Sensitization of colorectal and pancreatic cancer cell lines to the prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954) by retroviral transduction and expression of the E. coli nitroreductase gene.

Expression of genes encoding prodrug-activating enzymes can increase the susceptibility of tumor cells to prodrugs, and may ultimately achieve a better therapeutic index than conventional chemotherapy. CB1954 is a weak, monofunctional alkylating agent which can be activated by Escherichia coli nitroreductase to a potent dysfunctional alkylating agent which crosslinks DNA. We have inserted the nitroreductase gene into an LNCX-based retroviral vector, to allow efficient gene transfer and expression in colorectal (LS174T) and pancreatic (SUIT2, BxPC3, and AsPC1) cancer cell lines. A clone of LS174T cells expressing nitroreductase showed > 50-fold increased sensitivity to CB1954, and nitroreductase-expressing clones of pancreatic tumor lines were up to approximately 500-fold (SUIT2) more sensitive than parental cells. Concentrations of CB1954 minimally toxic to nontransduced cells achieved 100% cell death in a 50:50 mix of parental cells with SUIT2 cells expressing nitroreductase; and marked "bystander" cell killing was seen with just 10% of cells expressing nitroreductase. Significant bystander cell killing was dependent on a high cell density. In conjunction with regional delivery of vectors and tumor selectivity of cell entry and/or gene expression, nitroreductase and CB1954 may be an attractive combination for prodrug-activating enzyme gene therapy of colorectal and pancreatic cancer.

A pathophysiologic study of diversion proctitis.

Diversion proctitis occurs with variable frequency after exclusion of the fecal stream. Its importance lies in the inability to differentiate it from other types of proctitis that may result in inappropriate therapy and a reluctance to recommend stoma closure. The effect of fecal diversion (n = 18) and restoration of intestinal continuity (n = 10) on human rectal mucosa in patients without inflammatory intestinal disease has been prospectively evaluated. Fecal diversion was associated with macroscopic inflammation in 55 percent of the patients and histologic inflammation in 72 percent, with a variable incidence of aphthoid ulceration, crypt abscess formation and submucosal nodularity. Restoration of continuity was associated with improvement in histologic features in all patients, but the mucosa returned to normal in only 50 percent of the patients. Onset or resolution of diversion proctitis was not associated with any significant changes in colonic cellular proliferation, glycoprotein synthesis or mucosa-associated or luminal flora. The only diagnostic feature of defunctioned proctitis remains its resolution on reintroducing the fecal stream.

Candidacidal activity of Crohn's disease neutrophils.

The ability of normal and Crohn's disease neutrophils to kill Candida albicans has been studied using neutrophils isolated from peripheral blood and suspended in phosphate buffered saline at 5 x 10(6) cells per ml. C albicans was grown to a stationary phase in broth culture and suspended in phosphate buffered saline at 10(7) organisms/ml. Neutrophils and Candida were then incubated together at 37 degrees C in a shaking water bath in the presence of fresh serum. At 30 and 60 minutes samples were withdrawn, neutrophils lysed, and Candida survival assessed by colony counting. Results were compared with control suspensions of Candida incubated with serum alone. After 30 and 60 minutes in the presence of autologous serum normal neutrophils had killed significantly more Candida than Crohn's disease neutrophils (mean (SD) 61.0 (16.7)% v 40.5 (16.2)% at 30 minutes, p less than 0.0001; 83.2 (7)% v 70.8) 16)% at 60 minutes, p less than 0.005). The results did not alter significantly when normal neutrophils were incubated with Candida in the presence of Crohn's disease serum instead of normal serum. When Crohn's disease neutrophils were incubated with Candida in the presence of normal serum instead of autologous serum there was some improvement in candidacidal ability at 30 minutes (48.9 (20.6)% v 40.5 (16.2)%, p less than 0.03) but not at 60 minutes. Phagocytosis, measured using a radiometric assay, was normal. Neutrophils from patients with Crohn's disease have an impaired ability to kill this granuloma provoking organism. It is not due to serum inhibitors or defective phagocytosis.

A randomised prospective controlled study of ciprofloxacin with metronidazole versus amoxicillin/clavulanic acid with metronidazole in the treatment of intra-abdominal infection.

A prospective randomised study was undertaken in 80 patients to assess the combined regimen of ciprofloxacin with metronidazole against amoxicillin/clavulanic acid with metronidazole as treatment for established intra-abdominal infection. Treatment was for five days. Seventy-eight patients were clinically evaluable (38 patients on ciprofloxacin with metronidazole and 40 patients on amoxicillin/clavulanic acid with metronidazole). The overall clinical success rate in the treatment of intra-abdominal infections was 96% for the ciprofloxacin with metronidazole group, and 90% for the amoxicillin/clavulanic acid with metronidazole group. Over half of all patients were able to change from intravenous to oral antibiotic administration within the study period. One patient receiving ciprofloxacin with metronidazole developed pruritus near the injection site.

The penetration of aztreonam, a monobactam antibiotic, into intra-abdominal abscesses.

We have studied the penetration of aztreonam into pus with a low mortality intra-abdominal abscess model in the Wistar rat. The mean peak serum concentration (standard error) of aztreonam was 74.6 +/- 9.88 mg/l at 30 min falling to 2.31 +/- 1.28 mg/l at 8 h. The mean concentration in pus was 17.04 +/- 2.01 mg/l at 2 h and was 14.47 +/- 2.23 mg/l at 8 h. These concentrations are in excess of the MICs of most Gram-negative aerobic bacilli commonly isolated from intra-abdominal abscesses.

The fecal microflora in pruritus ani.

Pruritus ani is a common condition in which there is a tendency for liquids to leak from the anal canal, resulting in perianal soiling. In order to ascertain if an abnormal fecal flora contributes to the irritant effects of fecal material, qualitative and quantitative measurement of the fecal microflora was performed in 20 patients with pruritus ani and 20 matched controls. No differences were found between the two groups. This study has failed to provide evidence for a microbiologic basis for pruritus ani.

A comparison of the penetration of two quinolones into intra-abdominal abscess.

A low-mortality model of an intra-abdominal abscess in the rat has been used to study the penetration of two quinolone agents into pus. Maximum concentrations in pus after intravenous injections were achieved at four hours (ciprofloxacin: 12.7 +/- 3.69 mg/L, fleroxacin: 2.25 +/- 1.82 mg/L), whereas fleroxacin given orally reached the maximum level at two hours (13.39 +/- 3.13 mg/L). Higher concentrations of fleroxacin were recorded in pus than in serum at each time point up to eight hours after administration, but pus levels of ciprofloxacin only exceeded serum levels after 1.5 hours. These antibiotics appear to have a unique property of high penetration into established abscesses and may have an important therapeutic role in the treatment of patients with multiple interloop abscesses.

The penetration of fleroxacin into intra-abdominal abscesses.

Using a recently developed, low mortality model of an intra-abdominal abscess in the Wistar rat, we have studied the penetration of fleroxacin into the abscess. Maximum serum concentration was 1.83 +/- 0.39 mg l and occurred 1 h after iv injection (20 mg/kg), but even at 4 h after administration the mean serum level was 1.21 +/- 0.27 mg/l. By contrast, levels in pus were 6.27 +/- 0.83 mg/l at 1 h rising steadily to a value of 12.7 +/- 3.69 mg/l at 4 h. The study has confirmed exceptional antibiotic penetration into the abscess, with levels at all time intervals between 0.5 and 8 h after administration in excess of the MIC50 for Escherichia coli, Proteus vulgaris and Clostridium perfringens.

Comparison of short-term antibiotic cover with a third-generation cephalosporin against conventional five-day therapy using metronidazole with an aminoglycoside in emergency and complicated colorectal surgery.

In a prospective, randomized control trial, 152 consecutive patients requiring emergency or complicated colorectal surgery were allocated either to two doses of cefotetan or to five-day cover with gentamicin, and a single dose of metronidazole. Twenty-one patients received 6 gm of cefotetan before prolongation of prothrombin time dictated a change in the dose regimen such that all remaining patients (N = 55) received only 4 gm of cefotetan. The groups were well matched for diagnosis and surgical procedure. Rates of postoperative infection did not differ significantly between the groups, with wound infection rates occurring in 17 of 75 patients receiving gentamicin and metronidazole (22.7 percent) compared with ten of 75 receiving cefotetan (13 percent). Although wound infection rates were lower in the cefotetan group, the incidence of intra-abdominal abscess was similar in both groups. Eight patients receiving cefotetan developed intra-abdominal abscesses (11 percent), compared with seven receiving gentamicin and metronidazole (9 percent). Prolongation of prothrombin time in excess of 13 seconds occurred in six patients receiving cefotetan compared with no patients receiving gentamicin and metronidazole. None of these patients developed clinical bleeding, however.

Oral neomycin and erythromycin compared with single-dose systemic metronidazole and ceftriaxone prophylaxis in elective colorectal surgery.

A prospective randomized trial was performed to compare oral neomycin and erythromycin with single-dose intravenous metronidazole and ceftriaxone in elective colorectal surgery. The study was discontinued after 60 patients were entered. The overall rate of infection was 41 percent in the oral neomycin and erythromycin group (n = 29) compared with 9.6 percent in those who received intravenous metronidazole and ceftriaxone (n = 31) (p less than 0.01). Infections in the oral group were principally due to resistant Staphylococcus aureus, Bacteroides fragilis, and Escherichia coli. Preoperative administration of oral neomycin and erythromycin was associated with a significant reduction of Escherichia coli counts (1 X 10(7) to 3 X 10(5) organisms/ml, p less than 0.05) compared with the intravenous group, but there was no significant reduction in the counts of Bacteroides fragilis (2 X 10(8) to 1 X 10(7) organisms/ml) and there was an increase in the counts of Clostridia (2 X 10(4) to 1 X 10(6) organisms/ml). These results indicate that single-dose systemic prophylaxis with appropriate antibiotics is superior to oral neomycin and erythromycin.

The effect of peritoneal lavage with tetracycline solution on postoperative infection. A prospective, randomized, clinical trial.

A prospective randomized trial was performed to determine the value of tetracycline lavage in addition to systemic antibiotic prophylaxis in 159 patients undergoing elective and emergency intestinal operations. Tetracycline lavage was associated with a significant overall reduction in postoperative infection rates in 25 of 74 patients (34 percent) receiving saline lavage compared with 15 of 85 patients (18 percent) having tetracycline lavage (P less than 0.05). Tetracycline lavage was associated with a significant reduction in the counts of aerobic and anaerobic bacteria in the peritoneal fluid at the end of the operation (P less than 0.05 and P less than 0.01, respectively) and with a significant reduction of aerobes 24 hours postoperatively (P less than 0.02). Tetracycline lavage would appear to confer clinical benefit in preventing postoperative infection.

What is the role of histidine in studies of faecal mutagenicity?

Mutagenicity testing can be used to assay faeces for genotoxic substances and the results are reported to correlate with population risk for colorectal cancer (Ehrich et al., 1979). It has been suggested that histidine in faeces may cause false positive results (Venitt and Bosworth, 1983). To determine the relationship between histidine and false positive mutagenicity assays aliquots of non-mutagenic faecal extract and saline were supplemented with histidine and subjected to the Ames Salmonella/mammalian microsome mutagenicity assay (Ames et al., 1975). Using high-pressure liquid chromatography the analytical recovery of histidine from water and faecal extract supplemented with histidine was equivalent (r = 0.998, p less than 0.001). Histidine was measured in faecal extracts (1 in 10 dilutions) from 35 volunteers, 10 patients with inflammatory bowel disease and 4 with rectal cancer. These extracts were also assayed for mutagens using the Salmonella/mammalian microsome mutagenicity assay. None of the faecal extracts gave mutagenicity ratios above 2. Faecal extracts from volunteers were free of detectable histidine. Although 9 of those from inflammatory bowel disease patients contained histidine (mean +/- SEM 255 +/- 34 mumoles l-1) as did 1 extract from a rectal cancer patient (50 mumoles l-1), none contained sufficient histidine to give a false positive Salmonella/mammalian microsome mutagenicity assay result (800 mumoles l-1 in test solution). Our results do not implicate histidine as a cause of error in faecal mutagenicity testing by the Salmonella/mammalian microsome mutagenicity assay.

Cimetidine is unlikely to increase formation of intragastric N-nitroso-compounds in patients taking a normal diet.

Studies in fasting subjects have suggested that cimetidine therapy might lead to nocturnal hypochlorhydria, allowing bacterial overgrowth and the production of intragastric carcinogens. This hypothesis was investigated in normal subjects taking full-dose and maintenance cimetidine with food. Nocturnal hypochlorhydria wa rarely found and the incidence of bacterial overgrowth was correspondingly low; gastric-juice nitrite concentrations were rarely raised. These findings suggest that long term treatment with cimetidine is unlikely to promote gastric cancer as a result of bacterial metabolic activity.