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Thirty-one herbal preparations produced and sold on the Ghanaian market were randomly purchased from sales outlets and analyzed for their microbiological quality by testing for the presence of total coliform bacteria, faecal coliform bacteria, and total heterotrophic bacteria count. Also tested for was detection of pathogenic bacteria such as the Salmonella spp. and Clostridium spp. Opportunistic bacterial pathogens (Aeromonas spp., Enterococcus spp. and Pseudomonas spp.) and mould were also tested for. The herbal preparations tested came from different processing companies and included those labeled as suitable for treating arthritis, asthma, anaemia, diabetes mellitus, epilepsy, cough, hypertension, dysmenorrhoea, malaria, urine retention and loss of appetite. Aliquots of the various herbal products were cultured on various selective media. Eight (8) of the products showed the presence of all microorganism analyzed for including the pathogenic ones and are recommended not be used. Five (5) of the products did not have any microorganism present. Eleven (11) products showed the presence of only total heterotrophic bacteria and the values ranged from 1 to 94 cfu per ml. These two groups of total of sixteen (16) products can be used without any microbiological risk. Another three (3) products showed presence of only total heterotrophic bacteria but the values ranged from 118 to 1648 cfu per ml. Majority of the herbal preparations showed the presence of pathogenic bacteria. These three products may pose danger to the user can be used with caution. None of the herbal products recorded the presence of Enterococcus spp.

The use of eco-technologies for wastewater treatment such as algal and duckweed-based pond systems is becoming popular in developing countries owing to its affordability and efficiency of pathogen removal in warm climates. The pathogen removal mechanisms of these treatment systems however is still not clearly understood and existing knowledge is also scattered in journals and books of different disciplines. The purpose of this paper is to provide a concise review of knowledge acquired in recent times on faecal coliform removal mechanisms in algal and duckweed ponds in a comparative way while identifying knowledge gaps that still exist. This review pays particular attention to little known removal mechanisms such as the role of algal biomass, attachment and sedimentation of faecal coliforms and the role of predation by macroinvertebrates and protozoans. Recent experiments showed that algal ponds, in comparison with duckweed ponds, are more efficient in faecal coliform removal due to the high pH and oxygenation that occur in the former and the rate of inactivation of faecal coliforms increases with increased algal biomass till a certain optimum concentration after which it decreases. This optimal algal concentration for maximum destruction of faecal coliforms can be affected by the quality and strength of the wastewater. Algae also appeared to have a destructive effect on faecal coliforms even in darkness, a phenomenon that may be the effect of toxic substances from the algae. Results also show that the role of invertebrates, particularly macroinvertebrates may be more important in duckweed pond systems. Removal of faecal coliforms through attachment and sedimentation in both duckweed and algal ponds appear to be dependent largely on concentrations of faecal coliforms present and to some extent on suspended plant and particulate matter concentrations. Wide variations in removal efficiencies were however observed. We conclude that the wide variations in removal efficiencies can be addressed by standardizing operating conditions of treatment systems. Further work is necessary to identify the substances produced by algae which appeared to be toxic to faecal coliforms as well as establishing the relative importance of predation by protozoans and macro-invertebrates in the removal of faecal coliforms.

A B S T R A C TThe relationship between sunlight effect, algal biomass and faecal coliform inactivation in wastewater pond treatment systems is still not clearly understood. Increased pH and dissolved oxygen concentration in treatment ponds results in an increased destruction of faecal coliforms. Increased algal growth however results in a decreased destruction of faecal coliforms due to light attenuation. Algae also releases variable amounts and types of organic matter at various rates and quantities depending on environmental conditions and this can either aid or retard faecal bacteria destruction. We investigated the effect of algal density on faecal coliform destruction under field conditions in sunlight and darkness and how this can be affected by light intensity. In darkness, increased inactivation of faecal coliform occurred with increasing algal density. Rates of decay of faecal coliforms were much faster in sunlight than in darkness even in the absence of algae. In sunlight, rates of decay of faecal coliforms increased with increasing algal density up to a chlorophyll-a concentration of 1.3 ± 0.1 mg/L after which rates of decay decreased. Increased decay rates of faecal coliforms occurred with increasing light intensity or light input. With decreased light input of 20% of 213 W/m 2 , the optimum algal density for maximum faecal coliform decay decreased to a value which is 6-7 times the value of that under normal insolation of 213 W/m 2 . It is recommended that in future studies relating to the assessment of performance and estimation of rate of Escherichia coli or faecal coliform inactivation, one of the parameters that need to be reported as well is the insolation.

Summary In African public health systems, Listeria monocytogenes is a pathogen of relatively low priority. Yet, the biggest listeriosis outbreak recorded to date occurred in Africa in 2018. This review highlights the factors that potentially impact L. monocytogenes transmission risks through African food value chains (FVCs). With the high rate of urbanisation, African FVCs have become spatially longer yet still informal. At the same time, dietary diversifications have resulted in increased consumption of processed ready‐to‐eat (RTE) meat, poultry, fishery and dairy products typically associated with a higher risk of L. monocytogenes consumer exposure. With frequent cold chain challenges, the potential of L. monocytogenes growth in contaminated RTE foods can further amplify consumer exposure risks. Moreover, the high prevalence of untreated HIV infections, endemic anaemia, high fertility rate and a gradually increasing proportion of elderly persons expands the fraction of listeriosis‐susceptible groups among African populations. With already warmer tropical conditions, the projected climate change‐induced increases in ambient temperatures are likely to exacerbate listeriosis risks in Africa. As precautionary approaches, African countries should implement systems for the detection and reporting of listeriosis cases and food safety regulations that provide L. monocytogenes standards and limits in high‐risk RTE foods.

a b s t r a c tThe effect of pulsed ultra violet (PUV) light on high (10 3 cfu/mL, 3 pulses of PUV light treatment were required to inactivate completely all four bacteria. Efficacy of PUV light disinfection decreased with increased water depth. E. coli was more susceptible to PUV light treatment than V. cholerae. It may therefore not be appropriate to use E. coli as an indicator of potability when PUV light is the means of disinfection. Vibrio cholerae cells in the exponential growth phase (6 h of incubation) and stationary growth phase (30 h of incubation) responded differently to inactivation by 5 pulses of PUV light, with V. cholera cells in the stationary phase showing more vulnerability to 5 pulses of PUV light.

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