# Isothiocyanates: An Overview of Their Antimicrobial Activity against Human Infections
## 4 Isothiocyanates Antimicrobial Properties against Human Pathogens
### Staphylococcus Aureus and Methicillin-Resistant S. aureus (MRSA)  
Staphylococci are Gram-positive bacteria that are commonly found on the skin and hair, as well as in the respiratory tract of many people, without causing infection or disease. _Staphylococcus aureus_ (_S. aureus_) however is commonly associated with serious skin and systemic infections, especially in people with cancer, vascular and pulmonary diseases [100; 101]. The greater incidence of _Staphylococcus_ invasive infections is registered in hospitalized patients, due to the compromised immune system, to the surgery procedures and to the use of medical devices [102; 103]. These parameters make _S. aureus_ one of the main pathogens that cause nosocomial infections. Over the years, the rise of _S. aureus_ phenotypes resistant to antibiotics such as methicillin has been recorded [104]. Moringa oleferan antimicrobial activity against _S. aureus_ has been investigated in depth [62; 30; 63; 64; 66; 68]. [PERSON] et al. [62] assessed the antimicrobial properties of _Moringa oleifera_ leaf extract against _S. aureus_ (BMLRU1002 strain) indicating that water extracts from fresh leaf displayed similar antibacterial effect (IZ = 12.00 \(\pm\) 0.12 mm) to the antibiotic tetracycline used as a control (IZ = 12.76 \(\pm\) 0.02) [62]. This property was also confirmed by [PERSON] et al. (IZ = 25.4 mm) [63]. In addition [PERSON] et al. [66] investigated about the antimicrobial activity of _M. oleifera_ seed extracts against _S. aureus_. The authors indicated that aqueous (IZ = 25 mm) and ethanol (IZ = 28 mm) extracts from _Moringa oleifera_ seeds showed similar antimicrobial activity against _S. aureus_ ATCC 25923 strain, exerting their activity in a dose-dependent manner [66]. Furthermore, seed extracts obtained with dichloromethane allowed [PERSON] et al. [30] to demonstrate that the two structurally-related ITCs isolated from the _M. oleifera_ seed extract--4(\(\alpha\)-L-rhammopyranosyloxy)benzylITC (moringin) and its 4\({}^{\prime}\)-O-acetylated derivative (4\({}^{\prime}\)-Ac-moringin)--showed to inhibit _S. aureus_ ATTC 6538 growth with inhibition halo similar to those observed for the canonical antibiotic ofloxacin [30]. As demonstrated by [PERSON] et al [68] morningin was also able to counteract the growth of _S. aureus_ BAA-977 strain (clindamycin-resistant strain) with an inhibition halo of about 25 \(\pm\) 1 mm. Finally, ethyl acetate extract of _M. oleifera_ bark showed the higher antimicrobial activity against _S. aureus_ (MTCC-740 strain) compared to methanol and chloroform extracts [64]. These studies were done using different _S. aureus_ strains and different doses of the extracts determining a difficult comparison of the results and an incorrect evaluation of the best extract against _S. aureus_. Despite this evidence, altogether these studies suggested that _Moringa oleifera_ showed good antimicrobial activity against _S. aureus_ and moringin was a promising structurally-related ITC to develop further investigations. On another note, the antimicrobial effect of synthetic AITC, BITC, PEITC, SFN, and a mixture of AITC, BITC and PEITC (containing 3 \(\upmu\)mol of each ITC)--on _S. aureus_ was also investigated [50]. [PERSON] et al., [50] demonstrated that the mixture of ITCs showed the most effective antimicrobial activity against _S. aureus_ clinical isolate followed by BITC, PEITC and finally by SFN. No inhibition effect was observed for AITC. In addition, BITC, PEITC, SFN and the ITC mixture displayed a better antimicrobial activity compared to vancomycin (IZ = 18 mm). It is worth noting that the ITC mixture showed inhibitory activity similar to BITC alone, which suggests that BITC is the best inhibiting compound in the ITC mixture and that no synergistic effect arises with AITC and PEITC [50]. Similar results were obtained by [PERSON], et al. [46]. The authors tested the antimicrobial activity of AITC, BITC, PEITC, SFN, ERN and IBN and their combined effect with the vancomycin antibiotic.