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1.
In vitro susceptibility of eight antibiotics was compared using three groups of pneumococci and agar dilution method comprising 30
penicillin-susceptible, 30 intermediately penicillin-resistant, and 30 highly penicillin-resistant pneumococci. Decreased
sensitivity to all β-lactam agents of intermediately penicillin-resistant and highly penicillin-resistant pneumococci is shown.
MIC50 and MIC90 was lower with amoxicillin with and without clavulanate by one dilution than with penicillin. Cephalosporin MIC90S were all significantly higher for intermediately resistant and fully resistant strains. Only imipenem was more active than
penicillin with MIC90 of susceptible pneumococci 0.015 mg/L, intermediately resistant pneumococci 0.25 mg/L, resistant pneumococci 1 mg/L. 相似文献
2.
Emel Banu Buyukunal Bal Suleyman Bayar Mehmet Ali Bal 《Journal of microbiology (Seoul, Korea)》2010,48(3):267-274
The prevalence and antimicrobial susceptibilities of Staphylococci and Streptococci were assessed from subclinical mastitis
cases. One hundred Coagulase-Negative Staphylococci (CNS) and 34 Streptoccocci were identified. The most frequently isolated
species were Staphylococcus haemolyticus (27%) and Staphylococcus simulans (24%). Susceptible CNS species revealed the highest resistance to penicillin G (58%), ampicillin (48%), neomycin (20%), and
oleandomycin (14%). CNS methicillin resistance rates within 82 isolates were 21.95% and 1.22% by disk diffusion and PCR methods,
respectively. These results suggested the disk diffusion method was more prone to yield false positives. Partial sequencing
of the 16S rRNA region from the mecA carrying isolate (S. haemolyticus) was homologous with S. haemolyticus sequences/accessions obtained from GenBank. However, the mecA gene sequence from this isolate was more closely allied with the S. aureus mecA gene of human origins. Identical sequence data was acquired from the National Center for Biotechnology Information (NCBI)
database, suggesting horizontal gene transfer between the two species. CNS β-lactamase activity within 81 isolates was 29.63%.
The most frequently isolated Streptococcus species were S. uberis (52%) and S. agalactiae (15%). Oleandomycin was the least effective antimicrobial agent on these isolates with 59% susceptibility. Results indicated
that CNS and Streptococci exhibited various antimicrobial resistance responses. Consequently, isolation and identification
of udder pathogens in herds suffering from subclinical agents is essential to select the most effective antimicrobial agent.
Moreover, multiple resistance features of methicillin resistant (MR) isolates should be considered during antimicrobial susceptibility
tests. 相似文献
3.
Seventy-eight staphylococcal strains were isolated from surgical-site, blood-stream and other hospital-acquired infections.
Eighteen isolates were determined as methicillin (MET)-resistant S. aureus (MRSA), while the remaining were MET-resistant coagulase-negative staphylococci (CoNS). Fifty percent of CoNS strains were
multiresistant, while 10 % of isolates were resistant only to β-lactams. Clinical isolates of CoNS were generally more resistant
to antimicrobial agents than S. aureus strains. Thirty-nine % of S. aureus strains were resistant only to β-lactams. None of the MRSA strains carried ileS-2 gene; this gene was found in two strains of S. epidermidis. 相似文献
4.
Christopher G. Dowson Tracey J. Coffey Christopher Kell Robert A. Whiley 《Molecular microbiology》1993,9(3):635-643
Penicillin-resistant strains of Streptococcus pneumoniae possess forms of penicillin-binding proteins (PBPs) that have a low affinity for penicillin compared to those from penicillin-sensitive strains. PBP genes from penicillin-resistant isolates are very variable and have a mosaic structure composed of blocks of nucleotides that are similar to those found in PBP genes from penicillin-sensitive isolates and blocks that differ by up to 21%. These chromosomally encoded mosaic genes have presumably arisen following transformation and homologous recombination with PBP genes from a number of closely related species. This study shows that PBP2B genes from many penicillin-resistant isolates of S. pneumoniae contain blocks of nucleotides originating from Streptococcus mitis. In several instances it would appear that this material alone is sufficient to produce a low affinity PBP2B. In other examples PBP2B genes possess blocks of nucleotides from S. mitis and at least one additional unidentified species. Mosaic structure was aiso found in the PBP2B genes of penicillin-sensitive isolates of S. mitis or S. pneumoniae. These mosaics did not confer penicillin resistance but nevertheless reveal something of the extent to which localized recombination occurs in these naturally transformable streptococci. 相似文献
5.
Role of interspecies transfer of chromosomal genes in the evolution of penicillin resistance in pathogenic and commensal Neisseria species 总被引:10,自引:0,他引:10
Brian G. Spratt Lucas D. Bowler Qian-Yun Zhang Jiaji Zhou John Maynard Smith 《Journal of molecular evolution》1992,34(2):115-125
Summary The two pathogenic species of Neisseria, N. meningitidis and N. gonorrhoeae, have evolved resistance to penicillin by alterations in chromosomal genes encoding the high molecular weight penicillin-binding proteins, or PBPs. The PBP 2 gene (penA) has been sequenced from over 20 Neisseria isolates, including susceptible and resistant strains of the two pathogenic species, and five human commensal species. The genes from penicillin-susceptible strains of N. meningitidis and N. gonorrhoeae are very uniform, whereas those from penicillin-resistant strains consist of a mosaic of regions resembling those in susceptible strains of the same species, interspersed with regions resembling those in one, or in some cases, two of the commensal species. The mosaic structure is interpreted as having arisen from the horizontal transfer, by genetic transformation, of blocks of DNA, usually of a few hundred base pairs. The commensal species identified as donors in these interspecies recombinational events (N. flavescens and N. cinerea) are intrinsically more resistant to penicillin than typical isolates of the pathogenic species. Transformation has apparently provided N. meningitidis and N. gonorrhoeae with a mechanism by which they can obtain increased resistance to penicillin by replacing their penA genes (or the relevant parts of them) with the penA genes of related species that fortuitously produce forms of PBP 2 that are less susceptible to inhibition by the antibiotic. The ends of the diverged blocks of DNA in the penA genes of different penicillin-resistant strains are located at the same position more often than would be the case if they represent independent crossovers at random points along the gene. Some of these common crossover points may represent common ancestry, but reasons are given for thinking that some may represent independent events occurring at recombinational hotspots.
Offprint requests to: B.G. Spratt 相似文献
6.
Tytti Niemelä Tuomas Virén Jukka Liukkonen David Argüelles Nikae C R te Moller Pia H Puhakka Jukka S Jurvelin Riitta-Mari Tulamo Juha Töyräs 《Acta veterinaria Scandinavica》2014,56(1):1-8
Background
Staphylococcus aureus is an important cause of clinical mastitis in dairy cows worldwide. The cure rate after antimicrobial treatment of clinical S. aureus mastitis is very variable due to both cow and bacterial factors. Studies have shown that bacterial genotype might affect short-term bacteriological and clinical cure, but the long-term outcome has been less studied. The objectives of this study were to investigate associations between bacterial genotype and long-term outcome of veterinary-treated clinical mastitis (VTCM) caused by S. aureus during a follow-up period of 120 days and to study genotype variation among Swedish S. aureus isolates. S. aureus isolates from cases of VTCM were genotyped by pulsed-field gel electrophoresis. Long-term outcome measurements used were somatic cell count (SCC), additional diagnoses of VTCM, milk yield and culling. Isolates were classified into clusters (>80% similarity) and pulsotypes (100% similarity). Clusters and pulsotypes were grouped according to occurrence. Multivariable mixed-effect linear regression models including cow and bacterial factors with possible influence on SCC or milk yield were used to calculate differences in SCC or milk yield between groups. Additional outcome measures were calculated using a test of proportions.Results
The isolates (n?=?185) were divided into 18 clusters and 29 pulsotypes. Two pulsotypes were classified as common, and were found in 64% of the cases of VTCM. Remaining isolates were classified as less common or rare pulsotypes. The distribution was similar at cluster level. Outcome was calculated from follow-up data on 111 cows. Significantly lower SCC during the follow-up period was found in cows infected with common clusters compared to in cows infected with less common/rare clusters. The proportion of cows with SCC <200 000 cells/ml during the whole follow-up period was significantly higher in the group common clusters than in the group less common/rare clusters. Bacterial genotype did not influence the other outcome parameters.Conclusions
In Sweden, two S. aureus pulsotypes, identified in about 64% of clinical S. aureus cases, were widespread. Cows infected with the common genotypes had significantly lower SCC during 120 days after treatment compared to cows infected with less common or rare genotypes. 相似文献7.
Ravinder Kumar B. R. Yadav S. K. Anand R. S. Singh 《World journal of microbiology & biotechnology》2011,27(3):513-521
Staphylococcus aureus is recognized as a major etiological agent of the most important udder disease; mastitis. The virulence potential of S. aureus isolates is attributed to a combination of extracellular factors and invasive properties that are controlled at the genomic
level. In this study molecular variations were studied among the 128 S. aureus isolates obtained from the mastitic crossbred cattle. The polymorphic patterns of protein A, coagulase, and IG genes were
studied in the isolates using the PCR and PCR–RFLP methods. In addition, presence of other virulence genes responsible for
the expression of adhesins and toxins was also screened. A considerable genetic variation was observed in amplified fragment
of SPA, IG and CLF genes. The PCR–RFLP of COA gene yielded five different patterns. Occurrence of EBP, ENO and FNBA was found
to be common in both high and low virulence isolates. However, the prevalence of FNBB and toxin genes was higher in clinical
than subclinical isolates. The distribution proportions of adhesin genes EBP, FIB, FNBB, CNA, BBP, MAP CAP5, and CAP8 were
60.2, 59.4, 21.9, 6.3, 5.5, 80.5, 56.3, and 22.7%; for AGR I, II, III, and IV were 44.5, 32.8, 12.5, and 10.2%; and for toxins
genes HLB, SEB, SEC, SED, SEE, SEG, and SEI were 82.0, 3.1, 5.5, 3.9, 0.8, 16.4, and 55.5%, respectively. The proportions
of FNBB, EBP, FIB, HLB, BBP, SEG, and SEI genes were observed more in clinical cases. The significant genetic variations in
SPA, COA, IG, and CLF genes were useful to differentiate the isolates that might be valuable for mastitis reduction programme. 相似文献
8.
Cefditoren is the active form of cefditoren pivoxil, a new, broad-spectrum oral cephalosporin with strong in vitro activity against penicillin-susceptible and resistant Streptococcus pneumoniae. In this study, the minimum inhibitory concentrations (MICs) of cefditoren were determined for a special selection of S. pneumoniae isolates known to be susceptible, moderately susceptible or fully resistant to penicillin; these isolates originated from the lower respiratory tract of adults with pneumonia or the upper respiratory tract of children with or without symptoms of infection. Some of this latter group of isolates exhibited extremely high MICs to penicillin (> or = 32 mg/l), whereas the MICs of cefditoren did not exceed 2 mg/l. The MIC50 and MIC90 of cefditoren proved to be 0.25 and 1.0 mg/l, respectively, with a range of MICs < or = 0.015-2.0 mg/l for all the tested S. pneumoniae isolates. Its good activity suggests that cefditoren is expected to be a potent drug in infections caused by penicillin-resistant and multidrug-resistant S. pneumoniae. 相似文献
9.
Siti Ma Chao Cong Xiaohui Meng Shasha Cao Hongkun Yang Yuanyuan Guo Xueyi Lu Shutao Ma 《Bioorganic & medicinal chemistry letters》2013,23(14):4076-4079
Novel 3-elongated arylalkoxybenzamide derivatives were designed, synthesized and evaluated for their cell division inhibitory activity and antibacterial activity. Among them, the subseries of 3-alkyloxybenzamide derivatives exhibited greatly improved on-target activity against Bacillus subtilis and Staphylococcus aureus, and remarkably increased antibacterial activity against B. subtilis ATCC9372, penicillin-susceptible S. aureus ATCC25923, methicillin-resistant S. aureus ATCC29213 (MRSA) and penicillin-resistant S. aureus PR compared with 3-methoxybenzamide. In contrast, the subseries of 3-phenoxyaklyloxybenzamide, 3-heteroarylalkyloxybenzamide and 3-heteroarylthioalkyloxybenzamide derivatives only showed a significant improvement in on-target activity and antibacterial activity against B. subtilis ATCC9372. 相似文献
10.
《Small Ruminant Research》2007,73(2-3):197-199
Staphylococcus aureus is one of the major causes of dairy sheep mastitis. The S. aureus agr locus (accessory gene regulator) regulates the production of most staphylococcal exoproteins, including exoenzymes, toxins, surface proteins, and other virulence factors. S. aureus have four agr groups (alleles) determined by PCR. In this study, 46 S. aureus isolates, recovered in south-east of France, were also characterized by their properties of adherence to smooth surfaces, slime production and resistance to 10 antibiotics. For 46 S. aureus associated with dairy sheep mastitis (subclinical mastitis, clinical mastitis, environment of dairy sheep farm), 80% (37/46) belonged to agr group 3, 39% (18/46) were adherent (adherent, strongly adherent or with maximal adherence). For the same isolates, 26% (12/46) were slime producers (moderate or strong producers). All the 46 isolates were susceptible to oxacillin, except for two isolates including two sheep subclinical mastitis isolates. The dairy sheep subclinical mastitis isolates were for 79% (22/28), susceptible to nine other antibiotics tested. 相似文献
11.
Males with acute gonococcal urethritis were treated at random with 2.4 million units aqueous procaine penicillin G intramuscularly plus 1.0 g. probenecid orally, 3.5 g. ampicillin orally plus 1.0 g. probenecid orally, or 2.0 g. spectinomycin intramuscularly. The overall follow-up was 97%. All treatments were of equal efficacy, eradication of gonococcal disease being observed in 93 to 97% of treated patients. Treatment failures occurred in each drug group and pre-treatment isolates recovered from these cases showed decreased susceptibility to the agent used. Aqueous procaine penicillin G plus probenecid remains the preferred therapy for gonorrhea. For patients hypersensitive to penicillin, spectinomycin is currently a reasonable alternative drug. This agent, unlike procaine penicillin-probenecid, is probably ineffective against concurrent incubating syphilis, and future development of bacterial resistance is a definite possibility. 相似文献
12.
Hoang Vu-Thien Katia Hormigos Gaëlle Corbineau Brigitte Fauroux Harriet Corvol Didier Moissenet Gilles Vergnaud Christine Pourcel 《BMC microbiology》2010,10(1):24
Background
Staphylococcus aureus infection in patients with cystic fibrosis (CF) is frequent and may be due to colonization by a few pathogenic lineages. Systematic genotyping of all isolates, methicillin-susceptible S. aureus (MSSA) as well as methicillin-resistant S. aureus (MRSA) is necessary to identify such lineages and follow their evolution in patients. Multiple-locus variable-number tandem repeat analysis (MLVA/VNTR) was used to survey S. aureus clinical isolates in a French paediatric CF centre. 相似文献13.
Songmee Bae Jaehoon Lee Eunah Kim Jaehwa Lee Jaeyon Yu Yeonho Kang 《Journal of microbiology (Seoul, Korea)》2010,48(1):84-88
Haemophilus influenzae is a frequent causative bacterial pathogen of respiratory tract infections. Resistance to β-lactam antibiotics has been a
significant clinical problem in treatment for H. influenzae respiratory infections. This study describes the serotype, antibiotic resistance and distribution of TEM-1 or ROB-1 β-lactamase
in H. influenzae isolates from local private hospitals from 2002 to 2004. Among the 100 H. influenzae respiratory isolates, only 7% were identified as serotypes a, b, e, and f, with the remaining 93% being nontypeable. Resistance
to ampicillin, cefaclor, and tetracycline was 57%, 46%, and 16%, respectively. All strains were susceptible to azithromycin
and ciprofloxacin, whereas amoxicillin/clavulanate, cefotaxime, and imipenem exhibited reduced susceptibilities of 99%, 99%,
and 91%, respectively. All 57 ampicillinresistant strains (minimum inhibitory concentration, MIC≥4 μg/ml) were β-lactamase-positive
and possessed the TEM-1 type β-lactamase. One β-lactamase-positive amoxicillin/clavulanate-resistant isolate that was resistant
to ampicillin (MIC>128 μg/ml) had the TEM-1 type β-lactamase and not susceptible to cefaclor and cefotaxime. Analysis of penicillin
binding protein 3 revealed six residues (Asp-350, Met-377, Ala-502, Asn-526, Val-547, and Asn-569) that were substituted by
Asn, Ile, Val, Lys, Ile, and Ser, respectively. 相似文献
14.
The penicillin-binding protein (PBP) profiles of penicillin-susceptible and-resistant clinical isolates ofStreptococcus mitis varied even with strains with similar minimal inhibitory concentrations (MICs).S. mitis NCTC 10712 was used as a DNA recipient to investigate PBP alterations which could occur as a result of spontaneous mutation and intra- and interspecific transfer of penicillin resistance genes.S. mitis NCTC 10712 possesses seven major PBPs ranging in molecular mass from 49–82 kDa. TwoS. mitis and twoStreptococcus pneumoniae penicillin-resistant clinical isolates were used as donors in transformation experiments withS. mitis NCTC 10712 (MIC 0.03 g/ml) as the recipient. Transformants with MICs greater than 1 g/ml were obtained with bothS. mitis andS. pneumoniae donor DNA. Depending on the source of the donor DNA and level of resistance achieved, transformants showed reduced penicillin-binding affinities of PBPs 2, 3, 4, 5, and 6. The most consistent PBP alteration associated with increasing resistance inS. mitis NCTC 10712 was seen with PBP 3 (74 kDa). 相似文献
15.
Moon JS Kim HK Koo HC Joo YS Nam HM Park YH Kang MI 《Applied microbiology and biotechnology》2007,75(5):989-998
Based on our previous study evaluating the in vivo cure efficacy of chitosan on bovine mastitis, a more water-soluble chitosan-oligosaccharide
(OCHT) with a high degree of deacetylation and low molecular weight was prepared to obtain high antibiotic efficacy. The growth
of Staphylococcus aureus isolated from bovine mastitis was inhibited within 10 min of treatment with OCHT in concentrations ranging from 0.0001 to
0.5%. Additionally, electron microscopic observation indicated that the surface of the OCHT-treated bacteria was expanded,
distorted, and lysed compared to that of the control bacteria. In mice, the proportion of monocytes was elevated, and the
levels of interleukin-6 and interferon-γ sharply increased l h after the peritoneal inoculation of the OCHT (0.5 to 1 mg per
mouse). Mice challenged intraperitoneally with S. aureus (2.5 × 108 colony forming units) after oral treatment with OCHT (0.5 to 2 mg per day) for 7 days showed a higher survival rate (70–100%)
than that of the control (10%). We suggest that the OCHT prepared in this study is a potential agent for the prevention and
treatment of bovine mastitis based on its strong antibacterial activity against S. aureus as well as the immunostimulative effect it exhibits on murine infection by S. aureus.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
Sakwinska O Morisset D Madec JY Waldvogel A Moreillon P Haenni M 《Applied and environmental microbiology》2011,77(10):3428-3432
Staphylococcus aureus is a major bovine mastitis pathogen. Although the reported antimicrobial resistance was generally low, the emergence of new genetic clusters in bovine mastitis requires examination of the link between antimicrobial resistance and genotypes. Here, amplified fragment length polymorphism (AFLP) profiles and standard antimicrobial resistance profiles were determined in order to characterize a total of 343 S. aureus cow mastitis isolates from two geographically close regions of Switzerland and France. AFLP profiles revealed similar population compositions in the two regions, with 4 major clusters (C8, C20, C97, and C151), but the proportions of isolates in each cluster significantly diverged between the two countries (P = 9.2 × 10−9). Antimicrobial resistance was overall low (<5% resistance to all therapeutically relevant molecules), with the exception of penicillin resistance, which was detected in 26% of the isolates. Penicillin resistance proportions differed between clusters, with only 1 to 2% of resistance associated with C20 and C151 and up to 70% associated with bovine C97. The prevalence of C20 and C8 was unexpectedly high and requires further investigation into the mechanism of adaptation to the bovine host. The strong association of penicillin resistance with few clusters highlights the fact that the knowledge of local epidemiology is essential for rational choices of antimicrobial treatment in the absence of susceptibility testing. Taken together, these observations argue in favor of more routine scrutiny of antimicrobial resistance and antibiotic-resistant clones in cattle and the farm environment. 相似文献
17.
An internal fragment of the ddl gene, encoding the cytoplasmic enzyme D-alanyl-D-alanine ligase, was sequenced from 566 isolates of Streptococcus pneumoniae and single isolates of Streptococcus mitis and Streptococcus oralis. The 52 alleles found among the S. pneumoniae isolates fell into two groups. Group A alleles were very uniform in sequence and were present in both penicillin-susceptible and penicillin-resistant pneumococci. Group B alleles were much more diverse and were found only in penicillin-resistant isolates. The Streptococcus oralis and Streptococcus mitis alleles were less diverged from group A alleles than some of the group B pneumococcal alleles, suggesting that the latter alleles contain interspecies recombinational replacements. The ddl gene was located 783 bp downstream of the penicillin-binding protein 2b gene (pbp2b). Sequencing of the pbp2b-recR-ddl-murF region of three penicillin-resistant pneumococci that had diverged ddl alleles showed that the whole region from pbp2b to ddl (or beyond) was highly diverged (about 8%) compared with the sequences from three penicillin-susceptible isolates. The high levels of diversity in the group B ddl alleles from penicillin-resistant isolates were ascribed to a hitchhiking effect whereby interspecies recombinational exchanges at pbp2b, selected by penicillin usage, often extend into, or through, the ddl gene. The data allow the average size of the interspecies recombinational replacements to be estimated at about 6 kb. 相似文献
18.
Genetic Determinants of Antibiotic Resistance in Staphylococcus aureus Isolates from Milk of Mastitic Crossbred Cattle 总被引:1,自引:0,他引:1
Staphylococcus aureus is one of the major causes of mastitis in dairy animals and its resistance against multiple antimicrobials always remains
crucial concern. Present investigation was carried out to detect the distribution of antibiotic-resistant genes of S. aureus isolates. Isolates (128) of S. aureus from mastitic milk were collected, tested for antibiotics with disc-diffusion method, and resistant genes mecA, linA, msrA msrB, vatA, vatB, vatC ermA, ermC tetK, tetM and aacA-D were detected by PCR. The phenotypic antibiotics resistance percent in S. aureus isolates was classified as tetracycline (36.7), gentamycin (30.5), streptomycin (26.6), kanamycin (25.8) and penicillin G
(22.7). All the isolates were susceptible to vancomycin. Among isolates, 10.2% were observed as methicillin-resistant. The
distribution of antibiotic-resistant genes was linA (51.6) followed by msrB (46.1), tetK + M (34.4), msrA and aacA-D (26.6%). Different antibiotic-resistant genes combinations (mecA/linA-2; mecA/aacA-D/tetK/linA/msrB-3; mecA/linA/msrA/msrB-3; aacA-D/linA/msrA/msrB-4; aacA-D/linA/msrB-7; linA/msrA/msrB-10; tetK/linA/msrA/msrB-11; aacA/tetK/linA/msrB-12 isolates) were observed. All the isolates lacked amplification of vatA, vatB, ermA and ermC genes. Molecular typing resulted genetic variation in protein A (6–12 repeats) and coagulase genes (A–E patterns) were observed.
Coagulase A and D genotypes were more prevalent in antibiotic-resistant isolates, while E, B and C in susceptible ones. The
significant observation was the prevalence of methicillin-resistant S. aureus, which were resistant to multiple antibiotics. Findings revealed the status of resistant isolates in herd that might be helpful
in treatment, controlling of resistant strains and culling of cows for mastitis reduction. 相似文献
19.
20.
Francisella tularensis ssp. tularensis is a category A select agent and the causal organism for the zoonotic disease tularemia. The vast majority of F. tularensis isolates are β-lactamase-positive. β-lactamase production is widely believed to be responsible for the inefficacy of β-lactams in the treatment of tularemia. In this study, we report the cloning and characterization of the two chromosomally encoded F. tularensis ssp. holarctica live-vaccine strain (LVS) β-lactamases. The two LVS β-lactamases were homologous to F. tularensis Schu S4 open reading frames FTT0681c and FTT0611c and have been named bla1
LVS
and bla2
LVS
, respectively. Recombinant expression in Escherichia coli suggested that bla1
LVS
did not encode a functional β-lactamase, whereas bla2
LVS
encoded a functional β-lactamase that hydrolyzed penicillins but was inactive against third-generation cephalosporins, including cefprozil. As both LVS and Schu S4 were susceptible to cefprozil, we developed three new shuttle vectors based on selection for the production of the Blashv-2 extended-spectrum β-lactamase with cefprozil. The resulting shuttle vectors were suitable for recombinant gene expression and complementation studies in LVS and Schu S4. 相似文献