Rodríguez-Cerrato Violeta, García Pedro, Del Prado Gema, García Ernesto, Gracia Matilde, Huelves Lorena, Ponte Carmen, López Rubens, Soriano Francisco
Department of Medical Microbiology and Antimicrobial Chemotherapy, Fundación Jiménez Díaz, Avenida de Reyes Católicos 2, 28040 Madrid, Spain.
J Antimicrob Chemother. 2007 Nov;60(5):1159-62. doi: 10.1093/jac/dkm342. Epub 2007 Sep 7.
In an innovative therapeutic exploitation against antibiotic-resistant Streptococcus pneumoniae, here we have evaluated the in vitro activity of a purified bacterially-encoded cell wall lytic enzyme, LytA (the major pneumococcal autolysin), and compared it with those of Cpl-1 and Pal (pneumococcal phage lytic enzymes) and two antibiotics versus four pneumococcal strains.
Two serotype 3, penicillin-susceptible strains and two penicillin-resistant (serotypes 19F and 19A, respectively) S. pneumoniae clinical isolates were used. The effect of several combinations of lytic enzymes and antibiotics (cefotaxime and moxifloxacin) was studied by chequerboard and time-kill assays, the latter at concentrations of 0.25 x MIC.
LytA was more active than Cpl-1 and Pal. By the chequerboard technique, the combination of LytA and cefotaxime was synergistic for one of the two cefotaxime-resistant strains studied. The combined use of Cpl-1 and Pal was synergistic for three of the four strains, as was Cpl-1 with antibiotics for two of the three strains studied. In the time-kill assays, after 5 h of exposure to LytA, Cpl-1 or Pal, the mean differences in colony counts versus controls were -3.55, -2.66 and -2.71 log(10) cfu/mL, respectively. The combination of LytA/Pal reduced the bacterial inoculum >2 log units for three of the four strains. LytA combined with cefotaxime or moxifloxacin achieved >3 log units decrease for the strains tested. Particularly, a strong synergism was observed with LytA/cefotaxime for one cefotaxime-resistant meningeal strain. LytA/moxifloxacin was synergistic for the quinolone-resistant strain when tested by time-kill methodology, and just close to synergistic (fractional inhibitory concentration index of 0.58) by the chequerboard technique. Antagonism was not observed for any combination when assayed by either method.
LytA, Cpl-1 or Pal, alone or in combination, might prove to be effective in combination therapy, as well as in monotherapy against S. pneumoniae. These results suggest avenues of research to study the cell wall lytic enzymes as anti-pneumococcal therapeutic agents.
在针对耐抗生素肺炎链球菌的创新性治疗探索中，我们评估了一种纯化的细菌编码细胞壁溶解酶LytA（主要的肺炎球菌自溶素）的体外活性，并将其与Cpl-1和Pal（肺炎球菌噬菌体溶解酶）以及两种抗生素针对四种肺炎球菌菌株的活性进行了比较。
使用了两株3型青霉素敏感菌株和两株青霉素耐药（分别为19F和19A血清型）的肺炎链球菌临床分离株。通过棋盘法和时间杀菌试验研究了几种溶解酶与抗生素（头孢噻肟和莫西沙星）组合的效果，时间杀菌试验采用0.25×MIC的浓度。
LytA比Cpl-1和Pal更具活性。通过棋盘法技术，LytA与头孢噻肟的组合对所研究的两株头孢噻肟耐药菌株中的一株具有协同作用。Cpl-1和Pal的联合使用对四株菌株中的三株具有协同作用，Cpl-1与抗生素的联合使用对所研究的三株菌株中的两株具有协同作用。在时间杀菌试验中，暴露于LytA、Cpl-1或Pal 5小时后，与对照相比，菌落计数的平均差异分别为-3.55、-2.66和-2.71 log(10) cfu/mL。LytA/Pal组合使四株菌株中的三株细菌接种量减少>2个对数单位。LytA与头孢噻肟或莫西沙星联合使用使受试菌株的菌落计数减少>3个对数单位。特别是，对于一株头孢噻肟耐药的脑膜菌株，观察到LytA/头孢噻肟具有强烈的协同作用。通过时间杀菌方法测试时，LytA/莫西沙星对喹诺酮耐药菌株具有协同作用，通过棋盘法技术测试时接近协同作用（分数抑制浓度指数为0.58）。两种方法检测时，任何组合均未观察到拮抗作用。
LytA、Cpl-1或Pal单独或联合使用可能在联合治疗以及针对肺炎链球菌的单药治疗中被证明是有效的。这些结果为研究细胞壁溶解酶作为抗肺炎球菌治疗药物提供了研究途径。
