Multivessel percutaneous coronary intervention: a new paradigm for a new century

Percutaneous coronary intervention (PCI) was introduced in 1977, to treat single, discrete lesions in patients with stable symptoms, and favorable anatomy. Increased operator experience and numerous technical advances, notably including bare-metal stents (BMS) and then drug-eluting stents (DES), and a number of adjunctive pharmacologic modalities, have allowed for the gradual application of PCI to far more diverse clinical and anatomic subsets. The proper role of PCI, compared with both medical therapy and coronary artery bypass graft (CABG) surgery, is evolving. This manuscript is synthesized from literature review of randomized clinical trials, and some cohort investigations, and 21 years of PCI experience, which has been focused on high-risk patients. Current American College of Cardiology/ American Heart Association/ Society for Cardiac Angiography and Interven-tions (ACC/AHA/ SCA&I) Guidelines, and most research, are based upon a perspective (conventional paradigm') that categorizes patients primarily based upon number of major' coronary (left anterior descending artery, circumflex and right) arteries with a >70% stenosis, and whether left ventricular function is normal or abnormal (left ventricular ejection fraction < or >0.50). This paradigm developed when: a) CABG was the only revascularization option, and b) medical therapy was quite limited. All of the trials demonstrating survival benefit with aspirin, clopidogrel, statins, angiotensin-converting-enzyme inhibition (ACE-I) or angiotensin receptor blockers (ARB), and beta-blockers; coupled with the PCI versus thrombolytics trials in ST-elevation myocardial infarction (STEMI), and non-STEMI strategy trials, both of which include revascularization almost exclusively by PCI, make this conventional paradigm, outdated and counterproductive. Attempts to compare CABG and PCI have de-emphasized their very different advantages and disadvantages. The new paradigm makes major division of patients based upon whether patients have stable or unstable: a) ischemia and b) hemodynamics, and c) whether they are having acute myocardial infarction (MI). The first issue to be settled is whether the patient is likely to benefit from revascularization. If little or no benefit can be envisioned, the patient should be managed medically. Unstable ischemia and unstable hemodynamics, and acute MI, all favor emergent or urgent revascularization. Clinical features, which generally favor PCI for revascularization, include hemodynamic instability, STEMI and non-STEMI; and severe comorbidity, particularly cerebral, pulmonary, or hepatic comorbidity. Anatomic features, which generally favor CABG, include unprotected left main stenosis, especially involving the bifurcation, one or more graftable chronic total occlusions (CTO), and bifurcation disease with large important side-branches. Old age and severely reduced left ventricular function are associated with higher risks, with either CABG or PCI. Small caliber and diffusely diseased vessels may imply lower expectation of success, by either CABG or PCI.

Characterization of an atypical antigen fromSarcoptes scabieicontaining an MADF domain

We have cloned a cDNA encoding a novel antigen from aSarcoptes scabiei(Acari) cDNA library by immunoscreening with sera fromS. scabiei-infected dogs. The antigen is encoded by a 2157 bp mRNA with a predicted open reading frame of 719 amino acids (molecular weight 79 kDa). Our sequence analysis identified the presence of a MADF domain in the N-terminus, and downstream of this domain there was a region of low sequence complexity. This latter region contained several blocks of triplets and quadruplets of polar amino acids (Asn, Gln and Ser), and these 3 amino acids represented 39·7% of all amino acids. The antigen was named Atypical Sarcoptes Antigen 1 (ASA1) since the MADF domain normally is found in proteins involved in transcriptional regulation. In addition, 15 out of 62S. scabiei-infected dogs reacted with a purified recombinant version of ASA1 in Western blot analysis. With immunohistochemistry we could show that ASA1 is expressed throughout the parasite, and that IgG specific for ASA1 binds to the inside wall of the mite's burrow. To our knowledge, this is the first description of an antigen containing an MADF domain.

What is the evidence for percutaneous coronary intervention or coronary artery bypass graft in ischemic cardiomyopathy?

Coronary artery disease has supplanted hypertension as the leading cause of congestive heart failure in the United States. The recognition that contraction abnormalities could accrue from gradual stunning, or longer-term 'hibernation,' raised the possibility that revascularization of viable but hypocontractile elements could improve myocardial performance. This review focuses on the data from randomized trials and registries regarding the potential benefits and risks of either coronary artery bypass grafting (CABG) or percutaneous coronary intervention for patients with severe left ventricular dysfunction secondary to coronary artery disease. For patients with medically refractory angina and ischemic cardiomyopathy, revascularization with CABG or percutaneous coronary intervention is recommended. The ongoing National Institutes of Health-sponsored Surgical Treatment for Ischemic Heart Failure (STICH) trial, a multicenter, prospective, randomized trial comparing contemporary medical therapy with CABG for patients with ischemic cardiomyopathy, should provide important information regarding patients who do not have angina. The conclusion of this review is that a trial of medical therapy vs. percutaneous coronary intervention could be of additional value, especially for patients at particularly high risk, when undergoing CABG.

Testing the hypothesis of recent population expansions in nematode parasites of human-associated hosts

It has been predicted that parasites of human-associated organisms (eg humans, domestic pets, farm animals, agricultural and silvicultural plants) are more likely to show rapid recent population expansions than are parasites of other hosts. Here, we directly test the generality of this demographic prediction for species of parasitic nematodes that currently have mitochondrial sequence data available in the literature or the public-access genetic databases. Of the 23 host/parasite combinations analysed, there are seven human-associated parasite species with expanding populations and three without, and there are three non-human-associated parasite species with expanding populations and 10 without. This statistically significant pattern confirms the prediction. However, it is likely that the situation is more complicated than the simple hypothesis test suggests, and those species that do not fit the predicted general pattern provide interesting insights into other evolutionary processes that influence the historical population genetics of host-parasite relationships. These processes include the effects of postglacial migrations, evolutionary relationships and possibly life-history characteristics. Furthermore, the analysis highlights the limitations of this form of bioinformatic data-mining, in comparison to controlled experimental hypothesis tests.

How old are the extant lineages of Toxoplasma gondii?

Most known isolates of Toxoplasma gondii belong to one of only three lineages, which are presumed to be clonal. Three models have been proposed for the evolutionary relationship of these lineages to the other extant lineages: Model (a) proposing that all lineages are derived from a most recent common ancestor (MRCA) in the distant past, Model (b) that all lineages are derived from a MRCA in the very recent past, and Model (c) that the clonal lineages share a recent MRCA but are related to the other lineages only in the distant past. Here, I test these models using DNA intron and coding-sequence data for loci at 14 genes, using three different methods to calculate the time of the MRCA. All of the calculations agree that the MRCA of the clonal lineages was > 70% of the age of the MRCA of all lineages, thus favouring Model (a). The MRCA may have existed approximately 150,000 years ago, with the clonal lineages expanding in prevalence approximately 10,000 years ago.

Impact of stents and abciximab on survival from cardiogenic shock treated with percutaneous coronary intervention

This retrospective observational review compares patient characteristics and in-hospital and long-term outcomes of cohorts of patients undergoing percutaneous coronary intervention (PCI) for cardiogenic shock complicating acute myocardial infarction (MI) prior to the use of stents (as well as glycoprotein IIb/IIIa inhibitor and dual-antiplatelet therapy) with PCI in the stent era. Cardiogenic shock remains the leading cause of hospital mortality from acute MI. This is a report of consecutive patients with cardiogenic shock complicating acute MI, without mechanical complication, referred for emergency catheterization to a single operator at two consecutive Veterans Affairs medical centers over a 15-year period (1988 to August 2003). PCI was attempted in all 93 cases: 44 consecutive patients in the present era and 49 consecutive patients in the stent era. Patients with comparable extent of coronary disease, more ST elevation myocardial infarction, multiple areas of infarction, and greater comorbidity underwent PCI in the stent era. Nevertheless, PCI in the stent era was associated with higher rates of acute success and improved in-hospital survival. Kaplan-Meier curves and log-rank testing showed highly significant improvement in overall survival (P < 0.0001). Logistic regression of in-hospital survival demonstrated that stent use (colinear with glycoprotein IIb/IIIa use and dual-antiplatelet therapy) was significantly associated with survival in a model adjusting for extent of coronary disease and comorbidities (P = 0.007). Stents and abciximab have been associated with improved acute angiographic and procedural success of PCI for cardiogenic shock, leading to improved survival.

Outcome of percutaneous coronary intervention versus coronary bypass grafting for patients with low left ventricular ejection fractions, unstable angina pectoris, and risk factors for adverse outcomes with bypass (the AWESOME Randomized Trial and Registry)

The recently concluded Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) was a randomized clinical trial of percutaneous coronary intervention versus coronary bypass graft surgery among patients with medically refractory ischemia who were at high risk for coronary bypass graft surgery because of > or =1 risk factors that included severely reduced left ventricular (LV) function, defined as LV ejection fraction <35%. This study reports the outcome of patients with LV ejection fraction <35% in the randomized clinical trial and the physician-directed and patient choice registries of the AWESOME study.

Genetic diversity assessed by amplified fragment length polymorphism analysis of the parasitic nematode Dictyocaulus viviparus the lungworm of cattle

We have examined the population genetic structure in a collection of nine isolates of the parasitic lungworm Dictyocaulus viviparus. Eight of the isolates were sampled from cattle in geographically separated farms throughout south-central Sweden, and one isolate was a laboratory strain that has been maintained in experimentally infected calves for almost four decades. A total of 72 worms were examined, with eight individual worms from the same individual host representing each isolate. The genetic variation as revealed by amplified fragment length polymorphism analysis using four selective primer combinations was high. Depending on the primer combination a total of 66-79 restriction fragments were amplified, with 26-44 peaks of similar complexity from each of the isolates. The heterozygosity within populations was relatively small, as were the population mutation and immigration rates, which seemed to be in neutral equilibrium. The genetic diversity was therefore reasonably well structured in the field; and the laboratory isolate was quite distinct from the field samples. There was no relationship between the patterns of genetic diversity and the geographical proximity of the farms. The estimates of heterozygosity were much larger and more consistent than those previously estimated for this nematode species using mitochondrial sequencing, and the genetic structuring was thus much less pronounced and the gene flow greater. We attribute these differences in estimation to the broader sampling of loci available using amplified fragment length polymorphism markers, which may therefore constitute a superior technique for the study of patterns of lungworm diversity. Furthermore, the data estimating gene flow for D. viviparus was less than previously reported for closely related species in North America. This might be related to different rates of movements of infected hosts. It seems likely that lungworm infections are rather persistent on different farms, and the sudden outbreaks of disease that can be observed with host movements are most likely to be related to the introduction of susceptible stock.

Balancing benefit against risk in the choice of therapy for coronary artery disease. Lesson from prospective, randomized, clinical trials of percutaneous coronary intervention and coronary artery bypass graft surgery

The ageing world population faces a coming pandemic of high-risk coronary artery disease (CAD). Patients with CAD have 3 therapeutic options, which are based on objective clinical outcome: medical therapy and risk factor modification (Medicine), and 2 forms of revascularization, coronary artery bypass graft surgery (CABG), and percutaneous coronary intervention (PCI). More than 50 large (>100 patients), multicenter, prospective, randomized clinical trials (RCT) have compared these treatment options in terms of clinical benefits and patient risks. The randomized trials which demonstrated hard outcome (survival, myocardial infarction, stroke) benefits from statins, angiotensin-converting enzyme inhibition and thienopyridines have all been completed subsequent to the publication of most Medicine versus revascularization trials. These medical therapies, plus aspirin, beta-blockers, and risk factor modification, should be made available to patients regardless of the decision to revascularize, or the decision by what means (CABG or PCI). This review integrates the information from these trials, comparing the clinical benefits against the risks inherent in the 3 therapeutic options. The results of our review show that: trials of medicine versus revascularization (either CABG or PCI) support the revascularization paradox, in that the patients at highest risk of adverse outcome, from myocardial ischemia, have a hard outcome benefit (survival, MI, or stroke) from revascularization. This paradox, first seen in the Medicine versus CABG trials of the 1970s, is evident in the trials comparing fibrinolysis and other medicines, with primary PCI for ST-elevation myocardial infarction (MI). The paradox is evident in the conservative versus invasive strategy trials of non-ST-elevation MI and unstable angina, where the benefit of revascularization occurs only in high-risk subsets. The paradox often results in sicker patients, who have more to gain from revascularization, being denied it because of the elevated perception of risk (comparable to a reperfusion paradox in ST-elevation MI, where patients most likely to benefit from thrombolytics are denied them because of the perception of risk). Trials that compared medicine with revascularization for the treatment of acute MI support the use of PCI as the preferred early stabilization strategy (90% of all PAMI trial patients). The majority of the PCI versus CABG trials enrolled populations that were at relatively low risk for ischemic clinical events. These trials demonstrated few hard outcome (survival, MI, or stroke) differences between CABG and PCI. On the basis of the results obtained the following conclusions may be drawn: medicines are the primary options for stable, low-risk CAD, and should be given to all CAD patients. Medically refractory is a useful high-risk marker of potential benefit from revascularization. CABG continues to be the complete revascularization option for patients with multivessel, multi-lesion CAD, in part because of its application to chronic occlusions. PCI is the acute stabilization method of choice for patients with on-going ischemia and acute MI, especially among patients with hemodynamic compromise, and/or major comorbidity.

Phylogeny of Dictyocaulus (lungworms) from eight species of ruminants based on analyses of ribosomal RNA data

In this study, we conducted phylogenetic analyses of nematode parasites within the genus Dictyocaulus (superfamily Trichostrongyloidea). Lungworms from cattle (Bos taurus), domestic sheep (Ovis aries), European fallow deer (Dama dama), moose (Alces alces), musk ox (Ovibos moschatus), red deer (Cervus elaphus), reindeer (Rangifer tarandus) and roe deer (Capreolus capreolus) were obtained and their small subunit ribosomal RNA (SSU) and internal transcribed spacer 2 (ITS2) sequences analysed. In the hosts examined we identified D. capreolus, D. eckerti, D. filaria and D. viviparus. However, in fallow deer we detected a taxon with unique SSU and ITS2 sequences. The phylogenetic position of this taxon based on the SSU sequences shows that it is a separate evolutionary lineage from the other recognized species of Dictyocaulus. Furthermore, the analysis of the ITS2 sequence data indicates that it is as genetically distinct as are the named species of Dictyocaulus. Therefore, either this taxon needs to be recognized as a new species, or D. capreolus, D. eckerti and D. viviparus need to be combined into a single species. Traditionally, the genus Dictyocaulus has been placed as a separate family within the superfamily Trichostrongyloidea. The present molecular phylogenetic analyses support the placement as a separate family, but the current data do not support the placement of the Dictyocaulidae within the Trichostrongyloidea without a reassessment of the placement of the superfamily Strongyloidea. While D. eckerti has been regarded as the one and only lungworm species of cervids, this study showed that 4 host species including 3 members of Cervidae (moose, reindeer, red deer) and 1 Bovidae (musk ox) were infected with this parasite. Host ranges of D. viviparus (cattle), D. filaria (sheep) and D. capreolus (moose and roe deer) were more restricted. No clear pattern of co-evolution between the dictyocaulid taxa and their bovid and cervid hosts could be determined.

Characterization of an alpha tubulin gene sequence from Neospora caninum and Hammondia heydorni, and their comparison to homologous genes from Apicomplexa

The gene coding for a tubulin has been isolated by the polymerase chain reaction and sequenced from 2 isolates of Neospora caninum (Nc-Liverpool and Nc-SweB1). The data show that the gene, as in Toxoplasma gondii, is single copy and contains 3 exons and 2 introns and is identical in sequence in the 2 isolates studied. Comparison of the predicted protein sequence shows it to be identical to the a tubulin protein encoded by the T. gondii gene. The majority of the nucleotide substitutions that have occurred during the evolution of the T. gondii and N. caninum genes from their common ancestor have occurred in the third codon position. A partial coding sequence for a tubulin was also obtained from Hammondia heydorni and compared to other a tubulin sequences from Apicomplexa. The results show the sequences of the T. gondii, N. caninum and H. heydorni a tubulin genes to be similar but not identical in sequence, thereby providing new evidence that N. caninum and H. heydorni are genetically distinct species.

Health-related quality of life after percutaneous coronary intervention versus coronary bypass surgery in high-risk patients with medically refractory ischemia

OBJECTIVES

We compared six-month health-related quality of life (HRQL) for high-risk patients with medically refractory ischemia randomized to percutaneous coronary intervention (PCI) versus coronary artery bypass graft (CABG) surgery.

BACKGROUND

Mortality rates after PCI and CABG surgery are similar. Therefore, differences in HRQL outcomes may help in the selection of a revascularization procedure.

METHODS

Patients were enrolled in a Veterans Affairs multicenter randomized trial comparing PCI versus CABG for patients with medically refractory ischemia and one or more risk factors for adverse outcome; 389 of 423 patients (92%) alive six months after randomization completed an Short Form-36 (SF-36) health status survey. Primary outcomes were the Physical Component Summary (PCS) and Mental Component Summary (MCS) scores from the SF-36. Multivariable analyses were used to evaluate whether PCI or CABG surgery was associated with better PCS or MCS scores after adjusting for over 20 baseline variables.

RESULTS

There were no significant differences in either PCS scores (38.7 vs. 37.3 for PCI and CABG, respectively; p = 0.23) or MCS scores (45.5 vs. 46.1, p = 0.58) between the treatment arms. In multivariable models, there remained no difference in HRQL for post-PCI versus post-CABG patients (for PCS, absolute difference = 0.56 +/- standard error of 1.14, p = 0.63; for MCS, absolute difference = -1.23 +/- 1.12, p = 0.27). We had 97% power to detect a four-point difference in scores, where four to seven points is a clinically important difference.

CONCLUSIONS

High-risk patients with medically refractory ischemia randomized to PCI versus CABG surgery have equivalent six-month HRQL. Therefore, HRQL concerns should not drive decision-making regarding selection of a revascularization procedure for these patients.

Percutaneous coronary intervention versus repeat bypass surgery for patients with medically refractory myocardial ischemia: AWESOME randomized trial and registry experience with post-CABG patients

OBJECTIVES

This report compares long-term percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) survival among post-CABG patients included in the Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) randomized trial and prospective registry.

BACKGROUND

Repeat CABG surgery is associated with a higher risk of mortality than first-time CABG. The AWESOME is the first randomized trial comparing CABG with PCI to include post-CABG patients.

METHODS

Over a five-year period (1995 to 2000), patients at 16 hospitals were screened to identify a cohort of 2,431 individuals who had medically refractory myocardial ischemia and at least one of five high-risk factors. There were 454 patients in the randomized trial, of whom 142 had prior CABG. In the physician-directed registry of 1,650 patients, 719 had prior CABG. Of the 327 patient-choice registry patients, 119 had at least one prior CABG. The CABG and PCI survivals for the three groups were compared using Kaplan-Meier curves and log-rank tests.

RESULTS

The CABG and PCI three-year survival rates were 73% and 76% respectively for the 142 randomized patients (75 and 67 patients) (log-rank = NS). In the physician-directed registry, 155 patients were assigned to reoperation and 357 to PCI (207 received medical therapy); 36-month survivals were 71% and 77% respectively (log-rank = NS). In the patient-choice registry, 32 patients chose reoperation and 74 chose PCI (13 received medical therapy); 36-month survivals were 65% and 86% respectively (log-rank test p = 0.01).

CONCLUSIONS

Percutaneous coronary intervention is preferable to CABG for many post-CABG patients.

Percutaneous coronary intervention versus coronary bypass graft surgery for diabetic patients with unstable angina and risk factors for adverse outcomes with bypass: outcome of diabetic patients in the AWESOME randomized trial and registry

OBJECTIVES

This study compared survival after percutaneous coronary intervention (PCI) with survival after coronary artery bypass graft surgery (CABG) among diabetics in the Veterans Affairs AWESOME (Angina With Extremely Serious Operative Mortality Evaluation) study randomized trial and registry of high-risk patients.

BACKGROUND

Previous studies indicate that CABG may be superior to PCI for diabetics, but no comparisons have been made for diabetics at high risk for surgery.

METHODS

Over five years (1995 to 2000), 2,431 patients with medically refractory myocardial ischemia and at least one of five risk factors (prior CABG, myocardial infarction within seven days, left ventricular ejection fraction <0.35, age >70 years, or an intra-aortic balloon being required to stabilize) were identified. A total of 781 were acceptable for CABG and PCI, and 454 consented to be randomized. The 1,650 patients not acceptable for both CABG and PCI constitute the physician-directed registry, and the 327 who were acceptable but refused to be randomized constitute the patient-choice registry. Diabetes prevalence was 32% (144) among randomized patients, 27% (89) in the patient-choice registry, and 32% (525) in the physician-directed registry. The CABG and PCI survival rates were compared using Kaplan-Meier curves and log-rank tests.

RESULTS

The respective CABG and PCI 36-month survival rates for diabetic patients were 72% and 81% for randomized patients, 85% and 89% for patient-choice registry patients, and 73% and 71% for the physician-directed registry patients. None of the differences was statistically significant.

CONCLUSIONS

We conclude that PCI is a relatively safe alternative to CABG for diabetic patients with medically refractory unstable angina who are at high risk for CABG.

Percutaneous coronary intervention versus coronary bypass graft surgery for patients with medically refractory myocardial ischemia and risk factors for adverse outcomes with bypass: The VA AWESOME multicenter registry: comparison with the randomized clinical trial

OBJECTIVES

This study was designed to compare the three-year survival after percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery (CABG) in physician-directed and patient-choice registries with the Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) randomized trial results.

BACKGROUND

The AWESOME multicenter randomized trial and registry compared the long-term survival after PCI and CABG for the treatment of patients with medically refractory myocardial ischemia and at least one additional risk factor for adverse outcome with CABG. The randomized trial demonstrated comparable three-year survival.

METHODS

Over a five-year period (1995 to 2000), 2,431 patients with medically refractory myocardial ischemia and at least one of five risk factors (prior heart surgery, myocardial infarction within seven days, left ventricular ejection fraction <0.35, age >70 years, intra-aortic balloon required to stabilize) were identified. By physician consensus, 1,650 patients formed a physician-directed registry assigned to CABG (692), PCI (651) or further medical therapy (307), and 781 were angiographically eligible for random allocation; 454 of these patients constitute the randomized trial, and the remaining 327 constitute a patient choice registry. Survival for CABG and PCI was compared using Kaplan-Meier curves and log-rank tests.

RESULTS

The CABG and PCI 36-month survival rates for randomized patients were 79% and 80%, respectively. The CABG and PCI 36-month survival rates were both 76% for the physician-directed subgroup; comparable survival rates for the patient-choice subgroup were 80% and 89%, respectively. None of the global log-rank tests for survival demonstrated significant differences.

CONCLUSIONS

Both registries support the randomized trial conclusion: PCI is an alternative to CABG for some medically refractory high-risk patients.

An rpsL cassette, janus, for gene replacement through negative selection in Streptococcus pneumoniae

Natural genetic transformation offers a direct route by which synthetic gene constructs can be placed into the single circular chromosome of Streptococcus pneumoniae. However, the lack of a general negative-selection marker has hampered the introduction of constructs that do not confer a selectable phenotype. A 1.3-kb cassette was constructed comprising a kanamycin (Kn) resistance marker (kan) and a counterselectable rpsL(+) marker. The cassette conferred dominant streptomycin (Sm) sensitivity in an Sm-resistant background in S. pneumoniae. It was demonstrated that it could be used in a two-step transformation procedure to place DNA of arbitrary sequence at a chosen target site. The first transformation into an Sm-resistant strain used the cassette to tag a target gene on the chromosome by homologous recombination while conferring Kn resistance but Sm sensitivity on the recombinant. Replacement of the cassette by an arbitrary segment of DNA during a second transformation restored Sm resistance (and Kn sensitivity), allowing construction of silent mutations and deletions or other gene replacements which lack a selectable phenotype. It was also shown that gene conversion occurred between the two rpsL alleles in a process that depended on recA and that was susceptible to correction by mismatch repair.

A functional genomic analysis of type 3 Streptococcus pneumoniae virulence

Streptococcus pneumoniae remains a serious cause of morbidity and mortality in humans, but relatively little is known about the molecular basis of its pathogenesis. We used signature-tagged mutagenesis together with an analysis of S. pneumoniae genome sequence to identify and characterize genes required for pathogenesis. A library of signature-tagged mutants was created by insertion-duplication mutagenesis, and 1786 strains were analysed for their inability to survive and replicate in murine models of pneumonia and bacteraemia. One hundred and eighty-six mutant strains were identified as attenuated, and 56 were selected for further genetic characterization based on their ability to excise the integrated plasmid spontaneously. The genomic DNA inserts of the plasmids were cloned in Escherichia coli and sequenced. These sequences were subjected to database searches, including the S. pneumoniae genome sequence, which allowed us to examine the chromosomal regions flanking these genes. Most of the insertions were in probable operons, but no pathogenicity islands were found. Forty-two novel virulence loci were identified. Five strains mutated in genes involved in gene regulation, cation transport or stress tolerance were shown to be highly attenuated when tested individually in a murine respiratory tract infection model. Additional experiments also suggest that induction of competence for genetic transformation has a role in virulence.

Complete genome sequence of a virulent isolate of Streptococcus pneumoniae

The 2,160,837-base pair genome sequence of an isolate of Streptococcus pneumoniae, a Gram-positive pathogen that causes pneumonia, bacteremia, meningitis, and otitis media, contains 2236 predicted coding regions; of these, 1440 (64%) were assigned a biological role. Approximately 5% of the genome is composed of insertion sequences that may contribute to genome rearrangements through uptake of foreign DNA. Extracellular enzyme systems for the metabolism of polysaccharides and hexosamines provide a substantial source of carbon and nitrogen for S. pneumoniae and also damage host tissues and facilitate colonization. A motif identified within the signal peptide of proteins is potentially involved in targeting these proteins to the cell surface of low-guanine/cytosine (GC) Gram-positive species. Several surface-exposed proteins that may serve as potential vaccine candidates were identified. Comparative genome hybridization with DNA arrays revealed strain differences in S. pneumoniae that could contribute to differences in virulence and antigenicity.