Genome plasticity in Neisseria gonorrhoeae

Abstract The pathogenic Neisseria have exploited the processes of horizontal DNA transfer and genetic recombination as mechanisms for the generation of extensive protein variation and modulation of gene expression. Localized recombinations have been well documented in members of multigene families as have alterations in short repetitive sequences. Here we report an analysis of the chromosomal structure of a defined lineage of Neisseria gonorrhoeae strain MS 11 pilin variants. This study reveals the occurrence of large rearrangements, including the amplification of a 26 kb region and an inversion involving more than a third of the chromosome. Additionally, a restriction site polymorphism that correlates with pilin expression has been observed. These findings highlight the flexibility of the gonococcal genome.     

Autoplaquing in Neisseria gonorrhoeae.

Irregularly shaped autoplaques were observed on a lawn of two different strains of Neisseria gonorrhoeae. Autoplaquing occurred on gonococcal genetic medium lacking arginine and was noninducible on complete gonococcal genetic medium. The cell density, incubation temperature, and agar base influenced autoplaquing. Single-colony suspensions varied in plaque morphology. We were unable to isolate a stable nonplaquing variant but separated strain RUN5287 into two plaquing phenotypes.     

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.     

Penicillinase-producing Neisseria gonorrhoeae in Canada.

The incidence of infection with penicillinase-producing Neisseria gonorrhoeae (PPNG) reported to the Laboratory Centre for Disease Control in Ottawa has steadily increased since the first Canadian isolation of such a strain in 1976. As of September 1980 a total of 66 PPNG isolates had been referred for biological and genetic characterization as well as for central documentation of the epidemiologic aspects of each case. Over 90% of the infections were firmly traced to patients or contacts who had acquired the infection abroad; this indicates that Canada does not, as yet, have an epidemic focus of PPNG infection. This report includes a synopsis of the biological characteristics of these isolates and an analysis of the results of primary antibiotic treatment that illustrates the importance of considering spectinomycin as the antibiotic of choice for PPNG infections.     

Autolysis of Neisseria gonorrhoeae.

Autolysis of Neisseria gonorrhoeae was studied under different conditions. It was found that low pH and temperature, as well as the presence of divalent cations, spermine, sucrose, and polyvinylpyrrolidone, stabilized nongrowing gonococci. Ethylenediaminetetraacetic acid alone promoted lysis, whereas lysozyme had only a limited additive effect. The autolytic behavior of gonococci appears to be connected with their prolonged cell division process. The relative dependence on the outer membrane and the peptidoglycan layer for the mechanical stability of gonococci is discussed.     

L form of Neisseria gonorrhoeae

Roberts, Richard B. (Walter Reed Army Institute of Research, Washington, D.C.). L form of Neisseria gonorrhoeae. J. Bacteriol. 92:1609-1614. 1966.-L forms were produced by the penicillin gradient plate technique from a recently isolated strain of Neisseria gonorrhoeae. To date, these L forms have had 30 serial passages on medium containing penicillin. Stabilized L forms developed on penicillin-free medium after 10 or more passages in the presence of penicillin. Morphological characteristics of these organisms were identical to L forms of meningococci. Medium and environmental conditions necessary for optimal growth included: Brain Heart Infusion of pH 7.2 to 7.4, 1.1 to 1.3% agar, 10 to 20% sucrose, 10 to 20% horse serum, temperature at 35 to 36 C, and increased CO(2) tension (candle jar). L forms were more resistant than the parent gonococcus to penicillin, ampicillin, methicillin, cycloserine, and cephalothin, whereas both organisms had similar sensitivities to bacitracin, vancomycin, ristocetin, novobiocin, tetracycline, and erythromycin. Revertant gonococci were produced on penicillin-free medium from L forms which had had 1, 5, and 10 serial passages. Morphology and fermentative reactions of revertant strains were identical to those of the parent gonococcus. Revertant strains produced L forms more readily than the parent organism; in fact, L forms from certain revertants did not require penicillin, but only serum and sucrose for their production and propagation on artificial medium.     

Autolysis of Neisseria gonorrhoeae.

Physiological conditions that would provide maximal rates of autolysis of Neisseria gonorrhoeae were examined. Autolysis was found to occur over a broad pH range with the optimum at pH 9.0 IN 0.05 M tris(hydroxymethyl)amino-methane-maleate buffer. The temperature optimum was found to be 40 C. Potassium ions greatly stimulated autolysis at a concentration of 0.01 M. Exposure of growing N. gonorrhoeae cells to penicillin, vancomycin, or D-cycloserine influenced the susceptibility to the autolysis, whereas chloramphenicol afforded some protection against autolysis. The primary structure of the peptidoglycan is composed of muramic acid/glutamic acid/alanine/diaminopimelic acid/glucosamine in approximate molar ratios of 1:1:2:1:1, respectively. Exogenous radioactive diaminopimelic acid, D-glucosamine, and D-alanine were incorporated into peptidoglycan. During autolysis these radioactive fragments were released from cells.     

The epidemiology of Neisseria gonorrhoeae in Europe

This review addresses the occurrence, the trends, and the risk groups of Neisseria gonorrhoeae in Europe over the past decade. A decline has been observed in most of Europe since the 1980s, except for an increase in the Baltic countries (early 1990s) and an increase among men who have sex with men (between 1989 and 1991), and heterosexuals in some countries (between 1995 and 1997). Despite the overall fall in the incidence of gonorrhoea, plasmid-mediated resistance to penicillin and tetracycline increased in Europe. More recently, resistance to fluoroquinolones has been documented, mainly imported from Southeast Asia. Until now, no resistance to third-generation cephalosporins has been observed.     

Survival of Neisseria gonorrhoeae in the Mail

Cultures of Neisseria gonorrhoeae, which used Thayer-Martin slants as transport medium, survived at least 1 day in the mail.     

Genetic exchange mechanisms in Neisseria gonorrhoeae.

There are two mechanisms for genetic exchange in Neisseria gonorrhoeae. Plasmid deoxyribonucleic acid can be transferred by conjugation, which is dependent on the presence of a 24.5-megadalton plasmid in the donor cell. We have shown that chromosomal deoxyribonucleic acid can be exchanged between all colonial variants by transformation, but not by conjugation. In the nonpiliated variants, however, this exchange was dependent on the presence of the 24.5-megadalton plasmid in the recipient cell.     

淋病奈瑟球菌的耐药性检测

目的了解淋病奈瑟球菌对临床常见药物的耐药性。方法采用琼脂稀释法测定13种抗菌药物对35株淋病奈瑟球菌的MICs;Nitrocefin(头孢硝噻酚)纸片检测β-内酰胺酶,并采用PCR测定其基因型。结果淋病奈瑟球菌对青霉素、四环素、环丙沙星与头孢呋辛的耐药率分别为65．7％、60．0％、88．6％与14．3％,对第3、4代头孢菌素、大观霉素非常敏感,耐药率均为0％;42．9％的菌株产生TEM型β-内酰胺酶。结论淋病奈瑟球菌对青霉素、四环素类和氟喹诺酮类的耐药性高,治疗宜选用第3、4代头孢菌素和大观霉素等,同时加强耐药性监测。