ABSTRACT
Canarium odontophyllum Miq. is an indigenous fruit found in Sarawak, Malaysia. Methicillin-resistant Staphylococcusaureus (MRSA) is a deadly pathogen that causes to hospital (health-care-acquired MRSA [HA-MRSA]) and community(CA-MRSA) infections worldwide. Vancomycin has been the therapeutic drug of choice against MRSA, but unfortunatelythis pathogen has developed some degree of resistance to vancomycin. This research aimed to evaluate the antimicrobialactivity of the stem bark extract of C. odontophyllum against MRSA Mu50 strain. The minimum inhibitory concentration(MIC) and minimum bactericidal concentration (MBC) of extract and vancomycin against MRSA were determined usingbroth microdilution method and streak plate method. The rate of killing by the extract against Mu50 strain was determinedusing time-kill assay (TKA) at ×1 MIC, ×2 MIC, ×4 MIC, and ×8 MIC of the extract. The post-antibiotic effect (PAE) timeof extract ×10 MIC against MRSA was also investigated. The extract exhibited bacteriostatic effect against MRSA Mu50strain with MIC and MBC values of 1.563 mg/ml and 3.125 mg/ml, respectively. From TKA analysis, the extract was notcapable of killing the Mu50 strain at ×1 MIC and ×2 MIC, but it displayed bactericidal activity at higher concentrationstested. Interestingly, the acetone stem bark extract of C. odontophyllum at ×4 MIC showed comparable time-killingkinetic with the standard antibiotic in the study. The PAE time of the extract was 3.6 ± 0.51 h against MRSA Mu50compared to vancomycin at 2.4 ± 0.68 h. In conclusion, the stem bark acetone extract from C. odontophyllum demonstratedconcentration-dependent bactericidal effect with prolonged PAE time against MRSA Mu50 strain.
ABSTRACT
The minimum inhibitory concentration and post-antibiotic effects of an antimicrobial agent are parameters to be taken into consideration when determining its dosage schedules. The in vitro post-antibiotic effects on cell surface hydrophobicity and bacterial adherence were examined in one strain of group B streptococci. Exposure of the microorganism for 2 h at 37 °C to 1 x MIC of penicillin induced a PAE of 1.1 h. The cell surface charge of the Streptococcus was altered significantly during the post-antibiotic phase as shown by its ability to bind to xylene: hydrophobicity was decreased. Bacterial adherence to human buccal epithelial cells was also reduced. The results of the present investigation indicate that studies designed to determine therapeutic regimens should evaluate the clinical significance of aspects of bacterial physiology during the post-antibiotic period.
A concentração mínima inibitória e os efeitos pós-antibióticos (EPA) de um agente antimicrobiano são parâmetros que devem ser levados em consideração quando da determinação do esquema de dosagem. Os efeitos pós-antibióticos in vitro na hidrofobicidade de superfície celular e na aderência foram pesquisados em uma amostra de estreptococos do grupo B. A exposição do microrganismo por 2 h a 37 °C a 1 x CMI de penicilina induziu um EPA de 1,1 h. A carga da superfície celular da bactéria foi alterada significativamente durante a fase pós-antibiótica revelada através da capacidade de ligação ao xileno, indicada pela diminuição da hidrofobicidade. A aderência bacteriana às células epiteliais bucais humanas também foi reduzida. Os resultados da investigação demonstram que estudos clínicos destinados a determinar regimes terapêuticos deveriam incluir o conhecimento da fisiologia bacteriana durante o período pós-antibiótico.