Molecular characterization of antibiotic resistance in clinical Salmonella typhi isolated in Ghana

Fifty-eight clinical Salmonella typhi strains isolated from patients suspected of suffering from typhoid fever were obtained at the Korle-Bu Teaching Hospital and the Noguchi Memorial Institute for Medical Research, both located in Ghana, Africa. Each isolate was examined for susceptibility to ampicillin, chloramphenicol, streptomycin, tetracycline, and trimethoprim/sulfamethoxazole by the disk diffusion assay. Five of the isolates were resistant to all five antibiotics while 10 isolates were resistant to ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole, which are considered 'first line' antibiotics in the treatment of typhoid fever. Thirty-four isolates were resistant to at least one of the antibiotics tested and 62% of these isolates possessed conjugable plasmids belonging to incompatibility group IncHI. Ninety percent of the conjugable plasmids conferred a multiple drug-resistant phenotype on the strains harboring them. Additionally, 14 strains contained plasmids that were transformable and six of them encoded multiple drug resistance. Our findings indicate that multiple drug resistance to the 'first line' antibiotics in S. typhi may be more prevalent in Africa than previously thought.     

139株空肠弯曲菌耐药性分析

空肠弯曲菌(Campylobacter jejuni)是最常见的食源性病原菌之一。本研究采用微量肉汤稀释法对分离得到的139株空肠弯曲菌(117株为禽源样本分离株,22株为人源样本分离株)进行耐药性检测。通过对最小抑菌浓度(MIC)的判定结果得出:120株(86. 33%)空肠弯曲菌分离株对6类9组临床常用的抗生素表现出不同程度的耐药,其中禽源空肠弯曲菌耐药率为83. 76%,22株人源空肠弯曲菌均表现出耐药性。对喹诺酮类抗生素表现出高度耐药(环丙沙星80. 58%,萘啶酸77. 70%);对四环素类表现为中等耐药(四环素53. 24%);对部分大环内酯类、氨基糖苷类、林可酰胺类表现为低耐药(庆大霉素7. 19%,阿奇霉素5. 76%,克林霉素6. 47%);对酰胺醇类、部分大环内酯类表现为敏感(氟苯尼考0%,红霉素0%、泰利霉素0%)。139株空肠弯曲菌共产生14种耐药谱型,以TET-CIP-NAL谱型最多,占比38. 13%,耐三重及以上抗生素的多重耐药菌株占比53. 24%。禽源菌株中多重耐药占比46. 15%,人源菌株中多重耐药占比90. 91%。研究结果显示空肠弯曲菌耐药现状不容乐观,尤其对喹诺酮类与四环素类抗生素耐药性较为突出,且过半数菌株为多重耐药。本研究为食源性空肠弯曲菌的防控及临床用药提供参考。     

Frequency of antibiotic and heavy metal resistance, pigmentation, and plasmids in bacteria of the marine air-water interface

A field investigation of marine coastal waters revealed that the frequency of pigmented bacteria and the occurrence of bacterial antibiotic resistance were higher at the air-water interface than in the bulk water. The differences in the frequency of pigmented colonies at the surface and in the bulk-water samples could not be explained by the degree of cell surface hydrophobicity or by bacterial adhesion to air-water interfaces. Pigmented strains exhibited a higher degree of multiple drug resistance than did nonpigmented strains. However, the frequency of multiple drug resistance in nonpigmented strains was also substantial. An average of 91% of all strains were resistant to more than one antibiotic, and 21% of the bacteria isolated were resistant to five of the eight antibiotics tested. High numbers of plasmid-carrying strains were found among selected surface isolates, but the presence of detectable plasmids could not be correlated with either pigmentation or multiple drug resistance. Furthermore, selected surface isolates were significantly more resistant to mercury than were bulk-water bacteria. The higher frequency of pigmented, antibiotic-resistant, and mercury resistant strains at the air-water interface than in the bulk water are discussed in terms of various forms of selective pressure and genetic exchange at the surface.     

Frequency of antibiotic and heavy metal resistance, pigmentation, and plasmids in bacteria of the marine air-water interface.

A field investigation of marine coastal waters revealed that the frequency of pigmented bacteria and the occurrence of bacterial antibiotic resistance were higher at the air-water interface than in the bulk water. The differences in the frequency of pigmented colonies at the surface and in the bulk-water samples could not be explained by the degree of cell surface hydrophobicity or by bacterial adhesion to air-water interfaces. Pigmented strains exhibited a higher degree of multiple drug resistance than did nonpigmented strains. However, the frequency of multiple drug resistance in nonpigmented strains was also substantial. An average of 91% of all strains were resistant to more than one antibiotic, and 21% of the bacteria isolated were resistant to five of the eight antibiotics tested. High numbers of plasmid-carrying strains were found among selected surface isolates, but the presence of detectable plasmids could not be correlated with either pigmentation or multiple drug resistance. Furthermore, selected surface isolates were significantly more resistant to mercury than were bulk-water bacteria. The higher frequency of pigmented, antibiotic-resistant, and mercury resistant strains at the air-water interface than in the bulk water are discussed in terms of various forms of selective pressure and genetic exchange at the surface.     

In vitro activity of cefamandole, cefoxitin, cefuroxime, and carbenicillin, alone and in combination with aminoglycosides against Serratia marcescens.

Synergistic antibiotic studies were undertaken to compare the effectiveness of two new beta-lactamase resistant cephalosporins, cefamandole, and carbenicillin, with four aminoglycosides against clinical strains of Serratia marcescens. The strains demonstrated various combinations of resistance and/or susceptibility to the antibiotics tested. Tobramycin was the most effective aminoglycoside when used in combination with beta-lactam antibiotics. Carbenicillin and cefamandole demonstrated similar activity with aminoglycosides in synergy experiments. Tobramycin-carbenicillin was found to be the superior pairs as indicated by the total number of strains inhibited. This combination was the only one effective against certain high drug resistant strains and the strain resistant to all four aminoglycosides. Carbenicillin or cefamandole with tobramycin exhibited comparable activity against multiple drug resistant organisms. However, mutants significantly more resistant to cefamandole developed during susceptibility testing. The findings of this study have clinical relevance for treating infections by this formidable pathogen.     

Drug Resistance in Strains of Escherichia Coli Isolated from the Intestinal Tract of Pigs in Norway

Faecal samples from 95 healthy pigs and samples of jejunal content from 85 piglets suffering from colienterotoxaemia were tested for the presence of drug resistant E. coli strains. Practically all pigs in both groups harboured E. coli strains resistant to one or more of the 6 antibiotics/chemotherapeutic agents tested (Oxytetracycline, streptomycin, sulphaisodimidin, neomycin, ampicillin, chloramphenicol). Almost 100% of healthy and approx. 90% of diseased pigs harboured strains resistant to Oxytetracycline, streptomycin and sulphaisodimidin. Pigs with strains resistant to neomycin, ampicillin and chloramphenicol were less frequently found. The predominant coliform flora consisted of E. coli strains” resistant to Oxytetracycline, streptomycin and sulphaisodimidin in 71% to 81% of diseased pigs and in 47% to 69% of the healthy pigs. In diseased pigs ¾ of the animals had a coliform flora dominated by neomycinresistant E. coli strains. Of the 721 resistant E. coli strains isolated from healthy pigs, 11% were single resistant while the corresponding figure for the 518 resistant strains isolated from diseased pigs was 6%. Thus 89% and 94% of strains showed simultaneous resistance to 2 or more antibiotics. E. coli strains resistant to 3 or more drugs were found in approx. 60% and 70% of the isolates from healthy and diseased animals, respectively. Oxytetracycline/streptomycin/sulphaisodimidin resistance was most commonly found, approx. 22% and 38% of the strains from healthy and diseased pigs, respectively, showing this resistance pattern. Transmission of drug resistance which was examined in E. coli strains originating from the diseased pigs was demonstrated in approx. 76% of the isolates. The incidence of drug resistance transfer in single, double, triple and quadruple resistant strains was 11%, 68%, 97% and 98%, respectively.     

2016‒2017年辽宁省沙门菌耐药菌谱与分子分型

摘要：目的 分析2016?2017年辽宁省沙门菌分离株的耐药特性与脉冲场凝胶电泳（PFGE）分子分型特征,为沙门菌引起的食源性疾病暴发、防控及抗生素使用提供参考数据。方法 对分离的54株沙门菌进行血清分型和药物敏感试验。根据PulseNet沙门菌标准PFGE分型技术,选取全部菌株进行PFGE分子分型分析,应用BioNumerics软件对菌株条带进行分析,确定菌株间的特征及相关性。结果 54株沙门菌血清型居首位的是肠炎沙门菌,占46.30％;其次是鼠伤寒沙门菌,占24.07％;共分为10个血清型。对13种抗生素的耐药分析显示多重耐药菌株为36株,占66.7％,其中耐3～5种的13株（24.1%）,耐6～8种的13株（24.1%）,耐9～11种的10株（18.5%）。54株沙门菌经聚类分析获得36种带型,相似度区间为49.7%～100.0％。结论 辽宁省沙门菌分离株多重耐药状况比较严重,相同血清型其PFGE带型相似度相对较高,同时具有较显著的优势带型特点;而且发现同一PFGE型菌株的耐药谱相对比较接近。     

Multiple antibiotic resistance in Rhizobium japonicum.

A total of 48 strains of the soil bacterium Rhizobium japonicum were screened for their response to several widely used antibiotics. Over 60% of the strains were resistant to chloramphenicol, polymyxin B, and erythromycin, and 47% or more of the strains were resistant to neomycin and penicillin G, when tested by disk assay procedures. The most common grouping of resistances in strains was simultaneous resistance to tetracycline, penicillin G, neomycin, chloramphenicol, and streptomycin (25% of all strains tested). The occurrence of multiple drug resistance in a soil bacterium that is not a vertebrate pathogen suggests that chemotherapeutic use of antibiotics is not required for the development of multiple drug resistance.     

Multiple antibiotic resistance in Rhizobium japonicum.

A total of 48 strains of the soil bacterium Rhizobium japonicum were screened for their response to several widely used antibiotics. Over 60% of the strains were resistant to chloramphenicol, polymyxin B, and erythromycin, and 47% or more of the strains were resistant to neomycin and penicillin G, when tested by disk assay procedures. The most common grouping of resistances in strains was simultaneous resistance to tetracycline, penicillin G, neomycin, chloramphenicol, and streptomycin (25% of all strains tested). The occurrence of multiple drug resistance in a soil bacterium that is not a vertebrate pathogen suggests that chemotherapeutic use of antibiotics is not required for the development of multiple drug resistance.     

Clinical relevance and virulence factors of pigmented Serratia marcescens

Pigmented Serratia marcescens isolated in a Brazilian hospital were studied with respect to frequency of isolation, serotyping, antibiotic resistance and virulence factors. The serotype most frequent was O6:K14 (53%) and all isolates were resistant to ampicillin, cephalothin and tetracycline. The majority of the isolates (92%) were resistant to the action of human serum and all produced cytotoxins on Vero, CHO, HEp-2 and HeLa cells. These isolates were virulent for mice (LD(50)=10(7) bacteria ml(-1)) and showed virulence factors, but were isolated with low frequency (3. 4%) and caused infection in only 31% of cases. Analysis of serotyping, phage typing and chromosomal DNA revealed at least 13 unrelated strains among pigmented S. marcescens. In conclusion, this work describes a low frequency of isolation of pigmented S. marcescens from clinical specimens, indicating that non-pigmented strains are clinically more significant.     

Serratia marcescens: Biochemical, Serological, and Epidemiological Characteristics and Antibiotic Susceptibility of Strains Isolated at Boston City Hospital

The biochemical, serological, and epidemiological characteristics of 95 strains of Serratia marcescens isolated at the Boston City Hospital were examined. Several strains were shown to be endemic, and the majority of isolates were cultured from urine or respiratory secretions. Serratia species were highly resistant to polymyxin B and the cephalosporins, and various proportions were also resistant to other antibiotics including kanamycin, but all of the isolates were sensitive to gentamicin. The appearance of resistance to kanamycin and nalidixic acid among endemic strains was demonstrated. The nosocomial nature of Serratia infections, particularly those involving the urinary tract, was confirmed. Many clinical bacteriology laboratories currently fail to identify the nonpigmented strains.     

R—Factors of Escherichia coli from Dressed Beef and Humans

One hundred eighty Escherichia coli strains isolated from raw and cooked dressed beef and from healthy humans were screened for resistance to each of nine antibiotics: chlortetracycline, ampicillin, chloramphenicol, kanamycin, neomycin, nalidixic acid, dihydrostreptomycin, oxytetracycline, and tetracycline. Nearly 80% of the 98 beef isolates and 54% of the 82 human isolates were resistant to one or more of the antibiotics tested. Ampicillin resistance was most frequent among beef isolates, and dihydrostreptomycin resistance was most frequent among isolates of human origin. About 74% of the multiply resistant beef strains and 85% of the multiply resistant human strains transferred all or part of their resistance to E. coli K-12 recipients.     

临床分离肠球菌的分布特征及耐药性分析

目的:了解我院临床分离肠球菌的分布特征及耐药现状,为临床合理用药提供依据。方法:对我院2010年1月至2012年12月期间所有临床分离的肠球菌分布情况及药敏结果进行回顾性分析。结果:临床共分离肠球菌242株,粪肠球菌分离率(55.0%)高于屎肠球菌(40.9%),屎肠球菌分离率有增高的趋势。标本来源以尿液(62.9%)、分泌物(10.3%)、血液(6.9%)为主。肠球菌对万古霉素、替考拉宁的敏感性最高,均高于90%。发现耐万古霉素的肠球菌(VRE)7株,其中5株同时耐高浓度的氨基糖苷类抗生素(HLAR);对克林霉素、复方磺胺、阿米卡星、庆大霉素、妥布霉素、苯唑西林耐、头孢西丁耐药率最高,均高于95%。屎肠球菌对青霉素类、氨苄西林、红霉素、呋喃妥因、环丙沙星耐药率均高于粪肠球菌;对四环素、奎努普丁/达福普汀耐药率低于粪肠球菌。结论:肠球菌是临床感染重要病原菌,且具有多重耐药性,屎肠球菌和粪肠球菌耐药水平差异较大,临床应根据药敏结果合理选择抗菌药物。     

凝固酶阴性葡萄球菌耐药基因和粘附基因检测及耐药性分析

目的了解凝固酶阴性葡萄球菌（CoNS）耐药基因和粘附基因的分布及其耐药性情况。方法收集45株凝固酶阴性葡萄球菌临床分离株,采用PCR检测其耐药基因mecA和粘附基因c弘知如B,并分析其耐药性。结果（1）凝固酶阴性葡萄球菌中mecA、cva、fn6pB的阳性率依次为86．7％（39／45）、11．1％（5／45）、71．1％（32／45）。（2）凝固酶阴性葡萄球菌中耐甲氧西林凝固酶阴性葡萄球菌（MRCoNS）的检出率为88．9％,对β-内酰胺类抗生素的耐药率都在80％以上,对利福平、左氧氟沙星、林可霉素的耐药率较低,未发现对万古霉素、利奈唑胺耐药菌株。结论CoNS中MRCoNS检出率很高,对常用抗生素耐药率高,且有一定的粘附能力,临床上应该根据药敏试验结果慎重及合理的使用抗生素。     

健康猪直肠粪便中沙门菌I类整合子与耐药基因的检测

目的了解安徽省规模化猪场健康猪直肠粪便中沙门菌分离株多重耐药情况及其与I类整合子和耐药基因的携带关系。方法采用标准K-B纸片法对22株沙门菌分离株进行15种抗生素敏感试验;应用PCR技术对沙门菌分离株进行I类整合子及耐药基因检测。结果 22株沙门菌分离株中有20株(90.91%)对2种以上抗生素耐药,属于多重耐药株,羧氨苄青霉素-四环素-卡那霉素-氯霉素-氟苯尼考是主要多重耐药谱;22株沙门菌中有19株(86.4%)携带I类整合子,tetB、aph(3)-IIa和cmlA基因分别检出最高。结论沙门菌多重耐药性与整合子携带之间的关系密切,耐药表型测定结果与耐药基因检测结果基本一致,基因组DNA携带的耐药基因种类多于质粒。     

Inhibition of quorum sensing regulated biofilm formation in Serratia marcescens causing nosocomial infections

Serratia marcescens is an opportunistic pathogen causing severe urinary tract infections in hospitalized individuals. Infections of S. marcescens are of great concern because of its increasing resistance towards conventional antibiotics. Quorum sensing (QS)-a cell to cell communication-system of S. marcescens acts as a global regulator of almost all the virulence factors and majorly its biofilm formation. Since, the QS system of S. marcescens directly accords to its pathogenesis, targeting QS system will provide an improved strategy to combat drug resistant pathogens. In the present study, QS system of S. marcescens has been used as target and its inhibition has been studied upon exposure to bioactives from coral associated bacteria (CAB). This study also emphasises the potential of CAB in producing bioactive agents with anti-QS and antibiofilm properties. Two CAB isolates CAB 23 and 41 have shown to inhibit biofilm formation and the production of QS dependent virulence factors like prodigiosin, protease, lipase and swarming motility. The study, on the whole explicates the potential of QS system as a target to treat drug resistant bacterial infections.     

Antibiotic-resistance profile in environmental bacteria isolated from penicillin production wastewater treatment plant and the receiving river

The antibiotic‐resistance characteristics of bacterial strains in antibiotic production wastewater treatment plants (WWTP) that contain high concentrations of antibiotics are unknown, as are the environmental effects of the discharge of wastewater from such facilities. In this study, 417 strains were individually isolated from the effluent of a WWTP that treated penicillin G production wastewater, as well as from downstream and upstream areas of the receiving river. The minimum inhibition concentrations (MICs) of 18 antibiotics representing seven classes were then determined for each of these strains. Relatively high similarity in the bacterial composition existed between the wastewater and downstream river samples when compared with the upstream sample. High resistance ratios and MIC values were observed for almost all antibiotics in wastewater isolates, followed by strains from downstream river, of which the resistance ratios and levels were still significantly higher than those of upstream strains. The resistance ratios and levels also significantly differed among strains belonged to different species in the penicillin production wastewater effluent and downstream river. In both samples, the resistances to β‐lactam antibiotics were more frequent, with much higher levels, than the other class antibiotics. Then five clinically important resistant genes mainly coding for extended‐spectrum β‐lactamases (ESBLs) were determined for all strains, only bla_TEM‐1 which did not belong to ESBL was detected in 17.3% and 11.0% of strains isolated from wastewater and downstream river respectively. Class I integrons were detected in 14% of wastewater isolates and 9.1% of downstream isolates, and primarily contained gene cassettes conferring resistance to aminoglycoside antibiotics. The unexpectedly high levels of multiple antibiotic resistance in strains from wastewater and downstream river were speculated to be mainly due to multidrug efflux systems.     

Antibiotic resistance of Lactobacillus strains]

One hundred and thirty six Lactobacillus strains isolated from poultry and 23 Lactobacillus strains isolated from long-living persons were tested for their antibiotic sensitivity. Occurrence of some type determinants of resistance to aminoglycoside antibiotics and tetracyclines in the Lactobacillus strains resistant to these antibiotics was studied. The majority of the strains from the both collections were resistant to aminoglycosides (73 and 79 per cent, respectively). The isolates from the poultry were characterized by multiple resistance. The isolates from the long-living persons were most frequently resistant to one of two antibiotics. All the tested Lactobacillus strains isolated from the long-living persons were sensitive to tetracyclines. The species composition of the isolates was different. The antibiotic-resistant strains were detected in all the species involved in the study. By hybridization of Lactobacillus colonies with the probes containing various genes of the resistance it was shown that in 14 per cent of the antibiotic-resistant strains belonging to Lactobacillus the antibiotic resistance was controlled by the genes homologous to resistance genes widely distributed in gramnegative organisms. This indicated a possible wide exchange and heterologous expression of the antibiotic resistance determinants between microorganisms of various taxonomic groups.     

Comparative study of the effect of antibiotics and antiseptics on Staphylococcus aureus

The routinely used antibiotics and antiseptics were compared with the same staphylococcal isolates by MIC ranges, the mean MIC for the strains, proportion of the variants resistant to the drugs, distribution of the strains by the resistance spectra and the number increase rate for the resistant variants in natural populations within 5-10-year periods. It was concluded that when used locally the antiseptics had some advantages over the antibiotics especially with respect to hospital strains. The authors believe that in developing new drugs, ++re-estimation of the routinely used ones, choosing the optimal drug for a particular case it is more important to consider the heterogeneity of microbial populations, the frequency of resistant variants and activity of the mechanisms of their selection under hospital conditions.