Effects of Mentha suaveolens essential oil on Chlamydia trachomatis

Abstract

Chlamydia trachomatis, the most common cause of sexually transmitted bacterial infection worldwide, has a unique biphasic developmental cycle alternating between the infectious elementary body and the replicative reticulate body. C. trachomatis is responsible for severe reproductive complications including pelvic inflammatory disease, ectopic pregnancy, and obstructive infertility. The aim of our study was to evaluate whether Mentha suaveolens essential oil (EOMS) can be considered as a promising candidate for preventing C. trachomatis infection. Specifically, we investigated the in vitro effects of EOMS towards C. trachomatis analysing the different phases of chlamydial developmental cycle. Our results demonstrated that EOMS was effective towards C. trachomatis, whereby it not only inactivated infectious elementary bodies but also inhibited chlamydial replication. Our study also revealed the effectiveness of EOMS, in combination with erythromycin, towards C. trachomatis with a substantial reduction in the minimum effect dose of antibiotic. In conclusion, EOMS treatment may represent a preventative strategy since it may reduce C. trachomatis transmission in the population and, thereby, reduce the number of new chlamydial infections and risk of developing of severe sequelae.

Figure 1

Cytotoxic effect of EOMS on HeLa cells. HeLa cell monolayers were treated with different concentrations of EOMS for 1 h or 48 h and, then, cell viability was determined by MTT assay.

Figure 2

Inhibition of C. trachomatis EBs by EOMS treatment. Chlamydial EBs suspensions were treated with different concentrations of EOMS for 30, 60, or 120 min and then the mixture was used to infect HeLa cell monolayers. After 48 h of incubation, treated and untreated HeLa cell monolayers were recovered to determine the chlamydial infectivity yield. ^* P < 0.05 versus untreated cells.

Figure 3

Inhibition of C. trachomatis replication by EOMS treatment. HeLa cell monolayers were infected with C. trachomatis (MOI 0.05) and then treated with different concentrations of EOMS. After 48 h of incubation, treated and untreated HeLa cell monolayers were recovered to determine the chlamydial infectivity yield. ^* P < 0.05 versus untreated cells.

Figure 4

Immunohistological staining of C. trachomatis infected cell monolayers in the presence or absence of EOMS. HeLa cell monolayers were infected with C. trachomatis (MOI 0.05) and incubated in the presence ((a) 16 μg/mL; (b) 32 μg/mL; and (c) 64 μg/mL) or absence of EOMS (d). After 48 h of incubation, HeLa cell monolayers were fixed, stained, and visualised by fluorescence microscopy (400x magnification). Bars: 50 μm.

Figure 5

Effects of EOMS (64 μg/mL) on different phases of C. trachomatis infection. (A) chlamydial EBs pretreatment with EOMS for 2 h. (B) HeLa cell monolayer pretreatment with EOMS for 2 h. (C) Addition of EOMS during chlamydial infection. (D) Addition of EOMS during postinfection period. After 48 h of incubation, treated and untreated HeLa cell monolayers were recovered to determine the chlamydial infectivity yield. ^* P < 0.05 versus untreated cells.