect antimicrobial resistance, but there still remains no consensus as to the breakpoints for agents used in the treatment of H. pylori infection other than clarithromycin. This article will address the controversies associated with the reporting of antibiotic resistance data and the interpretation of these data.     

Pneumococcal resistance to the third-generation cephalosporins: clinical, laboratory and molecular aspects

Widespread use of third-generation cephalosporins appears to have selected cephalosporin-resistant pneumococci associated with the failure of these agents in the management of meningitis. Breakpoints of 0.5 mg/l for intermediate and 2 mg/l for full resistance are proposed for the treatment of pneumococcal meningitis. As no disc tests reliably identify these breakpoints, MIC or E test confirmation of third-generation cephalosporin resistance is recommended for all strains found resistant to a 1 mug oxacillin disk. Resistant strains can be selected in a single transformation event, with PBP 2X gene rearrangements conferring low level resistance and PBP 1A gene rearrangements conferring full resistance.     

Clinical laboratory approach for estimating the effective administrative dose of latamoxef. Significance of a 4-category system interpretation of the latamoxef disc susceptibility test

In vitro activities of latamoxef (LMOX) against 249 clinical isolates were determined using the agar dilution method at an inoculum level of 10(6) CFU/ml. LMOX was highly active against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis (except 2 out of 30 strains) and Proteus vulgaris with MIC values below 3.13 micrograms/ml. It was also active against Enterobacter aerogenes with MIC80 of 1.56 micrograms/ml. LMOX was less active against Serratia marcescens, inhibiting about 43% of strains at a level of 6.25 micrograms/ml. It was also less active against Staphylococcus aureus and Staphylococcus epidermidis, showing MIC80 of 12.5 and 50 micrograms/ml, respectively. LMOX was not active against Enterococcus faecalis and Pseudomonas aeruginosa. The reliability of the LMOX disc diffusion susceptibility test for quantitative estimation of antimicrobial activities was also investigated using 8 mm diameter discs (Showa) and 6 mm diameter discs (Difco), both of which contained 30 micrograms/disc of LMOX. These disc susceptibility test results were well correlated with MICs, hence the LMOX disc susceptibility test should be useful for the estimation of proper dose levels of LMOX. For the interpretation of LMOX disc test results, if uniform break points of zone diameters were used to test all bacteria, inhibitory zone diameters of Showa discs used on Staphylococcus were relatively large compared to MICs determined, probably due to decarboxylation of LMOX sodium salt in the discs. However, those of Difco discs were not, because Difco discs use LMOX ammonium salt. Both discs also showed relatively large inhibitory zone diameters compared to MICs determined against P. aeruginosa. Using different break points from those used for other bacteria to interpret inhibition zones for Staphylococcus and P. aeruginosa, these disc susceptivility tests should be useful to estimate approximate MICs. A 3 category system for the interpretation of disc test results has been used in USA and Europe, but a 4 category system is generally used in Japan. The 3 category system uses break points to classify bacteria into 3 categories of susceptibility according to MIC values as follows: Resistant (R) MIC greater than or equal to 64 micrograms/ml, intermediate (I) MIC 16-32 micrograms/ml, and susceptible (S) MIC less than or equal to 8 micrograms/ml. The 4 category system uses break points as follows: MIC less than or equal to 3 micrograms/ml, MIC greater than 3-15 micrograms/ml, (+) MIC greater than 15-60 micrograms/ml, (-) MIC greater than 60 micrograms/ml.(ABSTRACT TRUNCATED AT 400 WORDS)     

Clinical laboratory approach for estimating effective administrative dose of cephalothin. Reevaluation of MIC break points in 4 category system of disc susceptibility test

The reliability of the cephalothin (CET) disc susceptibility test in estimating approximate values of MICs was studied using various clinical isolates totaling 248 strains and using Showa discs (8 mm diameter containing 30 micrograms of CET) and Difco discs (6 mm diameter containing 30 micrograms of CET). Clinical significance of a 4 category system for the interpretation of the CET disc tests, which is widely used in Japan, was reevaluated to determine whether this system would be suitable or not for the evaluation of proper dose levels of administration. The results obtained with the disc methods were compared with MICs determined using the agar dilution method at an inoculum level of 10(6) CFU/ml. The results of the CET disc susceptibility test were well correlated with MICs, showing the reliability of the disc method to estimate approximate values of MICs. Break points in MIC values proposed for the classification of bacteria into 4 categories of susceptibility are ( ) MIC less than or equal to 3 micrograms/ml, (++) MIC greater than 3-15 micrograms/ml, (+) MIC greater than 15-60 micrograms/ml, (-) MIC greater than 60 micrograms/ml. With the Showa disc susceptibility test, 15 out of the 248 strains (6.0%) tested showed false positive results and 6 strains (2.4%) showed false negative results. With the Difco disc test, 18 out of the 248 strains (7.3%) tested showed false positive results and 6 (2.4%) showed false negative results. Excluding Enterococcus faecalis from the test, results because better in the quantitative estimation of MICs, resulting false positive rates of 3.2% (Showa), and 4.4% (Difco). A 3 category system of the interpretation of disc test is generally used in the USA and Europe. MIC break points proposed for the classification of the CET test are sensitive, MIC less than or equal to 8 micrograms/ml, and resistance, MIC greater than or equal to 32 micrograms/ml. With the Showa disc susceptibility test, 14 out of the 248 strains (5.6%) tested showed false positive results and 6 strains (2.4%) showed false negative results. With the Difco disc test 7 out of the 248 strains (2.8%) showed false positive results and 21 strains (8.5%) showed false negative results. In this study, MIC70S of CET against Staphylococcus aureus and Staphylococcus epidermidis were 1.56 and 0.78 micrograms/ml, respectively. CET was not so effective against Gram-negative rods except Klebsiella pneumoniae, Proteus mirabilis and Escherichia coli. MIC70S against K. pneumoniae, P. mirabilis, and E. coli were 6.25, 3.13, and 3.13 micrograms/ml, respectively.     

Clinical laboratory approach for estimating effective administrative dose of cefuzonam. Evaluation of disc susceptibility test and its interpretation system

In vitro activities of cefuzonam (CZON) against 273 clinical isolates were studied through the evaluation of MIC's and the results of disc susceptibility test. The MIC's were determined using the agar dilution method at an inoculum level of 10(6)CFU/ml. The MIC80's of CZON against Streptococcus pneumoniae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, Haemophilus influenzae and Citrobacter spp. were less than 0.20 microgram/ml. The MIC80's against Serratia marcescens and Enterobacter aerogenes were both 6.25 micrograms/ml, and that against Pseudomonas aeruginosa was 100 micrograms/ml. The MIC80's against Staphy-lococcus epidermidis were 25 and 6.25 micrograms/ml, respectively. Approximately 70% of strains of S. aureus were inhibited at concentrations less than 1.56 microgram/ml. For the interpretation of the CZON Showa 30 micrograms disc susceptibility test a 4 category system was used. In the 4 category system for Showa disc containing CZON, the following classification inhibitory zone diameters has been proposed: ( ) MIC less than or equal to 3 micrograms/ml, (++) MIC greater than 3-15 micrograms/ml, (+) MIC greater than 15-60 micrograms/ml, (-) MIC less than 60 micrograms/ml. Reliability of the CZON disc tests in estimating approximate MIC values was studied using Showa 30 micrograms discs and discs prepared in this laboratory containing 1-10 micrograms CZON. A good negative correlation was observed between inhibitory zone diameters and MIC's, showing the reliability of the disc method. The results of the test using Showa 30 micrograms disc against various clinical isolates were accurately classified into the 4 groups except those against P. aeruginosa. Some strains of P. aeuruginosa showed false positive results, exhibiting relatively larger inhibitory zone diameters compared with MIC's against these organisms. As CZON is not effective against P. aeruginosa a much better overall correlation between MIC's and the disc test would result when P. aeruginosa was excluded. With Showa 30 micrograms discs of various cephalosporins, sub-classification of strains with MIC less than 3 micrograms/ml cannot be achieved. In this study, however, it was demonstrated that differentiation of strains with MIC's less than 0.5-1.56 micrograms/ml was possible when discs containing 1-10 micrograms of CZON were used. According to recent concepts on pharmacokinetics for antibiotics including penetration of drugs into tissues and inflammatory fluids, serum protein binding of drugs appears to be one of the important determinants of drug distribution in the body.(ABSTRACT TRUNCATED AT 400 WORDS)     

2018-2019年安徽省滁州地区细菌耐药性监测

目的了解临床分离菌的分布及耐药情况。方法收集2018年1月1日-2019年12月31日滁州地区五所综合性医院临床分离的非重复细菌,采用纸片扩散法、VITEK 2和E试验法进行抗菌药物敏感性实验,根据CLSI 2018年标准判读结果,使用软件WHONET 5.6进行数据分析。结果收集到9932株不重复细菌,其中革兰阳性菌2950株(29.7%),革兰阴性菌6982株(70.3%)。甲氧西林耐药金黄色葡萄球菌(MRSA)和甲氧西林耐药凝固酶阴性葡萄球菌(MRCNS)检出率分别为34.6%(409/1182)和69.9%(403/576)。没有发现葡萄球菌、肠球菌对利奈唑胺和万古霉素耐药。大肠埃希菌、肺炎克雷伯菌中产超广谱β-内酰胺酶(ESBLs)菌株分别占46.6%(977/2096)和27.2%(318/1170)。肠杆菌科细菌对碳青霉烯类抗生素依然比较敏感,总耐药率为8.1%(351/4340)。鲍曼不动杆菌、铜绿假单胞菌对亚胺培南的耐药率分别为55.8%(556/996)和17.2%(123/715)。结论定期进行细菌耐药监测有利于了解该地区细菌对抗菌药物整体耐药情况,能够更好地促进抗菌药物科学应用和院感控制。     

Breakpoints: current practice and future perspectives

Much of the discussion over the past decades on the value and setting of breakpoints has been due to the fact that the breakpoint was used in two ways; as an indicator to predict the probability of clinical success and also to detect resistant (sub) populations. It is apparent that these two meanings have lead to a different approach to setting, interpretation and use of breakpoints based on clinical efficacy on the one hand and breakpoints based on detection of resistance on the other. Nevertheless, several of the current guidelines make no perceptible distinction between these two meanings. A case is therefore strongly made to recognize that there is a difference between clinical and microbiological breakpoints. The microbiological breakpoint may be used to detect organisms that do not belong to the natural bacterial population, but somehow have acquired resistance and might be useful in recognizing emergence of resistant subpopulations and may lead to subsequent measures to be taken. Alternatively, the clinical breakpoint is of principal value to the clinician in that it results in a classification of S (susceptible), I (intermediate susceptible) and R (resistant) and is used in clinical practice and correlate with a measure of clinical efficacy. Methods developed during the last few years to arrive at meaningful clinical breakpoints are discussed, such as CART analysis and Monte Carlo simulation. In discussing future developments, it is suggested that current reports containing S, I, and R be at least supplemented with the MICs measured and, using current techniques available such as Monte Carlo simulation, provide the probability of successful eradication of the micro-organism and successful treatment based on population pharmacokinetics and Minimal Inhibitory Concentration (MIC) distributions.     

Disc agar diffusion antimicrobial susceptibility tests with beta-lactamase producing Neisseria gonorrhoeae.

The emergence of beta-lactamase-producing strains of Neisseria gonorrhoeae has led to a reexamination of the role of the disc agar diffusion method in susceptibility testing of gonococci. Our data show that the disc agar diffusion test can be used to screen for beta-lactamase production by these organisms. The disc tests were done on GC Agar Base supplemented with 1% IsoVitaleX. An inoculum of 10(8) colony forming units/ml and either a 10-unit-penicillin or a 10-microgram-ampicillin disc were used. A zone diameter of less than or equal to 19 mm was indicative of beta-lactamase production. These results were compared with results of chemical tests for beta-lactamase and with minimal inhibitory concentrations. Recommondations were also made for a disc test with tetracycline and spectinomycin, but these methods must remain tentative because of the lack of resistant strains.     

Susceptibility testing of urinary isolates of Escherichia coli to mecillinam using NCCLS methodology

Criteria for susceptibility testing of mecillinam against 533 isolates of Escherichia coli and a further 309 Enterobacteriaceae, according to NCCLS methodology, were determined. Correlation of MIC to inhibition zones was good for all species. For urinary isolates of E. coli, the following agar dilution breakpoints and corresponding interpretive zone diameters seem appropriate: < or = 8 mg/L/> or = 15 mm for susceptible; 16 mg/L/12-14 mm for intermediate susceptible and > or = 32 mg/L/< or = 11 mm for resistant. The appearance of isolated colonies within the inhibition zone was sometimes noted with disc diffusion, particularly for non-E. coli Enterobacteriaceae. The relevance of these colonies to clinical (bacteriological) efficacy was determined and the results suggested that they could be ignored when testing urinary E. coli.     

In vitro activity of piperacillin/tazobactam and other broad-spectrum antibiotics against bacteria from hospitalised patients in the British Isles

Piperacillin/tazobactam is used for empirical therapy of severe and complex infections. We assessed its activity, 9 years after launch, against consecutive, clinically significant isolates from in-patients in UK and Ireland. Standardised disc susceptibility tests were performed on 5031 isolates at 28 hospitals. For quality assurance purposes, 5% of these isolates were collected centrally for MIC tests, as were those with exceptional resistances. Compared with a similar pre-launch survey in 1991, there were major increases in the proportions of Staphylococcus aureus, Pseudomonas aeruginosa, beta-haemolytic streptococci and Enterococcus faecium isolates collected, balanced by decreases in Escherichia coli, Proteus mirabilis and coagulase-negative staphylococci. These changes in species prevalence mostly favoured organisms with inherent resistance(s) or-in the case of S. aureus-reflected the massive increase of MRSA, up from 0.7% of all isolates in 1991 to 14.8% in 2001. Based on the disc tests, piperacillin/tazobactam retained activity against 87% of Enterobacteriaceae isolates, 95% of P. aeruginosa, 99% of streptococci and 96% of Enterococcus faecalis. Resistance nevertheless had increased since 1991 in E. coli from 4 to 10%, Klebsiella spp. (5 to 21%) and in AmpC-inducible Enterobacteriaceae (17 to 23%), though not in P. mirabilis or P. aeruginosa. MIC tests confirmed most of the piperacillin/tazobactam resistance found by disc tests in Enterobacter spp., but indicated susceptibility for about half of the E. coli isolates recorded as resistant in disc tests. This situation might be remedied by reducing the zone breakpoint, but this would increase the "false susceptible" rate unacceptably. Thus, if disc tests suggest that an isolate is marginally resistant to piperacillin/tazobactam and the drug is sought as therapy, it is recommended that MIC be determined with, e.g., an Etest.     

Interpreting streptomycin susceptibility test results for Salmonella enterica serovar Typhimurium

Resistance or susceptibility of Salmonella enterica to streptomycin is widely used as an epidemiological marker. However, there is no clear consensus on the interpretation of streptomycin susceptibility test results. Comparison of results obtained with the Clinical and Laboratory Standards Institute (CLSI) disk diffusion method, the minimum inhibitory concentration (MIC) determined by Etest and streptomycin resistance genotype for 90 isolates of S. enterica serovar Typhimurium suggests that appropriate interpretive criteria for MIC results are susceptible at ≤8 mg/L and resistant at ≥16 mg/L. For CLSI disk diffusion, we propose susceptible at a zone diameter ≥13 mm and resistant at ≤10 mm.     

Clinical laboratory approach for estimating effective administrative dose of tobramycin. Reevaluation of in vitro MIC break points of disk susceptibility test

The reliability of the tobramycin (TOB) disc susceptibility test in estimating approximate values of MICs was studied using various clinical isolates totaling 261 strains and using Showa discs (8 mm diameter containing 30 micrograms of TOB) and Difco discs (6 mm diameter containing 10 micrograms of TOB). Clinical significance of a 4 category system for the interpretation of the disc tests, which is widely used in Japan, and that of a 3 category system used in USA and Europe, were also evaluated to determine which system would be more suitable for the evaluation of proper dose levels of administration. Furthermore, the evaluation was made using these discs with respect to the in vitro MIC break points for therapeutic use of antibiotics proposed by the British Society for Antimicrobial Chemotherapy (J. Antimicr. Chemoth. 21:701-710, 1988). The results obtained with the disc method were compared with MICs determined using the agar dilution method at an inoculum level of 10(6) CFU/ml. The results of the TOB disc susceptibility test either with Showa or Difco discs were well correlated with MICs, showing the reliability of the disc method to estimate approximate values of MICs. Break points in MIC values proposed for the classification of bacteria into the 4 categories of susceptibility are () MIC less than or equal to 2 micrograms/ml, (++) MIC greater than 2-10 micrograms/ml, (+) MIC greater than 10-50 micrograms/ml, (-) MIC greater than 50 micrograms/ml. Those proposed in the 3 categories of susceptibility are Sensitive (S) MIC less than or equal to 4 micrograms/ml, Intermediate (I) MIC greater than 4-8 micrograms/ml, Resistance (R) MIC greater than 8 micrograms/ml. In the 4 category classification system of the Showa disc susceptibility test, 16 out of 261 strains (6.1%) tested showed false positive results and 7 (2.7%) did false negative results. If the classification was modified as follows: ( ) MIC less than or equal to 3 micrograms/ml, (++) MIC greater than 3-15 micrograms/ml, (+) MIC greater than 15-60 micrograms/ml, (-) MIC greater than 60 micrograms/ml, false positive results were markedly reduced. Only 6 out of 261 strains (2.3%) showed false positive results, and 7 (2.7%) did false negative results. With Difco disc, in the 4 category interpretation system, 8 out of 261 strains (3.1%) tested showed false positive and 35 (13.4%) did false negative results. No inhibitory zones were observed against a majority of strains with MIC greater than 25 micrograms/ml, thus unable to assess (+) susceptibility.(ABSTRACT TRUNCATED AT 400 WORDS)     

动物源性细菌抗生素耐药判定标准的研究现状

抗生素在解决了许多细菌感染性疾病治疗问题的同时，其广泛不合理的应用以及细菌自身适应性的改变也加速了细菌耐药性的产生，对全球经济和公共健康带来严重危害。为了能够很好地监测细菌耐药性的变化和有效的指导临床用药，控制细菌的耐药性，建立细菌的耐药判定标准成为了一项具有实践意义的重要任务。建立耐药判定标准需要收集大量的信息，包括野生型细菌的最小抑菌浓度(minimal inhibitory concentration, MIC)分布，体外药效学和体内药动学的数据以及临床治疗相关的数据，主要包括野生型临界值、药效学临界值和临床临界值3个方面。本文综述了动物源性耐药判定标准的研究进展，总结了目前应用最广泛的两个折点制定组织美国临床实验室标准化协会(CLSI)和欧洲药敏实验标准化委员会(EUCAST)建立耐药判定标准的方法，为建立符合我国耐药现状的耐药判定标准提供理论基础。     

葡萄球菌属红霉素对克林霉素诱导耐药性检测

目的:了解葡萄球菌对红霉素及克林霉素的耐药性,结合药敏试验结果,为临床合理选择抗生素提供可靠依据。方法:按照2004年版美国临床实验室标准化委员会(NCCLs)推荐的纸片扩散方法测定并判读葡萄球菌对红霉素和克林霉素的耐药性,并以D一试验测定红霉素对克林霉素的诱导耐药表型。结果:红霉素和克林霉索同时耐药在耐甲氧西林葡萄球菌(MRSA)和甲氧西林敏感型葡萄球菌(MSSA)中分别占51.65%和34.57%,对红霉素耐药而克林霉素敏感的MRsA和MSSA中,D一试验阳性即对克林霉素具有诱导耐药性者分别为69.72%和30.58%。D-试验阳性占所测葡萄球菌的24.48%,占红霉素耐药而克林霉素敏感菌株的"30.58%。结论:医院微生物室开展药敏试验中加上D-试验,检测葡萄球菌中克林霉素诱导性耐药,可以指导临床医师合理选用大环内酯类、克林霉素类抗菌药物。     

兽用抗菌药耐药判定标准的研究进展

兽用抗菌药因其可以有效地预防和治疗动物疾病而被广泛使用，造成了严重的细菌耐药。目前，兽药抗菌药的耐药判定主要参考美国临床和实验室标准协会(CLSI)和欧盟药敏试验标准委员会(EUCAST)公布的标准，但数据并不完整。我国近些年也开始建立适合自己国情的兽用抗菌药的耐药判定标准，但成果并不多。因此，急需建立和完善兽用抗菌药的耐药判定标准，以便于监测兽用抗菌药耐药性和指导临床准确使用兽用抗菌药。本文主要综述了CLSI和EUCAST两大组织已经公布的部分兽用抗菌药的耐药判定标准，以及近年来国内外兽用抗菌药耐药判定标准的研究进展，以期为兽用抗菌药耐药判定标准的发展提供理论参考。