# Preliminary Findings on Antibacterialativity of Selected Marine Invertebrates
## 4 Discussion
These results suggest that the selected organisms may be a promising source for further pharmacological research in the search of novel antibiotic substances. In this study, _Geobacillus_ sp. was inhibited by three out of four extracts and interesting sensitivity results were found in the literature; these bacteria are generally antibiotic-sensitive but resistant to heavy metals [28]. The extract of _M. galloprovincialis_ showed antibacterial activity against 8 of the 13 strains tested (Tables 2 and 3). This is not surprising as their immune system is very effective and makes them particularly resistant to adverse conditions and pathogens [13]. When compared to the results of the present study, some differences can be found in the literature; for example, the protamine-like proteins of _M. galloprovincialis_ exhibited bactericidal activity against _E. coli_ (ATCC 8739), _E. aerogenes_ (ATCC 13048), _Proteus mirabilis_ (ATCC 7002), _P. vulgaris_ (ATCC 12454), _Pseudomonas aeruginosa_ (ATCC 27853), _Salmonella typhi_ (ATCC 19430), _Enterobacter cloaca_ (ATCC 10699) and _Klebsiella pneumoniae_ (ATCC 27736) as well as _Enterococcus faecalis_ (ATCC 14428) and two strains of _S. aureus_ (ATCC 13709, ATCC 6738) [11]. However, some authors indicated different results with respect to the use of different solvent extracts; the ethyl acetate extract showed the highest activity against _E. coli_ and _K. pneumoniae_ and no activity against _S. aureus_, while the glycerol-water extract showed inhibitory activity against _S. aureus_ and _E. coli_ but no effect against _K. pneumoniae_[29]. To our knowledge, this is the first record that _L. monocytogenes_ and _Salmonella enterica_ ATCC 13076 and _S. enterica_ NCTC 12023 were inhibited by _M. galloprovincialis_. It is interesting to note that _Salmonella enterica_ subsp. enterica serotype Typhimurium was found in big claims _Callista chione_ but not in the mussel _M. galloprovincialis_ when commercial mussels from the north coast of Morocco were analysed [6]. The extract from _Patella_ sp. had an antibacterial effect and inhibited the growth of 8 of the 13 bacteria tested (Tables 2 and 3), but had no effect on _S. aureus_ ATCC 25923, _K. aerogenes_ ATCC 13048 or _E. coli_ NCTC 12241. Comparable results were found in the literature; extracts of _P. rustica_ inhibited the growth of _S. aureus_, _B. subtilis_, _S. typhi_, _E. faecalis_, _K. pneumoniae_ and _P. aeruginosa_, but had no effect on _E. coli_ or _Streptococcus pneumoniae_[30]. It appears that this is the first evidence of inhibition of _L. monocytogenes_ and _Salmonella enterica_ ATCC 13076 and _S. enterica_ NCTC 12023 by _Patella_ sp. extract, making this organism a valuable source for potential studies on new antibiotic agents. The extract from _Gibbula_ sp. also showed inhibitory activity against 8 out of 13 bacteria (Tables 2 and 3) and based on the available information, this is the first report of the inhibition of _L. monocytogenes_ and _Salmonella enterica_ ATCC 13076 as well as _S. enterica_ NCTC 12023 by extracts from this snail. However, tetrodotoxin, a potent low-weight marine toxin, was found in gastropod species _Gibbula umbilicalis_[31], as well as some other biotoxins (paralytic shellfish toxin, okadaic acid and 13-Desmethyl Spirolide C) [32]. The results of the present study and those found in the literature could place this organism at the center of future research on new farmaeticals from the marine environment. Extract from _Arbacia lixula_ showed an antibacterial effect on 5 out of 13 different bacterial strains (Tables 2 and 3), but among the reference pathogens only on _L. monocytogenes_, in fact, this is the first notice of _L. monocytogenes_ inhibition using an extract from this sea urchin. Information on its antibacterial effects is scarce; in a study of coelomic fluid and coelomocyte lysate antimicrobial activity on _S. aureus_, _P. aeruginosa_ or _Enterococcus_ sp., an inhibitory effect was not noticed [33]. However, it was found that _A.