High-frequency conjugal transfer of a gonococcal penicillinase plasmid

Mobilization of the gonococcal 5.2 kb beta-lactamase plasmid pSJ5.2 into Escherichia coli by cointegration with several gram-conjugative plasmids

We report the mobilization by cointegration of the gonococcal 5.2 kb beta-lactamase plasmid pSJ5.2 in an Escherichia coli background. Transfer of pSJ5.2 was measured by filter mating assays with five different conjugative plasmids from Enterobacteriaceae and the gonococcal 41 kb tet(M). Plasmid pSJ5.2 was mobilized to E. coli at frequencies of 1.7x10(-6), 9.3x10(-8) and 2.7x10(-5) by the tet(M), R64 drd-33 and N3 conjugative plasmids, respectively. Mobilization of pSJ5.2 by the 41 kb tet(M) conjugative plasmid resulted in stable Amp(R) E. coli transconjugants consisting of pSJ5.2 plasmid with an insertion located in the 2.4 kb BamHI-BamHI fragment. Mobilization of pSJ5.2 by R64drd-33 and N3 conjugative plasmids involved stable cointegrates as detected by Southern Blot with a DIG-labelled PstI-digested pSJ5.2 probe. Restriction analysis of the R64::pSJ5.2 and N3::pSJ5.2 cointegrates and Southern Blot with the pSJ5.2 probe showed that cointegrates formed by deletion of DNA regions within the 1.8 kb BamHI-HindIII fragment of pSJ5.2. The plasmid thus appears to use multiple recombination mechanisms for cointegration with different conjugative plasmids. The complete nucleotide sequence of pSJ5.2 was determined, and will be a useful tool to further investigate the molecular mechanisms leading to its cointegrative transfer.

Gonococcal infections in neonates and young children

Gonorrhea has been recognized since antiquity, and more than 60 million new cases occur yearly worldwide. Much has been learned about the molecular pathogenesis of infection by Neisseria gonorrhoeae, but immunity from natural infection does not protect against reinfection with the same strain, and the goal of a protective vaccine remains elusive. Gonococcal ophthalmia neonatorum is the most common manifestation in infants born to mothers with gonococcal genital tract infections. Genital and pharyngeal gonococcal infections in young children almost always are acquired from sexual abuse by an infected adult. Invasive disease can occur at any age but is uncommon. Nonculture diagnostic tests are widely used in adults, but culture is required in children for medicolegal purposes. N. gonorrhoeae strains have developed resistance to many antibiotic classes, and resistance profiles vary among geographic regions and within regions over time. Current guidelines for treatment of gonococcal infections in children in the United States are reviewed.

Molecular analysis of oriT and MobA protein in the 7.4 kb mobilizable beta-lactamase plasmid pSJ7.4 from Neisseria gonorrhoeae

The mobilization region of the 7.4 kb beta-lactamase plasmid pSJ7.4 from Neisseria gonorrhoeae was characterized. The 3.2 kb HindIII-BamHI fragment of pSJ7.4 was mobilized between Escherichia coli strains by conjugative plasmid RK2. Selected restriction enzyme-generated deletions of this fragment were subcloned in pACYC177 to obtain constructs that were suitable for analysis of the mobilization region. Mating experiments showed that a highly conserved 1.9 kb DNA region within coordinates 4096-5997 is required for mobilization of pSJ7.4. This region contains two genes encoding the mobilization protein MobA, another protein, MobC, putatively involved in mobilization from some hosts, and an intergenic oriT. The 168 bp intergenic sequence also contains the promoters for mobA and mobC in an arrangement that suggests divergent transcription and autoregulation from oriT. The 56 kDa MobA was expressed in E. coli as a (6x)His-Tag fusion protein. Purified MobA specifically induced plasmid relaxation by nicking at the oriT. MobA is exceptional because the N-terminal region alone can mobilize pSJ7.4, albeit at a lower frequency than the full-length protein, even in the absence of MobC. The carboxyl terminal region of MobA did not share homology with other mobilization proteins, but may be involved in promoting efficient transfer of pSJ7.4.

[Gonorrhea]

Gonorrhea is a common bacterial infection caused by Neisseria gonorrhoeae, a Gram-negative diplococcus that is transmitted almost exclusively by sexual contact or perinatally. It primarily affects the mucous membranes of the lower genital tract and less frequently those of the rectum, oropharynx, and conjunctivae. Ascending genital infection in women leads to the predominant complication, acute salpingitis, one of the most common causes of female infertility in the world. Since the 1990s, a remarkable surge of information ensued regarding the pathogenesis of gonorrhea and its agent. Gonorrhea has proven difficult to control in most populations and remains a prime example of the influence that social, behavioral, and demographic factors can have on the epidemiology of an infectious disease. The management of gonorrhea and other sexually transmitted infections requires both treatment of the patient as an individual and of his or her sexual partner(s) as a public health measure to interrupt the onward spread of infection and prevent long-term complications.

Transfer of beta-lactamase plasmids by conjugation in Neisseria gonorrhoeae

Conjugation experiments in vitro have been used in an attempt to explain certain epidemiological phenomena seen amongst penicillinase producing Neisseria gonorrhoeae (PPNG) isolated at St Mary's Hospital, London. These include changes in plasmid profiles, a lack of beta-lactamase encoding plasmids in PAOU-requiring strains and a difference in the serological classification of strains of PPNG and non-PPNG isolated from the same clinic. It was shown that acquisition of the conjugative plasmid by beta-lactamase producing transconjugants does vary, but is not related to the auxotype/serovar (A/S) class of, or type of beta-lactamase plasmid carried by the donor. It was not possible to transfer either the 3.2MDa or 4.4MDa plasmids to PAOU-requiring strains of N gonorrhoeae. The conjugation frequency from a single donor to different recipients was shown to be variable, but was not influenced by the serovar of the recipients. It was shown that the transfer and acceptance of beta-lactamase encoding plasmids is variable but it was not possible to identify the factors responsible.

BRO beta-lactamases of Branhamella catarrhalis and Moraxella subgenus Moraxella, including evidence for chromosomal beta-lactamase transfer by conjugation in B. catarrhalis, M. nonliquefaciens, and M. lacunata

Two closely related beta-lactamases, BRO-1 and BRO-2 (formerly called Ravasio and 1908), are found in Moraxella (Branhamella) catarrhalis. We screened strains of B. catarrhalis recovered in the United States since 1952 and identified the first beta-lactamase-positive isolate in August 1976. The prevalence of the enzymes among 394 clinical isolates from one Texas hospital has averaged 75% since testing began in 1983. Screening of isolates of Moraxella subgenus Moraxella revealed the BRO enzymes in two other human respiratory tract species, M. lacunata and M. nonliquefaciens, beginning in 1978. A different beta-lactamase with a pI of 6.4 predominated in other species of subgenus Moraxella. BRO-2 had a different isoelectric focusing pattern and was produced in lesser amounts than BRO-1, but the two enzymes were indistinguishable by substrate or inhibitor profile. BRO enzymes from B. catarrhalis, M. nonliquefaciens, and M. lacunata could be transferred by conjugation and, for B. catarrhalis, also by transformation to B. catarrhalis. Plasmid bands were demonstrated in 90% of M. nonliquefaciens and in one previously reported strain of B. catarrhalis, but no change in plasmid profiles was seen in beta-lactamase-positive recombinants, supporting previous studies that suggested the beta-lactamase genes are chromosomal.

Evaluation of plasmids in tetracycline resistant strains of Neisseria gonorrhoeae and Ureaplasma urealyticum in a case of severe urethritis

A young man who acquired gonococcal urethritis in the Far East was not cured by repeated i.v. treatment with a broad-spectrum penicillin. Cultures of pre- and post-treatment urethral specimens grew tetracycline-resistant penicillinase-producing Neisseria gonorrhoeae (PPNG) and tetracycline-resistant Ureaplasma urealyticum. The patient was successfully treated with erythromycin, to which both isolates were sensitive. The strain of N. gonorrhoeae carried a novel plasmid of 10.5 Md molecular mass in addition to plasmids previously observed in this organism. The strain of U. urealyticum carried two distinct plasmids, one with mass 4.9 Md and the other one with mass 8.1 Md. This report demonstrates that ureaplasmas can contain plasmids and raises the question if tetracycline resistance is controlled by plasmids or by the chromosome.

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).

Mobilization of nonconjugative antibiotic resistance plasmids in Haemophilus ducreyi

A clinical isolate of Haemophilus ducreyi was found to harbor three plasmids: a 23.5-megadalton (Mdal) phenotypically cryptic plasmid, a 7.0-Mdal ampicillin resistance plasmid, and a 4.0-Mdal sulfonamide resistance plasmid. The two smaller plasmids were transferable by conjugation to Haemophilus recipients, but only if the donor cell harbored the 23.5-Mdal plasmid as well, indicating that this large plasmid had mobilizing capabilities. Transfer was also possible to Escherichia coli recipients. Haemophilus influenzae transconjugants which had acquired both the 23.5-Mdal plasmid and one of the R-plasmids could subsequently retransfer the R-plasmid to other Haemophilus recipients at higher frequencies. A derivative of the 23.5 Mdal plasmid was isolated which was shown by restriction endonuclease analysis to contain an ampicillin resistance transposon and to have retained its conjugative ability.