Identification of spoilage bacteria
This study was carried out to explore resistance and virulence genes of spoilage bacteria isolated from shrimps in Cameroun. Results of this study are similar to those of Dabadé et al. (2015) who mainly found Gram positives, especially lactic bacteria and Enterobacteria in black tropical brackish water shrimp. Authors revealed that, these microorganisms are H2S-producing dominant group of bacteria potentially spoilage bacteria of tropical shrimps in Benin. Finding in this study suggests that Bacillus and staphylococci species are probably spoilage bacteria to tropical shrimp. Srinivasan and Saranraj. (2017) also found Vibrio cholerae, Pseudomonas fluorescens, Salmonella Typhi, Staphylococcus aureus and Escherichia coli but these microorganisms are common in polluted water. Staphylococci species in shrimp were explained by Al Bulushi et al. (2010) who related that the frequencies of Staphylococci species in marine environments depend on geographic location. Bacillus species in coastal fisheries is common, despite the relative abundance of Staphylococcus spp. (Al bulushi et al., 2010). Abundance of Bacillus in coastal waters and marine fisheries depends on temperature; depth and decline distance from the coast and, suggests that Bacillus species in coastal water originate from runoff (Rüger et al., 2000). Mohammadou et al. (2014) reported Bacillus species such as Bacillus cereus, Bacillus thuringiensis and Bacillus anthracis well-known as food poisoning in spoilage food. Gram-positive bacteria was more abundant than Gram-negative in tropical water and their influence in spoilage remain little probed (Al bulushi et al., 2010). Findings of this study also showed low frequency of Enterobacteria such as Serratia and Plantoea strains who grow in a broad range of temperatures and substrates (Garrity et al., 2005). Many species related with food spoilage, have been described as opportunistic human pathogens (Mardanehand and Mohammad, 2013; Mahlen, 2011; Déletoile et al., 2009).
Antimicrobial susceptibility profile
Plantoea and Serratia genus presence in food is often neglected, when compared to classic multidrug-resistant Gram-negative pathogens (Melo et al., 2018, Halpern and Lev-Yadun, 2013, Dennis et al., 2019) likewise in this study. They are opportunistic pathogens among the most common causes of nosocomial diseases and transmissible by food ingestion. Resistance diversity of Bacillus strains in the study is not similar to the works of Mohammadou et al. (2014) who showed relative susceptibility of Bacillus strains to antibiotics unlike our results. Chaves et al. (2011) also found susceptibilities of Bacillus isolated from Brazilian food to gentamicin and tetracycline. Drug resistance of strains in this study may be attributed to bacterial spores of Bacillus species. Many studies also carried out the protective potential of bacillus strains in safe fermented food. Mohammadou et al. (2014) found that B. subtilus was able to produce bacteriocins such as subtilin in Mbuja.
Resistance and enterotoxins-virulence genes
Tetracycline resistance gene can be explored to current and emerging multidrug-resistant pathogens including carbapenem-resistant Enterobacteriaceae. None enterobacteria presented tetracycline resistance genes, although they were all resistant to Ertapenem. Many researches has been directed towards MecA genes as presented in this study on the genus of staphylococci and results are similar to those of Igbinosa and Beshiru. (2019) and Ali. (2014). MecA gene is present in all S. aureus strains and is known to encode penicillin binding protein 2a (PBP2a). Beta-lactam resistance is mostly attributed to mutations in mecA gene, but other genetic elements may also be considered for the explanation of the mechanism of resistance. Half of Bacillus strains were positive to HBL genes. These results are similar to those of Chaves et al. (2011). The same authors demonstrated prevalence of hemolytic toxins in Bacillus strains isolated from fermented foods. According to Mohammadou et al. (2010), none Bacillus strains showed enterotoxins in Mbuja foods in Cameroon. In this study, only Bacillus strains do not exhibit enterotoxin NHE genes. Many authors correlate prevalence of enterotoxins HBL-NHE (Boonchai et al., 2008). According to Trans et al. (2010), wall peptidase (sph genes and PIPLC genes) are involved in adhesion, biofilm formation and virulence. Prevalence of entFM genes in more than half of Bacillus strains is located on the chromosome and appears to be common to Bacillus thuringiensis and B. cereus. Detection of EntFM is similar to the results of Arima et al. (2011). Presence of Bcet gene is evidence of presence of B. cereus among isolates. Agata et al. (1995) also demonstrated that prevalence of this gene carried out other strains than B. cereus. The majority of the strains isolated pose a potential risk of food poisoning due to their resistance and the prevalence of toxin genes found in Bacillus strains.