Detection of multiple potentially pathogenic bacteria in Matang mangrove estuaries, Malaysia

Highlights

• FIBs and potential human pathogens were detected in Matang mangrove estuaries.

• Klebsiella pneumoniae, vibrios, enterobacters and other bacteria were isolated.

• FIB levels were higher at downstream sampling sites from the fishing village.

• It indicates a possible source of anthropogenic pollution to the estuary.

• Microbial contamination of the estuaries might pose a health risk to the public.

Abstract

The deltaic estuarine system of the Matang Mangrove Forest Reserve of Malaysia is a site where several human settlements and brackish water aquaculture have been established. Here, we evaluated the level of fecal indicator bacteria (FIB) and the presence of potentially pathogenic bacteria in the surface water and sediments. Higher levels of FIB were detected at downstream sampling sites from the fishing village, indicating it as a possible source of anthropogenic pollution to the estuary. Enterococci levels in the estuarine sediments were higher than in the surface water, while total coliforms and E. coli in the estuarine sediments were not detected in all samples. Also, various types of potentially pathogenic bacteria, including Klebsiella pneumoniae, Serratia marcescens and Enterobacter cloacae were isolated. The results indicate that the Matang estuarine system is contaminated with various types of potential human bacterial pathogens which might pose a health risk to the public.

Introduction

Few estuaries in Malaysia or the region have the reputation of being a world-class demonstration site of exemplary mangrove forestry management as the estuaries of the Matang Mangrove Forest Reserve (MMFR), Perak state, Malaysia. MMFR is a silviculture production forest managed on a sustainable basis without a single hectare loss of forest since its reservation in 1902, mainly for the production of charcoal and piling poles. While timber production is the main objective for the reservation of MMFR, the protection of fisheries resources for food security is perhaps a greater socio-economic and ecological role played by MMFR. Perak produces the highest or 28.7% of the total fish landings in Malaysia. The MMFR with its large expanse of sheltered waters is site to 7666 floating fish cages, and cockle culture covers an extensive area of 4726 ha within and outside the estuaries (Ariffin and Nik Mustafa, 2013). Brackish water shrimp ponds thrive outside the perimeters of the MMFR but draw and discharge sea water into it. There are presently 385 shrimp ponds covering a total area of about 223 ha.

Although the MMFR demonstrates how a sustainably managed forest could provide significant ecological services and economic benefits, it also illustrates a coastal zone of increasing multiple-use conflicts and the dilemma of land and water management practiced on a sectoral basis (Chong et al., 2010). Increasingly, anthropogenic influences on water quality in the MMFR may take a toll of its resources in spite of the excellent (land) management of the mangrove. Of the total of 34 permanent settlements in the MMFR, 28 are fishing villages sited by the mangrove estuaries. A survey by Lim and Mohamad Parit (2001) indicated 5300 households with a total population of 31,800 people mostly (79%) associated with sea fishing in some way. Kuala Sepetang is now a striking fishing settlement of both old and modern homes. The quaint human abodes that line the watercourse are built on tall stilts made from the nibong palm (Oncosperma tigillarium), and alarmingly, among them the stark presence of ‘open-discharge’ toilets.

In this study, we aimed to investigate the general public health risk related to human bacterial pathogens, which could be contributed by fecal contamination due to human settlement along the estuaries. In most countries, microbiological quality and safety monitoring of coastal and estuarine waters is an essential component of the national risk management program (Touron et al., 2007), due to the growing number of human bacterial infections associated with recreational and commercial uses of marine resources (Tamplin, 2001). In general anthropogenic activities, including human settlements, industrialization, agricultural and aquacultural practices, contribute greatly to the degradation of water quality and safety (May et al., 2006). An increasing number of potential human bacterial pathogens, including pathogenic Escherichia coli (E. coli), and species of Vibrio, Klebsiella, and Salmonella have been reported from estuarine and marine environments globally (Peng et al., 2005, Islam and Tanaka, 2004, Lee et al., 2011).

The level of pollution in the coastal environment requires particular attention due to potential microbiological risks that are linked to the consumption of contaminated aquaculture products, with eventual socio-economic consequences (Touron et al., 2007, Retnam et al., 2013). In 2008, a ban was placed on Malaysian seafood products by the European Union (EU) due to health risks posed by seafood from Malaysia which caused export losses amounting to almost 200 million USD dollars (Retnam et al., 2013). Therefore, it is important to monitor the presence of waterborne pathogens in the coastal and estuarine environments, not just to protect the people from infectious diseases, but also to protect Malaysia’s developing aquaculture industry.

In this study, the Matang mangrove estuary was investigated for its water quality (enumeration of total coliforms, E. coli and Enterococci) and safety (Enterobacteriaceae) using a chromogenic medium that allows for simultaneous isolation and identification of various species of Enterobacteriaceae. CHROMagar Orientation™ (CHROMagar, Paris, France) was used in this work as the single detection and isolation medium for isolation of Enterobacteriaceae and Gram-positive Enterococci (Merlino et al., 1996).