Walter P. Weber

The timing of surgical antimicrobial prophylaxis.

Objective:To obtain precise information on the optimal time window for surgical antimicrobial prophylaxis. Summary Background Data:Although perioperative antimicrobial prophylaxis is a well-established strategy for reducing the risk of surgical site infections (SSI), the optimal timing for this procedure has yet to be precisely determined. Under todays recommendations, antibiotics may be administered within the final 2 hours before skin incision, ideally as close to incision time as possible. Methods:In this prospective observational cohort study at Basel University Hospital we analyzed the incidence of SSI by the timing of antimicrobial prophylaxis in a consecutive series of 3836 surgical procedures. Surgical wounds and resulting infections were assessed to Centers for Disease Control and Prevention standards. Antimicrobial prophylaxis consisted in single-shot administration of 1.5 g of cefuroxime (plus 500 mg of metronidazole in colorectal surgery). Results:The overall SSI rate was 4.7% (180 of 3836). In 49% of all procedures antimicrobial prophylaxis was administered within the final half hour. Multivariable logistic regression analyses showed a significant increase in the odds of SSI when antimicrobial prophylaxis was administered less than 30 minutes (crude odds ratio = 2.01; adjusted odds ratio = 1.95; 95% confidence interval, 1.4–2.8; P < 0.001) and 120 to 60 minutes (crude odds ratio = 1.75; adjusted odds ratio = 1.74; 95% confidence interval, 1.0–2.9; P = 0.035) as compared with the reference interval of 59 to 30 minutes before incision. Conclusions:When cefuroxime is used as a prophylactic antibiotic, administration 59 to 30 minutes before incision is more effective than administration during the last half hour.

Surgical Glove Perforation and the Risk of Surgical Site Infection

HYPOTHESIS Clinically apparent surgical glove perforation increases the risk of surgical site infection (SSI). DESIGN Prospective observational cohort study. SETTING University Hospital Basel, with an average of 28,000 surgical interventions per year. PARTICIPANTS Consecutive series of 4147 surgical procedures performed in the Visceral Surgery, Vascular Surgery, and Traumatology divisions of the Department of General Surgery. MAIN OUTCOME MEASURES The outcome of interest was SSI occurrence as assessed pursuant to the Centers of Disease Control and Prevention standards. The primary predictor variable was compromised asepsis due to glove perforation. RESULTS The overall SSI rate was 4.5% (188 of 4147 procedures). Univariate logistic regression analysis showed a higher likelihood of SSI in procedures in which gloves were perforated compared with interventions with maintained asepsis (odds ratio [OR], 2.0; 95% confidence interval [CI], 1.4-2.8; P < .001). However, multivariate logistic regression analyses showed that the increase in SSI risk with perforated gloves was different for procedures with vs those without surgical antimicrobial prophylaxis (test for effect modification, P = .005). Without antimicrobial prophylaxis, glove perforation entailed significantly higher odds of SSI compared with the reference group with no breach of asepsis (adjusted OR, 4.2; 95% CI, 1.7-10.8; P = .003). On the contrary, when surgical antimicrobial prophylaxis was applied, the likelihood of SSI was not significantly higher for operations in which gloves were punctured (adjusted OR, 1.3; 95% CI, 0.9-1.9; P = .26). CONCLUSION Without surgical antimicrobial prophylaxis, glove perforation increases the risk of SSI.

Somatic mutations of KIT in familial testicular germ cell tumours

Somatic mutations of the KIT gene have been reported in mast cell diseases and gastrointestinal stromal tumours. Recently, they have also been found in mediastinal and testicular germ cell tumours (TGCTs), particularly in cases with bilateral disease. We screened the KIT coding sequence (except exon 1) for germline mutations in 240 pedigrees with two or more cases of TGCT. No germline mutations were found. Exons 10, 11 and 17 of KIT were examined for somatic mutations in 123 TGCT from 93 multiple-case testicular cancer families. Five somatic mutations were identified; four were missense amino-acid substitutions in exon 17 and one was a 12 bp in-frame deletion in exon 11. Two of seven TGCT from cases with bilateral disease carried KIT mutations compared with three out of 116 unilateral cases (P=0.026). The results indicate that somatic KIT mutations are implicated in the development of a minority of familial as well as sporadic TGCT. They also lend support to the hypothesis that KIT mutations primarily take place during embryogenesis such that primordial germ cells with KIT mutations are distributed to both testes.

Phenotypic differences in familial adenomatous polyposis based on APC gene mutation status

Background—Familial adenomatous polyposis (FAP) is a clinically well defined hereditary disease caused by germline mutations within the adenomatous polyposis coli (APC) gene. Although several techniques are applied in the mutation analysis of FAP kindreds about 20–50% of cases remain unclear, with no APC mutation identified (APC negative). Aims—To delineate phenotypic differences between APC positive and APC negative patients with respect to colonic and extracolonic disease in order to determine whether additional mechanisms are involved in the pathogenesis of FAP. Methods—The entire coding region of the APC gene was analysed using single stranded conformation polymorphism and protein truncation tests in 50 Swiss FAP families with a total of 161 affected individuals. Differences in phenotypic manifestation were statistically evaluated by Student’s t test, Fisher’s exact test, and χ2 test. Results—Thirty six families (72%) were APC positive. Statistically significant differences between APC positive and APC negative groups were found for the mean age at diagnosis of colonic polyposis (35.2 versus 45.3 years, respectively) and for the occurrence of stomach polyps (14 patients, all APC positive). Additionally, APC negative patients displayed lower polyp numbers at diagnosis and less extracolonic manifestations. Conclusions—FAP kindreds without detected APC gene mutations present with a notably milder disease phenotype compared with APC positive families, suggesting that different genetic factors might be involved.

Propensity scores and the surgeon

Evidence‐based surgery has been established as a cornerstone of good clinical practice, promising to improve the treatment of patients and the quality of surgical education. However, evidence‐based surgery requires dedicated clinicians trained to perform methodologically sound clinical investigations. Statistical knowledge is therefore invaluable. Surgical studies often cannot be randomized. Propensity scores offer a powerful alternative to multivariable analysis in the assessment of observational, non‐randomized surgical studies. Unfortunately, many surgeons are unaware of this important analytical approach that has gained increasing stature in medical research. Thus, propensity score analyses are not used often in surgical studies.

Detection of new mutations in six out of 10 Swiss HNPCC families by genomic sequencing of the hMSH2 and hMLH1 genes.

The cancer predisposition in most HNPCC families is believed to be associated with mutations in the human mismatch repair gene homologues hMSH2 and hMLH1. We searched for mutations in our collection of 10 Swiss HNPCC families by sequencing the exons and exon/intron boundaries of the hMSH2 and hMLH1 genes. In four families we found different mutations which are expected to lead to protein truncations of either the hMSH2 or the hMLH1 proteins owing to premature in frame stop codons or splice defects. In two more families we detected mutations leading to an amino acid deletion and an amino acid substitution in an evolutionary conserved residues respectively. None of these mutations has been reported in other families, which is consistent with the notion that HNPCC associated hMSH2 and hMLH1 mutations are heterogeneous and there is no striking founder effect in the Swiss population. Whenever this could be investigated, the presence of the mutations was confirmed in other family members who showed manifestations of HNPCC. Interestingly, an obligate carrier in one of the families developed a brain tumour at the age of 29, histologically verified as a glioblastoma multiforme, which was recently linked to HNPCC in the context of Turcots syndrome.

Differential effects of the tryptophan metabolite 3-hydroxyanthranilic acid on the proliferation of human CD8 + T cells induced by TCR triggering or homeostatic cytokines

Production of indoleamine 2,3‐dioxygenase (IDO) by tumor cells, leading to tryptophan depletion and production of immunosuppressive metabolites, may facilitate immune tolerance of cancer. IDO gene is also expressed in dendritic cells (DC) upon maturation induced by lipopolysaccarides or IFN. We investigated IDO gene expression in melanoma cell lines and clinical specimens as compared to mature DC (mDC). Furthermore, we explored effects of L‐kynurenine (L‐kyn) and 3‐hydroxyanthranilic acid (3‐HAA) on survival and antigen‐dependent and independent proliferation of CD8+ cells. We observed that IDO gene expression in cultured tumor cells and freshly excised samples is orders of magnitude lower than in mDC, providing highly efficient antigen presentation to CD8+ T cells. Non toxic concentrations of L‐kyn or 3‐HAA did not significantly inhibit antigen‐specific CTL responses. However, 3‐HAA, but not L‐kyn markedly inhibited antigen‐independent proliferation of CD8+ T cells induced by common receptor γ‐chain cytokines IL‐2, ‐7 and ‐15. Our data suggest that CD8+ T cell activation induced by antigenic stimulation, a function exquisitely fulfilled by mDC, is unaffected by tryptophan metabolites. Instead, in the absence of effective T cell receptor triggering, 3‐HAA profoundly affects homeostatic proliferation of CD8+ T cells.

Impaired DNA-repair synthesis in lymphocytes of breast cancer patients

UV-C light induced DNA-repair synthesis was studied in unstimulated lymphocytes of 41 female patients (aged 33-83 years) with invasive breast cancer and of 27 healthy women (aged 37-68 years). As a parameter for the determination of the DNA-repair synthesis the incorporation of [3H] thymidine was taken in the presence of 2 mM hydroxyurea (HU). The [3H] thymidine incorporation levels were reduced in 20 of the 41 patients and in only 3 of the 27 controls. This difference between the two groups was significant. An impaired DNA-repair synthesis might be involved in the etiology of breast cancer in some patients.

Multiple mechanisms underlie defective recognition of melanoma cells cultured in three-dimensional architectures by antigen-specific cytotoxic T lymphocytes.

Cancer cells’ growth in three-dimensional (3D) architectures promotes resistance to drugs, cytokines, or irradiation. We investigated effects of 3D culture as compared to monolayers (2D) on melanoma cells’ recognition by tumour-associated antigen (TAA)-specific HLA-A*0201-restricted cytotoxic T-lymphocytes (CTL). Culture of HBL, D10 (both HLA-A*0201+, TAA+) and NA8 (HLA-A*0201+, TAA−) melanoma cells on polyHEMA-coated plates, resulted in generation of 3D multicellular tumour spheroids (MCTS). Interferon-gamma (IFN-γ) production by HLA-A*0201-restricted Melan-A/MART-127–35 or gp100280–288-specific CTL clones served as immunorecognition marker. Co-culture with melanoma MCTS, resulted in defective TAA recognition by CTL as compared to 2D as witnessed by decreased IFN-γ production and decreased Fas Ligand, perforin and granzyme B gene expression. A multiplicity of mechanisms were potentially involved. First, MCTS per se limit CTL capacity of recognising HLA class I restricted antigens by reducing exposed cell surfaces. Second, expression of melanoma differentiation antigens is downregulated in MCTS. Third, expression of HLA class I molecules can be downregulated in melanoma MCTS, possibly due to decreased interferon-regulating factor-1 gene expression. Fourth, lactic acid production is increased in MCTS, as compared to 2D. These data suggest that melanoma cells growing in 3D, even in the absence of immune selection, feature characteristics capable of dramatically inhibiting TAA recognition by specific CTL.

High expression of indoleamine 2,3-dioxygenase gene in prostate cancer

Arginase 2, inducible- and endothelial-nitric-oxide synthase (iNOS and eNOS), indoleamine 2,3-dioxygenase (IDO) and TGF-beta, might impair immune functions in prostate cancer (PCA) patients. However, their expression was not comparatively analysed in PCA and benign prostatic hyperplasia (BPH). We evaluated the expression of these genes in PCA and BPH tissues. Seventy-six patients (42 BPH, 34 PCA) were enrolled. Arginase 2, eNOS and iNOS gene expression was similar in BPH and PCA tissues. TGF-beta1 gene expression was higher in BPH than in PCA tissues (p=0.035). IDO gene expression was more frequently detectable (p=0.00007) and quantitatively higher (p=0.00001) in PCA tissues than in BPH. IDO protein, expressed in endothelial cells from both BPH and PCA, was detectable in tumour cells in PCA showing evidence of high specific gene expression. In these patients, IDO gene expression correlated with kynurenine/tryptophan ratio in sera. Thus high expression of IDO gene is specifically detectable in PCA.