Therapeutic efficacy of bicyclomycin for shigellosis experimentally induced in rhesus monkeys

Mastering the control of the Rho transcription factor for biotechnological applications

The present review represents an update on the fundamental role played by the Rho factor, which facilitates the process of Rho-dependent transcription termination in the prokaryotic world; it also provides a summary of relevant mutations in the Rho factor and the insights they provide into the functions carried out by this protein. Furthermore, a section is dedicated to the putative future use of Rho (the 'taming' of Rho) to facilitate biotechnological processes and adapt them to different technological contexts. Novel bacterial strains can be designed, containing mutations in the rho gene, that are better suited for different biotechnological applications. This process can obtain novel microbial strains that are adapted to lower temperatures of fermentation, shorter production times, exhibit better nutrient utilization, or display other traits that are beneficial in productive Biotechnology. Additional important issues reviewed here include epistasis, the design of TATA boxes, the role of small RNAs, and the manipulation of clathrin-mediated endocytosis, by some pathogenic bacteria, to invade eukaryotic cells. KEY POINTS: • It is postulated that controlling the action of the prokaryotic Rho factor could generate major biotechnological improvements, such as an increase in bacterial productivity or a reduction of the microbial-specific growth rate. • The review also evaluates the putative impact of epistatic mechanisms on Biotechnology, both as possible responsible for unexpected failures in gene cloning and more important for the genesis of new strains for biotechnological applications • The use of clathrin-coated vesicles by intracellular bacterial microorganisms is included too and proposed as a putative delivery mechanism, for drugs and vaccines.

Rifaximin versus ciprofloxacin for the treatment of traveler's diarrhea: a randomized, double-blind clinical trial

Rifaximin is a poorly absorbed rifamycin derivative under investigation for treatment of infectious diarrhea. Adult students from the United States in Mexico and international tourists in Jamaica were randomized to receive either rifaximin (400 mg twice per day) or ciprofloxacin (500 mg twice per day) for 3 days, following a double-blinded model, from June 1997 to September 1998. A total of 187 subjects with diarrhea were studied. Time from initiation of therapy to passage of last unformed stool was comparable for those receiving rifaximin or ciprofloxacin (median, 25.7 hours versus 25.0 hours, respectively). There was no significant difference in the proportion of subjects in the 2 groups with respect to clinical improvement during the first 24 hours (P=.199), failure to respond to treatment (P=.411), or microbiological cure (P=.222). The incidence of adverse events was low and similar in each group. Rifaximin is a safe and effective alternative to ciprofloxacin in the treatment of traveler's diarrhea.

Colonization of the mouse intestine by an avirulent Salmonella typhimurium strain and its lipopolysaccharide-defective mutants

For study of the role of lipopolysaccharide (LPS) character in colonization of the mouse large intestine, use was made of S. typhimurium strain SL5316, which is streptomycin resistant and smooth (wild-type LPS) but nonvirulent because it is Aro- (aromatic dependent). Several rough variants of different LPS chemotype derived from strain SL5316 comprised: an rfb deletion transductant making type Ra (complete core) LPS; an rfaJ mutant making incomplete core of type Rb2; and an rfa-990 mutant making LPS core less complete than chemotype Rb2. We tested these strains for colon-colonizing ability by feeding them to male CD-1 mice receiving streptomycin sulfate (5 g/liter) in their drinking water. Each strain, if fed alone, was found in the feces throughout the 15 days of the experiment at about 10(8) CFU/g for the smooth strain or 10(7) CFU/g for each of its rough derivatives. However, when mice were fed equal numbers of two strains (with differentiating antibiotic resistance characters), the strain with the more complete LPS was found in the feces in great excess, 1000- to 100,000-fold, according to the pair. Thus, when strains were placed in direct competition with one another, their relevant colon-colonizing abilities were found to be wild type greater than rfb much greater than rfaJ greater than rfa-990, showing that the ability of a Salmonella strain to colonize the mouse large intestine decreases as its LPS structure becomes more defective.

Efficacy of bicozamycin in preventing traveler's diarrhea

Bicozamycin was compared with a placebo in a prospective, randomized, double-blind study of the prevention of acute diarrhea among 30 American travelers newly arrived in Guadalajara, Mexico. None of the 11 subjects given bicozamycin orally for 3 wk at a dosage of 500 mg four times a day developed diarrhea as compared with an incidence of 53% diarrhea (10 of 19 subjects) in the placebo group (p = 0.003). Bicozamycin was well tolerated. Studies of changes in predominant aerobic fecal flora among the 11 subjects treated with bicozamycin showed the appearance of only one highly resistant Citrobacter freundii at the end of 1 wk of therapy and only a total of six resistant isolates at the end of 3 wk. All resistant isolates failed to transfer this resistance to a recipient Escherichia coli. Bicozamycin seems to be well suited and safe as a prophylactic agent against traveler's diarrhea.

Bacteriological studies of the enteric flora of patients treated with bicozamycin (CGP 3543/E) for acute nonparasitic diarrhea

During a therapeutic trial of bicozamycin (BI) for traveler's diarrhea, aerobically grown, gram-negative bacteria, predominantly Escherichia coli, were decreased by 2 to 3 logs per g of stool; the number of BI-resistant gram-negative bacteria did not increase. Resistant species were most often Citrobacter freundii, Klebsiella pneumoniae, and Morganella morganii, and few BI-resistant E. coli strains were isolated. Cross-resistance between BI and other antimicrobial agents was not found. Resistance to BI could not be transferred or mobilized to an E. coli K-12 recipient.