耐红霉素葡萄球菌和β溶血链球菌的诱导型克林霉素耐药

耐大环内酯类(Macrolide)的葡萄球菌和β溶血链球菌可发生诱导型克林霉素(Clindamycin)和链阳霉素B(strep-togramin B)耐药,即大环内酯类-林可酰胺类-链阳性菌素B类(macrolide-lincosamide-streptogramin group B,MLSB)耐药表型。此种耐药表型可以是结构型的,也可是诱导型的,由不同的耐药基因所决定。诱导型耐药在应用红霉素治疗后会诱导出对克林霉素的耐药。结构型的红霉素或克林霉素耐药用普通的纸片法、MIC法或自动仪器法均可检出,而诱导型的耐药则需用纸片法的D试验来检出。1耐红霉素的葡萄球菌的诱导则克林霉素耐药早在90年代初,…     

溶血葡萄球菌对8种抗菌药敏感性及多重耐药分析

目的：分析我院新生儿分离溶血葡萄球菌对8种抗菌药的敏感性及多重耐药特点，指导临床用药。方法：使用琼脂稀释法测定8种抗菌药对63株溶血葡萄球菌的最低抑茵浓度（MIC）。采用D试验检测大环内酯类诱导型克林霉素耐药（MLSB耐药），按临床实验室标准委员会（CLSI）2006年标准判读结果。结果：利奈唑胺抗菌活性最高，敏感率为100％，MIC50/MIC90为2、2μg／mL；其次为万古霉素和替考拉宁，敏感率均为98．4％，MIC50/MIC90分另4为1、2μg／mL和2、4μg／mL；红霉素、庆大霉素和环丙沙星抗菌活性较差，耐药率为66．7％～77．8％．大环内酯类诱导型MLSB耐药占23．8％，多重耐药的耐甲氧西林溶血葡萄球菌占64．5％，结论：我院新生儿分离溶血葡萄球菌多重耐药率高。应加强细菌耐药的监控。     

对大环内酯类、林可酰胺类、链阳菌素抗生素耐药葡萄球菌检测

目的了解复旦大学附属华山医院临床分离株中诱导型克林霉素耐药葡萄球菌的检出率及其相关耐药基因erm的分布情况。方法根据NCCLS推荐的15pg／片红霉素和2μg／片克林霉素的纸片协同试验（D试验）对90株红霉素耐药的葡萄球菌检测诱导型克林霉素（iMLS）耐药；PCR检测与诱导型克林霉素耐药相关的ermA、ermC基因。结果90株红霉素耐药葡萄球菌中，56株克林霉素敏感或中敏者显示D试验阳性（iMLS型），占62．2％；另有22株克林霉素敏感者显示D试验阴性（MS型），占24．4％；12株克林霉素耐药者（cMLS型）亦显示D试验阴性，为13．4％。PCR结果显示56株iMLS型葡萄球菌均具有ermA或ermC基因，并以ermC基因为主，为91．1％（51／56）。12株cMLS型葡萄球菌中8株具有ermA或ermC基因。22株MS型均未检测到该2种基因。结论诱导型克林霉素耐药的葡萄球菌检出率为62．2％（56／90），其主要编码基因为ermC（91．1％，51／56）。临床分离株金葡菌0417的ermA基因序列与GenBank金葡菌M661的ermA序列完全一致，可能可作为D试验阳性的质控对照株。     

葡萄球菌属对抗菌药物的耐药性分析

目的了解葡萄球菌属临床分离株的耐药性及对大环内酯类、林可霉素类及链阳霉素类（MLS）的耐药表型。方法用Kirby-Bauer法测定葡萄球菌属对14种抗菌药的敏感性，进行D试验测定MLS耐药表型。结果在230株葡萄球菌属中，耐甲氧西林金葡菌（MRSA）和耐甲氧西林凝固酶阴性葡萄球菌（MRSCN）分别为9．9％和79．8％。对青霉素都呈现高度耐药。未发现万古霉素及替考拉宁耐药菌株，126株葡萄球菌属对红霉素耐药，54．8％（23／42）株金葡菌为结构型耐药；在凝固酶阴性葡萄球菌中（CNS），44．0％（37／84）为结构型耐药，41．7％（35／84）为外排型耐药。对红霉素耐药但对克林霉素敏感的葡萄球菌中，17株为诱导型克林霉素耐药。结论应加强对葡萄球菌的耐药性监测，临床微生物实验室应进行D试验。指导临床合理使用抗生素。     

葡萄球菌对克林霉素诱导耐药表型及基因型检测研究

目的了解葡萄球菌对红霉素及克林霉素的耐药性,测定红霉素诱导克林霉素耐药状况和基因型特征。方法收集我院2005～2007年分离到的350株葡萄球菌采用K-B法做药敏试验,对红霉素耐药、克林霉素敏感和中介葡萄球菌临床分离株做D试验检测,PCR检测细菌的ermA、ermB、ermC、msrA、msrB和linA/linA’基因。结果350株葡萄球菌中克林霉素诱导耐药64株,D试验阳性为18.3%。基因型分别是ermA9株、ermB2株、ermC48株、msrA7株、msrB11株、全部阴性的5株、linA/linA’64株、ermC＋msrB7株。结论红霉素核糖体甲基化酶基因ermC是诱导耐药的主要基因,检测葡萄球菌中红霉素对克林霉素的诱导耐药性可帮助临床医生正确选用大环内酯类、林可酰胺类和链阳霉素B类抗生素。     

耐红霉素葡萄球菌对克林霉素诱导型耐药的检测

目的了解本院临床分离的葡萄球菌对克林霉素诱导型耐药的发生率，帮助临床医师正确选择药物。方法采用K-B纸片琼脂扩散法检测葡萄球菌对红霉素和克林霉素的耐药性，按照CLSI／NCCLS推荐的D-试验方法检测克林霉素诱导型耐药。结果133株受试葡萄球菌对红霉素和克林霉素耐药菌株数分别为66株（49．6％）和43株（33．3％），66株耐红霉素葡萄球菌中有20株（其中金黄色葡萄球菌10株、表皮葡萄球菌9株、腐生葡萄球菌1株）为克林霉素诱导型耐药株，占红霉素耐药株的30．3％。在红霉素耐药金黄色葡萄球菌和凝固酶阴性葡萄球菌中，克林霉素诱导型耐药的检出率分别达38．5％和25．0％。对红霉素和克林霉素同时敏感或克林霉素耐药株中，未检到克林霉素诱导型耐药株。结论对红霉素耐药而克林霉素敏感的葡萄球菌应进行D-试验，报道克林霉素诱导耐药性结果，以便临床正确选择药物。     

耐红霉素葡萄球菌对克林霉素诱导型耐药的检测

目的：了解117医院临床分离的葡萄球菌对克林霉素诱导型耐药的发生率，帮助临床医师正确选择药物。方法：采用K—B纸片琼脂扩散法检测葡萄球菌对红霉素和克林霉素的耐药性，按照CLSI／NCCLS推荐的D-试验方法检测克林霉素诱导型耐药。结果：133株受试葡萄球菌对红霉素和克林霉素耐药菌株数分别为66（占49．6％）和43（占33．3％），66株耐红霉素葡萄球菌中有20株（其中金黄色葡萄球菌10株、表皮葡萄球菌9株、腐生葡萄球菌1株）。为克林霉素诱导型耐药株，占红霉素耐药株的30．3％。在红霉素耐药金黄色葡萄球菌和凝固酶阴性葡萄球菌中，克林霉素诱导型耐药的检出率分别达38．5％和25％。对红霉素和克林霉素同时敏感或克林霉素耐药株中，未检到克林霉素诱导型耐药株。结论：对红霉素耐药克林霉素敏感葡萄球菌应进行D试验，报告克林霉素诱导耐药性结果，以便临床正确选择药物。     

可诱导型克林霉素耐药的葡萄球菌检测及耐药性调查

目的了解可诱导型克林霉素耐药的葡萄球菌的耐药状况及发生率。方法用常规的方法对2005年1月至2007年12月临床各种标本进行培养及分离，Vitek-2全自动微生物鉴定仪进行鉴定及药物的敏感性试验检测，诱导型克林霉素耐药采用双纸片法进行检测。结果750株葡萄球菌中可诱导型克林霉素耐药的葡萄球菌有92株，占12．3％，387株金黄色葡萄球菌中有321株为红霉素耐药，其中235株为持续型克林霉素耐药，34株为可诱导型克林霉素耐药，占8．8％（34／387）；363株凝固酶阴性葡萄球菌中有294株为红霉素耐药，其中224株为持续性耐药，58株为可诱导型克林霉素耐药，占16．0％（58／363）。92株可诱导型克林霉素耐药的葡萄球菌对万古霉素、替考拉宁、磷霉素、喹努普汀／达福普汀、褐霉素及利奈唑烷均敏感，对其他抗生素存在不同程度耐药。结论临床微生物实验室应加强可诱导克林霉素耐药的检测，以指导临床合理使用林可霉素类抗生素。     

D-实验检测葡萄球菌中诱导型克林霉素耐药的实验研究

目的了解西安地区葡萄球菌对红霉素和克林霉素的不同耐药表型及其诱导型克林霉素耐药的发生率。方法采用K-B法检测葡萄球菌对红霉素和克林霉素的耐药性,头孢西丁纸片扩散法检测耐甲氧西林葡萄球菌,D试验检测诱导型克林霉素耐药表型。结果所有204株葡萄球菌中,90株（44.12%）为结构型耐药（cM LS）,即对红霉素和克林霉素同时耐药;57株（27.94%）为诱导型耐药（iM LS）,即对红霉素耐药对克林霉素敏感,但D试验阳性;32株（15.69%）为M S表型,即对红霉素耐药,对克林霉素敏感,但D试验阴性（M S）;其中在红霉素耐药、克林霉素敏感体外表型中,显示诱导型克林霉素耐药在M RSA,M SSA,M RCN S和M SCN S中的比例分别为65.22%,58.33%,67.65%和60%;在所有耐红霉素菌株所占比例分别为31.25%,36.84%,31.94%和30%。结论西安地区耐红霉素葡萄球菌中诱导型克林霉素耐药的发生率处于相对较高水平,临床细菌室应重视D-试验以指导临床合理选择抗生素。     

D试验和多重PCR检测红霉素耐药葡萄球菌

目的了解红霉素耐药的葡萄球菌对克林霉素的耐药表型和基因型，指导临床合理使用抗生素。方法用NCCLS标准D试验检测红霉素和克林霉素的耐药表型，通过多重PCR检测耐药基因ermA、ermC和msrA。结果所有144株葡萄球菌中，84株（58．3％）对红霉素和克林霉素耐药（cMLS），27株（18．8％）对红霉素耐药对克林霉素敏感但D试验阳性（iMLS），33株（22．9％）对红霉素耐药，对克林霉素敏感但D试验阴性（MS）。在MS型耐药的菌株中均只检测到msrA基因，在cMLS和iMLS型耐药的菌株中，除了1株3种基因均阴性外，其他均检测到ermA或ermC基因。在金葡菌中iMLS型耐药的菌株以ermC基因稍多（3／5），而cMLS型耐药的菌株以ermA基因居多（56／62）；在凝固酶阴性葡萄球菌中iMLS型和cMLS型耐药的菌株均以ermC基因居多（分别为22／22和11／14）结论iMLS型耐药的葡萄球菌在临床比较多见，多重PCR和D试验均可对其鉴别，临床微生物实验室应常规进行D试验。     

A new evolutionary variant of the streptogramin A resistance protein, Vga(A)LC, from Staphylococcus haemolyticus with shifted substrate specificity towards lincosamides

We found a new variant of the streptogramin A resistance gene, vga(A)LC, in clinical isolates of Staphylococcus haemolyticus resistant to lincomycin and clindamycin but susceptible to erythromycin and in which no relevant lincosamide resistance gene was detected. The gene vga(A)LC, differing from the gene vga(A) at the protein level by seven amino acid substitutions, was present exclusively in S. haemolyticus strains resistant to both lincosamides and streptogramin A (LS(A) phenotype). Antibiotic resistance profiles of the ATP-binding cassette (ABC) proteins Vga(A)(LC) and Vga(A) in the antibiotic-susceptible host S. aureus RN4220 were compared. It was shown that Vga(A)LC conferred resistance to both lincosamides and streptogramin A, while Vga(A) conferred significant resistance to streptogramin A only. Detailed analysis of the seven amino acid substitutions, distinguishing the two related ABC proteins with different substrate specificities, identified the substrate-recognizing site: four clustered substitutions (L212S, G219V, A220T, and G226S) in the spacer between the two ATP-binding cassettes altered the substrate specificity and constituted the lincosamide-streptogramin A resistance phenotype. A transport experiment with radiolabeled lincomycin demonstrated that the mechanism of lincosamide resistance in S. haemolyticus was identical to that of the reported macrolide-streptogramin B resistance conferred by Msr(A).     

溶血葡萄球菌庆大霉素耐药表型与基因型分析

目的研究溶血葡萄球菌庆大霉素耐药表型与基因型。方法用琼脂稀释法测定63株溶血葡萄球菌对苯唑西林、庆大霉素和其他5种抗生素的最低抑菌浓度（MIC），用聚合酶链反应（PCR）检测mecA和aac（6’）．aph（2”）耐药基因。结果63株溶血葡萄球菌对庆大霉素的耐药率为74．6％，MIC50、MIC90分别为64和128μg／mL.庆大霉素不敏感的甲氧西林耐药溶血葡萄球菌（MRSH）对环丙沙星和红霉素的耐药率（85．7％和87．8％）远高于庆大霉素敏感的MRSH（0．0％和46．2％，P〈0．005）。13株庆大霉素敏感的溶血葡萄球菌扩增aac（6’）＋aph（2”）基因均阴性，50株庆大霉素不敏感的溶血葡萄球菌（MIC为8～≥128μg／mL）均携带aac（6’）-aph（2”）基因，其中49株同时携带mecA基因。结论aac（6’）-aph（2”）基因是溶血葡萄球菌对庆大霉素产生耐药的主要机制。     

146例金黄色葡萄球菌中红霉素对克林霉素诱导耐药分析

目的了解金黄色葡萄球菌(SA)对红霉素和克林霉素的耐药性,检测红霉素对克林霉素诱导耐药的发生率及诱导耐药基因。方法采用美国临床实验室标准化协会(CLSI)推荐的纸片扩散法,用头孢西丁纸片检测耐甲氧西林金黄色葡萄球菌(MRSA)并以红霉素、克林霉素双纸片法(D试验)分析红霉素对克林霉素诱导耐药表型,用聚合酶链反应(PCR)检测耐药基因。结果 146株SA中MRSA占57.5%。SA对红霉素及克林霉素同时耐药的有82株,占56.2%,红霉素耐药而克林霉素敏感或中介的有34株,其中D试验阳性26株,红霉素诱导克林霉素耐药率76.5%。红霉素耐药而克林霉素敏感或中介的MRSA和甲氧西林敏感金黄色葡萄球菌(MSSA)中D试验阳性分别为80.0%和71.4%。克林霉素耐药菌株主要由erm基因决定,结构型耐药菌株主要耐药基因为ermA,诱导型耐药菌株的主要耐药基因为ermC。结论临床微生物实验室应加强对SA中克林霉素诱导耐药的检测,以指导临床医师合理选用大环内酯类、林可酰胺类抗菌药物。     

Antimicrobial susceptibility patterns and macrolide resistance genes of viridans group streptococci from blood cultures in Korea

OBJECTIVES: Our aim was to study the antimicrobial susceptibilities and macrolide resistance mechanisms of viridans group streptococci (VGS) in a Korean tertiary hospital. METHODS: MICs of five antimicrobials were determined for 106 VGS isolated from blood cultures. The macrolide resistance mechanisms of erythromycin non-susceptible isolates were studied by the double-disc test and PCR. RESULTS: In all, 42.4% of the isolates were susceptible to penicillin. Nine of 61 penicillin non-susceptible isolates were fully resistant (MIC >/= 4 mg/L). Rates of non-susceptibility to erythromycin, clindamycin and ceftriaxone were 33.9%, 17.9% and 9.4%, respectively. Twenty-two (61.1%) of 36 erythromycin non-susceptible isolates expressed constitutive resistance to macrolide-lincosamide-streptogramin B antibiotics (a constitutive MLS(B) phenotype); 13 isolates (36.1%) expressed an M phenotype; and one isolate, a Streptococcus bovis isolate, had an inducible MLS(B) resistance phenotype. erm(B) was found in isolates with constitutive/inducible MLS(B) phenotypes, and mef(A) in isolates with the M phenotype. In three isolates (two isolates with a constitutive MLS(B) phenotype and in one isolate with the M phenotype), none of erm(A), erm(B), erm(C) or mef(A) was detected by PCR. CONCLUSIONS: Penicillin non-susceptible VGS were more resistant to erythromycin, clindamycin and ceftriaxone than were penicillin-susceptible isolates. A constitutive MLS(B) phenotype associated with erm(B) was the predominant mechanism of macrolide resistance among erythromycin non-susceptible isolates from this Korean hospital.     

Antimicrobial susceptibility patterns and macrolide resistance genes of viridans group streptococci from normal flora

OBJECTIVES: Our aim was to study the antimicrobial susceptibilities and macrolide resistance mechanisms of viridans group streptococci isolated from the normal flora. METHODS: In vitro susceptibilities of 16 antimicrobials were studied for 161 viridans streptococci (on average 5.8 isolates per person) from the normal flora of 28 elderly persons. Resistance mechanisms of erythromycin-resistant isolates were studied by the double disc test and PCR. RESULTS: In all, 16.8% of the isolates were non-susceptible (MIC > or =0.25 mg/L) to penicillin, but none showed high-level resistance (MIC > or =4 mg/L). Resistance to erythromycin, tetracycline, quinupristin/dalfopristin, levofloxacin and moxifloxacin was found in 22.4, 27.3, 13.0, 1.9 and 1.9% of the isolates, respectively. Combined resistance to erythromycin and tetracycline was found in 13.0% of the isolates. Erythromycin-resistant isolates were isolated from 57% of the study persons. Of the erythromycin-resistant isolates 80.6% were of the M phenotype and 19.4% were of the macrolide-lincosamide-streptogramin B (MLSB) phenotype (one isolate with constitutive and six with inducible expression). Isolates with the M phenotype were the least susceptible to telithromycin, a new ketolide. The mef(A) gene was found in the isolates with the M phenotype and the erm(B) gene in the isolates with the MLSB phenotype. CONCLUSIONS: The distribution of phenotypes among the viridans streptococci resembles that found in Streptococcus pyogenes, with predominance of the M phenotype. However, the coding gene for the MLSB phenotype, erm(B), is the same in viridans streptococci as in Streptococcus pneumoniae. Viridans group streptococci carrying different resistance traits provide a pool of resistant bacteria that may transfer resistance determinants to more pathogenic organisms.     

Macrolide resistance and erythromycin resistance determinants among Belgian Streptococcus pyogenes and Streptococcus pneumoniae isolates

Resistance of streptococci to macrolide antibiotics is caused by target-site modification or drug efflux. The phenotypic expression of target-site modification can be inducible or constitutive. The prevalence of the three phenotypes among Belgian erythromycin-resistant Group A streptococci (GAS) and Streptococcus pneumoniae isolates was surveyed, their MICs for seven antibiotics were determined and the clonality of the isolates was explored. Of the 2014 GAS isolates tested 131(6.5%) were erythromycin resistant (MIC > 1 mg/L): 110 (84.0%) showed the M-resistance phenotype whereas the remaining 21 strains (16.0%) were constitutively resistant. No inducibly resistant strains were detected. Of 100 S. pneumoniae isolates, 33 were erythromycin resistant (MIC > 1 mg/L). In contrast to the GAS isolates, only 9.1% of the 33 erythromycin-resistant S. pneumoniae isolates showed the M-resistance phenotype. The presence of mefA/E and ermB genes in the M-resistant and constitutively and inducibly resistant strains, respectively, was confirmed by PCR analysis. Genomic analysis based on pulsed-field gel electrophoresis (PFGE) using the restriction enzyme SfiI, revealed 54 different PFGE patterns among the 131 erythromycin-resistant GAS isolates, of which an M6 clone represented 16.0% of the strains; all other clones, exhibiting different M-types, represented <7% of the strains. The S. pneumoniae isolates also appeared to be polyclonally based, as determined by arbitrarily primed PCR. The macrolides miocamycin and rovamycin, the lincosamide clindamycin and the ketolide HMR 3647 showed excellent activity against the M-resistant GAS and S. pneumoniae strains.     

仪征地区红霉素耐药葡萄球菌对克林霉素诱导耐药的分析

[目的]了解本地区近年来葡萄球菌对红霉素和克林霉素的耐药性以及克林霉素诱导性耐药的发生率。[方法]用K—B纸片琼脂扩散法检测葡萄球菌对红霉素和克林霉素的耐药性,按照CLIS推荐的D试验方法检测其克林霉素诱导性耐药性。[结果]红霉素耐药的金黄色葡萄球菌79株中克林霉素敏感的为29株,其中D试验阳性为18株（62．1％）;红霉素耐药的凝固酶阴性的葡萄球菌123株中克林霉素敏感的为59株,其中D试验阳性为33株（55．9％）。[结论]对红霉素耐药而克林霉素敏感的葡萄球菌应做D试验,以检测其克林霉素诱导耐药性,便于临床合理选用抗菌药物。     

Macrolide resistance determinants of group A streptococci in Ankara,Turkey

OBJECTIVES: Macrolide-lincosamide-streptogramin B (MLSB) resistance determinants of group A streptococci (GAS) in Ankara, Turkey, were defined for the first time. ISOLATES AND METHODS: A total of 1355 GAS isolates, collected from three different regions of Ankara, were screened for erythromycin resistance. Resistance phenotypes were determined by a triple-disc test, and the gene determinants responsible were determined by PCR. MICs of erythromycin, clindamycin and spiramycin were measured for the resistant isolates, and susceptibility rates to some further antibiotics were determined. RESULTS: Thirty-six isolates (2.6%) were resistant to erythromycin. Of these, 17 (47.2%) expressed macrolide-restricted resistance (M phenotype), while the remainder expressed inducible (16 isolates, 44.4%) or constitutive (three isolates, 8.3%) MLSB resistance. All isolates of the M phenotype harboured the mef(A) gene. Of non-M isolates, 14 harboured erm(A) subclass erm(TR) and five had erm(B) genes. There was a significant relationship between tetracycline resistance and the inducible phenotype (P < 0.05). Macrolide resistance was significantly higher in adults (P < 0.05), and increased more than two-fold in 2002 compared with 2001 (P < 0.05). CONCLUSION: The prevalence of macrolide resistance in GAS is low in Ankara; therefore, routine antimicrobial susceptibility testing against these agents seems unwarranted.     

红霉素耐药葡萄球菌对克林霉素诱导性耐药的研究

目的：了解临床分离的红霉素耐药葡萄球菌对克林霉素诱导性耐药的发生率，比较双纸片扩散法（D试验）中纸片之间距离对试验结果的影响。方法VITEK-2微生物分析系统检测为红霉素耐药、克林霉素敏感或中介的葡萄球菌135株，其中金黄色葡萄球菌（SA）为55株，凝固酶阴性葡萄球菌（CNS）为80株。比较红霉素纸片与克林霉素纸片边距15 mm与26 mm对结果的影响。结果 D试验阳性率为57.0%，其中SA阳性率70.9%， CNS为47.5%（P＜0.01）。纸片边距15 mm组D试验阳性77株，26 mm组仅69株，漏检率10.4%（P＜0.05）。结论实验室应常规开展D试验，D试验中双纸片间距以15 mm为佳。