Chalkley L J, van Vuuren S, Ballard R C, Botha P L
Department of Medical Microbiology, University of the Orange Free State, Bloemfontein.
S Afr Med J. 1995 Aug;85(8):775-80.
To investigate penA and tetM resistance gene variation of Neisseria gonorrhoeae in order to define gene types for epidemiological monitoring and resistance development.
Isolates of N. gonorrhoeae which were susceptible and resistant to penicillin and/or tetracycline were selected. Strains comprised South African isolates (22 from Bloemfontein, 13 from Transvaal, 20 from the Cape) and 15 Botswana and 4 Namibia isolates. The penA genes (2 kb) of all strains and tetM genes (765 bp) of 11 high-level tetracycline-resistant strains were amplified and restricted with HpaII.
Twelve different HpaII fingerprint patterns were obtained from the 74 isolates analysed for penicillin-binding protein (PBP) 2 gene (penA) alterations. Focusing on the transpeptidase domain, 25 isolates (3 whole gene patterns, minimal inhibitory concentrations (MICs) < or = 0.03-0.125 micrograms/ml) had restriction sites equivalent to those previously described for a susceptible strain. Of the remaining 9 PBP 2 gene groups, 25 strains fell into a designated group E. Penicillin/ penicillin + clavulanic acid MICs determined on these group E isolates gave a range of 0.125-2.0 micrograms/ml, although MICs against 4 strains were < or = 0.03 micrograms/ml. MICs of penicillin/penicillin + clavulanic acid for the 24 isolates that contained altered PBP 2 transpeptidase gene regions not designated group E were only < or = 0.03-0.125 micrograms/ml. The lack of a HpaII restriction site at nucleotide 1934 in the PBP 2 gene of group E strains was indicative of a small terminal region of N. cinerea DNA. This gene block, which was found in all the southern African areas studied, appears to predispose isolates to increased penicillin resistance. The 25.2 MDa conjugative plasmid carrying the tetM resistance determinant was readily demonstrated in 11 Botswana/Namibia isolates exhibiting high-level resistance to tetracycline (MICs > or = 16 micrograms/ml). The tetM gene was shown to be of the American type.
研究淋病奈瑟菌的penA和tetM耐药基因变异情况，以确定用于流行病学监测和耐药性发展研究的基因类型。
选择对青霉素和/或四环素敏感及耐药的淋病奈瑟菌分离株。菌株包括南非分离株（22株来自布隆方丹，13株来自德兰士瓦，20株来自开普敦）以及15株博茨瓦纳分离株和4株纳米比亚分离株。扩增所有菌株的penA基因（2 kb）以及11株高耐四环素菌株的tetM基因（765 bp），并用HpaII进行酶切。
对74株用于分析青霉素结合蛋白（PBP）2基因（penA）改变的分离株进行检测，获得了12种不同的HpaII指纹图谱。聚焦于转肽酶结构域，25株分离株（3种全基因图谱，最低抑菌浓度（MIC）≤0.03 - 0.125微克/毫升）具有与先前描述的敏感菌株相同的酶切位点。在其余9个PBP 2基因组中，25株菌株属于指定的E组。对这些E组分离株测定的青霉素/青霉素 + 克拉维酸MIC范围为0.125 - 2.0微克/毫升，不过有4株菌株的MIC≤0.03微克/毫升。对于24株含有未指定为E组的改变的PBP 2转肽酶基因区域的分离株，青霉素/青霉素 + 克拉维酸的MIC仅≤0.03 - 0.125微克/毫升。E组菌株的PBP 2基因中第1934位核苷酸处缺乏HpaII酶切位点，这表明存在一小段灰质奈瑟菌DNA末端区域。在所有研究的南部非洲地区均发现了该基因片段，它似乎使分离株更易产生青霉素耐药性。在11株对四环素表现出高耐药性（MIC≥16微克/毫升）的博茨瓦纳/纳米比亚分离株中，很容易检测到携带tetM耐药决定簇的25.2 MDa接合质粒。tetM基因显示为美国型。
