Characterisation of antimicrobial resistance patterns and class 1 integrons among Escherichia coli and Salmonella enterica serovar Choleraesuis strains isolated from humans and swine in Taiwan

Escherichia coli isolates from humans (n=110) and swine (n=61) and Salmonella enterica serovar Choleraesuis isolates (n=95) from swine in southern Taiwan were characterised for antimicrobial resistance patterns and class 1 integrons. All E. coli isolates and S. Choleraesuis isolates were multidrug resistant and demonstrated high resistance to beta-lactams, aminoglycosides, tetracycline, sulfonamides, spectinomycin, chloramphenicol and nalidixic acid. By polymerase chain reaction and DNA sequencing, 104 (61%) E. coli isolates and 31 (33%) S. Choleraesuis isolates were found to carry class 1 integrons. The gene cassette array dfrA12-orfF-aadA2 was the most prevalent (24%) among the human and swine E. coli isolates, whilst the gene cassette array dfrA12-orfF-aadA2-sul1 was the most prevalent (24%) among S. Choleraesuis strains. For E. coil isolates, all class 1 integrons were located on conjugated plasmids. Meanwhile, human and swine E. coli isolates carrying identical gene cassettes were genetically unrelated. Our results revealed that multidrug resistance and class 1 integrons were widely present in E. coli and S. Choleraesuis isolates obtained in Taiwan and that class 1 integrons might play an important role in contributing to the horizontal transfer of antimicrobial resistance.     

Antibiotic resistance in Escherichia coli isolates obtained from animals, foods and humans in Spain.

Antibiotic resistance was investigated in 474 Escherichia coli isolates recovered from animal faeces (broilers, pigs, pets, bulls and horses), human faeces (patients and healthy volunteers) and food products of animal origin. E. coli isolates (3260) recovered from human significant infectious samples were also included. There was a high frequency of nalidixic acid, ciprofloxacin and gentamicin resistance in E. coli isolates from broilers (88, 38 and 40%, respectively), and from foods (53, 13 and 17%). High levels of resistance to trimethoprim-sulphamethoxazole and tetracycline have been found in E. coli isolates from broilers, pigs and foods. These data raise important questions about the potential impact of antibiotic use in animals and the possible entry of resistant pathogens into the food chain.     

Susceptibilities of Escherichia coli, Salmonella and Staphylococcus aureus isolated from animals to ofloxacin and commonly used antimicrobial agents

Susceptibilities of Escherichia coli, Salmonella and Staphylococcus aureus isolated from chickens, pigs and cattle to ofloxacin (OFLX) and commonly used antimicrobial agents were investigated. 1. E. coli (28 isolates) demonstrated the highest level of susceptibility of OFLX (MIC 0.10-0.39 micrograms/ml for all the isolates) among all the test drugs. Commonly used antimicrobial agents to which these isolates responded with relatively high susceptibilities (MIC50 0.78-6.25 micrograms/ml) included oxolinic acid (OXA), ampicillin (ABPC), kanamycin (KM) and chloramphenicol (CP) with their MIC50 values in the increasing order as above. Drugs to which these isolates responded with moderate to weak susceptibilities (MIC50 25 approximately greater than 800 micrograms/ml) were doxycycline (DOXY), streptomycin (SM), spectinomycin (SPCM) and sulfadimethoxine (SDMX) in the increasing order of MIC50. E. coli isolates with resistances to all the test drugs other than OFLX and OXA amounted to 7.1-57.1% of the isolates examined and 20 isolates (71.4%) in total. 2. Susceptibilities to OFLX and 4 existing pyridonecarboxylic acid derivatives of E. coli (48 samples) isolated recently from diarrheal pigs were compared. When evaluated in terms of MIC50, the values of OFLX and norfloxacin were both 0.10 micrograms/ml. The values increased by differences of 0.39-3.13 micrograms/ml in an order of OXA, pipemidic acid and nalidixic acid. 3. Salmonella (28 isolates) demonstrated the highest level of susceptibility to OFLX (MIC 0.20-0.39 micrograms/ml for all the isolates) among all the test drugs. The drugs to which these isolates responded with relatively high to moderate susceptibilities (MIC50 0.78-12.5 micrograms/ml) included ABPC, OXA, DOXY, KM, CP and SM with their MIC50 values increasing in this order. The drugs to which the isolates responded with low susceptibilities (MIC50 above 100 micrograms/ml) were SPCM and SDMX. Of all the 28 Salmonella isolates tested, 7.1-32.1% were resistant to all the test drugs other than OFLX and OXA. These resistant isolates amounted to a total of 12 isolates (42.9%). 4. S. aureus (28 isolates) were highly susceptible to OFLX (MIC50 and MIC90 were both 0.78 micrograms/ml). Commonly used antimicrobial agents to which the isolates responded with high to relatively high susceptibilities (MIC50 0.10-6.25 micrograms/ml) were, in the increasing order of MIC50: DOXY, ABPC, tylosin, tiamulin, KM, OXA and CP. Drugs with moderate to low bacterial susceptibilities (MIC50 12.5-100 microns/ml) were SD, SDMX and SPCM. Isolates resistant to all the test drugs except OFLX and SDMX amounted to 3.6-50% of the 28 isolates examined and they totalled 20 isolates (71.4%).(ABSTRACT TRUNCATED AT 400 WORDS)     

Transferable antibiotic resistance in Escherichia coli isolated from healthy Nigerian school children

Three hundred and ninety-six E. coli isolates obtained from apparently healthy school children in Ile-Ife, Nigeria, were tested for their susceptibility to 11 different antibiotics. Of these, only gentamicin, cefotaxime and nalidixic acid were found to have significant in vitro activity against most of the isolates. The incidence of antibiotic resistances encountered varied between 24% for trimethoprim and 55.5% for the sulphonamide. It was further observed that 47.5% of the isolates were identified as being multiply resistant, since they were simultaneously resistant to at least three different antibiotics. The 86 trimethoprim-resistant isolates tested were found to be able to transfer this resistance trait together with resistance genes of to other antibiotics, into a plamidless strain of E. coli by conjugation. Seventy-seven of the trimethoprim-resistant isolates were also found to be classifiable into the types of dihydrofolate reductases responsible for the observed resistance on the basis of hybridization experiments. The results of this study indicate that there is a large reservoir of antibiotic resistances within the community, and that the resistance genes were easily transferable to other strains even without direct exposure to antibiotics.     

Clinical pharmacology of antimicrobial use in humans and animals

Veterinary public health is a frontier in the fight against human disease, charged to control and eradicate zoonotic diseases that are naturally transmitted between vertebrate animals and man. Currently there is a need for clinical pharmacologists and all health care givers to limit the development of bacterial resistance in humans to contain the increased health care expenditures related to morbidity and mortality associated with the use of antimicrobials. The development of resistance predates the use of antibiotics and will always be a problem to the successful treatment of patients. Ongoing discussion debates the extent to which antibiotic use in animals contributes to the development of antibiotic resistance in humans. The veterinary use ofantibiotics as antimicrobial growth promoters is thought to influence the prevalence of resistance in animal bacteria and to be a risk factor for the emergence of antibiotic resistance in human pathogens. Transfer of antibiotic resistant bacteria from animals to humans may occur via contact, including occupational exposure and via the food chain. Resistance genes may transferfrom bacteria of animals to human pathogens in the intestinal flora of humans. Prevention of the development of resistance in humans necessitates good animal husbandry and hygienic measures to prevent cross contamination and a decrease in the use of antibiotics. Appropriate use of antibiotics for food animals will preserve the long-term efficacy of existing antibiotics, support animal health and welfare, and limit the risk of transfer of antibiotic resistance to humans. Investigators must also develop new antimicrobial agents. Poole (J Pharmacy Pharmacol 2001;53:283) recommends targeting the three predominate mechanisms of development of resistance by antimicrobials (i.e., antibiotic inactivation, target site modification, and altered uptake via restricted entry and/or enhanced efflux) to specifically complement the development of novel agents with novel bacterial targets. Bacterial resistance and its selection may be evaluated by comparing the relationship to antibiotic pharmacokinetic (PK) values obtained from serum concentrations and organism MICs (minimum inhibitory concentrations; concentration-dependent killing) to reveal culture and sensitivity tests in patients. Pharmacodynamic (PD) models may be developed to identify factors associated with the probability that bacterial resistance will develop. Thomas et al (Antimicrobial Agents Chemotherapy 1998;42:521) used this combined approach of PK/PD and MICs to examine data retrospectively. The role of clinical pharmacology is to work with PK/PD models such as these to determine the best use of antibiotics in humans to minimize the development of resistance. The role of any regulatory body responsible for the protection of the public health and food safety for consumers is to assess risk and to then communicate and manage the risk. Scientific uncertainty must be interpreted to propose sound policy options. The conversion of sound science into an appropriate regulatory policy to protect the public health is most important.     

对临床分离的大肠埃希杆菌和肺炎克雷伯菌耐药状况分析

目的：调查和分析上海市杨浦区市东医院临床分离的大肠埃希杆菌和肺炎克雷伯菌分布特征与药敏结果。方法：收集本院2010年临床送检标本所分离的大肠埃希杆菌和肺炎克雷伯菌药敏资料,用WHONET 5.5软件进行数据分析。结果：共获得大肠埃希杆菌696株和肺炎克雷伯菌409株,在菌株总数中排名第一和第三。大肠埃希杆菌检出率较高的科室为普外科（20.3%）、急诊科（14.1%）、风湿肾病科（12.6%）,主要分离自尿（46.3%）、脓液（11.6%）和痰（10.8%）等标本。肺炎克雷伯菌检出率较高的科室为急诊科（17.6%）、呼吸科（14.2%）、肿瘤内科（11.7%）,主要分离自痰（40.8%）、咽拭子（26.4%）和尿（9.5%）等标本。大肠埃希杆菌和肺炎克雷伯菌中产超广谱β-内酰胺酶（ESBLs）菌株检出率分别为56.0%和17.1%,两者的检出率之间具有显著性差异（P〈0.01）,产ESBLs菌株的耐药率明显高于非产ESBLs菌株。结论：本院大肠埃希杆菌和肺炎克雷伯菌在泌尿系统、呼吸系统疾病高发的科室分离率高,其耐药率水平主要受产ESBLs菌株的影响。     

Antibiotic resistance of commensal Escherichia coli of food-producing animals from three Vojvodinian farms, Serbia

Commensal bacteria of food-producing animals are considered an important reservoir of antibiotic resistance. The aim of this study was to determine the current prevalence of resistance to 18 different antibiotics in animal commensal Escherichia coli isolated from food-producing animals from three different farms with specific modes of antimicrobial use. A very high prevalence of resistance was found to tetracycline, a moderate level to streptomycin, ampicillin, cefalothin and nalidixic acid and a low of resistance to the other tested antibiotics. Resistance to two or more antibiotics was observed among all swine E. coli, 63.2% of broiler isolates and 37.5% of cattle isolates. The results show that commensals of food-producing animals from Vojvodina region are important reservoirs of resistance to older-generation antibiotics.     

大肠埃希菌中Ⅰ类整合子耐药基因的分析

目的 对临床分离大肠埃希菌株携带的Ⅰ类整合子及相关耐药基因进行筛选和分析.探讨Ⅰ类整合子在大肠埃希菌耐药中的作用.方法 对43株大肠埃希菌临床分离株做药敏试验;采用PCR扩增、DNA测序、DNA序列比对的方法 对其携带的Ⅰ类整合子相关耐约基因进行分析.结果 43株大肠埃希菌分离株对10种抗菌药物的耐药率依次为亚胺培南4.7%、阿米卡星18.6%、头孢他啶、27.9%、头孢吡肟37.2%、头孢呋辛55.8%、复方磺胺甲嗯唑58.1%、妥布霉素74.4%、庆大霉素79.1%、头孢噻肟81.4%和哌拉两林83.7%.在43株大肠埃希菌分离株中有25株含有Ⅰ类整合子,其中18株携带整合子相关耐药基因,如介导对磺胺类和氨基糖苷类约物的耐药基因等;某些菌株携带的整合子相关耐药基因相同.结论 Ⅰ类整合子在大肠埃希菌中广泛存在,整合子相关耐约基因在该菌耐药性的形成和播散中发挥作用.     

大肠埃希菌生物膜形成与耐药机制的研究进展

生物膜细菌与浮游菌相比有着其独特的生理学特性、毒力作用及耐药机制,对其耐药机制及治疗成为近年来的研究热点。大肠埃希菌(Escherichia coli)是医院感染的重要病原菌之一,也是生物膜感染的常见病原菌。形成生物膜的大肠埃希菌具有高度的耐药性并能逃避免疫系统的攻击,其感染易慢性化并难于控制。本文通过对大肠埃希菌生物膜形成与耐药机制研究特点进行阐述,为寻找有效的控制手段,指导抗生素合理使用提供理论依据。     

Class 1 integrons and virulence genes in Salmonella enterica isolates from pork and humans

In this study, 183 Salmonella enterica isolates were characterised for integrons and virulence genes. Among the isolates, 46% were positive for intI1, but no isolates carried intI2 or intI3. Eighteen class 1 integrons (21%) contained resistance gene cassettes (i.e. dfrA1-orfC, dfrA12-aadA2, bla(PSE-1) and aadA2) and five class 1 integrons with the dfrA12-aadA2 array were conjugally transferable. Two Salmonella pork isolates of serotypes Albany and Kedougou possessed Salmonella genomic island 1 variants SGI1-G and SGI1-F, respectively. Four class 1 integrons contained an atypical 3'-CS linked to the qacH-sul3 domain, and three were not a sul type. Two novel GyrA mutations (Pro-45→Ser and Met-48→Ile) and three novel ParC mutations (Ser-5→Arg, Thr-31→Met and Leu-77→Arg) were identified in ciprofloxacin-resistant isolates. At least 90% of the Salmonella isolates contained pagC, prgH, sitC, sipB or spaN, whereas all isolates harboured invA, msgA, spiA and tolC.     

儿童社区获得性肺炎大肠埃希菌耐药性分析

目的:研究本社区获得性肺炎(CAP)患儿感染大肠埃希菌的耐药情况,以指导临床合理使用抗生素,方法:采集我院2009年1月～2010年12月86株大肠埃希菌,纸片扩散法(K-B法)进行抗菌药物敏感实验.结果:86株大肠埃希菌耐药率,氨苄青霉素89.5%、复方SMZ 84.9%、阿莫西林克/拉维酸钾44.2%、哌拉西林/他唑巴坦10.5%、头孢呋辛41.9%、头孢噻肟55.8%、头孢曲松53.5%、头孢哌酮/舒巴坦12.8%、头孢吡肟30.2%、亚胺堵南2.3%、阿米卡星9.3%和左氧氟沙星16.3%.结论:本社区儿童社区获得性肺炎患儿中大肠埃希菌对氨苄青霉素、复方SMZ、阿莫西林,克拉维酸、头孢呋辛、头孢噻肟、头孢曲松、头孢吡肟等常用抗生素耐药率高,可首选哌拉西林/他唑巴坦、头孢哌酮/舒巴坦抗感染.     

我国猪、鸡源沙门菌和大肠埃希菌的耐药研究进展

摘要：我国是猪、鸡养殖大国。沙门菌病和大肠埃希菌病作为猪、鸡养殖场最常见的细菌性疾病,常常呈混合感染,临床上多采用抗菌药物治疗。近年来,由于抗菌药物大范围的不合理使用,沙门菌和大肠埃希菌出现了严重的耐药性,养殖业、兽医临床治疗和公共卫生都受到影响。本文主要调查近3年(2017—2019年)我国报道的猪、鸡源沙门菌和大肠埃希菌的耐药性研究进展,包括猪、鸡源沙门菌和大肠埃希菌相关的耐药机制、常见的耐药基因、国内部分地区所分离的沙门菌和大肠埃希菌的耐药种类及耐药率等,加强耐药性的监测与控制。     

Pathogenecity of fosfomycin-resistant strains isolated from Escherichia coli

Two fosfomycin-resistant strains, FRC14 (parent strain, Escherichia coli [E.coli] c73-18) and FRK104 (parent strain, E. coli O124), were isolated from spleens before the bacterial disappearance, after inoculating the parent strains intraperitoneally into mice and treating them with a single oral dose of fosfomycin. The resistant strains were successfully isolated by a replica method from a mass of sensitive cells of respective parent. To elucidate the pathogenesis of the resistant strains, their characteristics were investigated. The MIC of fosfomycin for FRC14 was 25 micrograms/ml (4 times the MIC for the parent) and that for FRK104 was 100 micrograms/ml (8 times the MIC for the parent). The strain FRC14 showed a defective utilization of sn-glycerol 3-phosphate (G3P), but utilization of other carbohydrates was similar to that of the parent strain. Thus, the strain FRC14 seemed to be a glpT mutant. The strain FRK104 did not use variety of carbohydrates including G3P, but used glucose 6-phosphate. The utilization of G3P was recovered in the presence of cAMP. Thus, the strain FRK104 seemed to be a ptsI mutant. These resistant strains were diminished their killing activity for mice in comparison to that of the each parent strain when they were inoculated intraperitoneally. The cell number of FRC14 decreased or disappeared in blood and spleen in mice, while that of the parent increased. The strain FRK104 diminished its ability of producing keratoconjuctivitis in guinea pigs in comparison to that of the parent strain.     

肺炎克雷伯菌Ⅰ型整合子的检测与鉴定

目的研究Ⅰ型整合子参与肺炎克雷伯菌耐药的分子机制。方法收集2007年至2010年某院临床分离的297株肺炎克雷伯菌,应用K-B纸片扩散法检测耐药性,采用聚合酶链式反应进行I类整合子整合酶基因的检测;整合子可变区扩增、克隆测序,分析I类整合子基因结构。结果 297株肺炎克雷伯菌中,除MEM、IPM外,对其余11种抗菌素,Ⅰ类整合酶基因阳性菌株的耐药率明显高于Ⅰ类整合酶基因阴性菌株。57.91%(172/297)的菌株I类整合子整合酶基因阳性,共检测出10种不同基因盒。可变区编码耐药基因有aadA2、aadA1、aadA5、aadA3C、aacA4,介导氨基糖苷类抗菌素耐药;dhfrhI、dfrA12、dfrA14、dfrA17、dfrA1、dfrA25、dhfrhI,介导磺胺类抗菌素的耐药;aar-2,介导利福平耐药。结论Ⅰ类整合子在本院临床分离肺炎克雷伯菌中分布较广泛,主要介导氨基糖苷类和磺胺类抗菌素耐药。整合子与肺炎克雷伯菌的耐药有关,在肺炎克雷伯菌耐药性的形成和播散中具有重要作用。     

Antibiotic resistance and class 1 integron patterns of non-typhoidal human Salmonella serotypes isolated in Hungary in 2002 and 2003

The antibiotic resistance profiles of 5178 Salmonella strains representing 19 non-typhoidal serotypes isolated from human salmonellosis cases in Hungary in 2002 and 2003 were analysed for resistance to 10 antibiotic agents. The most frequent resistances were to nalidixic acid (Nx), streptomycin (S), tetracycline (Tc), ampicillin (Amp) and chloramphenicol (Cm) (ranging from 27% to 13%). Forty-five percent of the Salmonella Typhimurium strains were multiple resistant and belonged mainly to the definitive phage types 104 and U302. A prevalence of 83-94% of strains of serotypes S. Infantis, S. Hadar and S. Virchow was observed with the NxSTc resistance pattern, sometimes complemented with other resistances. Multiple resistance was uncommon in S. Enteritidis; nevertheless, 20% of the strains, most of which belonged to phage type 4, were nalidixic acid resistant. One strain of S. Typhimurium was found to be resistant to ciprofloxacin. Four S. Typhimurium strains were resistant to cefotaxime and produced extended-spectrum beta-lactamase. Selected isolates were screened for the presence of class 1 integrons by polymerase chain reaction (PCR). Nucleotide sequencing of the PCR products revealed nine different variable regions. One resistance gene was identified in five variable regions (aadA1, aadA2, aadA23, dfrV and pse-1), and four variable regions carried two resistance gene cassettes (aadB-catB3, dhfrI-aadA, dfrA17-aadA5 and oxa-1-aadA1).     

Relatedness of Escherichia coli strains with different susceptibility patterns isolated from beagle dogs during ampicillin treatment

The aim of this study was to investigate the effects of ampicillin treatment on selection and diversity of ampicillin-resistant intestinal Escherichia coli in beagles treated with ampicillin, ampicillin + beta-lactamase (targeted to degrade antibiotic residues in the gut) or placebo. Selected faecal (n = 339) and jejunal (n = 63) E. coli isolates with known resistance patterns were typed using pulsed-field gel electrophoresis (PFGE). Among the 25 detected PFGE types, ampicillin resistance was detected in 6, none of which was dominant over others among the dogs. The resistant types increased especially in the ampicillin group, whilst beta-lactamase inhibited their emergence. Selection of genetically unrelated resistant strains rather than emerging resistance among previously susceptible strains accounts for increasing resistance rates during ampicillin treatment.