SEARCH · PubMed Health

Results for “Infectious clone”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources

PubMed1993

Rapid in vitro selection of human immunodeficiency virus type 1 resistant to 3'-thiacytidine inhibitors due to a mutation in the YMDD region of reverse transcriptase.

Resistant variants of human immunodeficiency virus type 1 (HIV-1) have been selected by limited passage in MT4 cells of both wild-type and 3'-azido-3'-deoxythymidine (AZT, zidovudine)-resistant strains with the nucleoside analogues (-)-2'-deoxy-3'-thiacytidine (3TC) and (-)-2'-deoxy-5-fluoro-3'-thiacytidine (FTC). Virus variants selected independently were crossresistant to both inhibitors. This rapid in vitro selection of resistant virus has not previously been seen with nucleoside analogues but is reminiscent of that observed with the nonnucleoside reverse transcriptase inhibitors. However, passage of wild-type virus with a combination of AZT and FTC appreciably delayed emergence of FTC-resistant virus. DNA sequence analysis of the reverse transcriptase coding region from FTC-resistant virus revealed changes at codon 184 in the highly conserved Tyr, Met, Asp, Asp (YMDD) region. When the mutation Met184-->Val was introduced into the infectious clone HXB2, this change alone accounted for the resistance (> 1000-fold) seen with both 3TC and FTC, and for a 5- to 15-fold reduction in sensitivity to their (+) enantiomers. It had no effect on susceptibility to AZT or nevirapine and minimal effect on susceptibility to 2',3'-dideoxyinosine and 2',3'-dideoxycytidine. To determine the influence of this mutation in a background of mutations conferring resistance to AZT and nonnucleoside reverse transcriptase inhibitors, a series of HIV-1 variants were created by site-directed mutagenesis. All mutants with Met184-->Val were cross-resistant to 3TC and FTC. The Met184-->Val mutation did not influence nevirapine resistance, but resistance to AZT was suppressed. Similar suppression of AZT resistance was seen with Tyr181-->Cys. Interestingly, when both Met184-->Val and Tyr181-->Cys substitutions were present, highly resistant virus reverted to complete AZT sensitivity. Assessment of the interactive effects of multiple drug-resistance mutations may help to establish a rationale for using these drugs in the future therapy of HIV disease.

Amino Acid Sequence↗

PubMed1996

Evolutionary reconstruction of a hairpin deleted from the genome of an RNA virus.

The intercistronic region between the maturation and coat-protein genes of RNA phage MS2 contains important regulatory and structural information. The sequence participates in two adjacent stem-loop structures, one of which, the coat-initiator hairpin, controls coat-gene translation and is thus under strong selection pressure. We have removed 19 out of the 23 nucleotides constituting the intercistronic region, thereby destroying the capacity of the phage to build the two hairpins. The deletion lowered coat-protein yield more than 1000-fold, and the titer of the infectious clone carrying the deletion dropped 10 orders of magnitude as compared with the wild type. Two types of revertants were recovered. One had, in two steps, recruited 18 new nucleotides that served to rebuild the two hairpins and the lost Shine-Dalgarno sequence. The other type had deleted an additional six nucleotides, which allowed the reconstruction of the Shine-Dalgarno sequence and the initiator hairpin, albeit by sacrificing the remnants of the other stem-loop. The results visualize the immense genetic repertoire created by, what appears as, random RNA recombination. It would seem that in this genetic ensemble every possible new RNA combination is represented.

Base Sequence↗

PubMed1997

RNA folding kinetics regulates translation of phage MS2 maturation gene.

The gene for the maturation protein of the single-stranded RNA coliphage MS2 is preceded by an untranslated leader of 130 nt, which folds into a cloverleaf, i.e., three stem-loop structures enclosed by a long distance interaction (LDI). This LDI prevents translation because its 3' moiety contains the Shine-Dalgarno sequence of the maturation gene. Previously, several observations suggested that folding of the cloverleaf is kinetically delayed, providing a time window for ribosomes to access the RNA. Here we present direct evidence for this model. In vitro experiments show that ribosome binding to the maturation gene is faster than refolding of the denatured cloverleaf. This folding delay appears related to special properties of the leader sequence. We have replaced the three stem-loop structures by a single five nt loop. This change does not affect the equilibrium structure of the LDI. Nevertheless, in this construct, the folding delay has virtually disappeared, suggesting that now the RNA folds faster than ribosomes can bind. Perturbation of the cloverleaf by an insertion makes the maturation start permanently accessible. A pseudorevertant that evolved from an infectious clone carrying the insertion had overcome this defect. It showed a wild-type folding delay before closing down the maturation gene. This experiment reveals the biological significance of retarded cloverleaf formation.

Base Sequence↗

PubMed1998

Analysis of polypurine tract-associated DNA plus-strand priming in vivo utilizing a plant pararetroviral vector carrying redundant ectopic priming elements.

Initiation of DNA plus-strand synthesis in most reverse-transcribing elements requires primer generation by reverse transcriptase-associated RNase H at one or more template polypurine tracts (PPTs). We have exploited infectious clones of the plant pararetrovirus cauliflower mosaic virus carrying redundant ectopic plus-strand priming elements to study priming in vivo. Ectopic priming generated an additional discontinuity in progeny virion DNA during infection of plants. We found that altering the length of the 13-base pair PPT by +/-25% significantly reduced priming efficiency. A short pyrimidine tract 5' to the PPT, highly conserved among diverse reverse-transcribing elements, was shown to play an important role in PPT recognition in vivo. The predominant DNA plus-strand 5' end remained 3 nucleotides from the PPT 3' end in mutant primers that were longer or shorter than the wild-type primer. Use of an ectopic redundant primer to study replication-dependent priming was validated by demonstrating that it could rescue infectivity following destruction of the wild-type priming elements. We propose a model for plant pararetroviral plus-strand priming in which pyrimidines enhance PPT recognition during polymerase-dependent RNase H cleavages, and suggest that fidelity of primer maturation during polymerase-independent cleavages involves PPT length measurement and 3' end recognition by RNase H.

Amino Acid Sequence↗

PubMed2003

Tissue tropism in the chicken embryo of non-virulent and virulent Newcastle diseases strains that express green fluorescence protein.

The tissue tropism of non-virulent and virulent Newcastle disease virus (NDV) was investigated using 8-day-old and 14-day-old embryonating chicken eggs (ECE), inoculated with an infectious clone of the non-virulent La Sota strain (NDFL-GFP) or its virulent derivative (NDFLtag-GFP). Both strains expressed the gene encoding jellyfish green fluorescence protein (GFP) as a marker. The GFP was readily expressed in chicken embryo cells infected with the NDV strains indicating virus replication. Whereas both strains replicated in the chorioallantoic membrane (CAM) and infected the skin of 8-day-old ECE, only the virulent strain (NDFLtag-GFP) spread to internal organs (pleura/peritoneum). In 14-day-old ECE, the initial target organs appeared to be the CAM and the lungs for both strains. At 48 h after inoculation, the virulent strain (NDFLtag-GFP) had also spread to the spleen and heart and was detected in a wide-range of embryonic cell types. The kinetics of virus replication and spread in the CAM closely resembled each other in both the 8-day-old and 14-day-old ECE. Infection of 8-day-old and 14-day-old ECE forms a convenient model to investigate tissue tropism of NDV, as well as the kinetics of viral infection. The advantage of using GFP is that samples can be easily screened by direct fluorescence microscopy without any pre-treatment.

Animals↗

PubMed2005

Comparative sequence analysis of the eastern equine encephalitis virus pathogenic strains FL91-4679 and GA97 to other North American strains.

Eastern equine encephalitis (EEE) virus is a significant public health concern due to the high mortality rates observed in infected humans, equines and game birds. The EEE genomic sequences available prior to this report are based on laboratory strains with unknown passage histories that may contain an array of cell culture adaptations. Here we report the complete genomic sequences of two recently isolated EEE pathogenic strains with low passage histories. FL91-4697 was isolated in Florida from Aedes albopictus mosquitoes and GA97 was derived from brain tissue of a human fatality that occurred in 1997. Sequence alignment of these new genomes with the documented EEE's permitted us to generate a North American consensus sequence and identify regions of significant diversity. Sequence analysis of the FL91-4679 genome was essential to the production of an EEE infectious clone that is being used to create live attenuated vaccine candidates.

Aedes↗

PubMed1996

Mechanisms of mutations inhibiting fusion and infection by Semliki Forest virus.

Semliki Forest virus (SFV) infects cells by an acid-dependent membrane fusion reaction catalyzed by the virus spike protein, a complex containing E1 and E2 transmembrane subunits. E1 carries the putative virus fusion peptide, and mutations in this domain of the spike protein were previously shown to shift the pH threshold of cell-cell fusion (G91A), or block cell-cell fusion (G91D). We have used an SFV infectious clone to characterize virus particles containing these mutations. In keeping with the previous spike protein results, G91A virus showed limited secondary infection and an acid-shifted fusion threshold, while G91D virus was noninfectious and inactive in both cell-cell and virus-liposome fusion assays. During the low pH- induced SFV fusion reaction, the E1 subunit exposes new epitopes for monoclonal antibody (mAb) binding and forms an SDS-resistant homotrimer, the virus associates hydrophobically with the target membrane, and fusion of the virus and target membranes occurs. After low pH treatment, G91A spike proteins were shown to bind conformation-specific mAbs, associate with target liposome membranes, and form the E1 homotrimer. However, both G91A membrane association and homotrimer formation had an acid-shifted pH threshold and reduced efficiency compared to wt virus. In contrast, studies of the fusion-defective G91D mutant showed that the virus efficiently reacted with low pH as assayed by mAb binding and liposome association, but was essentially inactive in homotrimer formation. These results suggest that the G91D mutant is noninfectious due to a block in a late step in membrane fusion, separate from the initial reaction to low pH and interaction with the target membrane, and involving the lack of efficient formation of the E1 homotrimer.

Animals↗

PubMed2000

Deletion of the GPG motif in the HIV type 1 V3 loop does not abrogate infection in all cells.

The three amino acids glycine, proline, and glycine (GPG) constitute a conserved motif at the center of the V3 loop of HIV-1 surface glycoprotein 120. It has been indicated that deletion of this GPG motif is lethal for viral infectivity and abrogates the ability of the virus to form syncytia. In the present work, we studied the effects of GPG deletion on viral infectivity, cell tropism, syncytium formation, and initiation of apoptosis by constructing a mutant provirus based on the infectious clone pBRu-2. Successful infection and replication of GPG-deleted virus were detected in MT-2 cells, although the mutant virus showed lower infectivity. Infection could also be observed in the C8166, C91-PL, Molt-3, and THP-1 cell lines, and in PBMC-derived dendritic cells (DCs), but not in CEM-SS, HUT78, H9, Jurkat, and U937 cell lines or in PBMCs. Mutant virus also induced syncytia and apoptosis in the MT-2 cells. An intact GPG motif is probably necessary for unimpaired induction of fusion in some HIV-1-permissive cells. However, once the virus enters the cells, the GPG sequence does not seem to be indispensable for syncytium formation or apoptosis induction in MT-2 cells. Our data also imply that cell surface molecules other than CD4 and CXCR4 may be involved in entry of the GPG-deleted virus.

Amino Acid Motifs↗

PubMed2005

Characterization of a long terminal repeat region from an infectious Indian HIV type 2 isolate.

An infectious Indian human immunodeficiency virus type 2 isolate from Mumbai, propagated in this laboratory, was found to bear an unusually short long terminal repeat (LTR) region. Complete sequencing of the 601 bp LTR indicated a loss of around 250 nucleotide pairs from the unique 3' (U3) region as compared to other well-characterized HIV-2 isolates. Phylogenetic analysis of this LTR shows closest relatedness to the Guinea-Bissau subtype A isolates HIV-2(CAM2) and HIV-2(ALI). The LTR from the biologically active infectious clone with the observed deletion contained all functionally relevant promoter and polyadenylation sequences.

Base Sequence↗

PubMed1993

Recombinant LuIII autonomous parvovirus as a transient transducing vector for human cells.

Recombinants based on the genome of the autonomous parvovirus, LuIII, were constructed by replacing the viral coding sequences in an infectious clone (pGLu883) by a luciferase or beta-galactosidase reporter, which was linked to the viral P4 promoter. In cells cotransfected with either of these constructs, together with a plasmid supplying LuIII nonstructural and capsid proteins, excision and replication of the recombinant genome occurred. Transducing virions accumulated in the culture medium of the cotransfected cells, as assayed by reporter activity in recipient cells exposed to this medium. Transducing activity could be neutralized by antiserum to LuIII. Production of replicative form DNA and transducing virions were observed following cotransfection of HeLa, 293, or NB324K cells, in increasing order of efficiency. When homology existed between the recombinant genome and sequences flanking the viral genes in the helper construct, concomitant production of replication-competent, cytopathic virus was sometimes observed. This could be minimized by removal of the left end homology from the helper; by this means, preparations of luciferase transducing virus were obtained free from replication-competent virus. With such preparations, we observed luciferase expression (declining after 3 days) for up to 7 days in recipient HeLa cells. Hybridization of the recombinant viral DNA with strand-specific luciferase probes indicated packaging of both strands (as reported for LuIII), but with a several-fold excess of the (-) strand. We suggest that transducing-autonomous parvoviruses will be useful in gene transfer applications, possibly including gene therapy when only transient expression is desired.

Blotting, Southern↗

PubMed1997

Evaluation of PCR and ELISA assays for screening clinical trial subjects for replication-competent retrovirus.

Gene delivery via murine-based recombinant retroviral vectors is currently widely used in gene therapy clinical trials. The vectors are engineered to be replication defective by replacing the structural and nonstructural genes of a cloned infectious retrovirus with a therapeutic gene of interest. The retroviral particles are currently generated in packaging cell lines, which supply all retroviral proteins in trans. Recombination between short homologous regions of the retroviral vector and packaging cell line elements can theoretically generate replication-competent retrovirus (RCR) and hence the Food and Drug Administration (FDA) requires the monitoring of clinical trial subjects for the presence of RCR. Sensitive polymerase chain reaction (PCR) assays have been used for the detection of murine leukemia virus (MLV) nucleotide sequences in peripheral blood mononuclear cells (PBMCs). A novel serological enzyme-linked immunosorbent assay (ELISA) for the detection of anti-MLV specific immunoglobulin (Ig) has been developed to be used as an alternative to the PCR assay. Both assays were used to monitor human immunodeficiency virus (HIV)-positive clinical trial subjects who had received multiple injections of HIV-IT (V), a retroviral vector encoding HIV-1 IIIBenv/rev. Western blot analysis and an in vitro vector neutralization assay were used to characterize further a subset of serum samples tested by ELISA. Results show no evidence of RCR infection in clinical trial subjects. PCR and ELISA assays are discussed in terms of their advantages and limitations as routine screening assays for RCR. The PCR assay is our current choice for monitoring clinical trial subjects receiving direct administration of vector, and the ELISA is our choice for those receiving ex vivo treatment regimens.

Antibodies, Viral↗

PubMed2000

Inhibition of human immunodeficiency virus type 1 by packageable, multigenic antisense RNA.

Viral-based vectors can provide an efficient delivery mechanism for stable expression of antisense RNA. To enhance and propagate the antiviral effect of antisense RNA, two novel human immunodeficiency virus type 1 (HIV-1)-based vector DNAs, designated as pMAG7 and pMAG19, were constructed which contained HIV-1 cis-acting packaging elements and produced multigenic HIV-1 antisense RNA that could target the entire pol, env, vif, vpu, vpr, rev, and tat and portions of gag and nef. The two DNAs were identical except that pMAG19 had additional gag coding sequences. Cotransfection of pMAG DNA and infectious, cloned HIV-1 DNA in 293 cells inhibited virus production (81%-98% reduction in reverse transcriptase activity) of various T cell-tropic and macrophage-tropic clade B isolates, such as NL4-3, YU-2, and JR-CSF. In addition, virion-associated pMAG antisense RNA was detected in residual virus particles produced by pNL4-3 in the presence of pMAG7 DNA, and the antisense sequences were stably transferred by infection of 174 x CEM cells. The results suggest that pMAG DNA may confer broad protection against HIV-1 by reducing initial virus burden due to antisense RNA and subsequent virus spread by propagation of antisense sequences along with wild-type virus.

Anti-HIV Agents↗

PubMed2002

The human scavenger receptor class B type I is a novel candidate receptor for the hepatitis C virus.

We discovered that the hepatitis C virus (HCV) envelope glycoprotein E2 binds to human hepatoma cell lines independently of the previously proposed HCV receptor CD81. Comparative binding studies using recombinant E2 from the most prevalent 1a and 1b genotypes revealed that E2 recognition by hepatoma cells is independent from the viral isolate, while E2-CD81 interaction is isolate specific. Binding of soluble E2 to human hepatoma cells was impaired by deletion of the hypervariable region 1 (HVR1), but the wild-type phenotype was recovered by introducing a compensatory mutation reported previously to rescue infectivity of an HVR1-deleted HCV infectious clone. We have identified the receptor responsible for E2 binding to human hepatic cells as the human scavenger receptor class B type I (SR-BI). E2-SR-BI interaction is very selective since neither mouse SR-BI nor the closely related human scavenger receptor CD36, were able to bind E2. Finally, E2 recognition by SR-BI was competed out in an isolate-specific manner both on the hepatoma cell line and on the human SR-BI-transfected cell line by an anti-HVR1 monoclonal antibody.

Animals↗

PubMed1987

Sequence of figwort mosaic virus DNA (caulimovirus group).

The nucleotide sequence of an infectious clone of figwort mosaic virus (FMV) was determined using the dideoxynucleotide chain termination method. The double-stranded DNA genome (7743 base pairs) contained eight open reading frames (ORFs), seven of which corresponded approximately in size and location to the ORFs found in the genome of cauliflower mosaic virus (CaMV) and carnation etched ring virus (CERV). ORFs I and V of FMV demonstrated the highest degrees of nucleotide and amino acid sequence homology with the equivalent coding regions of CaMV and CERV. Regions II, III and IV showed somewhat less homology with the analogous regions of CaMV and CERV, and ORF VI showed homology with the corresponding gene of CaMV and CERV in only a short segment near the middle of the putative gene product. A 16 nucleotide sequence, complementary to the 3' terminus of methionine initiator tRNA (tRNAimet) and presumed to be the primer binding site for initiation of reverse transcription to produce minus strand DNA, was found in the FMV genome near the discontinuity in the minus strand. Sequences near the three interruptions in the plus strand of FMV DNA bear strong resemblance to similarly located sequences of 3 other caulimoviruses and are inferred to be initiation sites for second strand DNA synthesis. Additional conserved sequences in the small and large intergenic regions are pointed out including a highly conserved 35 bp sequence that occurs in the latter region.

Base Sequence↗

PubMed1989

The complete sequence of soybean chlorotic mottle virus DNA and the identification of a novel promoter.

The complete nucleotide sequence of an infectious clone of soybean chlorotic mottle virus (SoyCMV) DNA was determined and compared with those of three other caulimoviruses, cauliflower mosaic virus (CaMV), carnation etched ring virus and figwort mosaic virus. The double-stranded DNA genome of SoyCMV (8,175 bp) contained nine open reading frames (ORFs) and one large intergenic region. The primer binding sites, gene organization and size of ORFs were similar to those of the other caulimoviruses, except for ORF I, which was split into ORF Ia and Ib. The amino acid sequences deduced from each ORF showed only short, highly homologous regions in several of the corresponding ORFs of the three other caulimoviruses. A promoter fragment of 378 bp in SoyCMV ORF III showed a strong expression activity, comparable to that of the CaMV 35S promoter, in tobacco mesophyll protoplasts as determined by a beta-glucuronidase assay using electrotransfection. The fragment contained CAAT and TATA boxes but no transcriptional enhancer signal as reported for the CaMV 35S promoter. Instead, it had sequences homologous to a part of the translational enhancer signal reported for the 5'-leader sequence of tobacco mosaic virus RNA.

Amino Acid Sequence↗

PubMed2003

Pathways for the emergence of multi-dideoxynucleoside-resistant HIV-1 variants.

OBJECTIVE: To investigate the mechanism by which the Q151M mutation in reverse transcriptase (RT) that confers multi-dideoxynucleoside resistance on HIV-1 and that requires a two base change (CAG-->ATG) develops, and to understand the reason for the relatively lengthy period of time required for its emergence under therapy with multiple nucleoside RT inhibitors (NRTI). DESIGN AND METHODS: Propagation assays and competitive HIV-1 replication assays were used to evaluate the fitness of various infectious clones, including two putative intermediates (HIV-1(Q151K(AAG)) and HIV-(1Q151L(CTG))) for HIV-1(Q151M(ATG)), in terms of sensitivity to zidovudine and didanosine. Steady-state kinetic constants of recombinant RT were also determined. RESULTS: HIV-1(Q151L) replicated relatively poorly while HIV-1(Q151K) failed to replicate. When HIV-1(Q151L) was propagated further, it took three pathways in continuing to replicate: (i) HIV-1(Q151L) changed to HIV-1(Q151M) in eight of 16 experiments; (ii) HIV-1(Q151L) reverted to wild-type HIV-1 (HIV-1(WT)) in four of 16 experiments; and (iii) HIV-1(Q151L) acquired an additional mutation M230I in four of 16 experiments improving HIV-1 fitness. The relative order of replicative fitness without drugs was: HIV-1(Q151M) > HIV-1(WT) > HIV-1(Q151L/M230I) > HIV-1(M230I) >> HIV-1(Q151L) >>> HIV-1(Q151K), HIV-1(Q151K/M230I). HIV-1(Q151M) was less susceptible to drugs, while HIV-1(Q151L/M230I) was as sensitive as HIV-1(WT). Enzymatic assays corroborated that HIV-1(Q151L) is more replication-competent than HIV-1(WT) and HIV-1(Q151K) in the presence of drugs. CONCLUSION: HIV-1(Q151M) probably develops through a poorly replicating HIV-1(Q151L); however, it is also possible that it occurs through two concurrent base changes. The present data should explain the mechanism by which HIV-1(Q151M) emerges after long-term chemotherapy with NRTI.

Anti-HIV Agents↗

PubMed1999

Inhibition of replication of HIV-1 at both early and late stages of the viral life cycle by single-chain antibody against viral integrase.

Retroviruses including HIV-1 integrates a DNA copy of their RNA genome into cellular DNA of the infected cell. This reaction, essential and unique to replication of retroviruses, is mediated by the viral enzyme, integrase (IN). We constructed a recombinant gene encoding a single-chain, antigen-binding peptide (scAb2-19), which interacted with a carboxyl terminal part of HIV-1 IN. HeLa CD4 cells expressing scAb2-19 localized in either cytoplasmic or nuclear compartment were resistant to HIV-1 infection at an multiplicity of infection (MOI) of 0.25 or 0.063, but the resistance was overcome when MOI was increased to 1. To determine whether this resistance was due to inhibition of the early events, transduction experiments were performed with a replication-incompetent HIV-1 vector carrying bacterial lacZ driven by an internal Tat-independent cytomegalovirus immediate early promoter. Both cytoplasmic and nuclear expressions of scAb2-19 resulted in decrease in the transduction efficiency on HeLa CD4 cells. This implies that an early step of replication--before or during integration--was affected by the scAb2-19. Furthermore, cytoplasmic expression of scAb2-19 did not affect the viral amount released from the cells transfected with HIV-1 infectious clone DNA (pLAI). However, infectivity relative to reverse transcriptase activity was lower for virions released from the 293T cells cotransfected with pLAI and the cytoplasmic scAb2-19 expression plasmid than for those released from the 293T cells transfected with pLAI alone. This implies that scAb2-19 reduced infectivity of released virions by interfering a late step of the viral replication. The single-chain, antigen-binding peptide molecule may prove useful not only for studies of the functions of IN and its role in the viral life cycle but also for developing a gene therapy strategy against AIDS.

Amino Acid Sequence↗

PubMed2004

Nosocomial diarrhoea due to Clostridium difficile.

PURPOSE OF REVIEW: The purpose of this review is to summarize recent developments in the diagnosis, epidemiology, treatment and prevention of nosocomial diarrhoea due to Clostridium difficile. RECENT FINDINGS: Twenty-five years after its discovery, the diagnosis of C. difficile-associated diarrhoea is still problematic with laboratories trying to reconcile the time and expense of the diagnostic process. Newer molecular techniques may offer hope. With the introduction of new antibiotics into clinical practice, confusion has arisen about the risk they pose for C. difficile-associated diarrhoea. Strains of C. difficile that fail to produce an active toxin A are an emerging problem and good molecular epidemiology is required to determine whether highly infectious clones exist. Little progress has been made in the treatment of recurrent C. difficile-associated diarrhoea; however, the development of a vaccine is imminent. More effort is being made to rid the hospital environment of C. difficile through infection-control procedures or changes in antibiotic-prescribing policies. SUMMARY: C. difficile continues to be a major nosocomial infection in many health-care institutions throughout the world. Strategies that reduce exposure to the organism or to antibiotics will have an impact on rates of C. difficile-associated diarrhoea.

Anti-Bacterial Agents↗