Li-Oon Chuah

Antibiotic Application and Emergence of Multiple Antibiotic Resistance (MAR) in Global Catfish Aquaculture

Catfish is one of the most cultivated species worldwide. Antibiotics are usually used in catfish farming as therapeutic and prophylactic agents. In the USA, only oxytetracycline, a combination of sulfadimethoxine and ormetoprim, and florfenicol are approved by the Food Drug Administration for specific fish species (e.g., catfish and salmonids) and their specific diseases. Misuse of antibiotics as prophylactic agents in disease prevention, however, is common and contributes in the development of antibiotic resistance. Various studies had reported on antibiotic residues and/or resistance in farmed species, feral fish, water column, sediments, and, in a lesser content, among farm workers. Ninety percent of the world aquaculture production is carried out in developing countries, which lack regulations and enforcement on the use of antibiotics. Hence, efforts are needed to promote the development and enforcement of such a regulatory structure. Alternatives to antibiotics such as antibacterial vaccines, bacteriophages and their lysins, and probiotics have been applied to curtail the increasing emergence of antibiotic-resistant bacteria due to the imprudent application of antibiotics in aquaculture.

Prevalence of Salmonella in poultry processing environments in wet markets in Penang and Perlis, Malaysia

Aim: The aim of this study was to determine the prevalence of various Salmonella serotypes in chickens, carcass contact surfaces as well as environmental samples collected from wet markets and small scale processing plant. Materials and Methods: A total of 182 poultry and environmental samples were collected at random on separate occasions from wet markets and small scale processing plant, during the period of October 2014 to July 2015 in Penang and Perlis, Malaysia. The samples were analyzed for the presence of Salmonella using ISO 6579:2002 conventional culture-based method. Presumptive Salmonella colonies were subjected to various biochemical tests (such as triple sugar iron and lysine iron test), serologically confirmed using polyvalent O and H antisera and further serotyped at Public Health Laboratory, Ministry of Health, Perak, Malaysia. Results: Salmonella serotypes were isolated from 161 out of 182 samples (88.46%) with 100% prevalence in the whole chicken carcass and chicken cuts - as well as transport crate, cage, drum, knife, chopping board, display table, floor, bench wash water, wash water, and drain water. Salmonella was isolated from 91.67%, 83.33%, and 66.67% of defeathering machines, drain swabs, and apron, respectively. 17 serotypes were isolated in this study with Salmonella Albany (57/161), Salmonella Corvallis (42/161), and Salmonella Brancaster (37/161) being the predominant serovars. Conclusion: The most carcass contact and environmental samples collected along the wet market chicken processing line were consistently contaminated with Salmonella. This indicates that Salmonella has established itself in poultry processing environments by colonizing the surfaces of the equipment and survives in these environments by establishing biofilms. Our results highlight the need of implementing strict hygiene and sanitation standards to reduce the incidence of Salmonella. The prevalence of Salmonella in poultry can be reduced effectively by identifying and eliminating the sources and contamination sites during slaughter and processing of poultry.

Bifidobacterium longum BB536 alleviated upper respiratory illnesses and modulated gut microbiota profiles in Malaysian pre-school children

This 10-months randomised, double-blind, parallel and placebo-controlled study evaluated the effects of Bifidobacterium longum BB536 on diarrhoea and/or upper respiratory illnesses in 520 healthy Malaysian pre-school children aged 2-6 years old. The subjects randomly received a one-gram sachet containing either BB536 (5×109 cfu) or placebo daily. Data analysis was performed on 219 subjects who fully complied over 10-months (placebo n=110, BB536 n=109). While BB536 did not exert significant effects against diarrhoea in children, Poisson regression with generalised estimating equations model indicated significant intergroup difference in the mean number of times of respiratory illnesses over 10 months. The duration of sore throat was reduced by 46% (P=0.018), with marginal reduction for duration of fever (reduced by 27%, P=0.084), runny nose (reduced by 15%, P=0.087) and cough (reduced by 16%, P=0.087) as compared to the placebo. Principal coordinate analysis at genus level of the gut microbiota revealed significant differences between 0 and 10 months in the BB536 group (P<0.01) but not in placebo group (P>0.05). The abundance of the genus Faecalibacterium which is associated with anti-inflammatory and immuno-modulatory properties was significantly higher in the BB536 group (P<0.05) compared to the placebo group. Altogether, our present study illustrated the potential protective effects of BB536 against upper respiratory illnesses in pre-school Malaysian children, with gut microbiota modulating properties.

Genetic relatedness, antimicrobial resistance and biofilm formation of Salmonella isolated from naturally contaminated poultry and their processing environment in northern Malaysia

We investigated the genetic relatedness, antibiotic resistance and biofilm-producing ability of 114 strains of Salmonella, belonged to three serotypes (Corvallis, Brancaster and Albany), isolated from naturally contaminated poultry and their environment in wet markets and smale-scale processing plant from northern Malaysia. Pulsed-field gel electrophoresis revealed that Salmonella strains isolated from various wet markets were clonally related, suggesting the widespread dissemination of these three serotypes in northern Malaysia. All except one strain of Salmonella were resistant to more than two classes of antibiotics, hence regarded as multidrug resistant (MDR). Resistance to sulphonamide (96.5%), ampicillin (89.5%), tetracycline (85.1%), chloramphenicol (75.4%), trimethoprim (68.4%), trimethoprim-sulfamethoxazole (67.5%), streptomycin (58.8%) and nalidixic acid (44.4%) were observed. Resistance determinants, floR, cmlA, tetA, tetB, tetG, temB, blaPSE-1, sul1, sul2, qnrA, qnrS, strA and aadA were detected by PCR among MDR Salmonella strains. Seventy-six strains (66.7%) harboured class-I integrons. The gene cassettes identified were dfrA1, dfrA12, aadA2 and an open reading frame orfC with unknown function. All Salmonella strains produced biofilm and 69.3% of them were strong biofilm-producers. Our findings suggested that most likely, persistent Salmonella colonises various sites in the processing environment by producing biofilm, which leads to their widespread dissemination in wet markets located in northern Malaysia.

Data on antibiogram and resistance genes harboured by Salmonella strains and their Pulsed-field gel electrophoresis clusters

This article describes the Pulsed-field gel electrophoresis clustering of the predominant Salmonella strains (Salmonella ser. Albany, Salmonella ser. Brancaster, and Salmonella ser. Corvallis) isolated from poultry and processing environment in wet market and small-scale processing plant in Penang and Perlis, the northern states of Malaysia. Agar disk diffusion assay was performed to determine the phenotypic antibiotic resistance of these Salmonella strains. The most common antibiograms among the three predominant Salmonella serovars were reported. The presence of integrase genes and antibiotic resistance genes conferring to resistance against β-lactams, aminoglycosides, tetracyclines, quinolones, sulphonamides and chloramphenicol, was detected via PCR amplification.

Genome Sequence of “Anthococcus,” a Novel Genus of the Family Streptococcaceae Isolated from Flowers

ABSTRACT Here, we report the draft whole-genome sequence of “Anthococcus,” a novel genus of the family Streptococcaceae isolated from fresh flowers of a durian (Durio zibethinus) tree. The draft genome of Anthococcus sp. strain DF1 contains 2,157,756 bp, with a G+C content of 33.0%.

Corrigendum: Floricoccus tropicus gen. nov., sp. nov. and Floricoccus penangensis sp. nov. isolated from fresh flowers of durian tree and hibiscus

Three strains of Gram-staining-positive, coccus-shaped, lactic acid bacteria, designated as HibF3T, HibF2 and HibF5 were isolated from fresh flowers of hibiscus, and a fourth, DF1T, was isolated from fresh flowers of durian tree, in Penang, Malaysia. Taxonomic characterisation was performed by polyphasic analysis. Sequence similarities of the 16S rRNA gene and the housekeeping rpoA and pheS genes of these strains with their closely-related lactococcal and streptococcal relatives were 92-94, 78 and 81 %, respectively. The results of phylogenetic analysis indicated that strains DF1T, HibF2, HibF5 and HibF3T were clustered together but were clearly separated from species of the genera Streptococcus and Lactococcus, indicating that they represent members of a novel genus of the family Streptococcaceae. Calculation of average nucleotide identity (ANI) values between the genomes of DF1T and HibF3T yielded values of 92.50-92.93 %. ANI values below the cut-off value and distinctive chemotaxonomic characteristics supported the hypothesis that these strains represented two novel species. Major cellular fatty acids in DF1T, HibF2 and HibF5 were C18 : 1ω7c and C16 : 0, while C12 : 0 and C14 : 0 were also dominant, in addition to C18 : 1ω7c and C16 : 0, in HibF3T. A novel genus is proposed with the name Floricoccus gen. nov. which consists of two species, Floricoccus tropicus sp. nov as the type species, and Floricoccus penangensis sp. nov. The respective type strains are DF1T (=LMG 29833T=JCM 31733T) and HibF3T (=LMG 29831T=DSM 31735T).

Genetic Relatedness of Salmonella Serovars Isolated from Catfish (Clarias gariepinus) and Tilapia (Tilapia mossambica) Obtained from Wet Markets and Ponds in Penang, Malaysia

A total of 43 Salmonella enterica isolates belonging to different serovars (Salmonella Albany, Salmonella Agona, Salmonella Corvallis, Salmonella Stanley, Salmonella Typhimurium, Salmonella Mikawasima, and Salmonella Bovismorbificans) were isolated from catfish (Clarias gariepinus) and tilapia (Tilapia mossambica) obtained from nine wet markets and eight ponds in Penang, Malaysia. Thirteen, 19, and 11 isolates were isolated from 9 of 32 catfish, 14 of 32 tilapia, and 11 of 44 water samples, respectively. Fish reared in ponds were fed chicken offal, spoiled eggs, and commercial fish feed. The genetic relatedness of these Salmonella isolates was determined by random amplified polymorphic DNA PCR (RAPD-PCR) using primer OPC2, repetitive extragenic palindromic PCR (REP-PCR), and pulsed-field gel electrophoresis (PFGE). Composite analysis of the RAPD-PCR, REP-PCR, and PFGE results showed that the Salmonella serovars could be differentiated into six clusters and 15 singletons. RAPD-PCR differentiated the Salmonella isolates into 11 clusters and 10 singletons, while REP-PCR differentiated them into 4 clusters and 1 singleton. PFGE differentiated the Salmonella isolates into seven clusters and seven singletons. The close genetic relationship of Salmonella isolates from catfish or tilapia obtained from different ponds, irrespective of the type of feed given, may be caused by several factors, such as the quality of the water, density of fish, and size of ponds.