铜绿假单胞菌的药物敏感试验结果分析

目的了解铜绿假单胞菌在本院的分布及对抗生素的敏感情况,为临床治疗提供科学依据。方法回顾性调查本院2008年1月至2009年10月住院及门诊患者各种标本分离的铜绿假单胞菌的分布及对抗生素的敏感情况。结果铜绿假单胞菌在呼吸道标本的检出率最高,占63.8%,其次是伤口分泌物标本,占18.3%,尿液标本占9.2%,血液标本占2.5%;其对11种抗生素的敏感率最高是妥布霉素,其次是哌拉西林/他唑巴坦,检出多重耐药株约占35%,未出现泛耐药株。结论根据药敏结果合理使用抗生素,并重视对多重耐药株的监测工作,可有效控制感染。     

女性中段尿与生殖道标本中无乳链球菌检出特点及耐药性对比分析

目的 分析女性泌尿生殖道标本来源的无乳链球菌检出特点及耐药性,为临床诊断和治疗提供依据。方法 收集2016年1月至2021年12月北京积水潭医院门诊及住院女性人群的中段尿和生殖道标本培养结果,比较分析无乳链球菌检出特点及对抗菌药物的耐药性。药敏结果依据美国临床和实验室标准化协会(CLSI)2021年标准进行判读,应用BD Epicenter和SPSS 19.0对数据进行统计分析。结果 共送检13 355份标本,分离出484株无乳链球菌,其中中段尿标本中的检出率为2.7%,生殖道标本中的检出率为4.5%。无乳链球菌在这两类标本中所占构成比均呈逐年上升趋势。中段尿来源的无乳链球菌以50岁以上非妊娠女性多见,占62.9%;生殖道来源的以20～40岁围产期女性为主,占86.9%。两类标本均未发现对青霉素、氨苄西林、头孢吡肟、头孢噻肟、万古霉素及利奈唑胺的耐药菌株。两类标本对红霉素、克林霉素、左氧氟沙星及四环素的敏感率均<45.0%;且中段尿的无乳链球菌对红霉素和左氧氟沙星的敏感率均显著低于生殖道标本,差异有统计学意义(P<0.05)。结论 女性中段尿与生殖道标本来源的无乳链球菌在检...     

上颌窦炎及咽炎患者肺炎链球菌带菌及耐药性调查

目的 调查急慢性上颌窦炎及咽炎患者肺炎链球菌带菌及耐药情况。方法 用E—test法及纸片扩散法测定耐药情况．结果 86株肺炎链球菌中，对青霉素敏感64株(74.4％)，低度耐药18株(20．9％)，高度耐药4株(4．7％)，青霉素耐药菌株对红霉索、氯霉素、复方新诺明及四环素的耐药率比青霉素敏感株高，所有菌株对万古霉素敏感．结论 了解细菌耐药性的变化是合理应用抗生素的重要依据。     

广州地区肺炎住院患儿感染肺炎链球菌的血清型分布及耐药性研究

目的了解广州地区肺炎住院的患儿感染肺炎链球菌的耐药性及血清型分布情况。方法用吸痰法采集患儿痰标本进行涂片，革兰氏染色镜检，合格痰标本划线接种血平板，用E-test法检测分离到的肺炎链球菌对青霉素、阿莫西林、头孢曲松、头孢呋辛、亚胺培南、氧氟沙星、万古霉素、红霉素和克林霉素9种药物的耐药性，采用K-B法检测四环素、复方新诺明的耐药性，并采用荚膜肿胀技术对分离到的79株肺炎链球菌进行血清分型。结果79株肺炎链球菌中青霉素耐药肺炎链球菌（PRSP）11．4％，青霉素中介肺炎链球菌（PISP）77．2％，青霉素敏感肺炎链球菌（PSSP）11．4％，对红霉素、克林霉素的耐药率分别为100％和93．7％，对阿莫西林、氧氟沙星、万古霉素的耐药率均为0，对头孢曲松、头孢呋辛、亚胺培南的耐药率分别为3．8％、72．2％、2．5％。79株肺炎链球菌中只有1株PSSP仅对红霉素耐药．78株肺炎链球菌对两种以上药物耐药．多重耐药率为98．7％（78／79），同时对克林霉素、红霉素、四环素、复方新诺明耐药的菌株65株，占82．3％（65／79）。79株肺炎链球菌血清型分别为19F（70．9％），23F（16．5％），6B（5．1％），4（2．5％），15B（2．5％），不能分型（2．5％），7价疫苗涵盖率为94．9％（75／79）。结论广州地区肺炎住院患儿肺炎链球菌对大环内脂类抗生素红霉素和林可酰胺类抗生素克林霉素耐药情况严重，对二代头孢菌素头孢呋辛耐药率居高，临床治疗儿童肺炎链球菌感染的肺炎应首选阿莫西林和三代头孢菌素。7价疫苗覆盖率高。预防儿童肺炎链球菌感染所致的肺炎，采用7价疫苗可以达到很好效果。     

鲍曼不动杆菌的临床分布及耐药性变迁

目的了解鲍曼不动杆菌在临床标本的分离率和病区分布及耐药性变化趋势。方法菌株鉴定采用法国梅里埃VITEK32细菌鉴定系统进行鉴定,药敏试验采用K-B法,药敏试验结果判定以CLSI/NCCLS标准进行。结果 2004-2010年共收到26670份标本,分离出阳性细菌7065株,其中鲍曼不动杆菌471株（6.67%）,分离率为1.77%（471/7065）。在471株鲍曼不动杆菌中,从痰液标本分离出最多有409株（86.83%）,分离率最高的是ICU,占49.3%。鲍曼不动杆菌对抗菌药物的耐药性普遍较高,且呈逐年升高趋势,部分表现出多重耐药特征。结论鲍曼不动杆菌的耐药状况日益严重,应重视临床鲍曼不动杆菌的感染与分离,谨防多重耐药鲍曼不动杆菌的院内感染及暴发流行。     

新生儿血培养中病原菌的分布及耐药性分析

目的监测新生儿血流感染常见病原菌分布特征及其耐药性，指导新生儿感染的预防和控制。方法采用法国生物梅里埃ATB Expression鉴定及药敏仪进行细菌鉴定和药敏试验。结果372株病原菌中居前3位的依次为凝固酶阴性葡萄球菌（77．7％）、大肠埃希菌（4．8％）、金黄色葡萄球菌（4．0％）。药敏显示MRS菌株对β－内酰胺类抗生素100％耐药，对万古霉素100％敏感。G－杆菌对亚胺培南100％敏感。结论MRS菌株已成为新生儿血流感染的主要病原菌，应严格执行消毒隔离制度，根据新生儿生理特点及药敏试验结果合理用药。     

神经外科医院感染及产超广谱β-内酰胺酶菌株感染分析

目的 研究神经外科医院感染的主要病原菌分布及其耐药情况，以及产超广谱β-内酰胺酶（ESBLs）菌株感染特点，为临床治疗提供依据。方法 通过对患者病历及细菌培养和药敏试验结果的统计分析，计算各种病原菌的构成比和各种抗菌药物的耐药率，不同年份比例的变化趋势采用趋势检验。结果 2003～2005年神经外科281倒患者分离菌株共408株，其中革兰阴性菌占77．2％，革兰阳性菌22．8％。G^-菌对常用的大多数头孢类抗生素耐药率极高，对亚胺硫霉素的敏感率93．7％。G^＋菌对青霉素类抗生素已基本耐药，对万古霉素的敏感率80．6％。分离产ESBLs菌株36株，各年产ESBLs菌占各年总菌株数的比例呈逐年上升趋势。36株产ESBLs菌株对临床常用抗生素耐药率普遍较高，对亚胺硫霉素无耐药。结论 G^- 菌是神经外科医院感染的主要病原菌；病原菌耐药性普遍较高；产ESBLs菌株引起的感染率逐年升高；预防细菌耐药．必须积极采取综合措施，建立细菌耐药监测系统，合理使用抗菌素，以求达到控制或延缓细菌耐药。     

重症监护病房多重耐药菌感染分析及控制措施

目的 了解重症监护病房(ICU)多重耐药菌感染分布特点,为临床治疗和ICU预防控制多重耐药菌感染提供科学的依据.方法 使用商品诊断试剂做细菌鉴定及药物敏感试验,药物敏感试验为微量肉汤稀释法;耐药性数据用LIS系统统计.结果 共分离216株多重耐药菌中,178株分离自痰标本,占82.73％,其次是尿标本占15.27％,其中G-杆菌190株,占87.96％,G+杆菌仅26株,占12.04％.排在前三位的分别为大肠埃希菌(36.11％)、肺炎克雷伯菌(21.76％)、铜绿假单胞菌(18.06％).结论 分离的多重耐药菌主要来自痰标本,以革兰阴性杆菌分离率高,临床应合理使用抗生素,加强院内感染预防及控制措施,降低多重耐药菌院内感染发生率.     

广州地区老年人肺炎链球菌临床分离株的青霉素耐药研究与分子分型

目的调查广州地区老年患者肺炎链球菌分离株对青霉素的敏感性，并分析其亲缘关系。方法K—B纸片法对33株分离自老年住院病人的肺炎链球菌进行青霉素药敏试验；应用PCR技术检测青霉素结合蛋白基因pbp1a，pbp2x，pbp2b；用盒式PCR（BOX—PCR）分析菌株间亲缘关系。用多位点测序分型技术（multilocus sequence typing，MLST）检测青霉素耐药菌株的分子分型。结果青霉素的耐药率为3．03％（1／33）：用PCR方法鉴定PSSP的准确率为68．75％；BOX-PCR可将这33株肺炎链球菌分为21型。MIST分型显示，青霉素耐药菌株属ST271型。结论广州地区老年患者肺炎链球菌对青霉素耐药率较低．用PCR方法检测PSSP有一定的可行性。BOX—PCR显示了较高的分辨率，能快速可靠地检测菌株间的亲缘关系。广州地区流行的耐药克隆与Taiwan^19F-14株同源。     

青岛地区部分医院2005-2008年肺炎链球菌的耐药性分析

目的 监测青岛地区肺炎链球菌的耐药性,为临床合理应用抗菌药物提供依据.方法 采集青岛地区部分医院2005年1月到2008年12月门诊与住院感染患者呼吸道、血液、脑脊液等标本,培养、分离和鉴定肺炎链球菌.根据NCCLS的推荐,采用琼脂微茸稀释法测定分离出的231株肺炎链球菌对11种常用抗菌药物的耐药性,分析耐药趋势及年龄差异.结果 231株肺炎链球菌对青霉素不敏感率为23.38%[耐青霉素肺炎链球菌(PRSP):9.52%;低耐青霉素肺炎链球菌(PISP):13.85%].对头孢噻肟耐药率最低为9.96%(23/231),其次阿莫西林为12.55%(29/231).对红霉素耐药率最高为90.48%(209/231).14岁以下患者PRSP检出率为27.91%(12/43),明显高于成人的PRSP检出率5.38%(10/186).结论 本地区PRSP检出率较2004年前明显增加,并有逐年增加的趋势,肺炎链球菌的耐药性也有逐年上升的趋势.本地区对感染低耐青霉素肺炎链球菌的患者头孢噻肟、阿莫西林可为首选药物.     

Evaluation of the Rapid Mastitis Test for identification of Staphylococcus aureus and Streptococcus agalactiae isolated from bovine mammary glands.

A latex agglutination test system (Rapid Mastitis Test [RMT]; Immucell, Portland, Maine) containing reagents for the identification of Staphylococcus aureus and Streptococcus agalactiae from bovine intramammary infections was evaluated with 527 staphylococcal and 267 streptococcal isolates. The RMT Staphylococcus aureus reagent detected 94.2% of 242 Staphylococcus aureus isolates, 80% of 25 Staphylococcus intermedius isolates, and 42.8% of 21 tube coagulase-positive Staphylococcus hyicus isolates. All Streptococcus agalactiae isolates were correctly identified by the RMT Streptococcus agalactiae reagent. Cross-reactions were observed with one Streptococcus dysgalactiae and three Streptococcus uberis strains. The RMT was found to be an acceptable method for the detection of Staphylococcus aureus and Streptococcus agalactiae isolated from bovine mammary glands. The occurrence of coagulase-positive staphylococci other than Staphylococcus aureus requires biochemical testing for species level identification.     

Distribution of serotypes and antimicrobial resistance genes among Streptococcus agalactiae isolates from bovine and human hosts

To better understand the emergence and transmission of antibiotic-resistant Streptococcus agalactiae, we compared phenotypic and genotypic characteristics of 52 human and 83 bovine S. agalactiae isolates. Serotypes found among isolates from human hosts included V (48.1%), III (19.2%), Ia and Ib (13.5% each), and II (5.8%). Among isolates from bovine hosts, molecular serotypes III and II were predominant (53 and 14.5%, respectively). Four and 21 different ribotypes were found among human and bovine isolates, respectively. A combination of ribotyping and serotyping showed that two bovine isolates were indistinguishable from human isolates. Resistance to tetracycline and erythromycin was more common among human (84.6% and 26.9%, respectively) than bovine (14.5% and 3.6%, respectively) isolates. tetM was found in all tetracycline-resistant human isolates, while tetO was the predominant resistance gene among bovine isolates. tet genes were found among various ribotypes. ermB, ermTR, and mefA were detected among erythromycin-resistant human isolates, while ermB was the only erythromycin resistance determinant among isolates from bovine hosts. For isolates from human hosts, erythromycin resistance genes appeared to be associated with specific ribotypes. We conclude that (i) human and bovine S. agalactiae isolates represent distinct populations; (ii) human host-associated S. agalactiae subtypes may occasionally be transmitted to bovines; (iii) while emergence of erythromycin and tetracycline resistance appears to largely occur independently among human and bovine isolates, occasional cross-species transfer of resistant strains or transmission of resistance genes between human- and bovine-associated subtypes may occur; and (iv) dissemination of antibiotic-resistant S. agalactiae appears to include both clonal spread of resistant strains as well as horizontal gene transfer.     

Prevalence of erythromycin and clindamycin resistance among Streptococcus agalactiae isolates in Germany

The antimicrobial susceptibilities of 338 clinical Streptococcus agalactiae isolates from two geographical regions in Germany were determined by agar dilution. All isolates were susceptible to penicillin, cefotaxime and vancomycin. The overall frequencies of erythromycin and clindamycin resistance were 11% and 4.7%, respectively. Determination of resistance phenotypes among the 37 erythromycin-resistant isolates revealed constitutive and inducible MLS(B) resistance in 40.6% and 37.8% of isolates, respectively, and susceptibility to clindamycin in 21.6% of isolates. Only 14.3% of isolates with inducible MLS(B) resistance were identified as clindamycin-resistant by determination of clindamycin MICs. Pulsed-field gel electrophoresis suggested a clonal distribution pattern among the erythromycin-resistant isolates.     

In vitro activity of quinupristin/dalfopristin against selected bacterial pathogens isolated in Italy

Objectives: To evaluate the activity of quinupristin/dalfopristin, a new injectable streptogramin, against 732 clinical strains recently isolated in Italy.
Methods: Susceptibility tests were performed according to NCCLS-guided MIC methodology. Pathogens included in the evaluation included 108 Staphylococcus aureus isolates, 124 coagulase-negative staphylococcal isolates, 158 Streptococcus pyogenes isolates, 30 Streptococcus agalactiae isolates, 30 β-hemolytic streptococcal isolates, 18 Streptococcus sanguis isolates, 80 Streptococcus pneumoniae isolates, 69 Enterococcal isolates, 40 Haemophilus influenzae isolates, 30 Moraxella catarrhalis isolates and, finally, 30 Gram-positive and 25 Gram-negative anaerobes.
Results: Quinupristin/dalfopristin inhibited Staphylococcus aureus and other Staphylococcus spp., irrespective of their oxacillin or erythromycin resistance phenotypes. Similarly, streptococci were fully inhibited by quinupristin/dalfopristin. Enterococcus faecalis was not included in the spectrum of this streptogramin, while isolates of Enterococcus faecium were inhibited by the new compound. Respiratory pathogens such as H. influenzae and M. catarrhalis were inhibited by quinupristin/dalfopristin as well as all Gram-negative anaerobes tested.
Conclusions: These findings suggest a putative role for quinupristin/dalfopristin in the empirical treatment of severe nosocomial and community-acquired infections caused by pathogens often displaying resistance to multiple antibiotics. This drug may provide an alternative to glycopeptide compounds.     

Streptococcus agalactiae in a large Portuguese teaching hospital: antimicrobial susceptibility, serotype distribution, and clonal analysis of macrolide-resistant isolates

Group B streptococci are emerging as a cause of serious infection worldwide. The capsular polysaccharides are not only important virulence factors but also the target of vaccine development efforts. Serotypes III (24.6%), V (23.4%), Ia (17.8%), and II (16.3%) were the most prevalent among 252 Streptococcus agalactiae isolates collected during 1999-2002 in the largest hospital of Lisbon, Portugal. The substantial proportion of bacteremic patients (17 neonates and 21 adults) in this period illustrates the present importance of S. agalactiae as a cause of invasive disease. All isolates were fully susceptible to penicillin (MIC(50) = 0.064 microg/ml; MIC(90) = 0.094 microg/ml, range 0.008-0.094), cefotaxime, chloramphenicol, ofloxacin, and vancomycin. Resistance was found to tetracycline (75.4%), erythromycin (10.7%), and clindamycin (9.9%). Of the 27 erythromycin-resistant isolates, 70.4% had the cMLS(B), 22.2% the iMLS(B), and 7.4% the M phenotype. All isolates presenting the M phenotype carried the mef(A) gene, whereas the erm(B) gene was found in a large fraction of MLS(B) isolates (n = 17) and only a small proportion (n = 7) the erm(A) gene [erm(TR) variant]. All isolates carried a single macrolide-resistance determinant. Macrolide resistance was not attributable to a single clone as evidenced by distinct serotype and pulsed-field gel electrophoretic profiles. Careful surveillance of S. agalactiae invasive infections in Portugal is essential, and the treatment or intrapartum prophylaxis of patients who are allergic to penicillin should be guided by contemporary resistance patterns observed in the country.     

Susceptibility of strains of Streptococcus agalactiae to macrolides and lincosamides, phenotype patterns and resistance genes

The Group B streptococcus ( Streptococcus agalactiae ) is a pathogen of increasing importance in human disease. We therefore studied the susceptibility of clinical isolates of S. agalactiae to penicillin G, erythromycin, azithromycin and clindamycin using National Committee for Clinical Laboratory Standards methodology, and we also determined the phenotypes of macrolide-lincosamide susceptibility and the resistance genes implicated in a group of selected isolates of the different phenotypes. We used 221 isolates collected between 1997 and 1999 in two Health Authority Areas in Móstoles and Granada, Spain. The minimal concentration for 90% inhibition (MIC₉₀) for penicillin G was 0.12 mg/L and all the isolates tested were susceptible. One hundred and eighty-five (83.7%) were susceptible to erythromycin and azithromycin and 191 (86.4%) were susceptible to miocamycin and clindamycin. Twenty-three isolates (10.4%) had a constitutive MLS_B phenotype, seven (3.2%) an inducible phenotype, and six (2.7%) an M phenotype. All except one of the MLS_B phenotype isolates tested ( n  = 23) carried erm genes; in two strains with the mef (A) gene, all the M phenotype ( n  = 6) isolates tested carried mef genes, while erm and mef (A) genes were absent in all the macrolide-lincosamide-susceptible ( n  = 12) isolates tested. In our environment, resistance to macrolide and lincosamide in S. agalactiae was present in 10–16% of the isolates. The majority of resistant strains had the MLS_B phenotype.     

Macrolide resistance trends in beta-hemolytic streptococci in a tertiary Korean hospital

PURPOSE: Erythromycin-resistant beta-hemolytic streptococci (BHS) has recently emerged and quickly spread between and within countries throughout the world. In this study, we evaluate the antimicrobial susceptibility patterns and erythromycin resistance mechanisms of BHS during 2003-2004. MATERIALS AND METHODS: The MICs of seven antimicrobials were determined for 204 clinical isolates of BHS from 2003 to 2004. Resistance mechanisms of erythromycin-resistant BHS were studied by the double disk test as well as by polymerase chain reaction (PCR). RESULTS: Compared with our previous study, resistance among Streptococcus pyogenes isolates to a variety of drugs decreased strikingly: from 25.7% to 4.8% in erythromycin; 15.8% to 0% in clindamycin; and 47.1% to 19.0% in tetracycline. The prevalent phenotypes and genotypes of macrolide-lincosamide-streptograminB (MLSB) resistance in Streptococcus pyogenes isolates have been changed from the constitutive MLSB phenotype carrying erm(B) to the M phenotype with mef(A) gene. In contrast with Streptococcus pyogenes, resistance rates to erythromycin (36.7%), clindamycin (43.1%), and tetracycline (95.4%) in Streptococcus agalactiae isolates did not show decreasing trends. Among the Streptococcus dysgalactiae subsp. equisimilis isolates (Lancefield group C, G), resistance rates to erythromycin, clindamycin, tetracycline and chloramphenicol were observed to be 9.4%, 3.1%, 68.8%, and 9.4%, respectively. Conclusion: Continual monitoring of antimicrobial resistance among large-colony-forming BHS is needed to provide the medical community with current data regarding the resistance mechanisms that are most common to their local or regional environments.     

Polyclonal spread of erythromycin-resistant Streptococcus agalactiae in southern Taiwan

Resistance to erythromycin is common among Streptococcus agalactiae in Taiwan, however the genetic relatedness of erythromycin-resistant isolates has not yet been reported. From 1991 to 2001, 629 clinical isolates of S. agalactiae were collected in a medical center at Tainan in southern Taiwan, of which 189 (30.0%) were resistant to erythromycin. The isolation rate of erythromycin-resistant group B streptococcus (GBS) was stable, irrespective of the clinical sources or study period. Among them, 145 (76.7%) isolates showed the macrolide-lincosamide-streptogramin B (MLS)-resistant phenotype, and 44 (23.3%) had the macrolide (M)- resistant phenotype. Of the isolates with MLS phenotype, 141 (97.2%) isolates harbored the ermB gene alone and only three (2.1%) the ermTR gene, whereas 41 (93.2%) of 44 isolates with M phenotype harbored the mefA/E gene. Of 177 typeable isolates, there were 26 unrelated pulsed-field gel electrophoresis (PFGE) patterns. PFGE type 1 accounted for 17.8% (24/135) of MLS phenotype isolates with the ermB gene and 48.7% (18/37) of M phenotype isolates with the mefA/E gene. During the study period, the proportion of PFGE type 6 decreased significantly, whereas that of type 8 increased. Our results suggest that erythromycin resistance is not uncommon among clinical isolates of S. agalactiae and is, at least, partially related to polyclonal spread in southern Taiwan.     

Characterization of invasive and colonizing isolates of Streptococcus agalactiae in East African adults

Ninety-five colonizing isolates and 74 invasive isolates of Streptococcus agalactiae from Kenyan adults were characterized by using capsular serotyping and multilocus sequence typing. Twenty-two sequence types clustering into five clonal complexes were found. Data support the view that S. agalactiae isolates belonging to a limited number of clonal complexes are invasive in adults worldwide.     

Phenotypic and molecular characteristics of Streptococcus agalactiae isolates recovered from milk of dairy cows in Brazil

Information on the characteristics of Streptococcus agalactiae obtained from bovine sources in Brazil is still very limited. The aim of this study was to assess the phenotypic and genotypic diversity among S. agalactiae isolates from milk of dairy cows presenting clinical or subclinical mastitis in the southeast region of Brazil. Phenotypic characterization was based on physiological and serological tests. Antimicrobial susceptibility tests were carried out by the disk method. Genetic diversity was evaluated by using random amplified polymorphic DNA-PCR (RAPD-PCR) (by using the primer 1254) and pulsed-field gel electrophoresis (PFGE) (by using SmaI as the restriction enzyme) and by PCRs for detection of genes associated with resistance to erythromycin and tetracycline as well as PCRs for detection of genes coding for cell surface-associated proteins. According to the results of physiologic tests, 45 (52.9%) isolates showed beta-hemolysis and 44 (51.7%) were susceptible to bacitracin. Fourteen different biotypes were detected. The two most frequent biotypes comprised strains that were non-beta-hemolytic; fermented galactose, lactose, and salicin; produced protease; and were negative for DNase production. Serotype III was predominant (66 isolates [77.6%]), followed by serotypes II, Ia, Ib, and VI. Resistance to tetracycline and erythromycin was found in 38 (44.7%) and 9 (10.5%) isolates, respectively, with tet(O) (31.7%) and erm(B) (100%) being the most frequently occurring resistance genes. Three genes coding for surface proteins, bca, lmb, and scpB, were detected in 55 (64.7%), 7 (8.2%), and 43 (50.5%) isolates, respectively. In most cases, isolates from animals in the same herd presented closely related genetic profiles (determined by either RAPD-PCR or PFGE), which were distinct from those of isolates from different herds.