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

Prevalence of Extended-Spectrum Beta-Lactamase Resistance and CTX-M-Group 1 Gene in Escherichia coli from the Water and Sediment of Urbanized Mangrove Ecosystems of Kerala

The study aimed to determine the prevalence of extended-spectrum β-lactamase resistance and CTX-M-group 1 gene in Escherichia coli from the water and sediment of three urbanized mangrove ecosystems of Kerala. A total of 119 E. coli isolates were screened for antibiotic susceptibility to 16 antibiotics. According to the phylogenetic analysis of E. coli isolates, nonpathogenic group A and pathogenic group D (29.4% and 23.5%) were the predominant phylotypes found in water samples. The most frequent phylotypes found in sediment samples were nonpathogenic groups A and B1 (27.9% and 26.4%). The highest incidence of antibiotic resistance in E. coli was against cefotaxime and colistin (100%). A significant difference in the prevalence of CTX-M-group 1 gene was observed among E. coli isolates in water samples (p < 0.05). The results indicate a high prevalence of β-lactamase harboring E. coli in the mangrove ecosystems that can hamper mangrove-dependent aquaculture practices and human health.

Microbial Community Structure and Bacterial Lineages Associated with Sulfonamides Resistance in Anthropogenic Impacted Larut River

Anthropogenic activities often contribute to antibiotic resistance in aquatic environments. Larut River Malaysia is polluted with both organic and inorganic pollutants from domestic and industrial wastewater that are probably treated inadequately. The river is characterized by high biochemical oxygen demand, chemical oxygen demand, total suspended solids, ammonia, and heavy metals. In our previous study, sulfonamides (SAs) and sulfonamide resistance genes (sul) were detected in the Larut River. Hence, in this study, we further examined the microbial community structure, diversity of sulfonamide-resistant bacteria (SARB), and their resistance genes. The study also aimed at identifying cultivable bacteria potential carriers of sul genes in the aquatic environment. Proteobacteria (22.4–66.0%), Firmicutes (0.8–41.6%), Bacteroidetes (2.0–29.4%), and Actinobacteria (5.5–27.9%) were the most dominant phyla in both the effluents and river waters. SARB isolated consisted only 4.7% of the total genera identified, with SAR Klebsiella as the most dominant (38.0–61.3%) followed by SAR Escherichia (0–22.2%) and Acinetobacter (3.2–16.0%). The majority of the SAR Klebsiella isolated from the effluents and middle downstream were positive for sul genes. Sul genes-negative SAR Escherichia and Acinetobacter were low (<20%). Canonical-correlation analysis (CCA) showed that SAs residues and inorganic nutrients exerted significant impacts on microbial community and total sul genes. Network analysis identified 11 SARB as potential sul genes bacterial carriers. These findings indicated that anthropogenic activities exerted impacts on the microbial community structure and SAs resistance in the Larut River.

What drives putative bacterial pathogens removal within seagrass meadows?

To analyze the mechanism of bacterial pathogen removal in seagrass meadows, we compared bacterial pathogens abundance in trapped particles in different seagrass meadows under different intensities of human activities. We compared the particle deposition rates and abundances of bacterial pathogen in Thalassia hemprichii, Enhalus acoroides stands and adjacent unvegetated patches. The bacterial pathogens abundance was much higher in E. acoroides than in adjacent unvegetated patches, however, the trapped particles under T. hemprichii were lower than in nearby unvegetated areas with the exception of the pristine seagrass meadow. These results indicate that seagrass, at least E. acoroides, can remove bacterial pathogens by trapping particles. What is unknown, nevertheless, is how the trapped bacterial pathogens are removed by T. hemprichii. We put forward that antibacterial chemical compounds release from seagrass was stimulated by stress from human activities for inhibition of bacterial pathogen. This putative mechanism needs to be explored in future studies.

Seasonal variation in β-glucosidase-producing culturable bacterial diversity in a monsoon-influenced tropical estuary

The episodic monsoon condition in a tropical estuarine environment inputs high allochthonous materials that are rich in carbohydrates and are mainly broken down by enzymatic hydrolysis thus alter both organic matter and microbial community composition of an estuary. β-Glucosidases are one of the enzymes mediating the degradation of carbohydrates and are majorly produced by heterotrophic bacteria. The present study elucidated β-glucosidase-producing culturable bacterial diversity and measured their activity during non-monsoon and monsoon seasons in Zuari estuary. The results revealed that both bacterial abundance and β-glucosidase activity decreased significantly from non-monsoon to monsoon, whereas phylogenetic diversity increased. Majority of β-glucosidase producers during non-monsoon belonged to the members of Bacillales (53%), Pseudomonadales (26%), and Vibrionales (11%) which shifted to the members of Enterobacteriales (51%), Bacillales (14%), Alteromonadales (12%), Aeromonadales (9%), Xanthomonadales (7%), Pseudomonadales (5%), and Flavobacteriales (2%) during the monsoon. The shift in bacterial community structure points out the occurrence of different allochthonous forms with carbohydrate-metabolizing ability during the monsoon, and their relevance in ecology and health of this estuary can be elucidated by studying their functional diversity and is a step ahead.

Exploring biogeographic patterns of bacterioplankton communities across global estuaries

Estuaries provide an ideal niche to study structure and function of bacterioplankton communities owing to the presence of a multitude of environmental stressors. Bacterioplankton community structures from nine global estuaries were compared to understand their broad‐scale biogeographic patterns. Bacterioplankton community structure from four estuaries of Sundarbans, namely Mooriganga, Thakuran, Matla, and Harinbhanga, was elucidated using Illumina sequencing. Bacterioplankton communities from these estuaries were compared against available bacterioplankton sequence data from Columbia, Delaware, Jiulong, Pearl, and Hangzhou estuaries. All nine estuaries were dominated by Proteobacteria. Other abundant phyla included Bacteroidetes, Firmicutes, Acidobacteria, Actinobacteria, Cyanobacteria, Planctomycetes, and Verrucomicrobia. The abundant bacterial phyla showed a ubiquitous presence across the estuaries. At class level, the overwhelming abundance of Gammaproteobacteria in the estuaries of Sundarbans and Columbia estuary clearly stood out amidst high abundance of Alphaproteobacteria observed in the other estuaries. Abundant bacterial families including Rhodobacteriaceae, Shingomonadaceae, Acidobacteriaceae, Vibrionaceae, and Xanthomondaceae also showed ubiquitous presence in the studied estuaries. However, rare taxa including Chloroflexi, Tenericutes, Nitrospirae, and Deinococcus‐Thermus showed clear site‐specific distribution patterns. Such distribution patterns were also reinstated by nMDS ordination plots. Such clustering patterns could hint toward the potential role of environmental parameters and substrate specificity which could result in distinct bacterioplankton communities at specific sites. The ubiquitous presence of abundant bacterioplankton groups along with their strong correlation with surface water temperature and dissolved nutrient concentrations indicates the role of such environmental parameters in shaping bacterioplankton community structure in estuaries. Overall, studies on biogeographic patters of bacterioplankton communities can provide interesting insights into ecosystem functioning and health of global estuaries.

Distribution, genetic diversity and antimicrobial resistance of clinically important bacteria from the environment of a tertiary hospital in Malaysia

OBJECTIVES

Hospital environments are potential reservoirs of bacteria associated with nosocomial infections. In this study, the distribution of cultivable environmental bacteria of clinical importance from a Malaysian tertiary hospital was determined and their resistotypes and genotypes were investigated.

METHODS

Swab and fluid samples (n=358) from healthcare workers' hands, frequently touched surfaces, medical equipment, patients' immediate surroundings, ward sinks and toilets, and solutions or fluids of 12 selected wards were collected. Biochemical tests, PCR and 16S rRNA sequencing were used for identification following isolation from CHROMagar™ Orientation medium. Clinically important bacteria such as Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter spp., Pseudomonas aeruginosa and Enterobacter spp. were further characterised by disc diffusion method and rep-PCR.

RESULTS

The 24 Gram-negative and 19 Gram-positive bacteria species identified were widely distributed in the hospital environment. Staphylococci were predominant, followed by Bacillus spp. and P. aeruginosa. Frequently touched surfaces, medical equipment, and ward sinks and toilets were the top three sources of bacterial species. Nine S. aureus, four Acinetobacter spp., one K. pneumoniae and one Enterobacter spp. were multidrug-resistant (MDR). The ESKAPE organisms were genetically diverse and widely dispersed across the hospital wards. A MDR MRSA clone was detected in a surgical ward isolation room.

CONCLUSION

The large variety of cultivable, clinically important bacteria, especially the genetically related MDR S. aureus, K. pneumoniae, Acinetobacter spp. and Enterobacter spp., from various sampling sites indicated that the surfaces and fomites in the hospital were potential exogenous sources of nosocomial infection in the hospital.

Effects of nutrient loading on sediment bacterial and pathogen communities within seagrass meadows

Eutrophication can play a significant role in seagrass decline and habitat loss. Microorganisms in seagrass sediments are essential to many important ecosystem processes, including nutrient cycling and seagrass ecosystem health. However, current knowledge of the bacterial communities, both beneficial and detrimental, within seagrass meadows in response to nutrient loading is limited. We studied the response of sediment bacterial and pathogen communities to nutrient enrichment on a tropical seagrass meadow in Xincun Bay, South China Sea. The bacterial taxonomic groups across all sites were dominated by the Gammaproteobacteria and Firmicutes. Sites nearest to the nutrient source and with the highest NH₄⁺ and PO₄³⁻ content had approximately double the relative abundance of putative denitrifiers Vibrionales, Alteromonadales, and Pseudomonadales. Additionally, the relative abundance of potential pathogen groups, especially Vibrio spp. and Pseudoalteromonas spp., was approximately 2‐fold greater at the sites with the highest nutrient loads compared to sites further from the source. These results suggest that proximity to sources of nutrient pollution increases the occurrence of potential bacterial pathogens that could affect fishes, invertebrates and humans. This study shows that nutrient enrichment does elicit shifts in bacterial community diversity and likely their function in local biogeochemical cycling and as a potential source of infectious diseases within seagrass meadows.

Mapping discourses using Q methodology in Matang Mangrove Forest, Malaysia

The sustainable management of natural resources requires the consideration of multiple stakeholders' perspectives and knowledge claims, in order to inform complex and possibly contentious decision-making dilemmas. Hence, a better understanding of why people in particular contexts do manage natural resources in a particular way is needed. Focusing on mangroves, highly productive tropical intertidal forests, this study's first aim is to map the diversity of subjective viewpoints among a range of stakeholders on the management of Matang Mangrove Forest in peninsular Malaysia. Secondly, this study aims to feed the reflection on the possible consequences of the diversity of perspectives for the future management of mangroves in Malaysia and beyond. The use of the semi-quantitative Q methodology allowed us to identify three main discourses on mangrove management: i. the optimization discourse, stressing the need to improve the current overall satisfactory management regime; ii. the 'change for the better' discourse, which focuses on increasingly participatory management and on ecotourism; and iii. the conservative 'business as usual' discourse. The existence of common points of connection between the discourses and their respective supporters provides opportunities for modifications of mangrove management regimes. Acknowledging this diversity of viewpoints, reflecting how different stakeholders see and talk about mangrove management, highlights the need to develop pro-active and resilient natural resource management approaches.

Response of marine copepods to a changing tropical environment: winners, losers and implications

Background. Climate change concurrent with anthropogenic disturbances can initiate serial changes that reverberate up the food chain with repercussions for fisheries. To date, there is no information available concerning the combined effects of global warming and human impacts on tropical marine food webs. While temperate copepods respond differently to warming and environmental stressors, the extent to which tropical copepods can adapt to rising temperature of already warm waters remains unknown. We hypothesize that sea warming and other anthropogenic disturbances over the long term will have the greatest impact on the copepod community in nearshore waters where their effects are accentuated, and therefore vulnerable and resilient species could be identified.

Methods. Zooplankton samples were collected during two time periods (1985–86 and 2014–15) interposed by marked anthropogenic disturbances, and at the same five stations located progressively from inshore to offshore in Klang Strait, Malaysia, following the asymmetrical before-after-control-impact (BACI) design. Copepods were identified to species, and results were interpreted by univariate (ANOVA) and multivariate (PERMANOVA, PCO) analyses of the computed species abundance and diversity measures.

Results. Copepod total abundance was not significantly different among stations but higher after disturbance than before disturbance. However, changes in the abundance of particular species and the community structure between time periods were dramatic. Coastal large-bodied calanoid species (e.g., Acartia spinicauda, Calanopia thompsoni, Pseudodiaptomus bowmani and Tortanus forcipatus) were the most vulnerable group to disturbance. This however favored the opportunistic species (e.g., Oithona simplex, O. attenuata, Hemicyclops sp., Pseudomacrochiron sp. and Microsetella norvegica). Small-bodied copepods (e.g., Paracalanus sp., Parvocalanus crassirostris and Euterpina acutifrons) were unaffected. Centropages tenuiremis was likely an introduced species. There was no significant loss in species richness of copepods despite the dramatic changes in community structure.

Discussion. Sea warming and other human-induced effects such as eutrophication, acidification and coastal habitat degradation are likely the main factors that have altered copepod community structure. The large-bodied estuarine and coastal calanoid copepods are surmised to be vulnerable to eutrophication and hypoxia, while both resilient and opportunistic species are largely unaffected by, or adaptable to, degraded coastal environments and observed sea surface temperature (SST) rise. It is forecasted that SST rise with unmitigated anthropogenic impacts will further reduce large-bodied copepod species the favoured food for fish larvae with dire consequences for coastal fish production.

Isolation and Characterization of Aquatic-Borne Klebsiella pneumoniae from Tropical Estuaries in Malaysia

Klebsiella pneumoniae is an opportunistic pathogen that is responsible for causing nosocomial and community-acquired infections. Despite its common presence in soil and aquatic environments, the virulence potential of K. pneumoniae isolates of environmental origin is largely unknown. Hence, in this study, K. pneumoniae isolated from the estuarine waters and sediments of the Matang mangrove estuary were screened for potential virulence characteristics: antibiotic susceptibility, morphotype on Congo red agar, biofilm formation, presence of exopolysaccharide and capsule, possession of virulence genes (fimH, magA, ugE, wabG and rmpA) and their genomic fingerprints. A total of 55 strains of K. pneumoniae were isolated from both human-distributed sites (located along Sangga Besar River) and control sites (located along Selinsing River) where less human activity was observed, indicated that K. pneumoniae is ubiquitous in the environment. However, the detection of potentially virulent strains at the downstream of Kuala Sepetang village has suggested an anthropogenic contamination source. In conclusion, the findings from this study indicate that the Matang mangrove estuary could harbor potentially pathogenic K. pneumoniae with risk to public health. More studies are required to compare the environmental K. pneumoniae strains with the community-acquired K. pneumoniae strains.

Diverse and abundant multi-drug resistant E. coli in Matang mangrove estuaries, Malaysia

E.coli, an important vector distributing antimicrobial resistance in the environment, was found to be multi-drug resistant, abundant, and genetically diverse in the Matang mangrove estuaries, Malaysia. One-third (34%) of the estuarine E. coli was multi-drug resistant. The highest antibiotic resistance prevalence was observed for aminoglycosides (83%) and beta-lactams (37%). Phylogenetic groups A and B1, being the most predominant E. coli, demonstrated the highest antibiotic resistant level and prevalence of integrons (integron I, 21%; integron II, 3%). Detection of phylogenetic group B23 downstream of fishing villages indicates human fecal contamination as a source of E. coli pollution. Enteroaggregative E. coli (1%) were also detected immediately downstream of the fishing village. The results indicated multi-drug resistance among E. coli circulating in Matang estuaries, which could be reflective of anthropogenic activities and aggravated by bacterial and antibiotic discharges from village lack of a sewerage system, aquaculture farms and upstream animal husbandry.