Penicillinase-Producing Plasmid Types in Neisseria gonorrhoeae Clinical Isolates from Australia

Penicillinase-producing Neisseria gonorrhoeae (PPNG) carrying the bla_TEM-135 gene is of particular concern, as it is considered a stepping stone toward resistance to extended-spectrum cephalosporins. Here, we sought to characterize plasmid types and the occurrence of the bla_TEM-135 gene for N. gonorrhoeae clinical isolates from Australia. We found that bla_TEM-135 was prevalent in Australian PPNG and was detected on all three major plasmid types.     

Feasibility of Screening for Penicillinase-Producing Neisseria gonorrhoeae from Primary Culture Plates by Using a Rapid Microacidometric Test

We have shown that it is possible to screen for penicillinase-producing Neisseria gonorrhoeae directly from primary culture plates. Experiments involving the cocultivation of four genera of beta-lactamase-positive (beta-lac(+)) bacteria and a beta-lactamase-negative (beta-lac(-)) N. gonorrhoeae on modified Thayer-Martin medium indicated that suppressed or inhibited beta-lac(+) bacteria did not give false-positive results when isolated beta-lac(-) colonies of gonococci were tested. Colonies were assayed for beta-lac production by an adaptation of a microacidometric method in which bacteria could be tested before or after the addition of oxidase reagent.     

Purification by Affinity Chromatography and Properties of a β-Lactamase Isolated from Neisseria gonorrhoeae

beta-Lactamase activity was detected in cell-free preparations obtained from ultrasonic treatment of Neisseria gonorrhoeae after growth in liquid medium. Crude preparations of beta-lactamase were subjected to affinity chromatography, using several beta-lactam antibiotics as ligands bound to agarose supports. Affinity gels produced by coupling 7-aminocephalosporanic acid or 6-aminopenicillanic acid by their amino groups to carboxyl-terminal agarose via a five- to eight-carbon spacer arm proved to be effective chromatography media. beta-Lactamase preparations subjected to chromatography using these gels were purified 200-fold, with approximately 80% recovery of active material. Purified preparations were judged homogeneous by their behavior during electrophoresis on polyacrylamide in both the presence and absence of sodium dodecyl sulfate. Characterization of the purified enzyme established a molecular weight of approximately 25,000 and an isoelectric point of 5.4. Analyses of substrate specificity, effect of inhibitors, pH, and kinetic parameters were performed. The evidence suggests that the beta-lactamase produced in N. gonorrhoeae closely resembles the character of class IIIa (TEM-type) beta-lactamases.     

Multiple Antibiotic Resistance in Clinical Strains of Neisseria gonorrhoeae Isolated in South Carolina

A method of assaying colicin K is described. It makes use of two properties of sodium dodecyl sulfate to protect bacteria against colicin action and to dissolve those bacteria on which colicin K had started its action. By this method, the kinetics of bacterial killing by colicin K have been measured directly in the treated culture without intervening dilution. The kinetics are exponential with time and are a function of the colicin multiplicity, as described previously, but do not reach a final plateau. At any time during colicin treatment, free colicin is found in the medium. Procedures that eliminate or destroy this free colicin, such as centrifugation and resuspension of the treated bacteria in a fresh medium, or addition of trypsin or sodium dodecyl sulfate to the treated culture stop bacterial killing.     

Characterization of a gyrB mutation responsible for low-level nalidixic acid resistance in Neisseria gonorrhoeae

Nalidixic acid-resistant derivatives of Neisseria gonorrhoeae WR302 were identified and categorized into two classes on the basis of their susceptibilities to this antimicrobial agent. The MIC of nalidixic acid for the derivative strain MUG116 was fourfold greater than that for its isogenic parental strain WR302 (2 versus 0.5 micrograms/ml, respectively). MUG324 was significantly more resistant to nalidixic acid (greater than 64 micrograms/ml). The MICs of other antimicrobial agents known to interact with either the gyrA or gyrB gene products were determined. Although the nalidixic acid MIC for MUG116 increased, no significant increases in the MICs of other agents that interact with the gyrA gene product were seen. The MICs of all agents that interact with the gyrA gene product were significantly increased for MUG324. The gene that imparts low-level nalidixic acid resistance was cloned from strain MUG116. The DNA sequence of this gene was determined, and by comparing the deduced amino acid sequence with sequences of proteins in data bases, this protein was found to be approximately 70% homologous with the gyrB gene product of Escherichia coli.     

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.     

Emerging resistance in Neisseria meningitidis and Neisseria gonorrhoeae

The value of monitoring antimicrobial resistance is particularly significant for Neisseria meningitidis and Neisseria gonorrhoeae diseases, even if it is for different reasons. Although there is no global alert for the spread of resistant meningococcal strains, the emergence of resistance is correlated to the outcome of treatment and the successful prophylaxis of close contacts. Few cases of resistance among meningococci have been recorded worldwide; it remains unclear what intriguing mechanism is responsible for maintaining resistance in these cases in the absence of significant antibiotic selective pressure, as in the case of penicillin; on the contrary, although rifampicin is the antibiotic of choice in the prophylaxis of close contacts, there is a very low rate of resistance. The emergence of multidrug-resistant N. gonorrhoeae is a great challenge in controlling gonorrhea as one of the main sexually transmitted bacterial diseases. International surveillance programs permit the monitoring of the susceptibility of the pathogen and allow the revision of the standardized treatment regimen when the situation changes.     

Characterization of the Novel DNA Gyrase Inhibitor AZD0914: Low Resistance Potential and Lack of Cross-Resistance in Neisseria gonorrhoeae

The unmet medical need for novel intervention strategies to treat Neisseria gonorrhoeae infections is significant and increasing, as rapidly emerging resistance in this pathogen is threatening to eliminate the currently available treatment options. AZD0914 is a novel bacterial gyrase inhibitor that possesses potent in vitro activities against isolates with high-level resistance to ciprofloxacin and extended-spectrum cephalosporins, and it is currently in clinical development for the treatment of N. gonorrhoeae infections. The propensity to develop resistance against AZD0914 was examined in N. gonorrhoeae and found to be extremely low, a finding supported by similar studies with Staphylococcus aureus. The genetic characterization of both first-step and second-step mutants that exhibited decreased susceptibilities to AZD0914 identified substitutions in the conserved GyrB TOPRIM domain, confirming DNA gyrase as the primary target of AZD0914 and providing differentiation from fluoroquinolones. The analysis of available bacterial gyrase and topoisomerase IV structures, including those bound to fluoroquinolone and nonfluoroquinolone inhibitors, has allowed the rationalization of the lack of cross-resistance that AZD0914 shares with fluoroquinolones. Microbiological susceptibility data also indicate that the topoisomerase inhibition mechanisms are subtly different between N. gonorrhoeae and other bacterial species. Taken together, these data support the progression of AZD0914 as a novel treatment option for the oral treatment of N. gonorrhoeae infections.     

Changing Antimicrobial Resistance Profiles among Neisseria gonorrhoeae Isolates in Italy, 2003 to 2012

The emergence of Neisseria gonorrhoeae isolates displaying resistance to antimicrobial agents is a major public health concern and a serious issue related to the occurrence of further untreatable gonorrhea infections. A retrospective analysis on 1,430 N. gonorrhoeae isolates, collected from 2003 through 2012, for antimicrobial susceptibility by Etest and molecular characterization by Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) was carried out in Italy. Azithromycin-resistant gonococci decreased from 14% in 2007 to 2.2% in 2012. Similarly, isolates with high MICs to cefixime (>0.125 mg/liter) decreased from 11% in 2008 to 3.3% in 2012. The ciprofloxacin resistance rate remains quite stable, following an increasing trend up to 64% in 2012. The percentage of penicillinase-producing N. gonorrhoeae (PPNG) significantly declined from 77% in 2003 to 7% in 2012. A total of 81 multidrug-resistant (MDR) gonococci were identified, showing 11 different antimicrobial resistance patterns. These were isolated from men who have sex with men (MSM) and from heterosexual patients. Two sequence types (STs), ST661 and ST1407, were the most common. Genogroup 1407, which included cefixime-, ciprofloxacin-, and azithromycin-resistant isolates, was found. In conclusion, a change in the antimicrobial resistance profiles among gonococci was identified in Italy together with a percentage of MDR isolates.     

Neisseria gonorrhoeae endocarditis on a prosthetic valve

Neisseria gonorrhoeae is now a rare cause of infective endocarditis. We have reported the first case of N gonorrhoeae infection on a prosthetic valve, showing the possible consequences of a late diagnosis.     

2004～2005年南昌地区淋病奈瑟菌质粒谱型研究

目的：研究南昌地区淋病奈瑟菌质粒谱型的分布情况。方法：（1）采用碱裂解法提取淋病奈瑟菌质粒；（2）采用琼脂糖电泳法测定质粒分子量大小，并对菌株的青霉素耐药现象与4．5Md质粒的关系进行分析。结果：218株淋病奈瑟菌中有206株菌携带质粒，质粒总检出率为94．50％；质粒谱共分7型，以4．5Md＋2．6Md和24．5Md＋4．5Md＋2．6Md为主，分别占30．73％及24．77％，未检出3．2Md的R质粒。结论：南昌地区淋病奈瑟菌质粒谱型的分析对该地区淋病的防治有重要意义；4．5Md质粒与青霉素耐药密切相关。     

Phagocyte recognition of Neisseria gonorrhoeae

Human monocytes show an increased ability to bind pilate rather than non-pilate gonococci. Polymorphonuclear leucocytes (PMN) do not discriminate between pilate and non-pilate variants. PMN, however, bind appreciably more gonococci (either pilate or non-pilate) than monocytes. The results help to explain the role of pili on gonococci as virulence factors and in the immune response.     

细胞壁缺陷型淋病奈瑟菌cppB基因酶切图谱分析

目的探讨细胞壁缺陷对淋病奈瑟菌隐蔽性质粒B(cppB)基因的影响以及细胞壁缺陷型淋病奈瑟菌cppB的变异特点。方法用青霉素诱导淋病奈瑟菌成为细胞壁缺陷型并获得其纯培养物,cppB基因特异性引物PCR检测细胞壁缺陷型纯培养物的cppB基因,并对其cppB基因PCR扩增产物进行限制性核酸内切酶图谱分析。结果细菌型和细胞壁缺陷型均具有cppB基因扩增产物,经过限制性内切酶HindⅢ、HinfⅠ、HpaⅡ和MspⅠ消化和电泳,在5%PAGE凝胶电泳中,呈现出相同的电泳条带。结论淋病奈瑟菌细菌型及其细胞壁缺陷型对cppB基因限制性核酸内切酶(HindⅢ、HinfⅠ、MspⅠ、HpaⅡ)的分析没有发现淋病奈瑟菌L型具有与其亲代细菌型不同的图谱,提示细胞壁缺陷没有导致淋病奈瑟菌的cppB基因发生这些核酸酶切位点中核苷酸序列的改变。     

Multiple antibiotic resistance in Neisseria gonorrhoeae

The sensitivities of gonococcal isolates to six antibiotics were determined for gonococci isolated in Philadelphia in 1972. The degree of association between susceptibilities to any two antibiotics was determined (coefficient of correlation). The correlation between penicillin and tetracycline (r = 0.75) was almost as good as that between two penicillins, penicillin G and ampicillin (r = 0.85), but the difference was statistically significant. The lowest correlation found was between erythromycin and chloramphenicol (r = 0.62), two antibiotics seldom used in gonorrhea therapy. In addition, gonococci most resistant to one antibiotic were the most likely to be multiply resistant. This was found with respect to penicillin, tetracycline, erythromycin, and chloramphenicol. Approximately 40% of gonococci classified as "most resistant" (exceeding the resistance of 75% of all isolates) to one antibiotic were also "most resistant" to three others. Finally, multiply resistant mutants were isolated by selection for resistance to either penicillin or tetracycline. These results provide evidence for the existence of a common mechanism for multiple antibiotic resistance in the gonococcus.     

淋球菌基因诊断新进展

淋球菌是一类寄生于人体尿道黏膜,导致人类泌尿生殖系感染的的细菌。及时、准确地诊断淋球菌感染是控制淋病传染的关键。基因检测技术在淋球菌临床诊断中的应用将使淋球菌的检测更加灵敏、准确。本文就近年来应用于淋球菌临床诊断的目的基因和新的检测技术以及它们在临床诊断中的特异性和敏感性综述如下。     

Plasmid-Mediated Beta-Lactamase Production in Neisseria gonorrhoeae

Several beta-lactamase-producing, penicillin-resistant strains of Neisseria gonorrhoeae were examined for R plasmids. Penicillin-resistant strains isolated from men returning from the Far East and their contacts contained a 4.4 x 10(6)-dalton plasmid in common. Transformation studies and the isolation of a spontaneous penicillin-susceptible segregant showed that the structural gene for beta-lactamase was part of the 4.4 x 10(6)-dalton plasmid. An additional penicillin-resistant gonococcal strain isolated in London was found to harbor a 3.2 x 10(6)-dalton R plasmid. Deoxyribonucleic acid (DNA)-DNA duplex studies revealed that the penicillin-resistant gonococcal isolates contained a significant portion (about 40%) of the transposable DNA sequence, TnA, which includes the beta-lactamase gene commonly found on R plasmids of the Enterobacteriaceae and Haemophilus influenzae.     

Emerging resistance in Neisseria meningitidis and Neisseria gonorrhoeae - Retracted

This article was retracted on 14/10/2011 due to concerns regarding the similarity of some sections with previously published work. The journal believes this to have been an honest error on the author's part and the article was retracted with the author's full co-operation and agreement.