Gaudereto Juliana Januario, Neto Lauro Vieira Perdigão, Leite Gleice Cristina, Espinoza Evelyn Patricia Sanchez, Martins Roberta Cristina Ruedas, Villas Boa Prado Gladys, Rossi Flavia, Guimarães Thais, Levin Anna Sara, Costa Silvia Figueiredo
Laboratório de Investigação Médica 49 - LIM-49, Instituto de Medicina Tropical, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, Avenida Doutor Enéas de Carvalho Aguiar, 470, São Paulo, SP, 05403-000, Brazil.
Divisão de Laboratório Central - Serviço de Microbiologia Clínica, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brazil.
BMC Microbiol. 2020 Apr 16;20(1):97. doi: 10.1186/s12866-020-01756-0.
The use of combined antibiotic therapy has become an option for infections caused by multidrug-resistant (MDR) bacteria. The time-kill (TK) assay is considered the gold standard method for the evaluation of in vitro synergy, but it is a time-consuming and expensive method. The purpose of this study was to evaluate two methods for testing in vitro antimicrobial combinations: the disk diffusion method through disk approximation (DA) and the agar gradient diffusion method via the MIC:MIC ratio. The TK assay was included as the gold standard. MDR Gram-negative clinical isolates (n = 62; 28 Pseudomonas aeruginosa, 20 Acinetobacter baumannii, and 14 Serratia marcescens) were submitted to TK, DA, and MIC:MIC ratio synergy methods.
Overall, the agreement between the DA and TK assays ranged from 20 to 93%. The isolates of A. baumannii showed variable results of synergism according to TK, and the calculated agreement was statistically significant in this species against fosfomycin with meropenem including colistin-resistant isolates. The MIC:MIC ratiometric agreed from 35 to 71% with TK assays. The kappa test showed good agreement for the combination of colistin with amikacin (K = 0.58; P = 0.04) among the colistin-resistant A. baumannii isolates.
The DA and MIC:MIC ratiometric methods are easier to perform and might be a more viable tool for clinical microbiology laboratories.
联合抗生素治疗已成为耐多药（MDR）细菌所致感染的一种选择。时间杀菌（TK）试验被认为是评估体外协同作用的金标准方法，但它是一种耗时且昂贵的方法。本研究的目的是评估两种测试体外抗菌联合作用的方法：通过纸片逼近法（DA）的纸片扩散法和通过MIC:MIC比值的琼脂梯度扩散法。将TK试验作为金标准纳入。对62株耐多药革兰氏阴性临床分离株（28株铜绿假单胞菌、20株鲍曼不动杆菌和14株粘质沙雷氏菌）进行了TK、DA和MIC:MIC比值协同作用方法的检测。
总体而言，DA试验与TK试验之间的一致性范围为20%至93%。鲍曼不动杆菌分离株根据TK试验显示出不同的协同作用结果，在该菌种中，对于磷霉素与美罗培南联合使用（包括耐粘菌素分离株），计算得出的一致性具有统计学意义。MIC:MIC比值法与TK试验的一致性为35%至71%。kappa检验显示，在耐粘菌素的鲍曼不动杆菌分离株中，粘菌素与阿米卡星联合使用具有良好的一致性（K = 0.58；P = 0.04）。
DA法和MIC:MIC比值法操作更简便，可能是临床微生物实验室更可行的工具。
