Sisai Mpuchane

Occurrence of aflatoxins, fumonisin B1, and zearalenone in foods and feeds in Botswana.

Sorghum and maize form the main dietary staple foods in Botswana. Other products such as peanuts, peanut butter, phane (an edible larval stage of an emperor moth Imbrasia belina Westwood), and pulses (cowpeas and beans) are also widely used as food and for the manufacture of feeds. These important food and feed commodities were analyzed for the presence of aflatoxins, fumonisin B1, and zearalenone. Aflatoxins were detected in 40% of the samples analyzed. The concentration of total aflatoxins ranged from 0.1 to 64 microg/kg. The mean concentration ranged from 0.3 microg/kg in sorghum to 23 microg/kg in peanut butter. Peanut butter samples were the most contaminated (71%). No aflatoxins were detected in maize. Fumonisin B1 was detected in 36% of the samples. Maize samples were the most contaminated (85% of the samples) with the concentration ranging from 20 to 1,270 microg/kg. No fumonisin B1 was detected in peanuts, phane, and beans. Zearalenone was only found in 2.6% of the samples analyzed at 40 microg/kg. Aflatoxins were the most common toxins detected in foods and feeds in Botswana. However, fumonisin B1 was more prevalent in maize than aflatoxins or zearalenone.

Microbiological quality of milk from two processing plants in Gaborone Botswana

Abstract Raw and bottled commercial pasteurised milk from two processing plants in Gaborone, Botswana were assessed for mesophilic, psychrotrophic, proteolytic and lipolytic bacteria. Proteolytic-psychrotroph counts ranged between 101 and 105 CFU/ml in both milk types. Corynebacterium pseudodiphtheriticum (44%) and Bacillus brevis (72%) predominated in raw and commercial pasteurised milk respectively. Trypsin and chymotrypsin were detected in isolates of Bacillus circulans, Pseudomonas cichorii and Micrococcus lentus. Esterase and esterase lipase activity were observed in Corynebacterium nitrilophilus, Pseudomonas fragi, B. circulans, Bacillus coagulans, and M. lentus. The study demonstrated that post-process contamination and ineffective pasteurisation compromised the quality and shelf life of pasteurised milk.

Quality deterioration of phane, the edible caterpillar of an emperor moth Imbrasia belina.

Abstract The cause for the deterioration of quality in phane, the edible larva of the emperor moth, Imbrasia belina (Westwood) was investigated. Samples were subjected to bacteriological and mycological analyses. In addition insect pests which affect storage life of the product were also assessed. 70% of the bacterial isolates associated with phane were proteolytic and 75% were either chitinolytic, lipolytic or both. Most isolates were sporeformers. But, other Gram-positive and negative isolates were also present in significant numbers. The most frequent fungal isolates were species of Aspergillus, Penicillium, Fusarium, Cladosporium and phycomycetes. Some of the fungal isolates are known to be mycotoxin producers. The insect which were associated with phane were Dermestes maculatus, Sitophilus zeamais, Corcyra cephalonica, Tribolium confusum, Tribolium casteneum, Oryzaephilus surinamensis, Bracon hebetor, Anisopteromalus cavandrae, and Stathmopoda species. Mites were also found infesting stored phane. The postharvest deterioration of phane appeared to be a concerted effort by the bacteria, moulds and insects.

Shigella and Salmonella strains isolated from children under 5 years in Gaborone, Botswana, and their antibiotic susceptibility patterns

We isolated Shigella from 43/221 (21%) and Salmonella 8/221 (3%) rectal swabs from children under 5 years with diarrhoea, and found Shigella in two of 100 specimens from children without diarrhoea. Sh. boydii (13%) was the most prevalent Shigella species followed by Sh. flexneri (6%) and Sh. sonnei (2%). The prevalence of various types of Sh. boydii was type 7, 5%; type 9, 3%; type 12 and 16, 2%; and type 18, 1%. Other Shigella serotypes encountered were Sh. flexneri type 6 (4%), type 4 (2%), with Sh. sonnei phase II isolated from 2% of the specimens. The Salmonella species were S. typhimurium and S. paratyphi. The high rate of isolation of Shigella species from children with diarrhoea is indicative of a definite role of this enteropathogen in causing endemic diarrhoea in Gaborone, Botswana. Antibiograms of the predominant isolates showed that most Shigella species were resistant to ampicillin but susceptible to chloramphenicol, and with the exception of Sh. flexneri type 6, also susceptible to gentamicin. The Salmonella species were susceptible to chloramphenicol, collistin‐sulphate, gentamicin, cotrimoxazole, and ampicillin.

A mycological investigation of phane, an edible caterpillar of an emperor moth, Imbrasia belina.

Phane worm (an edible larval stage of the emperor moth Imbrasia belina Westwood) is an important food source, and its harvesting is an economic activity in rural Botswana. When the larva is feeding on leaves and later during processing, phane gets contaminated with fungi from the leaves and soil. We examined 73 jars, each containing approximately 608 g (+/-0.25 g) of processed phane stored under laboratory conditions (temperature range 20 to 24 degrees C and 50 to 80% relative humidity) and combined intestinal contents of five phane squeezed into each of 74 Duran bottles for fungi. Ninety seven percent of 74 samples of intestinal contents and 57.5% of 73 laboratory-stored phane were positive for either molds and/or yeasts. Yeast population in intestinal contents ranged from 2 x 10(1) CFU/g to 5 x 10(3) CFU/g, whereas molds ranged from 1 x 10(1) CFU/g to 2 x 10(2) CFU/g. Laboratory-stored phane had a mold population of 1 x 10(2) CFU/g to 6 x 10(5) CFU/g. Species of Chaetomium 13.8%, Aspergillus 12.4%, Fusarium 5.5%, and Mucor racemosus 4.1% were the most prevalent in intestinal contents of phane, whereas Aspergillus 42.1%, Penicillium 33.9%, and Mucorales 5.7% were predominant in laboratory-stored phane. The important mycotoxigenic fungi A. flavus, A. parasiticus, A. ochraceus, P. aurantiogriseum, P. citrinum, and P. verrucosum were isolated mainly from the laboratory-stored phane. The genera isolated from both intestinal phane contents and laboratory-stored phane were Alternaria, Aspergillus, Chaetomium, Drechslera, Fusarium, Mucor, Phoma, and Penicillium, suggesting recontamination of phane during drying and storage.

The microbiology of phane, an edible caterpillar of the emperor moth, Imbrasia belina

The larvae of Imbrasia belina (Westwood) are cooked and sun dried to make a product known as phane, which is consumed as a delicacy. A study was conducted to determine the sanitary quality of phane and the kinds of microorganisms associated with it. It also looked into the potential for the existence of health risk associated with its consumption. Laboratory- and field-processed phane and that from open markets were subjected to microbiological analyses. The total microbial population for the larvae was in the range of 3 × 105 to 2 × 107 CFU/g. Species belonging to seven genera of bacteria and five genera of fungi were isolated from the larvae. About 50% of the identified bacteria were gram-positive, yet their combined population was much lower than that of the gram-negative bacteria. Cooking (89 to 93°C) under both sets of conditions (laboratory and field) reduced the microbial population to less than 9 × 103 CFU/g. The survivors were mostly sporeformers. Laboratory-processed phane was contaminated during drying, but none of the isolates were coliforms and the population increment was marginal. Field-processed phane, on the other hand, had a population of 4 × 104 to 1 ×108 CFU/g after 24 h of drying. The high moisture content of phane (55%) and a high degree of contamination from the soil and air appeared to have contributed to the increased population. Aspergilli including A. flavus and phycomycetes were frequently isolated from the samples. Coliforms were present in 30% and 50% of the phane processed in the field and in market phane, respectively. Escherichia coli and Klebsiella pneumoniae were found in 33% and 21%, respectively, of samples acquired from the market. The presence of K. pneumoniae . E. coli , a toxin-producing sporeformer ( Bacillus cereus ), and mycotoxin-producing fungi ( A. flavus , Penicillium sp., and Fusarium sp.) all point to the possible existence of health risks associated with its consumption.

Prevalence of coliforms in traditionally dried leafy vegetables sold in open markets and food stores in Gaborone, Botswana

The aerobic mesophilic count, coliform count, and prevalence of Escherichia coli on two vegetables commonly consumed by a majority of people in Botswana were determined. The aerobic count was found to be >105 CFU/g in both kinds of vegetables and as many as 27 to 30% of the samples had counts >107 CFU/g. Escherichia coli was present in 82% of the Amaranthus leaves sold as morogo in food stores and 50% of the Phaseolus leaves purchased from open markets. Nonfecal coliforms were present in all samples. The nonfecal coliforms belong to species of Klebsiella and Enterobacter and were present in the samples at values of 1 × 101 to 4 × 104 CFU/g.

Microflora of minimally processed frozen vegetables sold in Gaborone, Botswana

Two hundred samples of minimally processed, frozen, and prepacked potato chips, peas, corn, and a variety of combined vegetables from supermarkets in Gaborone, Botswana, were examined microbiologically. Determination of aerobic mesophilic plate count, aerobic psychrotrophic plate count, lactic acid bacteria, yeasts and molds, coliforms, Listeria spp., and Staphylococcus aureus were done. Chips had the lowest mean log values for all of the microorganisms enumerated except yeasts and molds. The mean log values for single vegetables ranged from 3.6 to 9.1, 3.4 to 8.9, 2.9 to 5.6, and 2.1 to 6.5 log CFU/ g aerobic mesophilic plate count, aerobic psychrotrophic plate count, lactic acid bacteria, and yeasts and molds, respectively. The microbial profiles of peas and corn were almost similar (P < 0.001). The mean values for combined vegetables were clustered within 4.6 and 5.4 and 4.2 and 5.2 log CFU/g aerobic mesophilic plate count and aerobic psychrotrophic plate count, respectively. All of the vegetables had a coliform population distribution ranging from 0 to < 10(4) most probable number per g. The predominant gram-negative bacteria isolated included members of Enterobacteriaceae and Pseudomonaceae (86.2%). Escherichia coli was not detected in all of the samples. The organisms isolated included those responsible for spoilage in frozen vegetables, namely Pseudomonas, Klebsiella, Corynebacterium, lactic acid bacteria, and Flavobacterium. The predominant lactic acid bacteria were Lactobacillus spp. (55.9%). Other spoilage organisms were yeasts, and Cryptococcus spp. (55.4%) was predominant. Pathogens, namely Listeria monocytogenes, were also isolated at a rate of 2 to 10%, of which 4% was from corn, 2% each from peas and country crop, and 10% from stir-fry. Bacillus cereus was also isolated and accounted for 7.7% of the microorganisms from corn. S. aureus was isolated from all of the vegetables. Enterotoxigenic strains were from corn, peas, mixed vegetables, and stir-fry, and all of them produced enterotoxin A. In addition, the isolates from stir-fry vegetables also produced enterotoxins B and C. The study reveals the presence of pathogens and emerging opportunistic pathogens in the ready-to-use or ready-to-eat vegetables. If E. coli is the only indicator for safety and acceptability, consumers may be exposed to foodborne diseases. Inclusion of other groups as indicator organisms is suggested. Retailers are urged to invest in standby generators to maintain the cold chain.

Microbiological characterisation of southern African medicinal and cosmetic clays

The effects of traditionally used medicinal and cosmetic clays in southern Africa on selected microorganisms were studied using microbiological media. The clay pH, microchemical composition, kind of associated microorganisms and antimicrobial activity of clays against test microorganisms were determined. The clays contained varying numbers of microorganisms which ranged from 0 up to 105 CFU/g. Clay pH ranged from 2.3–8.9. Neither Escherichia coli, nor other faecal coliforms were detected. Clays of pH value of <4 displayed antimicrobial activities. Clays which were active against test microorganisms had Na2O, Al2O3, SiO2, SO3, CuO or Cl2O as major components. Microbial activity of clays was attributed mainly to low pH but cations such as Cu, Al, S or Cl and various anions might have contributed to the microbicidal effects. No antimicrobial activity was established for many of the clays commonly used in the treatment of common ailments of microbial origin.

Presence of Escherichia coli, Klebsiella pneumoniae and Enterobacter species in dried bush okra (Corchorus olitorius) and African spider herb (Cleome gynandra)

Abstract Aerobic mesophilic counts, prevalence of coliforms and antibiotic sensitivity of Klebsiella isolates were determined for bush okra (Corchorus olitorius) and African spider herb (Cleome gynandra). The aerobic mesophilic count was 1 × 104–8 × 108 CFU/g for both vegetables. Though bush okra harboured fewer micro-organisms, 24% of the African spider herb had counts > 108 CFU/g. Sporeformers were abundant. Coliform numbers were 10–100 fold higher in African spider herb than bush okra. Escherichia coli was isolated from 67% of the bush okra and 71% of African spider herb samples. Klebsiella pneumoniae subsp. pneumoniae was isolated from 33% and 59% of the bush okra and African spider herb samples, respectively. The Klebsiella pneumoniae subsp. pneumoniae isolates showed normal antibiotic susceptibility patterns. The presence of E. coli and K. pneumoniae in these vegetables indicate that a potential health risk exists and that cross-contamination to other ready-to-eat commodities sold by the street vendors is possible by these bacteria or other closely related pathogenic members.