2017-2018年山东省青岛地区畜禽源弯曲菌耐药性调查

目的调查2017—2018年山东省青岛地区畜禽源弯曲菌的流行与耐药现状。方法2017—2018年,从青岛地区的猪/鸡养殖场、屠宰场、农贸超市等场所采集畜禽泄殖腔(肛门)、盲肠、肉等样本,分离弯曲菌,对分离株进行种属鉴定和药敏试验,运用PCR方法检测大环内酯类基因erm(B)与增强型耐药外排泵基因RE-cmeABC。结果共采集畜禽源样本730份,分离到235株(34.66%)弯曲菌,包括空肠弯曲菌131株(55.74%)、结肠弯曲菌104株(44.26%)。其中鸡源菌株147株,分离率为29.40%(147/500);鸭源菌株80株,分离率为47.06%(80/170);猪源菌株8株,分离率为13.33%(8/60)。药敏试验结果显示,结肠弯曲菌对环丙沙星、四环素、卡那霉素、红霉素、庆大霉素、克林霉素和氟苯尼考的耐药性较为严重,耐药率分别为100.00%、99.04%、96.15%、92.31%、92.31%、87.50%、53.85%。空肠弯曲菌对四环素、环丙沙星、卡那霉素和氟苯尼考的药性较为严重,耐药率分别为100.00%、98.47%、70.99%、61.83%。PCR方法检测到12株(5.11%)erm(B)基因阳性菌株,125株(53.19%)REcmeABC基因阳性菌株。结论本研究提示应持续监测青岛地区畜禽源弯曲菌的耐药现状与耐药机制,为控制耐药弯曲菌的流行提供理论基础。     

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。     

深圳市南山区腹泻患者弯曲菌感染及病原学特征分析

目的获得本地区秋季腹泻患者弯曲菌的感染现状及病原学特征。方法收集深圳市南山区2018年9 — 11月腹泻患者的粪便标本,采用双孔滤膜法分离培养弯曲菌并应用荧光聚合酶链式反应（PCR）方法进行菌种鉴定。 应用脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）对分离菌株进行分子分型,应用琼脂稀释法获得菌株对11种抗生素的最小抑菌浓度（MIC）。 根据菌株的序列分型（ST）结果,结合既往菌株分型数据进行本地区菌株的遗传聚类分析。结果共采集腹泻患者粪便标本150份,其中男性患者74例,女性患者76例,年龄在1～86岁之间。 150份粪便标本中共分离到弯曲菌18株,检出率为12.00%（18/150）。 菌种鉴定发现,空肠弯曲菌占77.78%（14/18）,结肠弯曲菌占22.22%（4/18）。 14株空肠弯曲菌可分为11种PFGE带型,8个ST型别,以ST9763最多（35.71%,5/14）,是本研究新发现ST型别。 14株空肠弯曲菌对四环素全部耐药,对红霉素、阿奇霉素、泰利霉素、庆大霉素、链霉素及克林霉素100.00%敏感。 ST型别最小生成树聚类分析结果表明,不同宿主来源菌株没有显著聚集性,腹泻患者分离菌株分布在不同来源的组群中。结论采用双孔滤膜法提高了腹泻患者中弯曲菌的检出率。本地区弯曲菌的感染仍以空肠弯曲菌为主, 分离菌株对四环素类、喹诺酮类抗生素呈现较高的耐药特征,分离的空肠弯曲菌ST呈弥散分布特点。     

54株肺炎克雷伯菌氨基糖苷类抗生素耐药基因分析

目的了解临床分离的54株肺炎克雷伯菌对氨基糖苷类抗生素的耐药谱,分析氨基糖苷乙酰转移酶基因的分布规律及其与氨基糖苷类抗生素耐药的相关性,为临床抗感染治疗提供依据。方法采用MIC法测定临床分离的54株肺炎克雷伯菌对7种氨基糖苷类抗生素的耐药谱,应用Whonet5.4软件统计耐药率,通过聚合酶链反应进行氨基糖苷乙酰转移酶基因研究。结果 54株肺炎克雷伯菌对阿米卡星、庆大霉素、妥布霉素、卡那霉素、链霉素、大观霉素和奈替米星的耐药率分别为14.8%、77.8%、59.3%、68.5%、66.7%、61.1%、22.2%;测试菌株中存在aac(3)-Ⅱ、aac(6′)-Ⅰ、aac(3)-Ⅳ、aac(3)-Ⅰ4种耐药基因,aac(3)-Ⅱ和aac(6′)-Ⅰ是主要的产酶基因,检出率分别为78.5%和65.0%。结论产生氨基糖苷类钝化酶是临床分离的肺炎克雷伯菌对氨基糖苷类抗生素主要的耐药机制,临床分离菌的耐药表型和钝化酶基因关系较为复杂,可能与耐药菌中存在多钟耐药基因有关,临床实验室应加强检测,指导临床合理使用抗菌药物。     

利用基因芯片技术分析空肠弯曲菌的遗传特征

目的 为分析我国弯曲菌遗传特征,本研究根据已发表多株弯曲菌的全基因组测序特征及比对结果自行设计基因芯片,利用芯片对我国不同宿主来源菌株进行遗传特异性分析。方法 根据前期基因组水平比对分析的结果,利用Combimatrix tilingCustomArrayTM 90K芯片,设计DNA芯片。芯片包含已测序菌株 ICDCCJ07001、269.97、NCTC11168、81-176、81-116和RM1221共3384个CDS的探针序列,以及空肠弯曲菌耐药及致病性相关2个质粒共80个CDS的探针序列,与脂寡糖的合成相关基因簇16种共219个CDS的探针序列、荚膜多糖合成相关基因簇7种共160个CDS的所有序列。对我国不同宿主来源27株分离菌株提取DNA,利用芯片进行杂交,获得杂交信息并分析不同菌株CDS分布特征分析及聚类特点。结果 中国菌株的主要变异区域主要存在于与脂寡糖、荚膜多糖合成相关的基因簇、鞭毛修饰相关的基因簇、DNA限制/修饰相关的基因簇以及空肠弯曲菌Mu样噬菌体基因簇。基因组水平不同来源菌株CDS分布的聚类结果没有发现显著的宿主归因特点,但GBS相关菌株脂寡糖合成相关基因组成具有共性特征。结论 通过验证以及与过去研究的比较,本次研究中的基因芯片技术结果准确可信,本研究所用基因芯片在分析空肠弯曲菌基因多态性方面具有很好的优势,可用于弯曲菌遗传特征和重要毒力因子的分析和检测。     

广州地区儿童空肠弯曲菌感染的检测与分析

目的掌握广州地区空肠弯曲菌引起儿童感染性腹泻的现状,探索空肠弯曲菌的检测方法及耐药状况。方法对2011~2014年该院可疑空肠弯曲菌感染患儿的粪便进行病原菌的分离培养和常规生化鉴定,然后进行聚合酶链反应(PCR)测序确认,同时对所分离菌株进行药敏试验。结果近4年来从2 088例腹泻患儿粪便标本中共检出154株空肠弯曲菌,经生化反应鉴定和PCR检测确认,PCR检测限可达6CFU/mL;该地区儿童感染空肠弯曲菌对亚胺培南和氨基糖苷类药物敏感,对氯霉素、林可霉素和红霉素等抗菌药物耐药率10%,对氟喹诺酮、氨苄西林和四环素有较高耐药率(24.03%~44.16%),对复方磺胺甲噁唑和头孢菌素耐药。结论空肠弯曲菌是儿童腹泻的重要病原菌之一,重症患者可导致严重后果,应引起重视,积极开展对疑似患者的空肠弯曲菌检测;常规检测和特异性的PCR检测有利于提高检出率。     

IS256与医院感染表皮葡萄球菌耐氨基糖苷类抗菌药物的关系

目的了解医院感染表皮葡萄球菌对不同类型氨基糖苷类抗菌药物的敏感特征,分析插入序列(IS)256与表皮葡萄球菌耐氨基糖苷类抗菌药物的关系。方法收集2007年2月至2007年7月外科病区中引起医院感染的表皮葡萄球菌48株,利用纸片扩散法测定细菌对4种氨基糖苷类抗菌药物(庆大霉素、奈替米星、链霉素和阿米卡星)药敏特征;构建IS256特异性引物,利用聚合酶链反应(PCR)检测48株细菌中IS256分布状况。结果48株临床分离的表皮葡萄球菌对4种氨基糖苷类抗菌药物的药敏特征分别为:对庆大霉素的耐药率为69%,敏感率为31%;对奈替米星的耐药率为8%,敏感率为79%,中介率为13%;对链霉素的耐药率为42%,敏感率为35%,中介率为23%;对阿米卡星的耐药率为15%,敏感率为75%,中介率为10%。全部临床分离株中,有25株细菌检出IS256。在庆大霉素耐药菌株中,IS256检出率高达70%,与敏感菌相比差异具有统计学意义(P<0.01);而对其他3种抗菌药物耐药的菌株中,IS256的检出与耐药无明显相关性(P>0.05)。结论表皮葡萄球菌临床分离株对氨基糖苷类抗菌药物存在不同程度耐药。IS256与表皮葡萄球菌对庆大霉素耐药密切相关。     

2016－2018年北京市顺义区成年人腹泻患者弯曲菌感染监测及病原学特征分析

目的综合分析北京市顺义区3年期间基于过滤法从成年人腹泻患者分离的弯曲菌菌株的分型特征、耐药特点及分布特征,为我国弯曲菌感染的防控及风险评估提供基础数据。方法连续3年（2016 — 2018年）收集腹泻监测项目中的腹泻患者粪便标本,应用增强过滤法分离弯曲菌并进行菌种鉴定。 应用多位点序列分型（MLST）和脉冲场凝胶电泳（PFGE）2种方法进行细菌分子分型。 采用琼脂稀释法进行分离菌株的抗生素敏感性分析。结果2016 — 2018年,腹泻病例中弯曲菌的检出率分别为5.65%（17/301）、10.51%（39/371）和7.75%（29/374）。 共分离弯曲菌87株,空肠弯曲菌占87.36%（76/87）,结肠弯曲菌占12.64%（11/87）。 76株空肠弯曲菌被分为55种序列分型（ST）,11株结肠弯曲菌被分为9种ST型别。 病例发病时间聚集且分离的弯曲菌为相同ST型别的情况出现了6次,通过PFGE分析,5次聚集病例分离的菌株均呈现单一PFGE带型。 76株空肠弯曲菌的多重耐药率为55.26%（42/76）,11株结肠弯曲菌的多重耐药率为90.91%（10/11）。结论弯曲菌是北京市顺义区成年人腹泻患者的重要病原菌,过滤法可作为弯曲菌分离培养的有效技术方法。 从顺义区腹泻患者分离的结肠弯曲菌多重耐药严重,应引起公共卫生、临床等多部门的关注。     

我国非伤寒沙门菌对多粘菌素的耐药现况及mcr-1基因携带概况

目的 初步探究我国非伤寒沙门菌对多粘菌素的耐药情况。方法 利用微量肉汤稀释法,测定不同来源404株非伤寒沙门菌对多粘菌素B及多粘菌素E的最小抑菌浓度（MIC）,计算耐药率,推测野生沙门菌株的耐药阈值。同时利用聚合酶链式反应（PCR）方法检测菌株携带mcr-1基因的情况。结果 404株沙门菌对多粘菌素B及E的MIC范围为0.125 g/ml至16 g/ml,对多粘菌素B的MIC50、MIC90分别为1 g/ml和8 g/ml;对多粘菌素E的MIC50、MIC90分别为2 g/ml和8 g/ml。优势血清型鼠伤寒沙门菌、肠炎沙门菌及德尔卑沙门菌对多粘菌素B及E的MIC值分布不同。以8 g/ml为耐药阈值判定折点,实验菌株对多粘菌素B及E的耐药率分别为10.89%和15.84%;其中食源性沙门菌、人源性沙门菌及动物源性沙门菌对多粘菌素B的耐药率分别为12.50%、17.16%和0.00%（P0.01）;对多粘菌素E的耐药率分别为8.30%、27.94%和0.78%（P0.01）。发现7株同时耐多粘菌素及三代头孢的菌株。发现1株人源鼠伤寒沙门菌携带可转移的mcr-1基因,且该菌株产ESBLs。结论 发现我国人源产ESBLs的沙门菌携带mcr-1基因。根据体外药敏结果,非伤寒沙门菌对多粘菌素B及E的耐药折点设为8 g/ml较宜。沙门菌对多粘菌素的耐药率尚处于低水平,应加强不同来源沙门菌对多粘菌素的耐药监测。     

用琼脂稀释法检测产超广谱β内酰胺酶的大肠埃希菌和肺炎克雷伯菌的体外抗菌活性

目的用琼脂稀释法检测大肠埃希菌和肺炎克雷伯菌产超广谱β内酰胺酶(ESBLs)菌株与不产ESBLs菌株对13种抗生素的耐药情况。方法以双纸片协同试验对临床分离的29株大肠埃希菌和30株肺炎克雷伯菌检测ESBLs的产生,并以琼脂稀释法对亚胺培南等临床常用的13种抗生素作了最低抑菌浓度(MIC)检测及分析。结果双纸片协同试验对两种菌产ESBLs总得检出率为37.3%。其中大肠埃希菌为46.7%,肺炎克雷伯菌为33.3%。不产ESBLs菌株对各处抗生素的耐药率低于18%,MIC50为0.125至8,MIC90为0.5至64不等(氨曲南、环丙沙星、替卡西林/棒酸除外,耐药率分别为20%至40%不等)。产ESBLs菌株对亚胺培南,头孢美他醇全部敏感,亚胺培南的MIC50为0.25,MIC90为0.5。对头孢派酮/舒巴坦的耐药率低,为18.2%,MIC50为32。对喹诺酮类,氨基糖苷类及其他β-内酰胺类抗生素的耐药率大于50%,MIC50为64至256。对三代头孢菌素,氨曲南的耐药率大于80%,三代头孢菌素MIC50为256,MIC90为256至512。对环丙沙星、替卡西林/棒酸、氨曲南、庆大霉素呈交耐药,产ESBLs菌株,。大肠埃希菌耐药率高达58.3～100%,肺炎克雷伯菌耐药率高达40～60%。结论治疗ESBLs菌引起的感染,应用亚胺培南,头孢美他醇为好。可根据药敏结果合理选用高浓度的含酶抑制剂的复方β-内酰胺类抗     

Identification of a Novel Genomic Island Conferring Resistance to Multiple Aminoglycoside Antibiotics in Campylobacter coli

Historically, the incidence of gentamicin resistance in Campylobacter has been very low, but recent studies reported a high prevalence of gentamicin-resistant Campylobacter isolated from food-producing animals in China. The reason for the high prevalence was unknown and was addressed in this study. PCR screening identified aminoglycoside resistance genes aphA-3 and aphA-7 and the aadE-sat4-aphA-3 cluster among 41 Campylobacter isolates from broiler chickens. Importantly, a novel genomic island carrying multiple aminoglycoside resistance genes was identified in 26 aminoglycoside resistant Campylobacter coli strains. Sequence analysis revealed that the genomic island was inserted between cadF and COO1582 on the C. coli chromosome and consists of 14 open reading frames (ORFs), including 6 genes (the aadE-sat4-aphA-3 cluster, aacA-aphD, aac, and aadE) encoding aminoglycoside-modifying enzymes. Analysis by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing indicated that the C. coli isolates carrying this unique genomic island were clonal, and the clone of PFGE subtype III and sequence type (ST) 1625 was particularly predominant among the C. coli isolates examined, suggesting that clonal expansion may be involved in dissemination of this resistance island. Additionally, we were able to transfer this genomic island from C. coli to a Campylobacter jejuni strain using natural transformation under laboratory conditions, and the transfer resulted in a drastic increase in aminoglycoside resistance in the recipient strain. These findings identify a previously undescribed genomic island that confers resistance to multiple aminoglycoside antibiotics. Since aminoglycoside antibiotics are used for treating occasional systemic infections caused by Campylobacter, the emergence and spread of this antibiotic resistance genomic island represent a potential concern for public health.     

Aminoglycoside-streptothricin resistance gene cluster aadE-sat4-aphA-3 disseminated among multiresistant isolates of Enterococcus faecium

Seventy-two Enterococcus faecium isolates of different origins highly resistant to nourseothricin and streptomycin were studied. Sequencing of a genomic fragment from two isolates identified a gene cluster, aadE-sat4-aphA-3, which has been isolated recently in staphylococci and Campylobacter coli. Patterns of digested PCR products of aadE-sat4-aphA-3 were identical for all isolates.     

Antimicrobial susceptibility patterns of thermophilic Campylobacter spp. from humans, pigs, cattle, and broilers in Denmark.

The MICs of 16 antimicrobial agents were determined for 202 Campylobacter jejuni isolates, 123 Campylobacter coli isolates, and 6 Campylobacter lari isolates from humans and food animals in Denmark. The C. jejuni isolates originated from humans (75), broilers (95), cattle (29), and pigs (3); the C. coli isolates originated from humans (7), broilers (17), and pigs (99); and the C. lari isolates originated from broilers (5) and cattle (1). All isolates were susceptible to apramycin, neomycin, and gentamicin. Only a few C. jejuni isolates were resistant to one or more antimicrobial agents. Resistance to tetracycline was more common among C. jejuni isolates from humans (11%) than among C. jejuni isolates from animals (0 to 2%). More resistance to streptomycin was found among C. jejuni isolates from cattle (10%) than among those from humans (4%) or broilers (1%). A greater proportion of C. coli than of C. jejuni isolates were resistant to the other antimicrobial agents tested. Isolates were in most cases either coresistant to tylosin, spiramycin, and erythromycin or susceptible to all three antibiotics. More macrolide-resistant isolates were observed among C. coli isolates from swine (79%) than among C. coli isolates from broilers (18%) and humans (14%). Twenty-four percent of C. coli isolates from pigs were resistant to enrofloxacin, whereas 29% of C. coli isolates from humans and none from broilers were resistant. More resistance to streptomycin was observed among C. coli isolates from swine (48%) than among C. coli isolates from broilers (6%) or humans (0%). The six C. lari isolates were susceptible to all antimicrobial agents except ampicillin and nalidixic acid. This study showed that antimicrobial resistance was found only at relatively low frequencies among C. jejuni and C. lari isolates. Among C. coli isolates, especially from swine, there was a high level of resistance to macrolides and streptomycin. Furthermore, this study showed differences in the resistance to antimicrobial agents among Campylobacter isolates of different origins.     

A European survey of antimicrobial susceptibility among zoonotic and commensal bacteria isolated from food-producing animals

OBJECTIVE: To study antimicrobial resistance in zoonotic bacteria isolated from food animals in different countries using uniform methodology. METHODS: Samples were taken at slaughter from chickens, pigs and cattle in four EU countries per host. Escherichia coli (indicator organism; n = 2118), Salmonella spp. (n = 271) and Campylobacter spp. (n = 1325) were isolated in national laboratories and MICs tested in a central laboratory against, where appropriate, ampicillin, cefepime, cefotaxime, ciprofloxacin, chloramphenicol, erythromycin, gentamicin, nalidixic acid, streptomycin, tetracycline and trimethoprim/sulfamethoxazole. RESULTS: Isolation rates were high for E. coli, low for Salmonella and intermediate for Campylobacter. MIC results showed resistance prevalence varied among compounds, hosts and countries. For E. coli and Salmonella, resistance to newer compounds (cefepime, cefotaxime, ciprofloxacin) was absent or low, but to older compounds (except gentamicin), resistance was variable and higher. E. coli isolates from Sweden showed low resistance, whereas among isolates from Spain (pigs), resistance to ampicillin, chloramphenicol, streptomycin, tetracycline and trimethoprim/sulfamethoxazole was higher; the UK, France, the Netherlands, Germany, Italy and Denmark were intermediate. For Campylobacter spp. isolates from chickens, nalidixic acid and ciprofloxacin resistance was >30% in France and the Netherlands, >6% in the UK and zero in Sweden. Nalidixic acid resistance was high in cattle (20%-64%), whereas ciprofloxacin resistance was markedly lower in cattle, variable in pigs (3%-21%) and highest in Sweden. Generally, Campylobacter coli was more resistant than Campylobacter jejuni. CONCLUSION: Antimicrobial resistance among enteric organisms in food animals varied among countries, particularly for older antimicrobials, but resistance to newer compounds used to treat disease in humans was generally low.     

Susceptibilities to 10 antimicrobial agents of 1,220 Campylobacter strains isolated from 1987 to 1993 from feces of pediatric patients.

We report the in vitro antibiotic susceptibility of 1,220 strains belonging to the thermotolerant Campylobacter species, isolated from the feces of pediatric patients with diarrhea in the period from 1987 to 1993. The strains were identified as 1,148 C. jejuni isolates and 72 C. coli isolates. The overall results show that the strains showed drug resistance as follows: 51.8% to ampicillin, 4.4% to clindamycin, 2.6% to chloramphenicol, 21.2% to tetracycline, and 1% to gentamicin. Twenty-one strains (1.7%) displayed resistance to the combination of amoxicillin-clavulanic acid, and 3.2% of the strains were resistant to erythromycin (MIC of > or = 4 micrograms/ml), with a notable difference according to the species under consideration. While C. jejuni remained stable at 0.9 to 4% resistance to erythromycin, for C. coli the percentages detected ranged from 0 to 33%, with overall rates of 2.5 and 15.2% for the two species, respectively. Resistance to nalidixic acid (MIC of > or = 32 micrograms/ml) was found in 27.2% of the strains (27.8% for C. jejuni and 18% for C. coli), and resistance to ciprofloxacin (MIC of > or = 4 micrograms/ml) was found in 24.2% of the strains for C. jejuni and 15.2% for C. coli). Cross-resistance between nalidixic acid and ciprofloxacin was found in 89.1% of the strains (type 1 mutants), while 10.9% were resistant to nalidixic acid but susceptible to ciprofloxacin (type 2 mutants).     

Macrolide resistance in Campylobacter jejuni and Campylobacter coli: molecular mechanism and stability of the resistance phenotype

A collection of 23 macrolide-resistant Campylobacter isolates from different geographic areas was investigated to determine the mechanism and stability of macrolide resistance. The isolates were identified as Campylobacter jejuni or Campylobacter coli based on the results of the hippurate biochemical test in addition to five PCR-based genotypic methods. Three point mutations at two positions within the peptidyl transferase region in domain V of the 23S rRNA gene were identified. About 78% of the resistant isolates exhibited an A-->G transition at Escherichia coli equivalent base 2059 of the 23S rRNA gene. The isolates possessing this mutation showed a wide range of erythromycin and clarithromycin MICs. Thus, this mutation may incur a greater probability of treatment failure in populations infected by resistant Campylobacter isolates. Another macrolide-associated mutation (A-->C transversion), at E. coli equivalent base 2058, was detected in about 13% of the isolates. An A-->G transition at a position cognate with E. coli 23S rRNA base 2058, which is homologous to the A2142G mutation commonly described in Helicobacter pylori, was also identified in one of the C. jejuni isolates examined. In the majority of C. jejuni isolates, the mutations in the 23S rRNA gene were homozygous except in two cases where the mutation was found in two of the three copies of the target gene. Natural transformation demonstrated the transfer of the macrolide resistance phenotype from a resistant Campylobacter isolate to a susceptible Campylobacter isolate. Growth rates of the resulting transformants containing A-2058-->C or A-2059-->G mutations were similar to that of the parental isolate. The erythromycin resistance of six of seven representative isolates was found to be stable after successive subculturing in the absence of erythromycin selection pressure regardless of the resistance level, the position of the mutation, or the number of the mutated copies of the target gene. One C. jejuni isolate showing an A-2058-->G mutation, however, reverted to erythromycin and clarithromycin susceptibility after 55 subcultures on erythromycin-free medium. Investigation of ribosomal proteins L4 and L22 by sequence analysis in five representative isolates of C. jejuni and C. coli demonstrated no significant macrolide resistance-associated alterations in either the L4 or the L22 protein that might explain either macrolide resistance or enhancement of the resistance level.     

Incidence of antibiotic resistance in Campylobacter jejuni isolated in Alberta, Canada, from 1999 to 2002, with special reference to tet(O)-mediated tetracycline resistance

Of 203 human clinical isolates of Campylobacter jejuni from Alberta, Canada (1999 to 2002), 101 isolates (50%) were resistant to at least 64 microg of tetracycline/ml, with four isolates exhibiting higher levels of tetracycline resistance (512 microg/ml). In total, the MICs for 37% of tetracycline-resistant isolates (256 to 512 microg/ml) were higher than those previously reported in C. jejuni (64 to 128 microg/ml). In the tetracycline-resistant clinical isolates, 67% contained plasmids and all contained the tet(O) gene. Four isolates resistant to high levels of tetracycline (MIC = 512 microg/ml) contained plasmids carrying the tet(O) gene, which could be transferred to other isolates of C. jejuni. The tetracycline MICs for transconjugants were comparable to those of the donors. Cloning of tet(O) from the four high-level tetracycline-resistant isolates conferred an MIC of 32 microg/ml for Escherichia coli DH5alpha. In contrast, transfer to a strain of C. jejuni by using mobilization conferred an MIC of 128 microg/ml. DNA sequence analysis determined that the tet(O) genes encoding lower MICs (64 to 128 microg/ml) were identical to one other, although the tet(O) genes encoding a 512-microg/ml MIC demonstrated several nucleotide substitutions. The quinolone resistance determining region of four ciprofloxacin-resistant isolates (2%) was analyzed, and resistance was associated with a chromosomal mutation in the gyrA gene resulting in a Thr-86-Ile substitution. In addition, six kanamycin-resistant isolates contained large plasmids that carry the aphA-3 marker coding for 3'-aminoglycoside phosphotransferase. Resistance to erythromycin was not detected in 203 isolates. In general, resistance to most antibiotics in C. jejuni remains low, except for resistance to tetracycline, which has increased from about 8 to 50% over the past 20 years.     

Antimicrobial resistance in Campylobacter strains isolated from French broilers before and after antimicrobial growth promoter bans

OBJECTIVES: The antimicrobial susceptibility of Campylobacter strains isolated from standard and free-range broilers in 1992-1996 and 2001-2002 was studied. METHODS: Strains were isolated from caeca or skin samples collected from standard or free-range broilers arriving in slaughterhouses. The MICs of ampicillin, nalidixic acid, enrofloxacin, tetracycline, erythromycin and gentamicin were determined by agar dilution and compared according to species (Campylobacter jejuni or Campylobacter coli), production system and sampling period. RESULTS: Results showed that all chickens harboured Campylobacter. An increase over time of the C. coli/C. jejuni ratio for standard chickens occurred. A wide range of MICs was observed among isolates from the same broiler or from the same farm. Strains collected on entry to the slaughterhouse and after storage showed no significant difference in their antibiotic resistance. C. coli was more resistant than C. jejuni to tetracycline and erythromycin during the first period and to all tested molecules (except gentamicin) during the second period. Strains isolated from standard chickens were also more often resistant than those isolated from free-range broilers. The percentage of C. jejuni strains resistant to ampicillin decreased from 1992-1996 to 2001-2002, whereas no change could be observed for the other antimicrobial agents. However, for C. coli the resistance to ampicillin, nalidixic acid, enrofloxacin, tetracycline and erythromycin significantly increased. CONCLUSION: There was an increase in the incidence of antibiotic resistance of C. coli between 1992-1996 and 2001-2002.     

Antimicrobial resistance in Campylobacter jejuni and Campylobacter coli strains isolated in 1991 and 2001-2002 from poultry and humans in Berlin, Germany

The susceptibilities of 430 Campylobacter jejuni strains and 79 C. coli strains to six antimicrobial agents were tested and analyzed. The two sets of strains originated from retail market chicken and turkey samples and from humans, respectively, in Berlin, Germany. Two groups of isolates, one dating from 1991 and the other dating from 2001-2002, were tested. Of the Campylobacter sp. isolates recovered from humans in 2001-2002, 45.1% were resistant to ciprofloxacin, 37.8% were resistant to tetracycline, 12.8% were resistant to ampicillin, and 50.0% were resistant to trimethoprim-sulfamethoxazole. All isolates were susceptible to gentamicin, while the overall rate of resistance to erythromycin was 6.1%. During the 10 years between the two sampling times, the rates of resistance to ciprofloxacin (P<0.001), ampicillin (P=0.035), and tetracycline (P=0.01) increased significantly among strains isolated from humans. Furthermore, among human C. coli strains the rate of resistance to erythromycin rose from 7.1% in 1991 to 29.4% in 2001-2002. In comparison, Campylobacter sp. isolates from poultry already had high rates of resistance in 1991. Different rates of resistance to tetracycline among isolates from chickens and turkeys suggested the development of resistance during antimicrobial treatment in food animals. Thus, discrepancies in the antimicrobial resistance rates among Campylobacter isolates originating from poultry and humans support the hypothesis that at least some of the resistant Campylobacter strains causing infection in humans come from sources other than poultry products.