Identification of an envelope mutation (env-10) resulting in increased antibiotic susceptibility and pyocin resistance in a clinical isolate of Neisseria gonorrhoeae.

A mutation (env-10) conferring increased susceptibility to drugs, dyes, and detergents was detected in a clinical isolate of Neisseria gonorrhoeae. In certain strains, env-10 also affected susceptibility to pyocins. This mutation was phenotypically similar to but genotypically distinct from previously described env mutations.

Serum sensitivity of Neisseria gonorrhoeae: the role of lipopolysaccharide.

A lipopolysaccharide (LPS) mutant (FA5100) of a serum-resistant strain of Neisseria gonorrhoeae (FA19) was found to be highly sensitive to the bactericidal activity of normal human serum (NHS). Both strain FA5100 and an unrelated serum-sensitive clinical isolate (F62) were killed by NHS via the classical complement pathway since killing required C2 and Ca++. However, the fact that only strain FA5100 was sensitive to human hypogammaglobulinemic and cord serum suggested that this strain might activate the classical complement pathway in the absence of antibody. Anticomplementary concentrations of LPS from strain FA5100 inhibited the bactericidal activity of NHS against either strain FA5100 or strain F62. However, concentrations of LPS from strain FA5100 that exhibited marginal anticomplementary behavior also inhibited the killing of strain F62 by NHS. The ability of LPS from strain FA5100 to inhibit the bactericidal activity of NHS against strain FA5100 and to activate complement was reduced by treatment with mild alkali. However, alkali-treated LPS from strain FA5100 still inhibited the bactericidal activity of NHS against strain F62.

Pyocin-resistant lipopolysaccharide mutans of Neisseria gonorrhoeae: alterations in sensitivity to normal human serum and polymyxin B.

Pyocins from Pseudomonas aeruginosa were used to select several lipopolysaccharide (LPS) mutants of Neisseria gonorrhoeae strain FA19. Three classes of LPS mutans were found in the initial group selected for study. The LPS of one class lacked galactose. That of a second group lacked the typical heptose found in the parental LPS, was reduced in glucose, galactose, and N-acetylglucosamine content, appeared to contain a new unidentified sugar component, and consisted of two species of LPS separable on sodium dodecyl sulfate-polyacrylamide gels. The LPS of a third strain lacked the heptose, glucose, galactose, and N-acetylglucosamine found in the oligosaccharide portion of parental FA19 LPS. The minimal inhibitory concentration for polymyxin B of the mutant strains was 3 to 4 times that of the parental strain. The strains lacking only galactose were as resistant as the parent to the bactericidal action of normal human serum, but cells of the other two classes were quickly killed by serum. Gonococcal LPS thus appears to be important in determining phenotypic properties of the cells.

Identification of a new genetic site (sac-3+) in Neisseria gonorrhoeae that affects sensitivity to normal human serum.

A previously undescribed genetic site (sac-3) affecting susceptibility of the gonococcus to normal human serum was localized on the gonococcal chromosome. The presence of the sac-3+ allele in a clinical isolate (FA889) resulted in sensitivity only to relatively high concentrations of serum (greater than or equal to 12.5%). Genetic mapping experiments demonstrated that sac-3+ was tightly linked to another genetic site (sac-1+) involved in determining susceptibility to normal human serum and to a locus (nmp-3) involved in the replacement of outer membrane protein I. The sac-1+ and sac-3+ loci resulted in phenotypically distinct levels of sensitivity to human serum. The sac-3+ serum sensitivity and sac-1+ serum sensitivity loci recombined with high frequency, resulting in serum resistance. The results show that serum sensitivity in clinical isolates may be due to different serum sensitivity loci and suggest that different antigens and immunological mechanisms could be responsible for sensitivity of different gonococcal isolates to human serum.

Genetics of serum resistance in Neisseria gonorrhoeae: the sac-1 genetic locus.

A genetic locus affecting susceptibility to the bactericidal activity of normal human serum has been designated sac-1. This locus was shown to be closely linked to, but not identical with, a second locus (designated nmp-2) that affects protein 1 of the outer membrane. The sac-1 locus could be linked to known antibiotic resistance markers on the gonococcal chromosome by genetic transformation.

Cell envelope alterations in antibiotic-sensitive and-resistant strains of Neisseria gonorrhoeae.

The cell envelopes of antibiotic-resistant and -sensitive isogenic strains of Neisseria gonorrhoeae were analyzed to determine whether acquisition of genetic loci for altered antibiotic sensitivity was accompanied by alterations in cell envelope composition. No differences in the composition of phospholipids and lipopolysaccharides were noted. Acquisition of mtr-2, which results in low-level, nonspecific increased resistance to multiple antibiotics, dyes, and detergents, was accompanied by a sevenfold increase in the amount of a minor, 52,000-molecular-weight outer membrane protein and a 32% increase in the extent of peptidoglycan cross-linking. Subsequent addition of the nonspecific hypersensitivity loci env-1 or env-2 to a strain carrying mtr-2 resulted in reversal of the phenotypic resistance determined by mtr-2 and marked reduction in both the amount of the 52,000-molecular-weight outer membrane protein and the extent of peptidoglycan cross-linking. Introduction of penB2, which results in a fourfold increase in resistance to penicillin and tetracycline, was accompanied by the disappearance of the principal outer membrane protein of the wild-type strain (molecular weight, 36,900) and the appearance of a new species of the principal outer membrane protein (molecular weight, 39,400) in the transformant.

Altered outer membrane protein in different colonial types of Neisseria gonorrhoeae.

Dark-colored colony types of Neisseria gonorrhoeae (T3 and dark variants of T1 and T2) had markedly increased amounts of an approximately 28,000-dalton outer membrane protein, as compared with light-colored colony types (T4 and light variants of T1 and T2). The presence of this protein appeared to be unrelated to piliation. The apparent molecular weight of this protein on sodium dodecyl sulfate-polyacrylamide gels varied, depending on methods used to solubilize envelope proteins. In view of the location of this protein on the outer membrane, this protein could be important to the pathogenicity or antigenicity of the organism as well as to colonial characteristics in vitro.

Altered crystal violet permeability and lytic behavior in antibiotic-resistant and -sensitive mutants of Neisseria gonorrhoeae.

Wild-type, antibiotic-resistant and hypersensitive isogenic strains of Neisseria gonorrhoeae were studied for uptake of crystal violet, rates of autolysis, and response to lysozyme. Total uptake of crystal violet was similar in all strains at 0 C but varied significantly at 37 C. Mutation at the nonspecific resistance locus ery resulted in relative impermeability to crystal violet at 37 C, as compared to wild type. The penetration barrier to crystal violet at 37 C was overcome by addition of 5 mM ethylenediaminetetraacetic acid. Mutation at ery also resulted in reduced rates of autolysis and reduced sensitivity to high concentrations of lysozyme under conditions of divalent cation (Mg2+) depletion. In contrast, mutation at the nonspecific drug hypersensitivity locus env resulted in increased uptake of crystal violet at 37 C, due to increased binding of dye to crude envelope as well as increased penetration into cytoplasm. The env mutants were also more rapidly autolytic and more sensitive to lysozyme than wild type in the absence of Mg2+. These results suggest that the cell envelopes of ery mutants are more stable and less permeable and those of env mutants are less stable and more permeable than wild-type strains.

Transport of glucose, gluconate, and methyl alpha-D-glucoside by Pseudomonas aeruginosa.

Glucose transport by Pseudomonas aeruginosa was studied. These studies were enhanced by the use of a mutant, strain PAO 57, which was unable to grow on glucose but which formed the inducible glucose transport system when grown in media containing glucose or other inducers such as 2-deoxy-d-glucose. Both PAO 57 and parental strain PAO transported glucose with an apparent K(m) of 7 muM. Free glucose was concentrated intracellularly by P. aeruginosa PAO 57 over 200-fold above the external level. These data constitute direct evidence that glucose is transported via active transport by P. aeruginosa. Various experimental data clearly indicated that P. aeruginosa PAO transported methyl alpha-d-glucose (alpha-MeGlc) via the glucose transport system. The apparent K(m) of alpha-MeGlc transport was 7 mM which indicated a 1,000-fold lower affinity of the glucose transport system for alpha-MeGlc than for glucose. While only unchanged alpha-MeGlc was detected intracellularly in P. aeruginosa, alpha-MeGlc was actually concentrated intracellularly less than 2-fold over the external level. Membrane vesicles of P. aeruginosa PAO retained transport activity for gluconate. This solute was concentrated intravesicularly several-fold over the external level. A component of the glucose transport system is believed to have been lost during vesicle preparation since glucose per se was not transported. Instead; glucose was converted to gluconate by membrane-associated glucose dehydrogenase and gluconate was then transported into the vesicles. Although this may constitute an alternate system for glucose transport, it is not a necessary prerequisite for glucose transport by intact cells since P. aeruginosa PAO 57, which lacks glucose dehydrogenase, was able to transport glucose at a rate equal to the parental strain.