Binding and killing of bacteria by bismuth subsalicylate.

Bismuth subsalicylate (BSS) is a compound without significant aqueous solubility that is widely used for the treatment of gastrointestinal disorders. BSS was able to bind bacteria of diverse species, and these bound bacteria were subsequently killed. A 4-log10 reduction of viable bacteria occurred within 4 h after a 10 mM aqueous suspension of BSS was inoculated with 2 x 10(6) Escherichia coli cells per ml. Binding and killing were dependent on the levels of inoculated bacteria, and significant binding but little killing of the exposed bacteria occurred at an inoculum level of 2 x 10(9) E. coli per ml. Intracellular ATP decreased rapidly after exposure of E. coli to 10 mM BSS and, after 30 min, was only 1% of the original level. Extracellular ATP increased after exposure to BSS, but the accumulation of extracellular ATP was not sufficient to account for the loss of intracellular ATP. The killing of bacteria exposed to BSS may have been due to cessation of ATP synthesis or a loss of membrane integrity. Bactericidal activity of BSS was also investigated in a simulated gastric juice at pH 3. Killing of E. coli at this pH was much more rapid than at pH 7 and was apparently due to salicylate released by the conversion of BSS to bismuth oxychloride. It is proposed that the binding and killing observed for BSS contribute to the efficacy of this compound against gastrointestinal infections such as traveler's diarrhea.

Method for detecting viruses in aerosols.

A simple method with poliovirus as the model was developed for recovering human enteric viruses from aerosols. Filterite filters (pore size, 0.45 micron; Filterite Corp., Timonium, Md.) moistened with glycine buffer (pH 3.5) were used for adsorbing the aerosolized virus. No virus passed the filter, even with air flow rates of 100 liters/min. Virus recovery from the filter was achieved by rapid elution with 800 ml of glycine buffer, pH 10. The virus in the primary eluate was reconcentrated by adjusting the pH to 3.5, adding AlCl3 to 0.0005 M, collecting the virus on a 0.25-micron-pore Filerite disk (diameter, 25 mm) and and eluting with 6 ml of buffer, pH 10. With this method, virus could be detected regularly in aerosols produced by flushing when 3 X 10(8) PFU of poliovirus were present in the toilet bowl. Poliovirus-containing fecal material from two of four infants who had recently received oral polio vaccine also yielded virus in the aerosols when feces containing 2.4 X 10(7) to 4.5 X 10(7) PFU of virus had been added to the toilet bowl. Persons infected with a variety of natural enteric viruses are known to excrete this amount of virus in their daily stools.

Marker rescue by a homologous recipient plasmid during transformation of gonococci by a hybrid Pcr plasmid.

A 42-kilobase hybrid Pcr plasmid (pFA14) was formed when the naturally occurring 7.2-kilobase Pcr plasmid pFA3 was introduced by transformation into a competent gonococcal recipient containing the 36-kilobase conjugative plasmid pFA2 (Sox et al., J. Bacteriol. 138:510-518). Analysis of the structure of pFA14 showed that it was a stable recombinant between pFA3 and pFA2. The transformation efficiency of pFA14 was increased 300- to 10,000-fold by the presence in isogenic recipients of the homologous plasmid pFA2. The presence of a homologous plasmid in the recipient also markedly increased the likelihood of recovery of intact donor-size Pcr plasmids in the transformants. The presence of pFA2 had no effect on the competence of piliated or nonpiliated gonococci for transformation by either linear chromosomal DNA or a nonhomologous Pcr plasmid. Increased transformation efficiency of the hybrid Pcr plasmid pFA14 may have been due to recombination between the nicked or linearized donor plasmid and the homologous recipient plasmid (marker rescue).

Transformation-derived Neisseria gonorrhoeae plasmids with altered structure and function.

Plasmid deoxyribonucleic acid from Neisseria gonorrhoeae containing a 7.1-kilobase (kb) (4.7-megadalton) penicillinase (Pcr) plasmid transformed homogenic gonococci to penicillinase production at a low frequency. About 25% of the penicillinase-producing gonococcal transformants contained Pcr plasmids which were either larger or smaller than the 7.1 kb donor plasmid; these Pcr plasmids varied in size from 3.45 to 42 kb. Some of these altered plasmids differed from the donor plasmid in stability or in frequency of mobilization by a 36-kb (24-megadalton) conjugative plasmid. A restriction endonuclease cleavage map of the 7.1-kilobase Pcr plasmid and several of the smaller deleted plasmids was constructed. The most common size of altered Pcr plasmid was 5.1 kb (3.4 megadaltons). A Pcr plasmid isolated from a gonococcus in London, England, was identical with these 5.1-kb transformant plasmids in both size and restriction endonuclease cleavage profiles, suggesting that the 5.1-kb Pcr plasmid could have arisen from a 7.1-kb Pcr plasmid by a transformation-associated deletion in nature.

Conjugative plasmids in Neisseria gonorrhoeae.

A conjugation system initially discovered in beta-lactamase-producing gonococci mobilized small non-selftransmissible R plasmids encoding beta-lactamase (penicillinase) production into other gonococci, Neisseria, and Escherichia coli. This conjugation system was mediated by a separate selftransmissible plasmid of 23.9 X 10(6) daltons, pFA2. Conjugative plasmids capable of mobilizing R plasmids were also found in nearly 8% of the non-penicillinase-producing gonococci. These were similar to pFA2 in size, buoyant density, and restriction endonuclease digest patterns but were less efficient than pFA2 in mobilization of the penicillinase plasmid pFA3. The presence of conjugative plasmids in gonococci isolated before the appearance of penicillinase-producing strains indicates that a conjugation system for plasmid transfer predated the appearance of R plasmids in gonococci.

Conjugal transfer of the gonococcal penicillinase plasmid.

Certain gonococci, which heretofore have lacked a conjugal mating system, can sexually transfer a small plasmid (4.5 x 10)6) daltons) which carries the gene for beta-lactamase production. Frequencies of conjugal transfer were similar into diverse recipients (other gonococci, Neisseria flava, and Escherichia coli), which suggests that gonococci may transfer the plasmid promiscuously in nature.

Factors affecting genetic transformation of Neisseria gonorrhoeae.

Piliated gonococci were competent in genetic transformation in all stages of growth in minimal and enriched media, but nonpiliated cells were almost totally incompetent. Uptake of deoxyribonucleic acid into a deoxyribonuclease-insensitive state was observed only in competent piliated cells. Competence was not affected by washing of competent cells or treatment of competent cells with proteolytic enzymes. Expression of competence required presence of any of several different monovalent or divalent cations, as well as a utilizable source of energy. Efforts to produce genotypically or phenotypically competent derivatives of nonpiliated cells were unsuccessful. These experiments are consistent with the idea that pili may play a role in the irreversible uptake of transforming deoxyribonucleic acid by the gonococcus, but fail to provide evidence for other types of competence factors.