Susceptibility to antimicrobial drugs of enterotoxin producing strains of Bacteroides fragilis isolated from different countries

Twenty two Bacteroides fragilis strains isolated from clinical samples in different countries (England, France, the Netherlands, Poland and USA) were used in the experiments. In all strains the presence of enterotoxin (fragilysin) gene was found by PCR with primers 404/407. Drug susceptibility of B. fragilis strains was determined with Etest (MICs for penicillin G, ceftriaxone, amoxicillin/clavulanic acid, imipenem, clindamycin and metronidazole). MICs were estimated in accordance to the NCCLS recommendations (1997). All tested strains were susceptible to imipenem and metronidazole. Twenty one strains were susceptible and one was intermediate susceptible to amoxicillin/clavulanic acid. Fourteen strains were resistant to ceftriaxone and five were found highly resistant to clindamycin. All examined strains were resistant to penicillin G. Four tested strains were simultaneously resistant to penicillin G, ceftriaxone and clindamycin (three French human strains isolated from postoperative wound, peritoneal fluid and bone inflammation, and one strain isolated from a pig).     

鲍曼不动杆菌耐药程度与其主动外排泵蛋白的相关性研究

目的:探讨鲍曼不动杆菌耐药程度与其主动外排泵蛋白的相关性。方法:首先用纸片扩散法检测64株临床鲍曼不动杆菌对8种抗菌药物的敏感性;将其分为A组(0～2种抗生素耐药)、B组(对3～5种抗生素耐药)和C组(对6～8种抗生素耐药);检测64株临床鲍曼不动杆菌对罗丹明6G的外排情况,筛选出罗丹明6G外排明显增加的菌株;并用逆转录-聚合酶链反应(RT-PCR)方法检测主动外排泵基因AdeABC的表达水平。结果:64株鲍曼不动杆菌中有4株对0～2种抗生素耐药(A组),对3～5种抗生素耐药的有33株(B组),对6～8种抗生素耐药的有27株(C组);多重耐药组鲍曼不动杆菌罗丹6G外排明显增高,外排程度A组相似文献   

The vaginal Bifidobacterium flora in women of reproductive age

The composition of vaginal bifidoflora in 56 clinically healthy women of reproductive age was studied. The study revealed that four species of bifidobacteria, viz. Bifidobacterium bifidum, B. breve, B. adolescentis 2 and B. longum, dominated in the composition of this bifidobacterial population. Nine out of 11 isolated strains were found to be capable of inhibiting indicator microorganisms Staphylococcus aureus and Enterococcus faecalis when tested in vitro; in addition, strains B. adolescentis 2 F1, B. bifidum G1, B. breve P2 and B. longum Z4 inhibited Klebsiella ozaenae, Pseudomonas aeruginosa, Escherichia coli and were also active acid producers. Three of these 4 bifidobacterial strains were capable of adhesion to vaginal epitheliocytes, while B. bifidum G1 was practically incapable of adherence to these cells, similarly to B. bifidum strain 791 of intestinal origin. In addition, the spectra of antibiotic susceptibility varied from strain to strain, but all bifidobacterial strains were susceptible to benzylpenicillin and resistant to lomefloxacin, most of them being also resistant to cyprofloxacin and gentamicin. Thus the data presented in this work are indicative of the possibility and advantages of using bifidobacterial strains belonging to this ecological niche as probiotics for the correction of the microflora of the urogenital tract in females.     

Genetics of resistance to two strains of soybean mosaic virus in differential soybean genotypes

There are seven pathotypes of soybean mosaic virus (SMV) representing seven strain groups (G1-G7) in the United States. Soybean genotypes [Glycine max (L.) Merr.] may exhibit resistant (R), susceptible (S), or necrotic (N) reactions upon interacting with different SMV strains. This research was conducted to investigate whether reactions to two SMV strains are controlled by the same gene or by separate genes. Two SMV-resistant soybean lines, LR1 and LR2, were crossed with the susceptible cultivar Lee 68. LR1 contains a resistance gene Rsv1-s and is resistant to strains G1-G4 and G7. LR2 contains the Rsv4 gene and is resistant to strains G1-G7. Two hundred F(2:3) lines from LR1 x Lee 68 and 262 F(2:3) lines from LR2 x Lee 68 were screened for SMV reaction. Seeds from each F2 plant were randomly divided into two subsamples. A minimum of 20 seeds from each subsample were planted in the greenhouse and plants were inoculated with either G1 or G7. G1 is the least virulent, whereas G7 is the most virulent strain of SMV. The results showed that all the F(2:3) lines from both crosses exhibited the same reaction to G1 and G7. No recombinants were found in all the progenies for reactions to G1 and G7 in either cross. The results indicate that reactions to both G1 and G7 are controlled by either the same gene or very closely linked genes. This research finding is valuable for studying the resistance mechanism and interactions of soybean genotypes and SMV strains and for breeding SMV resistance to multiple strains.     

The correlation between phenotypes and genotypes of macrolides, lincosamides and streptogramins B resistance in Staphylococcus aureus

For 31 clinical strains of S. aureus the correlation between phenotype and genotype of resistance to macrolides, lincosamides and streptogramins B (MLSB) was established.. Phenotypes were determined on the basis of: susceptibility to erythromycin and clindamycin and the ability to an induction of the resistance (phenotypes S, susceptible; R , constitutive resistant, D, resistant after induction with erythromycin, D+, resistant after induction with erythromycin and with a presence of the small colonies inside inhibition zone between erythromycin and clindamycin discs), and on the basis of the resistance to spectinomycin (spR, resistant, spS, susceptible). Among examined S. aureus strains eight phenotypes of resistance to MLSB were recognized (the corresponding genotypes are given in brackets). Six phenotypes were typical: SspS (lack of MLS-B resistance genes), NEGspS (msrA/B, 1 strain), D+spS (ermCi, 4 strains),. DspR (ermAi, 11 strains and ermAi + msrA/B, 2 strains), RspR (ermAc, 4 strains and ermA + msrA/B,1 strain and ermA + ermC, 1 strain) and RspS (ermCc, 6 strains and ermB, 1 strain). Two rare phenotypes in two single strains were observed: SspR (ermAi, the strain with altered inducibility, inductor other than erythromycin) and DspS (ermAi, presumably mutation or lack of spc in Tn554).     

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.     

Genetic basis of macrolide and lincosamide resistance in Brachyspira (Serpulina) hyodysenteriae

Macrolide antibiotic resistance is widespread among Brachyspira hyodysenteriae (formerly Serpulina hyodysenteriae) isolates. The genetic basis of macrolide and lincosamide resistance in B. hyodysenteriae was elucidated. Resistance to tylosin, erythromycin and clindamycin in B. hyodysenteriae was associated with an A-->T transversion mutation in the nucleotide position homologous with position 2058 of the Escherichia coli 23S rRNA gene. The nucleotide sequences of the peptidyl transferase region of the 23S rDNA from seven macrolide and lincosamide resistant and seven susceptible strains of Brachyspira spp. were determined. None of the susceptible strains were mutated whereas all the resistant strains had a mutation in position 2058. Susceptible strains became resistant in vitro after subculturing on agar containing 4 micrograms ml-1 of tylosin. Sequencing of these strains revealed an A-->G transition mutation in position 2058.     

Quantitative differences in the expression of a 72,000 molecular weight cell surface glycoprotein (GP72) in Trypanosoma cruzi zymodemes

A high affinity monoclonal antibody, 8G2 B9, was used to assess the expression of a 72,000 m.w. glycoprotein ( GP72 ) in isoenzyme-typed T. cruzi strains ( zymodemes ). Western blotting analysis of T. cruzi clones showed that 8G2 B9 bound strongly to GP72 and also suggested that this antigen was absent or weakly detectable in T. cruzi zymodeme 1 (Z1) strains. Purified 8G2 B9 was radiolabeled with 125I and used in an inhibition radioimmune binding assay to compare the quantities of GP72 in different zymodemes . Ninety-six T. cruzi strains were assayed, of which 36 were Z1, 36 were Z2, five were Z3 , and 19 were Z2 (heterozygous). Most (64%) Z1 strains lacked detectable GP72 , whereas this antigen was always detected Z2 and Z2 (heterozygous) strains. There was an 18-fold difference between geometric mean values for the quantities of GP72 (expressed as nanograms per milligram total cell protein) in Z1 and Z2 strains (Z1, 36 ng/mg; Z2, 639 ng/mg; p less than 0.001). There were also significant differences between the geometric mean values for Z2 and Z2 (heterozygous) strains, i.e., 639 ng/mg and 1648 ng/mg, respectively (p less than 0.001). GP72 was detected in four of the Z3 strains in quantities ranging from 740 to 3640 ng/mg. The absolute amounts of antigen in GP72 -positive strains were low, comprising less than 1% of the total cell protein. The specificities of two other anti- GP72 monoclonal antibodies, 7C6 D7 and WIC 29.26, were compared with 8G2 B9. Both antibodies completely inhibited the binding of 8G2 B9 to GP72 in solid phase immunoassays, suggesting that they reacted with the same antigenic determinants. The results show that monoclonal antibody-based assessments of the expression of GP72 correlate with zymodeme classification, and they also suggest that the monoclonal antibodies recognize major antigenic determinants on GP72 . It should be possible to use 8G2 B9 as an immunologic marker to additionally investigate the clinical significance of T. cruzi zymodemes and the biologic significance of GP72 .     

Etest for assessing the susceptibility of filamentous fungi

The purpose of this study was to evaluate the Etest as an in vitro antifungal susceptibility test method for different moulds originating from human samples and from the environment. A total of 50 isolates (1 Acremonium, 18 Aspergillus, 2 Cladosporium, 1 Epicoccum, 15 Penicillium, 2 Scopulariopsis and 11 Trichoderma strains) were tested by the Etest. Forty-six of the tested moulds (92%) were resistant to fluconazole with minimal inhibitory concentrations (MICs) > or = 256 microg ml(-1). There were strains resistant to ketoconazole among Aspergillus niger, A. ochraceus and Cladosporium spp. with MICs > 32 microg ml(-1). For fluconazole, no differences were observed using two different inocula, while for itraconazole, ketoconazole and amphotericin B, a 1 or less step 2-fold dilution difference in MIC was seen for the most of 10 selected strains. The MICs of fluconazole and amphotericin B obtained for Trichoderma strains by the Etest and the agar dilution method were also compared. MICs for fluconazole were in agreement, while MICs for amphotericin B were higher with 1 or 2 steps of 2-fold dilutions for most of Trichoderma strains in the case of the agar dilution method.     

Prevalence of antibiotic resistance profile in relation to phylogenetic background among commensal Escherichia coli derived from various mammals.

The paper describes the prevalence of resistant strains within the genetic structure of E. coli (phylogenetic group A, B1, B2 and D). A total of 200 commensal E. coli strains have been derived from 10 species of healthy animals residing on ZOO Safari Park area, in Swierkocin, Poland. The phylogenetic structure of E. coli has been analysed with the use of a PCR-based method. The strains were tested in terms of their susceptibility to eight classes of antibiotics: aminoglycosides, penicillins, cephalosporins, tetracyclines, nitrofurans, sulphonamides, phinicols, and quinolones. The genetic structure of E. coli revealed a not uniform distribution of strains among the four phylogenetic groups with significantly numerous representation of groups A and B1. Resistant E. coli were found within each of the phylogenetic groups. Strains resistant to one class of antibiotics occurred significantly more frequently in phylogenetic groups B2 and D (potential pathogens), whereas strains resistant to more than one class of antibiotics belonged to phylogenetic groups A and B1 (typical commensals) in a prevailing number of cases.     

Highly pathogenic strains of Escherichia coli revealed by the distinct electrophoretic patterns of carboxylesterase B

One hundred and ninety one strains of Escherichia coli isolated from extra-intestinal infections and 85 strains isolated from the stools of healthy human beings were compared for electrophoretic mobility and isoelectric point of carboxylesterase B, and for production of alpha-haemolysin and the presence of mannose resistant haemagglutinin. Fast and slow electrophoretic mobilities were distinguished among the strains. The frequency of strains showing slow mobilities was considerably higher when they originated from extra-intestinal infections (40%) than when they were obtained from the stools of healthy individuals (7%). In a two-dimensional electrophoretic profile, the fast and slow mobility variants of carboxylesterase B were resolved into two patterns, B1 and B2, respectively. The frequency of pathogenic strains that concomitantly produced alpha-haemolysin and mannose resistant haemagglutinin was 48.7% for strains of pattern B2 but only 2.8% for strains of pattern B1. Thus, the electrophoretic pattern B2 of carboxylesterase B appears to be a molecular marker for a group of highly pathogenic E. coli strains which are frequently implicated in extra-intestinal infections.     

淡色库蚊酯酶等位基因及其在自然种群中的频率分布

酯酶基因扩增所产生的酯酶活性升高是库蚊Culex pipiens对有机磷杀虫剂抗性的主要机理之一。采用分子杂交技术和限制性酶切片段长度多态性(RFLP)分析,已鉴定出多种酯酶等位基因类型。该文通过酯酶基因特异性片段的PCR扩增及扩增片段的酶切片段分析,对淡色库蚊Culex pipiens pallens四种有机磷抗性品系的酯酶等位基因进行分型,并测定分析自然种群中不同酶型的频率分布。研究结果表明：PCR分型方法具有快速、准确的特点。不同的有机磷杀虫剂对酯酶等位基因具有明显的选择作用。双硫磷品系为B₁型;毒死蜱和敌百虫品系为B₂型;马拉硫磷品系为B₁型和B₁/B₂杂合型。不同地区采集的种群表现出不同的酶型频率分布。该文就杀虫剂对酯酶等位基因选择作用及自然种群的酶型频率分布进行了讨论。     

Genetics of Sensitivity of Salmonella Species to Colicin M and Bacteriophages T5, T1, and ES18

Nearly all of 62 strains of Salmonella paratyphi B were sensitive to colicin M and phage T5 but resistant to phages T1 and ES18 and to colicin B. All tested S. typhimurium strains were resistant to colicin M and phage T5, and many were sensitive to phage ES18. A rough S. typhimurium LT2 strain given the tonA region of Escherichia coli or S. paratyphi B became sensitive to colicin M and phage T5. We infer that the tonA allele of S. paratyphi B, like that of E. coli, determines an outer membrane protein that adsorbs T5 and colicin M but not phage ES18, whereas the S. typhimurium allele determines a protein able to adsorb only ES18. The partial T1 sensitivity of a rough LT2 strain with a tonA allele from E. coli or S. paratyphi B and also the tonB(+) phentotype of an E. coli B trp-tonB Delta mutant carrying an F' trp of LT2 origin showed that S. typhimurium LT2 has a tonB allele like that of E. coli with respect to determination of sensitivity to colicins and phage T1. Rough S. paratyphi B, although T5 sensitive, remained resistant to T1 even when given F' tonB(+) of E. coli origin. Classes of Salmonella mutants selected as resistant to colicin M included: T5-resistant mutants, probably tonA(-); mutants unchanged except for M resistance, perhaps tolerant; and Exb(+) mutants, producing a colicin inhibitor (presumably enterochelin). Some Exb(+) mutants were resistant to a bacteriocin inactive on E. coli but active on all tested S. paratyphi B and S. typhimurium strains (and on nearly all other tested Salmonella). A survey showed sensitivity to colicin M in several other species of Salmonella.     

青海湖裸鲤肠道乳酸菌多样性与抑菌活性

【目的】通过生理生化特性,结合16S r RNA基因序列分析研究青海湖裸鲤肠道乳酸菌分离株的多样性,并对这些代表株的抑菌活性进行初步探讨,以期筛选具有高效抑菌活性的鱼源益生菌。【方法】对分离的47株乳酸菌代表株进行p H、温度生长范围、耐盐性等生理生化特征检测,结合16S r RNA基因序列对已分离到的乳酸菌进行基因分型和菌种鉴定,采用牛津杯双层平板法检测乳酸菌代表株的抑菌活性。【结果】鉴定结果显示:23株为Lactobacillus fuchuensis(48.94%),12株为Lactobacillus curvatus(25.53%),3株为Leuconostoc fallax(6.38%),2株为Lactobacillus sakei(4.26%),2株为Weissella ceti(4.26%);2株为Lactococcus cremoris(4.26%),1株为Leuconostoc lactis(2.13%),1株为Weissella minor(2.13%),1株为Enterococcus devriesei(2.13%)。qz1217、qz1196、qz1220所在的A、B、C三组乳酸菌在5-50°C的温度范围内生长良好,qz1196、qz1220所在的B、C组在pH 3.0-10.0的范围内生长良好,几乎所有乳酸菌都具有耐6.5%盐浓度特性。13株乳酸菌菌株对6种病原菌都具有抑制作用。通过排除酸、过氧化氢实验,发现上清液仍然具有抑菌活性。对qz1251发酵液进行蛋白酶处理,抑菌活性消失,确定其抑菌物质属于蛋白类物质,是一种细菌素。【结论】青海湖裸鲤肠道附着乳酸菌的多样性为益生性乳酸菌的筛选提供优质资源及数据参考。     

Host immune responses accelerate pathogen evolution

Pathogens face a hostile and often novel environment when infecting a new host, and adaptation is likely to be an important determinant of the success in colonization and establishment. We hypothesized that resistant hosts will impose stronger selection on pathogens than susceptible hosts, which should accelerate pathogen evolution through selection biased toward effector genes. To test this hypothesis, we conducted an experimental evolution study on Xanthomonas citri subsp. citri (Xcc) in a susceptible plant species and a resistant plant species. We performed 55 rounds of repeated reinoculation of Xcc through susceptible host grapefruit (isolates G1, G2, G3) and resistant host kumquat (isolates K1, K2, K3). Consequently, only K1 and K3 isolates lost their ability to elicit a hypersensitive response (HR) in kumquat. Illumina sequencing of the parental and descendant strains P, G1, G2, G3, K1, K2 and K3 revealed that fixed mutations were biased toward type three secretion system effectors in isolates K1 and K3. Parallel evolution was observed in the K1 and K3 strains, suggesting that the mutations result from selection rather than by random drift. Our results support our hypothesis and suggest that repeated infection of resistant hosts by pathogens should be prevented to avoid selecting for adaptive pathogens.     

Differentiation of methicillin-resistant strains of Staphylococcus aureus by prophage specificity]

By inducing with mitomycin C the following phages were isolated from all the tested 32 methicillin resistant strains of S. aureus: the serogroup B phage was isolated from 2 strains, the serogroup B and F phages were isolated from 5 strains and the serogroup F phage was isolated from 25 strains. The phages were divided into 5 groups by the antiphage immunity. In group 1 of the phages 4 additional phages were specified. By the specificity of the prophages in the cultures all the strains were divided into 5 groups. Group 1 of the cultures was divided into 5 subgroups (A, B, C, D and E).     

In vitro Activity of Moxifloxacin Against 179 Strains of Anaerobic Bacteria Found in Pulmonary Infections

The activity of moxifloxacin (BAY 12-8039), a new 8-methoxyquinolone, was determined using the NCCLS-approved Wadsworth brucella laked blood agar method and compared to the activities of metronidazole, penicillin G, piperacillin/tazobactam and trovafloxacin. Breakpoints used to define susceptible and resistant categories were, respectively: ≤ 8 and ≥ 32 μg/mL for metronidazole, ≤ 2 and ≥ 8 μg/mL for moxifloxacin and trovafloxacin, ≤ 0.5 and ≥ 2 μg/mL for penicillin G and ≤ 32 and ≥128 μg/mL for piperacillin/tazobactam. A total of 179 anaerobic isolates from pulmonary infections were tested. Piperacillin/tazobactam was the most active antimicrobial, inhibiting 99% of strains at the susceptible breakpoint. Ninety-seven percent of these isolates were susceptible to moxifloxacin; 96% to trovafloxacin, 89% to metronidazole and 43% to penicillin G. Geometric mean moxifloxacin MIC values forBacteroides fragilis and the B. fragilis group were 0.5 and 0.8 μg/mL, respectively. Eighty-eight percent of B. fragilis and 100% of other B. fragilis group species were susceptible to both moxifloxacin and trovafloxacin. All of the strains of B. fragilis and most of the other B. fragilis group species were resistant to penicillin G. At least 99% of other Bacteroides species, Prevotella, and Fusobacterium strains were susceptible to moxifloxacin, metronidazole, piperacillin/tazobactam and trovafloxacin (88% were susceptible to trovafloxacin at 2 μg/mL and all were susceptible at 4 μg/mL). The strains of Clostridium difficile andClostridium ramosum found in these specimens were both resistant to penicillin G but susceptible to the other agents. All strains of Peptostreptococcus species were susceptible to all of the agents except penicillin G. Activities of the agents against non-spore-forming Gram-positive rods at the intermediate breakpoint were, respectively, moxifloxacin-100%, metronidazole-49%, penicillin G-86%, piperacillin/tazobactam-100%, and trovafloxacin-97%. The promising in vitro activity of moxifloxacin against anaerobic pulmonary isolates warrants further investigation, including clinical correlation studies.     

Mx1 causes resistance against influenza A viruses in the Mus spretus-derived inbred mouse strain SPRET/Ei

Inbred SPRET/Ei mice, derived from Mus spretus, were found to be extremely resistant to infection with a mouse adapted influenza A virus. The resistance was strongly linked to distal chromosome 16, where the interferon-inducible Mx1 gene is located. This gene encodes for the Mx1 protein which stimulates innate immunity to Orthomyxoviruses. The Mx1 gene is defective in most inbred mouse strains, but PCR revealed that SPRET/Ei carries a functional allele. The Mx1 proteins of M. spretus and A2G, the other major resistant strain derived from Mus musculus, share 95.7% identity. We were interested whether the sequence variations between the two Mx1 alleles have functional significance. To address this, we used congenic mouse strains containing the Mx1 gene from M. spretus or A2G in a C57BL/6 background. Using a highly pathogenic influenza virus strain, we found that the B6.spretus-Mx1 congenic mice were better protected against infection than the B6.A2G-Mx1 mice. This effect may be due to different Mx1 induction levels, as was shown by RT-PCR and Western blot. We conclude that SPRET/Ei is a novel Mx1-positive inbred strain useful to study the biology of Mx1.     

临床和非临床分离沙门菌的菌型分布及对抗生素的耐药性研究

目的：探讨沙门菌在腹泻病人粪便、外环境污水和部分动物标本中的菌型分布及其对抗生素的耐药性。方法：采用血清学方法对沙门菌进行分群和分型,采用K—B法进行抗生素耐药性测定。结果：410份临床腹泻病人标本和514份非临床标本共检出沙门菌93株,检出率为10．1％,其菌型分布为：腹泻病人粪便中检出的均为B群鼠伤寒沙门菌(6／93),非临床标本中的菌型主要为C2群纽波特沙门菌(72／93),还有E1群伦敦沙门菌(7／93)、B群鼠伤寒沙门菌(2／93)和未定型(6／93)。87株沙门菌对青霉素的耐药率最高(96．5％),其次为SMZ TMP(73．6％),未发现对新霉素、链霉素、四环素和阿米卡星的耐药株。结论：实验结果可为研究我省沙门菌的菌型分布及其对抗生素的耐药性提供参考;临床上应加强对鼠伤寒沙门菌引起腹泻的监测。