Research Journal of Microbiology

Year: 2011 | Volume: 6 | Issue: 2 | Page No.: 147-152
DOI: 10.17311/jm.2011.147.152

Non-plasmid Mediated Multi-drug Resistance in Vibrio and Aeromonas sp. Isolated from Seafoods in Lagos, Nigeria

I.A. Adeleye, R.O. Nwanze, F.V. Daniels, V.A. Eyinnia, S.I. Smith, M.A. Fowora and H.A. Goodluck

Abstract: This study was done to screen seafoods in Lagos for the presence of Vibrio and Aeromonas spp. that have multi-drug resistance plasmid. The samples were cultured on Thiosulphate Citrate Bilesalt Sucrose agar (TCBS) agar after enrichment in Alkaline Peptone Water (APW). Using API 20E system and complementary biochemical test, 83 VIbrio species and 3 Aeromonas hydrophila were identified from the samples. The Vibrio species encountered comprised of V. cholerae (3) V. parahaemolyticus (5) V. mimicus (16) V. alginolyticus (37) and V. harveyi (12), V. vulnificus (10) and Aeromonas hydrophila (3). Antimicrobial susceptibility carried out using standard procedures revealed that all the 86 (100%) isolates were resistant to Augmentin, Chloramphenicol and Amoxicillin (Amx-Au-Chl). Ten (11.6%) of the isolates had multiple resistance to all the 10 antibiotics tested: Gentamicin, Nitrofuratoin, Tetracycline, Chloramphenicol, Amoxicillin, Ofloxacin, Cotrimoxazole, Augmentin, Ciprofloxacin, Ceftriazone (Amx-Aug-Chl-Nit-Cip-Tet-Ofl-Gen-Cot-Cro). Plasmid characterization revealed that only four (4.7%) of the Eighty-six isolates haboured plasmid DNA. These were two strains of V. alginolyticus with plasmids of molecular weight of 25.0 and 9.416 Kbp each and two strains of V. mimicus with plasmids of molecular weight 4.361 Kbp each. None of the Aeromonas specie haboured plasmids. This shows that antibiotic resistance in Vibrio and Aeromonas species in this environment is not plasmid mediated.

Keywords: resistance, Aeromonas sp, Vibrio and non-plasmid

INTRODUCTION

Seafood, especially the shellfish can readily harbour pathogenic microorganisms because of the texture of their flesh and also the microbe laden habitat they inhabit. In the case of being contaminated with pathogenic bacteria, shellfish pose a serious threat to public health.

Vivekanandhan et al. (2005) reported that of the 536 samples of fishes and 278 samples of prawns from the major fish market of Coimbatore, South India, analyzed for the prevalence of Aeromonas hydrophila over a two year period, the prevalence level of A. hydophila varied from 17.62% in prawns to 33.58% in fishes. Considering the pychrotrophic nature and the role of A. hydrophila as a pathogen of emerging importance, the considerably high levels of this organism in popular food item such as fish and prawn raises serious concern.

Bauer et al. (2006) reported the occurrence of Vibrio parahaemolyticus, V. cholera and V. vulnificus in Mytilus edulis (Norwegian Blue Mussels). Similarly, Eja et al. (2008) reported the prevalence Vibrio parahaemoliticus, V. cholerae and V. alginolyticus in shellfish harvested from the Great Kwa River estuary in Calabar, Nigeria and their seasonal variability. The estuary was constantly faecally polluted, coupled with high rate of infection of shellfish by these Vibrio species thus posing a health risk. The isolation of Aeromonas sp. from seafoods has been reported in Gopalpur Coast (Udgata et al., 2009). Scoglio et al. (2000) also reported the isolation of Aeromonas sp. as well as Vibrio sp. from seafoods. Aeromonas sp. had been reported as aetiological agents of many diseases in man (Bremer et al., 2003) especially in developing countries (Sifaw et al., 2008). Other reports have that Aeromonas sp. have been implicated in extra-intestinal infections and these infections may be serious even in immunocompetent individuals (Mukhopadhyay et al., 2008).

Previous study carried out by Adeleye et al. (2008) revealed the prevalence of Vibrio species in seafood consumed in Lagos which were found to be multi-drug resistant.

This present study was therefore carried out to determine whether observed drug resistance was plasmid mediated, the knowledge of this will determine whether environmental isolates of Vibrio species and Aeromonas hydrophila may act as reservoir for potential spreading of virulent genes to other bacterial specie in this environment.

MATERIALS AND METHODS

Fifty samples comprising shrimps, crabs and cuttle fish were collected from different fishing companies in Lagos and ten samples from local fishermen at Agboyi-Ado and Oworonshoki areas of Lagos between September 2007 and May 2008. These samples were collected in sterile stainless steel plates and transported to the lab in cooler boxes. Microbiological analysis was carried out immediately after collection by culturing samples on TCBS agar after enrichment in APW. Using conventional biochemical characterization methods and API 20E systems as previously described by Adeleye et al. (2008).

Antimicrobial susceptibility of isolates was tested against the following antibiotics; Gentamycin, Nitrofuratoin, Tetracycline, Chloramphenicol Amoxicillin, Ofloxacin, Cotrimoxazole, Augmentin, Ciprofloxacin and Ceftriazone using disk diffusion method on Mueller Hinton agar. Inhibition zones were interpreted using NCCLS recommendations (NCCLS, 2000).

Plasmid DNA extraction was done using Alkaline lyses method of Birnboim and Doly (1979). The fragments were visualized by UV transillumination. Sizes of plasmids were estimated by comparing with previously characterized plasmids.

RESULTS

From these biochemical tests results the isolates were subsequently identified as Vibrio cholerae (3), V. parahaemolyticus (5), V. mimicus (16), V. harveyi (12), V. alginolyticus (37), V. vulnificus (10) and Aeromonas hydrophila (3). The later appeared as slightly raised circular yellow colonies on TCBS plates. It is important to note that the Aeromonas hydrophila isolated were not deliberately sought for; they grew on the plates along with the Vibrio specie isolated.

Table 1 and 2 show the antimicrobial susceptibility patterns and the antibiogram of the isolates. Multiple drug resistance was prevalent among the Vibrio and Aeromonas species. Ten (11.6%) of the total number of isolates obtained in this study were resistant to all 10 drugs tested and this represents the highest multiple drug resistance observed and least common (Amx-Aug-Chl-Nit-Cip-Tet-Ofl-Gen-Cot-Cro). At least 10 (11.6%) of the isolates were resistant to 8 drugs.

All the 86 (100%) isolate were resistant to three drugs, which represented the most common pattern (Amx-Aug-Chl).

Only four of the isolates carried plasmid DNA, Fig. 1 shows plasmid profile of the two plasmid carrying strains discovered, these are V. alginolyticus that carried plasmids of molecular weight 25.0 and 9.416 Kbp each. Two other isolates of V. mimicus harbored very small plasmids of molecular weight 4.361 Kbp each.

DISCUSSION

This study revealed a high prevalence of antibiotic resistances in the Vibrio and Aeromonas isolates. The resistance patterns detected ranged between three and ten drugs. Ten (11.6%) of the total number of isolates obtained in this study were resistant to all 10 drugs tested showing the following profile; Amx-Aug-Chl-Nit-Cip-Tet-Ofl-Gen-Cot-Cro and this represents the highest multiple drug resistance observed. Other multi-drug resistance profiles include Amx-Aug-Chl-Nit-Cip-Tet-Ofl-Gen-Cro shown by at least 14(16.2%) of the isolates and Amx-Aug-Chl-Nit-Tet-Gen-Cot-Cro seen in at least 17(19.7%) of the isolates. The observations are in agreement with previous studies by Adeleye et al. (2008) where resistance to 10, 9, 8 drugs occurred in the majority of the Vibrio isolates from same origin. Multi-drug resistant environmental Vibrio and Aeromonas species have been frequently reported from many part of the world (Ansary et al., 2006; Chowdhury et al., 1986; Ibara and Avarado, 2006; Periska et al., 2003; Wang et al., 2006).

In order to determine whether the observed multi drug resistance pattern observed in the isolates was plasmid mediated, the isolates were all screened for the presence of large conjugative plasmids. The presence of plasmids was detected in only four of the isolates (4.7%). The incidence of plasmids conferring resistance to a particular antibiotic(s) and/or to other harmful agents among acquatic bacterial population has been studied. However, according to Radus et al. (2000) the possible role of plasmid mediating resistance to antibiotics among Vibrio sp., has not been established. Since, the antimicrobial susceptibility patterns in the strains of V. alginolyticus and V. mimicus that carried plasmids did not differ from strains which did not habour plasmids it can be inferred that antimicrobial resistance observed in our Vibrio isolates may be chromosomally mediated. Similar conclusions had been drawn by Jun et al. (2003) while observing low plasmid carriage in fifty one multi-drug resistant Vibrio species isolated in Hong Kong. None of the three strains of the Aeromonas hydrophila haboured plasmid. Similarly, Ansary et al. (2006) had reported that of 34 Aeromonas hydrophila isolated from various fish species caught in Malaysia, only 5(14.7%) carried plasmid DNA and that there was no correlation between the presence of plasmids and antibiotic resistance. Similarly, Chang and Bolton (1987) reported that of 75 clinical isolates of Aeromonas hydrophila only one harbored plasmid DNA which mediated resistance to 10 antibiotics.

Over all, this current study suggest that multi-drug resistance observed in environmental isolates of potentially pathogenic Vibrio and Aeromonas species contaminating seafood in Lagos is non- plasmid mediated and therefore may not act as reservoir for spread of virulent genes.

ACKNOWLEDGMENTS

My gratitude goes to Mr. S.B. Bamiro for his assistance with API kits and the final identification of the isolates.

REFERENCES