Cirrhosis and Portal Hypertension Worsen Bowel Preparation for Screening Colonoscopy.

BACKGROUND: Colonoscopy is a diagnostic and therapeutic procedure that reduces colorectal cancer incidence and mortality but requires adequate bowel cleansing for high-quality examination. Past studies have suggested cirrhosis as a risk factor for worse bowel preparation. METHODS: We carried out a match-controlled retrospective study evaluating patients with and without cirrhosis who underwent outpatient screening colonoscopies to assess the effect of cirrhosis and portal hypertension complications on preparation quality and endoscopic measures. We also did a subgroup analysis excluding patients with obesity. RESULTS: We examined 1464 patients with cirrhosis and matched controls. Cirrhotic patients had lower mean Boston Bowel Preparation Scale (BBPS) scores and slower cecal intubation times. We found a single point increase in the Model for End-stage Liver Disease (MELD) score, as well as ascites, hepatic encephalopathy, and variceal hemorrhage were all associated with a longer cecal intubation time. Subgroup analysis excluding patients with obesity again found a significantly lower BBPS score and longer cecal intubation time while also finding a 24% drop in polyp detection. CONCLUSIONS: Patients with cirrhosis have worse BBPS scores and longer cecal intubation times. Nonobese cirrhotic patients additionally have a lower polyp detection rate. Portal hypertension complications were associated with worsened preparation quality and longer cecal intubation times. Each incremental increase in MELD score lengthened cecal intubation time. These findings support a more aggressive bowel preparation strategy for patients with cirrhosis, especially patients with severe disease or portal hypertension complications.

Discovery and Characterization of a Nitroreductase Capable of Conferring Bacterial Resistance to Chloramphenicol.

Widespread antibiotic resistance has led to the reappraisal of abandoned antibiotics including chloramphenicol. However, enzyme(s) underlying one form of chloramphenicol resistance, nitroreduction, have eluded identification. Here we demonstrate that expression of the Haemophilus influenzae nitroreductase gene nfsB confers chloramphenicol resistance in Escherichia coli. We characterized the enzymatic product of H. influenzae NfsB acting on chloramphenicol and found it to be amino-chloramphenicol. Kinetic analysis revealed reduction of diverse substrates including the incomplete reduction of 5-nitro antibiotics metronidazole and nitrofurantoin, likely resulting in activation of these antibiotic pro-drugs to their cytotoxic forms. We observed that expression of the H. influenzae nfsB gene in E. coli results in significantly increased susceptibility to metronidazole. Finally, we found that in this strain metronidazole attenuates chloramphenicol resistance synergistically, and in vitro metronidazole weakly inhibits chloramphenicol reduction by NfsB. Our findings reveal the underpinnings of a chloramphenicol resistance mechanism nearly 70 years after its description.