Effect of a staphylococcin on Neisseria gonorrhoeae.
Phage group 2 staphylococcal strain UT0002 contains a large 56S virulence plasmid with genes that code for both exfoliative toxin and a specific staphylococcin termed Bac R(1). Four penicillinase-producing strains and three penicillin-susceptible strains of Neisseria gonorrhoeae were killed by Bac R(1). After 30 min of growth of the penicillin-resistant TR1 strain in 62.5 arbitrary units of Bac R(1) per ml, loss of viability was approximately 90%, and, after 5 h, an approximately 99.99% loss of viability was observed. Lysis did not accompany cell death, and 84% of the Bac R(1) added to the growth medium was adsorbed to the gonococcal cells. The extracellular supernatant fluid from a substrain of staphylococcal strain UT0002 cured of the plasmid for Bac R(1) production had no lethal effect on the gonococcal strains. Bac R(1) was also shown to have bactericidal activity against an L-form of N. meningitidis, indicating that the outer envelope of a neisserial cell is not needed for bacteriocin activity. Ten different normal human sera were unable to neutralize Bac R(1) activity. The bacteriocin lacks adsorption specificity. It binds to but does not kill Escherichia coli cells, indicating that the cell envelope of gram-negative organisms can provide protection against the staphylococcin. (+info)
Invasion of human mucosal epithelial cells by Neisseria gonorrhoeae upregulates expression of intercellular adhesion molecule 1 (ICAM-1).
Infection of the mucosa by Neisseria gonorrhoeae involves adherence to and invasion of epithelial cells. Little is known, however, about the expression by mucosal epithelial cells of molecules that mediate cellular interactions between epithelial cells and neutrophils at the site of gonococcal infection. The aim of this study was to determine the expression of intercellular adhesion molecule 1 (ICAM-1) by epithelial cells during the process of gonococcal invasion. The highly invasive strain FA1090 and the poorly invasive strain MS11 were incubated with human endometrial adenocarcinoma (HEC-1-B) or human cervical carcinoma (ME-180) epithelial cells, after which ICAM-1 expression was measured by flow cytometry. After 15 h of infection with FA1090, expression of ICAM-1 increased 4.7- and 2.1-fold for HEC-1-B and ME-180 cells, respectively, whereas 15 h of infection of HEC-1-B cells with MS11 increased ICAM-1 expression only 1.6-fold. ICAM-1 expression was restricted to the cell surface, since no soluble ICAM-1 was detected. The distribution of staining was heterogeneous and mimicked that seen after treatment of HEC-1-B cells with the ICAM-1 agonist tumor necrosis factor alpha (TNF-alpha) in the absence of bacteria. PCR and dot blot analyses of ICAM-1 mRNA showed no change in levels over time in response to infection. Although TNF-alpha was produced by HEC-1-B cells after infection, the extent of ICAM-1 upregulation was not affected by neutralizing anti-TNF-alpha antiserum. Dual-fluorescence flow cytometry showed that the cells with the highest levels of ICAM-1 expression were cells with associated gonococci. We conclude that epithelial cells upregulate the expression of ICAM-1 in response to infection with invasive gonococci. On the mucosa, upregulation of ICAM-1 by infected epithelial cells may function to maintain neutrophils at the site of infection, thereby reducing further invasion of the mucosa by gonococci. (+info)
Longitudinal evaluation of serovar-specific immunity to Neisseria gonorrhoeae.
The serovars of Neisseria gonorrhoeae that are predominant in a community change over time, a phenomenon that may be due to the development of immunity to repeat infection with the same serovar. This study evaluated the epidemiologic evidence for serovar-specific immunity to N. gonorrhoeae. During a 17-month period in 1992-1994, all clients of a sexually transmitted disease clinic in rural North Carolina underwent genital culture for N. gonorrhoeae. Gonococcal isolates were serotyped according to standard methods. Odds ratios for repeat infection with the same serovar versus any different serovar were calculated on the basis of the distribution of serovars in the community at the time of reinfection. Of 2,838 patients, 608 (21.4%; 427 males and 181 females) were found to be infected with N. gonorrhoeae at the initial visit. Ninety patients (14.8% of the 608) had a total of 112 repeat gonococcal infections. Repeat infection with the same serovar occurred slightly more often than would be expected based on the serovars prevalent in the community at the time of reinfection, though the result was marginally nonsignificant (odds ratio = 1.5, 95% confidence interval 1.0-2.4; p = 0.05). Choosing partners within a sexual network may increase the likelihood of repeat exposure to the same serovar of N. gonorrhoeae. Gonococcal infection did not induce evident immunity to reinfection with the same serovar. (+info)
Natural competence for DNA transformation by Legionella pneumophila and its association with expression of type IV pili.
We have recently described the expression of two pili of different lengths on the surface of Legionella pneumophila (B. J. Stone and Y. Abu Kwaik, Infect. Immun. 66:1768-1775, 1998). Production of long pili requires a functional pilEL locus, encoding a type IV pilin protein. Since type IV pili in Neisseria gonorrhoeae are associated with competence for DNA transformation, we examined the competence of L. pneumophila for DNA transformation under conditions that allowed the expression of type IV pili. We show that L. pneumophila is naturally competent for DNA transformation by isogenic chromosomal DNA and by plasmid DNA containing L. pneumophila DNA. Many different L. pneumophila loci are able to transform L. pneumophila after addition of plasmid DNA, including gspA, ppa, asd, and pilEL. The transformation frequency is reduced when competing DNA containing either L. pneumophila DNA or vector sequences is added to the bacteria, suggesting that uptake-specific sequences may not be involved in DNA uptake. Competence for DNA transformation correlates with expression of the type IV pili, and a pilEL mutant defective in expression of type IV pili is not competent for DNA transformation. Complementation of the mutant for competence is restored by the reintroduction of a cosmid that restores production of type IV pili. Minimal competence is restored to the mutant by introduction of pilEL alone. We conclude that competence for DNA transformation in L. pneumophila is associated with expression of the type IV pilus and results in recombination of L. pneumophila DNA into the chromosome. Since expression of type IV pili also facilitates attachment of L. pneumophila to mammalian cells and protozoa, we designated the type IV pili CAP (for competence- and adherence-associated pili). (+info)
Identification of Neisseria gonorrhoeae from primary cultures by a slide agglutination test.
Hen antigonococcal lipopolysaccharide hen serum was used in a simple slide agglutination test for the identification of Neisseria gonorrhoeae from primary isolates. (+info)
Pseudomonas aeruginosa killing of Caenorhabditis elegans used to identify P. aeruginosa virulence factors.
We reported recently that the human opportunistic pathogen Pseudomonas aeruginosa strain PA14 kills Caenorhabditis elegans and that many P. aeruginosa virulence factors (genes) required for maximum virulence in mouse pathogenicity are also required for maximum killing of C. elegans. Here we report that among eight P. aeruginosa PA14 TnphoA mutants isolated that exhibited reduced killing of C. elegans, at least five also exhibited reduced virulence in mice. Three of the TnphoA mutants corresponded to the known virulence-related genes lasR, gacA, and lemA. Three of the mutants corresponded to known genes (aefA from Escherichia coli, pstP from Azotobacter vinelandii, and mtrR from Neisseria gonorrhoeae) that had not been shown previously to play a role in pathogenesis, and two of the mutants contained TnphoA inserted into novel sequences. These data indicate that the killing of C. elegans by P. aeruginosa can be exploited to identify novel P. aeruginosa virulence factors important for mammalian pathogenesis. (+info)
Antimicrobial susceptibilities and plasmid contents of Neisseria gonorrhoeae isolates from commercial sex workers in Dhaka, Bangladesh: emergence of high-level resistance to ciprofloxacin.
Commercial sex workers (CSWs) serve as the most important reservoir of sexually transmitted diseases (STD), including gonorrhea. Periodic monitoring of the antimicrobial susceptibility profile of Neisseria gonorrhoeae in a high-risk population provides essential clues regarding the rapidly changing pattern of antimicrobial susceptibilities. A study concerning the prevalence of gonococcal infection among CSWs was conducted in Bangladesh. The isolates were examined with regards to their antimicrobial susceptibility to, and the MICs of, penicillin, tetracycline, ciprofloxacin, cefuroxime, ceftriaxone, and spectinomycin by disk diffusion and agar dilution methods. The total plasmid profile of the isolates was also analyzed. Of the 224 CSWs, 94 (42%) were culture positive for N. gonorrhoeae. There was a good correlation between the results of the disk diffusion and agar dilution methods. Some 66% of the isolates were resistant to penicillin, and 34% were moderately susceptible to penicillin. Among the resistant isolates, 23.4% were penicillinase-producing N. gonorrhoeae (PPNG). 60.6% of the isolates were resistant and 38.3% were moderately susceptible to tetracycline, 17.5% were tetracycline-resistant N. gonorrhoeae, 11.7% were resistant and 26.6% had reduced susceptibility to ciprofloxacin, 2.1% were resistant and 11.7% had reduced susceptibility to cefuroxime, and 1% were resistant to ceftriaxone. All PPNG isolates contained a 3.2-MDa African type of plasmid, and a 24.2-MDa conjugative plasmid was present in 34.1% of the isolates. Since quinolones such as ciprofloxacin are recommended as the first line of therapy for gonorrhea, the emergence of significant resistance to ciprofloxacin will limit the usefulness of this drug for treatment of gonorrhea in Bangladesh. (+info)
Characterization of the recD gene of Neisseria gonorrhoeae MS11 and the effect of recD inactivation on pilin variation and DNA transformation.
Pilin antigenic variation in Neisseria gonorrhoeae may result following intrachromosomal recombination between homologous pil genes. Despite extensive study, recA is the only previously characterized gene known to be involved in this process. In this study, the gonococcal recD gene, encoding one subunit of the putative RecBCD holoenzyme, was characterized and its role in pilin variation assessed. The complete recD gene of N. gonorrhoeae MS11 was cloned and its nucleotide sequence determined. The gonococcal recD gene complemented a defined Escherichia coli recD mutant, based on plaque formation of bacteriophage lambda and the restoration of ATP-dependent nuclease activity. Inactivation of the gonococcal recD gene had no measurable effect on cell viability or survival following UV exposure, but did decrease the frequency of DNA transformation approximately threefold. The frequency at which non-parental pilin phenotypes were spawned was 12-fold greater in MS11 recD mutants compared with the parental MS11 rec+ strain. Similar results were obtained using recD mutants that were not competent for DNA transformation. Complementation of the MS11 recD mutant with a wild-type recD gene copy restored the frequency of pilin phenotypic variation to approximately wild-type levels. The nucleotide changes at pilE in the recD mutants were confined to the variable regions of the gene and were similar to changes previously attributed to gene conversion. (+info)