The frequency of resistance to seven different antimicrobial agents was examined in the aerobic gramnegative gut flora of over 600 individuals from hospitals, from laboratories where antibiotics were used, and from urban and rural communities. In a majority (62.5%) of fecal samples from people without a recent history of taking antibiotics, 10% or more of the total organisms were resistant to at least one of the antibiotics. In about 40% of the samples, resistance to more than one drug was present at this level. More than one-third of the samples contained resistant organisms comprising 50% or more of the total flora examined. Organisms with coresistance to multiple drugs were found frequently. Individuals taking antibiotics produced more samples with a higher proportion (>50%) of resistant bacteria, and these samples also had a significantly greater number of different resistance determinants. This extensive study revealed a high prevalence of resistant bacteria in the gut flora of ambulatory and hospitalized individuals whether or not they were taking antibiotics.There is worldwide concern about the appearance of antibiotic resistance in common pathogens of hospital-and community-acquired infections (4,9,20). While selective pressure caused by antibiotic usage has been linked to these findings (20), there have been little data on the natural frequency of antibiotic resistance genes in the nornial nonpathogenic flora of ambulating and hospitalized individuals. Such resistant bacteria would represent a constant pool of resistance genes potentially transferable, directly or indirectly, to human pathogens. We analyzed fecal specimens from humans in the greater Boston, Mass., area for both the presence and frequency of naturally occurring aerobic gramnegative bacteria with resistance to one or more of seven different antimicrobial agents. We found that resistance was common in the gut flora and the resistant strains constituted a major fraction of the total flora in more than one-third of the samples.

Rhizobium meliloti exhibited behavior resembling that of other chemotactic bacteria. Nonflagellated, nonmotile but flagellated, and nonchemotactic mutants were isolated, and genetic mapping placed all three types of lesions within a small region of the R. Meliloti chromosome. Results from nodulation experiments performed with these mutants indicate that members of the three classes (Fla-, Mot-, and Che-) infect and produce as many nodules on alfalfa plants as does the wild-type strain.

No abstract

Derivatives of bacteriophages lambda and M13 are in common use as vectors in recombinant DNA RESEARCH. These laboratory-derived phages have been designed to allow cloning of DNA fragments, but to be unable to survive outside a defined laboratory and/or host-cell environment. To assess the availability of wild-type lambda or M13 phages in the environment which might potentially rescue debilitated derivative phages, we have now examined the frequency of these and other bacteriophages in human and animal faeces. We detected coliphage in over two-thirds of the faecal samples. Of these, 1.2% of the samples contained lambda-like phage and 3.5% had phage indistinguishable from M13.

No abstract