Similar collagen distribution in full-thickness skin grafts in intraperitoneal and onlay positions, an experimental mice-study.

PURPOSE: Autologous full-thickness skin grafting (FTSG) has the potential to become an option in abdominal wall repair. An understanding of tissue remodelling in the extracellular matrix (ECM) is crucial as this interplay determines such parameters as tissue strength and flexibility. This cross-sectional preclinical laboratory study in mice provides information on the distribution of collagen types and matrix metalloproteinases (MMPs) in the ECM of FTSGs in the intraperitoneal and onlay positions compared with internal controls. The aim was to evaluate morphologic changes after tissue remodelling and repair in FTSGs applied in the two positions and to detect any adverse host response. METHODS: ECM components were evaluated as follows: qualitative examination of collagen bundle thickness using Picrosirius Red staining (collagen types I, III and IV); and evaluation of collagen types IV and V, as well as MMPs 1, 8 and 9 using immunohistochemical staining. Full-thickness grafts transplanted between female twin mice were examined as this best mimics autologous transplantation. RESULTS: At 8 weeks, FTSGs in the intraperitoneal position did not show any noticeable differences in morphologic appearance to those in the onlay position. Both intraperitoneal and onlay FTSGs showed increases in the amount of thick collagen bundles compared to internal controls. No correlation was seen between distribution of MMPs 1, 8 or 9 and distribution of collagen types I, III, IV or V. CONCLUSION: This preclinical study shows that FTSGs in both intraperitoneal and onlay positions are possible application site options and, by extension, promising application site options for abdominal wall reinforcement in hernia surgery. Clinical studies in humans are required to confirm these findings.

Results at 3-year follow-up of totally extraperitoneal (TEP) hernia surgery with long-term resorbable mesh.

INTRODUCTION: Synthetic non-resorbable mesh is almost standard in hernia surgery. However, several studies have showed negative effects of permanent implants such as chronic inflammation and complications involving different organs bordering the mesh. Such complications can raise the risk of chronic post-operative pain (CPP). Recently promising results regarding CPP have been published in patients with Lateral Inguinal Hernia (LIH) using a slowly resorbable mesh in Lichtenstein technique. For this reason the aim of the present study was to find the effect of a slowly resorbable implant on the long-term rate of hernia recurrence and chronic post-operative pain in patients with LIH repaired with TEP procedure. METHODS: Prospective pilot study of TEP repair using TIGR® Matrix Surgical Mesh in 35 primary LIH. At 3-year follow-up the Visual Analogue Scale (VAS) and the Inguinal Pain Questionnaire were employed to assess pain. Recurrence was determined by ultrasound and clinical examination. RESULTS: All patients completed the pain questionnaires but one patient did not attend the planned clinical examination for the 3-year follow-up. No patients had CPP, as defined in the World Guidelines for Groin Hernia Management. Almost all patients had lower VAS score in any activity 3 years following surgery in comparison to the preoperative period. Three patients (8.8%) suffered symptomatic recurrence during the 3-year follow-up. CONCLUSION: TEP repair in patients with LIH using a synthetic long-term resorbable mesh was found to be encouraging respecting chronic post-operative pain at 3-year follow-up but at the cost of an increased risk of recurrence.

Giant ventral hernia-relationship between abdominal wall muscle strength and hernia area.

BACKGROUND: Symptoms arising from giant ventral hernia have been considered to be related to weakening of the abdominal muscles. The aim of this study was to investigate the relationship between the area of the abdominal wall defect and abdominal wall muscle strength measured by the validated BioDex system together with a back/abdominal unit. METHODS: Fifty-two patients with giant ventral hernia (>10 cm wide) underwent CT scan, clinical measurement of hernia size and BioDex measurement of muscle strength prior to surgery. The areas of the hernia derived from CT scan and from clinical measurement were compared with BioDex forces in the modalities extension, flexion and isometric contraction. The Spearman rank test was used to calculate correlations between area, BMI, gender, age, and muscle strength. RESULT: The hernia area calculated from clinical measurements correlated to abdominal muscle strength measured with the Biodex for all modalities (p-values 0.015-0.036), whereas no correlation was seen with the area calculated by CT scan. No relationship was seen between BMI, gender, age and the area of the hernia. DISCUSSION: The inverse correlation between BioDex abdominal muscle strength and clinically assessed hernia area, seen in all modalities, was so robust that it seems safe to conclude that the area of the hernia is an important determinant of the degree of loss of abdominal muscle strength. Results using hernia area calculated from the CT scan showed no such correlation and this would seem to concur with the results from a previous study by our group on patients with abdominal rectus diastasis. In that study, defect size assessed clinically, but not that measured by CT scan, was in agreement with the size of the diastasis measured intra-operatively. The point at which the area of a hernia begins to correlate with loss of abdominal wall muscle strength remains unknown since this study only included giant ventral hernias.

Effect of a DACC dressing on the growth properties and proliferation rate of cultured fibroblasts.

OBJECTIVE: To study the morphology and proliferation of cultured fibroblasts in combination with an experimental wound-healing model using cultured fibroblasts, with and without the presence of a hydrophobic, dialkyl carbamoyl chloride (DACC) dressing (Sorbact; Abigo Medical AB). METHOD: Human dermal fibroblasts were cultured and cell morphology and viability were investigated. Proliferation was investigated using an XTT assay. An experimental wound-healing model was employed, whereby mechanical damage was inflicted to the surface of cultured fibroblasts. The healing and closure of the wound was then monitored with and without the presence of the DACC dressing. RESULTS: Fibroblasts did not adhere easily to the dressing material. The presence of the DACC dressing increased the average proliferation rate of cultured fibroblasts by 50% compared with the untreated control medium (p<0.05). The DACC dressing significantly increased the healing rate by more than 100% after 72 hours (p<0.05) in the experimental model of wound healing, compared with the medium only. CONCLUSION: The enhanced wound healing observed in different types of wounds using the DACC dressing might be explained by an increase in cell growth and proliferation rate of cells in the wound area.

Local and systemic expressions of MMP-9, TIMP-1 and PAI-1 in patients undergoing surgery for clinically suspected appendicitis.

BACKGROUND/AIMS: To examine, compare and correlate the expressions of matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1) and plasminogen activator inhibitor type 1 (PAI-1) in appendiceal tissue and pre- and postoperative blood samples in patients undergoing surgery for clinically suspected appendicitis. METHODS: Fifty-seven patients with complete tissue and blood samples were included and divided into groups of noninflamed appendix/lymphadenitis (n = 7), phlegmonous appendicitis (n = 30), gangrenous appendicitis (n = 11) and perforated appendicitis (n = 9). The protein expressions were assessed with ELISAs. The local expressions of MMP-9, TIMP-1 and PAI-1 were correlated with the systemic expressions at the time of surgery while the systemic individual differences between surgery and recovery were compared. RESULTS: There was a positive correlation between tissue and plasma PAI-1 (p < 0.05). The individual differences for plasma MMP-9 and PAI-1 were statistically nonsignificant, while they were higher for TIMP-1 in patients with perforated appendicitis compared with phlegmonous (p < 0.0001) and gangrenous appendicitis (p < 0.01). CONCLUSIONS: Plasma PAI-1 reflected the levels in appendiceal tissue at the time of surgery. Systemic TIMP-1 could have the potential of distinguishing perforated from nonperforated appendicitis.

High-dose therapy with hematopoietic stem cell rescue in patients with poor prognosis Ewing family tumors.

The purpose of the study was to evaluate the feasibility and safety of two cycles of high-dose chemotherapy (HDT) followed by autologous hematopoietic SCT (HSCT) in patients with poor prognosis Ewing family of tumors (EFT). Twenty patients with primary metastatic bulky disease or recurrent EFT were enrolled to a treatment protocol with two cycles of HDT and HSCT. Patients tolerated well the first (n=20) and second (n=13) cycles, with limited and predictable toxicities. Only one (5%) TRM occurred during the second cycle. Myeloid engraftment occurred at the median of 11 days after both cycles. At 3 years, the overall and EFS were 45% (confidence interval; CI 0.22, 0.69) and 47% (CI 0.25, 0.70), respectively, for the entire group and 58% (CI 0.30, 0.86) for patients who completed two cycles. Dose intensification with two cycles of HDT and HSCT is feasible and safe, with low and acceptable treatment-related morbidity and mortality. Adding a second course of therapy does not impair engraftment. However, only 65% of the patients were able to proceed to the second cycle. Further studies are required to define the optimal mode of delivery of HDT and HSCT in treatment of advanced EFT.

Heating of carbon dioxide during insufflation alters the peritoneal fibrinolytic response to laparoscopic surgery : A clinical trial.

BACKGROUND: Laparoscopic surgery is evolving rapidly. It involves the creation of a pneumoperitoneum, mostly using carbon dioxide. Cooling of the peritoneum, due to insufflation, might traumatize the peritoneum and disturb peritoneal fibrinolysis, important in peritoneal healing processes. The current study was performed to elucidate the effects of the temperature of insufflation gas on the peritoneal fibrinolytic response to laparoscopic surgery. METHODS: Thirty patients scheduled for laparoscopic cholecystectomy were randomized in two groups: one group in which the pneumoperitoneum was created with carbon dioxide at room temperature, and one wherein carbon dioxide at body temperature was used. Peritoneal biopsies were taken at the start and at the end of surgery. Tissue concentrations of tPA antigen, tPA activity, uPA antigen, and PAI-1 antigen were measured using ELISA techniques. RESULTS: Peritoneal PAI-1 antigen levels were significantly higher at the end of the procedure in patients operated with carbon dioxide at room temperature (p < .05). A slight, but not significant, decrease in tPA antigen and activity was observed in both groups during the procedure. Peritoneal concentrations of uPa antigen did not change during the procedure. CONCLUSIONS: The temperature of carbon dioxide used for insufflation of the abdominal cavity affects peritoneal biology. Cooling of the peritoneum by unheated carbon dioxide causes increased peritoneal PAI-1 levels, important in peritoneal healing processes.

Effect of acidosis on expression of mesothelial cell plasminogen activator inhibitor type-1.

BACKGROUND: Abdominal mesothelial cells are exposed to carbon dioxide during laparoscopy. Previous data indicate that carbon dioxide increases release and expression of plasminogen activator inhibitor type-1 (PAI-1) and induces acidification. METHODS: To assess the impact resulting from a range of pH, human mesothelial cells were exposed to culturing media balanced to pH levels of 6.0 to 8.0 for 90 min. Samples from cell media were withdrawn at several time points. Concentrations of PAI-1 and PAI-1 activity were measured using enzyme-linked immunoassay techniques. To focus on the effect of clinically relevant pH, cells were subjected to pH 6.4 and 7.4. Samples were withdrawn for PAI-1 assessments and for PAI-1 mRNA analyses. RESULTS: During exposure to various levels of pH, PAI-1 secretion and activity were variable. However, 5 h after exposure, greater concentration and activity of PAI-1 were observed in acidified cultures. More PAI-1 mRNA was isolated after exposure of cells to a pH of 6.4, apparently indicating transcriptional regulation. CONCLUSIONS: Mesothelial cells seem to respond to acidification by an increased release and production of PAI-1 in vitro.

Maintenance thalidomide following single cycle autologous peripheral blood stem cell transplant in patients with multiple myeloma.

Although autologous stem cell transplant is an effective therapy for patients with multiple myeloma and extends progression-free survival (PFS) and overall survival (OS), patients show a continued pattern of recurrent disease. Twenty-nine patients were enrolled in a phase II study investigating the tolerability and efficacy of maintenance thalidomide following single autologous peripheral blood stem cell transplant. Six to eight weeks after transplant, patients were started on maintenance thalidomide at 50 mg a day. The dose was gradually escalated to a target dose of 400 mg a day and continued until disease progression or 6 months after achieving complete remission (CR) for a maximum total duration of 18 months. At 6 months, 13 patients (45%) achieved CR or near complete remission (positive immunofixation without any evidence of disease). The estimated 2-year OS was 83% and PFS was 49%. Median tolerated dose of thalidomide was 200 mg a day. In conclusion, thalidomide as maintenance therapy is feasible and may improve outcome after single autologous stem cell transplant.

Cyclosporine and mycophenolate mofetil prophylaxis with fludarabine and melphalan conditioning for unrelated donor transplantation: a prospective study of 22 patients with hematologic malignancies.

In an attempt to decrease toxicity in high-risk patients undergoing unrelated donor hematopoietic stem cell transplantation (URD HSCT), we tested a combination of cyclosporine (CSP) and mycophenolate mofetil (MMF) as graft-versus-host disease (GVHD) prophylaxis with the reduced-intensity conditioning regimen fludarabine/melphalan (Flu/Mel). A total of 22 adult patients with advanced myeloid (n=15) and lymphoid (n=7) malignancies were treated. All patients received Flu 25 mg/m2 for 5 days and Mel 140 mg/m2, with CSP 3 mg/kg daily and MMF 15 mg/kg three times a day. The median age was 49 years (range 18-66). Durable engraftment was seen in all but one patient with myelofibrosis. The 1-year nonrelapse mortality was 32%, 27% from GVHD. The cumulative incidence of acute GVHD grade 2-4 and 3-4 was 63 and 41%, respectively. With a median follow-up of 18 months, the disease-free survival (DFS) and overall survival (OS) are 55 and 59%, respectively. For patients with AML and MDS (n=14), the DFS and OS is 71%. For patients undergoing a second transplant (n=14), the DFS and OS is 57%. In conclusion, this regimen is associated with acceptable toxicity but high rates of GVHD in high-risk patients undergoing URD HSCT. Encouraging disease control for patients with advanced myeloid malignancies was observed.

A long-term follow-up report on allogeneic stem cell transplantation for patients with primary refractory acute myelogenous leukemia: impact of cytogenetic characteristics on transplantation outcome.

The prognosis of patients with primary refractory acute myelogenous leukemia (AML) is poor. Our initial report suggested that some patients could achieve durable remission after allogeneic stem cell transplantation (SCT). Herein, we update our initial experience and report further analysis of this group of patients to determine whether there are pre-SCT prognostic factors predictive of posttransplantation relapse and survival. We reviewed the records of 68 patients who consecutively underwent transplantation at the City of Hope Cancer Center with allogeneic SCT for primary refractory AML between July 1978 and August 2000. Potential factors associated with overall survival and disease-free survival were examined. With a median follow-up of 3 years, the 3-year cumulative probabilities of disease-free survival (DFS), overall survival (OS), and relapse rate for all 68 patients were 31% (95% confidence interval [CI], 20%-42%), 30% (95% CI, 18%-41%), and 51% (95% CI, 38%-65%), respectively. In multivariate analysis, the only variables associated with shortened OS and DFS included the use of an unrelated donor as the stem cell source (relative risk, 2.23 [OS] and 2.05 [DFS]; P =.0005 and.0014, respectively) and unfavorable cytogenetics before SCT (relative risk: 1.68 [OS] and 1.58 [DFS]; P =.0107 and.0038, respectively). Allogeneic SCT can cure approximately one third of patients with primary refractory AML. Cytogenetic characteristics before SCT correlate with transplantation outcome and posttransplantation relapse.

Reduced-intensity allogeneic stem cell transplantation for patients whose prior autologous stem cell transplantation for hematologic malignancy failed.

Autologous hematopoietic stem cell transplantation (autoSCT) is an effective treatment for patients with various hematologic malignancies. Despite the significant improvement in the overall outcome, disease progression after transplantation remains the major cause of treatment failure. With longer follow-up, therapy-related myelodysplasia/acute myelogenous leukemia is becoming an important cause of treatment failure. The prognosis for these 2 groups of patients is very poor. Allogeneic hematopoietic stem cell transplantation (alloSCT) is a potential curative treatment for these patients. However, the outcome with conventional myeloablative alloSCT after failed autoSCT is typically poor because of high transplant-related mortality. In an attempt to reduce the treatment-related toxicity, we studied a reduced-intensity conditioning regimen followed by alloSCT for patients with progressive disease or therapy-related myelodysplasia/acute myelogenous leukemia after autoSCT. This report describes the outcomes of 28 patients with hematologic malignancies who received a reduced-intensity alloSCT after having treatment failure with a conventional autoSCT. Fourteen patients received a hematopoietic stem cell transplant from a related donor and 14 from an unrelated donor. The conditioning regimen consisted of low-dose (2 Gy) total body irradiation with or without fludarabine in 4 patients and the combination of melphalan (140 mg/m(2)) and fludarabine in 24. Cyclosporine and mycophenolate mofetil were used for posttransplantation immunosuppressive therapy, as well as graft-versus-host disease (GVHD) prophylaxis, in all patients. All patients engrafted and had >90% donor chimerism on day 100 after SCT. Currently, 13 patients (46%) are alive and disease free, 7 patients (25%) developed disease progression after alloSCT, and 8 (32%) died of nonrelapse causes. Day 100 mortality and nonrelapse mortality were 25% and 21%, respectively. With a median follow-up of 24 months for surviving patients, the 2-year probabilities of overall survival, event-free survival, and relapse rates were 56.5%, 41%, and 41.9%, respectively. Six patients (21%) developed grade III to IV acute GVHD. Among 21 evaluable patients, 15 (67%) developed chronic GVHD. We conclude that (1) reduced-intensity alloSCT is feasible and has an acceptable toxicity profile in patients who have previously received autoSCT and that (2) although follow-up was short, a durable remission may be achieved in some patients who would otherwise be expected to have a poor outcome.

Antifibrinolytic proCPU is present in the peritoneal cavity during surgery.

The fibrinolytic capacity of the peritoneum plays a pivotal role in peritoneal wound healing. During surgery the balance between fibrin deposition and degradation is tilted towards deposition, leading to the formation of adhesions. In blood, carboxypeptidase U (CPU) stabilizes clots by retarding fibrinolysis. The purpose of this study was to investigate whether the more stable zymogen, proCPU, is also present in the peritoneal cavity and, if so, to examine its origin. Levels of proCPU were measured in plasma and serosal peritoneal fluid collected during surgery. Peritoneal biopsies were stained for proCPU. Two-dimensional gel electrophoresis was performed to study the protein composition of the serosal fluid compared to plasma and Western blotting to identify differences in glycosylation of proCPU, indicating possible different cellular origin. Cultured human mesothelial cells were examined for proCPU production under normal conditions and conditions mimicking surgery. We found comparable and correlating levels of proCPU in serosal fluid and plasma. ProCPU was also found where fibrin covered the injured peritoneal surface. A protein composition very similar in serosal fluid and plasma was shown by two-dimensional gel electrophoresis, and the proCPU pattern did not indicate a different origin. No proCPU production was found in cultured mesothelial cells. This is the first study to report on the presence of proCPU in the peritoneal cavity, which seems to be the result of plasma oozing out during the inflammatory reaction to the surgical trauma. This is likely to be important for the balance between fibrin deposition and degradation and thereby in the formation of postoperative adhesions.

CO2 promotes plasminogen activator inhibitor type 1 expression in human mesothelial cells.

BACKGROUND: Previous observations have indicated that CO2 insufflation increases peritoneal plasminogen activator inhibitor type 1 (PAI-1) expression. METHODS: Primarily cultured human peritoneal mesothelial cells were exposed to either flowing or pressurized CO2 for 90 min. Unexposed cultures served as controls. Samples of cell culture media were taken at 0, 5, and 24 h after exposure to measure media pH, PAI-1, and tissue-type plasminogen activator (t-PA) protein release. Simultaneous samples were taken to measure PAI-1 and t-PA mRNA expression. RESULTS: Mesothelial cells exposed to flowing CO2 released more PAI-1 than those exposed to pressurized CO2 ( p < 0.001) and controls ( p < 0.001). Cells exposed to flowing CO2 had an increased PAI-1 mRNA expression at 5 h. CONCLUSIONS: CO2 increased mesothelial cell PAI-1 expression involving a transcriptional mechanism. These findings might provide a mechanism for adhesion formation and cancer progression following laparoscopic surgery.

Helicobacter pylori: resurrection of the cancer link.

Helicobacter pylori is one of the most common pathogenic bacterial infections, colonizing an estimated half of all humans. In a subset of individuals, the infection leads to serious gastroduodenal disease such as peptic ulcers and gastric adenocarcinoma. The factors contributing to skewing this, in most cases benign, relationship into disease development are largely unknown. However, factors emanating from the bacterium, host and the environment have been shown to affect the risk for disease, although no factor can be singled out to be most important. The known factors are associated with affecting the risk of disease, and are not absolute. Virulence of H. pylori is affected by the existence and regulation of certain genes present in the bacterial population in a stomach. The effects of H. pylori on gastric cancer development have been challenged and the risk associated with infection with virulent (i.e. Cag PAI positive) H. pylori has likely been underestimated.

The role of the gut flora in health and disease, and its modification as therapy.

The gut flora is a vast interior ecosystem whose nature is only beginning to be unravelled, due to the emergence of sophisticated molecular tools. Techniques such as 16S ribosomal RNA analysis, polymerase chain reaction amplification and the use of DNA microarrays now facilitate rapid identification and characterization of species resistant to conventional culture and possibly unknown species. Life-long cross-talk between the host and the gut flora determines whether health is maintained or disease intervenes. An understanding of these bacteria-bacteria and bacteria-host immune and epithelial cell interactions is likely to lead to a greater insight into disease pathogenesis. Studies of single organism-epithelial interactions have revealed the large range of metabolic processes that gut bacteria may influence. In inflammatory bowel diseases, bacteria drive the inflammatory process, and genetic predisposition to disease identified to date, such as the recently described NOD2/CARD15 gene variants, may relate to altered bacterial recognition. Extra-intestinal disorders, such as atopy and arthritis, may also have an altered gut milieu as their basis. Clinical evidence is emerging that the modification of this internal environment, using either antibiotics or probiotic bacteria, is beneficial in preventing and treating disease. This natural and apparently safe approach holds great appeal.

Time course of peritoneal tissue plasminogen activator after experimental colonic surgery: effect of hyaluronan-based antiadhesive agents and bacterial peritonitis.

BACKGROUND: This study assessed the peritoneal fibrinolytic response during the first week after colonic surgery in rats with and without bacterial peritonitis, and possible modulation of the response by two hyaluronan-based antiadhesive agents. METHODS: A colonic anastomosis was constructed in 90 male Wistar rats. Peritonitis was induced in another 108 rats and a colonic anastomosis was constructed after 24 h. Rats in both groups were randomized into an untreated group or one of two groups treated with hyaluronan-based agents. One-third of each group was killed at each of days 1, 3 and 7 after operation, and tissue plasminogen activator (tPA) antigen and activity were measured in peritoneal biopsies. RESULTS: One day after colonic surgery in normal rats, tPA antigen concentration was significantly (P < 0.005) increased, whereas tPA activity levels were normal. By day 3 after operation tPA antigen had returned to baseline values while tPA activity was significantly increased (P < 0.05). One day after inducing peritonitis tPA antigen was significantly increased (P < 0.001), while tPA activity was significantly reduced (P < 0.05). Three and seven days after colonic surgery in rats with peritonitis tPA activity was increased (P < 0.001) while tPA antigen had returned to baseline values. Neither of the hyaluronan-based agents affected peritoneal tPA antigen levels or activity after colonic surgery. CONCLUSION: Both abdominal surgery and infection caused an early increase in peritoneal tPA antigen levels, followed by an increase in tPA activity. Peritonitis severely depressed early tPA activity. Application of hyaluronan-based agents did not affect the peritoneal fibrinolytic response to surgery and/or infection.

Mutation frequency and biological cost of antibiotic resistance in Helicobacter pylori.

Among the several factors that affect the appearance and spread of acquired antibiotic resistance, the mutation frequency and the biological cost of resistance are of special importance. Measurements of the mutation frequency to rifampicin resistance in Helicobacter pylori strains isolated from dyspeptic patients showed that approximately 1/4 of the isolates had higher mutation frequencies than Enterobacteriaceae mismatch-repair defective mutants. This high mutation frequency could explain why resistance is so frequently acquired during antibiotic treatment of H. pylori infections. Inactivation of the mutS gene had no substantial effect on the mutation frequency, suggesting that MutS-dependent mismatch repair is absent in this bacterium. Furthermore, clarithromycin resistance conferred a biological cost, as measured by a decreased competitive ability of the resistant mutants in mice. In clinical isolates this cost could be reduced, indicating that compensation is a clinically relevant phenomenon that could act to stabilize resistant bacteria in a population.

Comparison of genetic divergence and fitness between two subclones of Helicobacter pylori.

Helicobacter pylori has a very plastic genome, reflecting its high rate of recombination and point mutation. This plasticity promotes divergence of the population by the development of subclones and presumably enhances adaptation to host niches. We have investigated the genotypic and phenotypic characteristics of two such subclones isolated from one patient as well as the genetic evolution of these isolates during experimental infection. Whole-genome genotyping of the isolates using DNA microarrays revealed that they were more similar to each other than to a panel of other genotyped strains recovered from different hosts. Nonetheless, they still showed significant differences. For example, one isolate (67:21) contained the entire Cag pathogenicity island (PAI), whereas the other (67:20) had excised the PAI. Phenotypic studies disclosed that both isolates expressed adhesins that recognized human histo-blood group Lewis(b) glycan receptors produced by gastric pit and surface mucus cells. In addition, both isolates were able to colonize, to equivalent density and with similar efficiency, germ-free transgenic mice genetically engineered to synthesize Lewis(b) glycans in their pit cells (12 to 14 mice/isolate). Remarkably, the Cag PAI-negative isolate was unable to colonize conventionally raised Lewis(b) transgenic mice harboring a normal gastric microflora, whereas the Cag PAI-positive isolate colonized 74% of the animals (39 to 40 mice/isolate). The genomic evolution of both isolates during the infection of conventionally raised and germ-free mice was monitored over the course of 3 months. The Cag PAI-positive isolate was also surveyed after a 10 month colonization of conventionally raised transgenic animals (n = 9 mice). Microarray analysis of the Cag PAI and sequence analysis of the cagA, recA, and 16S rRNA genes disclosed no changes in recovered isolates. Together, these results reveal that the H. pylori population infecting one individual can undergo significant divergence, creating stable subclones with substantial genotypic and phenotypic differences.