A Comparison of the Reverse Passive Latex Agglutination and Enzyme Linked Immunosorbent Assay Techniques for Detection of Staphylococcal Enterotoxins

A study was carried out to compare the Reverse Passive Latex Agglutination (RPLA) and Enzyme Linked Immunosorbent Assay (ELISA) techniques for detection of staphylococcal enterotoxins (SEs). One hundred and one Staphylococcus aureus (S. aureus) isolates were recovered from milk and meat samples. Isolates were tested for their ability to produce any of the staphylococcal enterotoxin types A, B, C, and D. Sixty seven S. aureus isolates were found to be enterotoxigenic, using ELISA, while 62 isolates were found to be enterotoxigenic with RPLA technique. Staphylococcal enterotoxin C was the most frequent enterotoxin detected by both ELISA and RPLA. This study found no significant difference in the sensitivity of ELISA and RPLA techniques for detection of staphylococcal enterotoxins (t=0.908; df=3; p=0.431). It was concluded that ELISA and RPLA are comparable tests and any of them can be used to test for staphylococcal enterotoxins. However, the RPLA test appears to be most suitable for screening a large number of isolates for staphylococcal enterotoxins because it is less cumbersome, less costly and rapid. Kenya Veterinarian Vol. 31 (1) 2007: pp. 20-2

Detection of staphylococcal enterotoxins in milk and meat in Nairobi Kenya using Enzymes Linked Immunosorbent Assay

Staphylococcus aureus is a cause of food poisoning in humans characterized by vomiting, headache, abdominal pain, and diarrhoea that occur 1-6 hours following consumption of contaminated food. This study was carried to determine the rate of contamination of milk and meat products with enterotoxigenic S. aureus in Nairobi. Analysis was done at the Department of Public Health, Pharmacology and Toxicology, University of Nairobi. A total of 400 milk and meat products were collected around Nairobi. The samples included 200 raw milk, 100 beef carcass swabs, 50 minced meat samples and 50 chicken carcasses. Mannitol salt agar was used as selective and indicator medium for isolation of S. aureus from food samples. Staphylococcus was identified using a number of different diagnostic tests, which included oxidative fermentation, Mannitol fermentation, coagulase production and deoxyribonuclease (Dnase) production assays. Enterotoxin production was detected using Enzyme linked immunosorbent assay (ELISA) using Staphylococcus Enterotoxin Enzyme Immunoassay (SET-EIA) kit. One hundred and one (101) S. aureus were isolated from food samples. Of these, 22 were from chicken, 16 from minced meat, 55 from raw milk and 8 from beef carcasses. Sixty-seven of S. aureus were found to be enterotoxigenic. Staphylococcal enterotoxins SEA, SEB, SEC and SED were tested for, and SEC was the most frequent accounting for 59 (88%). Twenty-four (38.5%) of the enterotoxigenic S. aureus produced single enterotoxins. Chicken carcasses accounted for the highest percentage (44%) of enterotoxigenic S. aureus in foodstuff with SEC producing strains having the highest percentage. Keywords: Staphylococcal enterotoxins among foodstuff > Journal of Tropical Microbiology and Biotechnology Vol. 3(1) 2007: pp. 23-2

Foodborne diseases in Kenya

(East African Medical Journal: 2001 78(1): 40-44

Relative Occurrence of Fasciola species in cattle, sheep and goats slaughtered at Dagoretti slaughterhouse in Kenya

A cross sectional survey was carried out in Nairobi\'s Dagoretti slaughter house, where routine postmortem meat inspection was done. All liver flukes detected in cattle, sheep and goats were collected and transported to laboratory for analysis to determine the relative occurrence of Fasciola gigantica and Fasciola hepatic in slaughtered cattle, sheep, and goats by observing their size and morphology. The study showed that all the liver flukes collected in Dagoretti were F. gigantica. A total of 1584 cattle, 989sheep and 954 goats originating from five out of the 8 provinces of Kenya were slaughtered at Dagoretti slaughter house, over the study period. 147 (9.3%) cattle, 8 (0.8%) sheep, 4 (0.4%) goats were shown to harbor liver fluke infection. It was concluded that fascioliasis is prevalent in cattle, sheep and goats of Kenya. This may be a cause of great economic losses at slaughter as a result of condemnation of infected livers. The Kenya Veterinarian Vol. 27 2004: pp. 124-12

Prevalence and Economic Importance of Fascioliasis in Cattle, Sheep and Goats in Kenya

A 10 year (1990-1999) retrospective study using post mortem records was carried out at Veterinary Department Headquarters Kabete to determine the prevalence and economic importance of fasciolosis in cattle, goats and sheep in Kenya. Records from abattoirs in 38 districts in 7 provinces of Kenya were examined. Fasciolosis prevalence was calculated. Using an average weight of (3kg) cattle and (0.5) sheep and goats and market price of approximately US $2.0 per Kg, the monetary loss occasioned by condemnation of Fasciola infected livers was calculated. Out of 5,421,188 cattle, 1,700,281 sheep and 2,062,828 goats slaughtered, 427,931 cattle (8$ 2.6million, US$61,995 and US$48,889 respectively. Fasciolosis is prevalent in cattle, sheep and goats in Kenya and a major cause of economic losses, as a result of condemnation of infected livers. The Kenya Veterinarian Vol. 27 2004: pp. 118-12

Molecular epidemiology of bacillus cereus food poisoning

(East African Medical Journal 2001 78 (10): 523-525

Antimicrobial resistance in Salmonella serotypes isolated from slaughter animals in Kenya

No Abstract. East African Medical Journal Vol. 84 (5) 2007: pp. 233-23

Antibiotic Resistance of Escherichia coli Isolated from Healthy Food Animals in Kenya

The antimicrobial resistance profile of 204 Escherichia coli isolates of bovine, swine and poultry origin to eight (8) antimicrobial agents was studied. Antimicrobial susceptibility tests were determined using the disk diffusion technique. Full sensitivity to all the eight antimicrobial agents in the test panel was observed in 46 % of all isolates. Resistance to at least one antimicrobial was observed in 10 % of the isolates while multi-drug resistance (two or more antibiotics) was observed in 26 % of the isolates. Generally, resistance was significantly higher for isolates from swine and poultry than in cattle. The overall prevalence was 22 % for sulfamethoxazole, 21 % for co-trimoxazole, 19 % for ampicillin, 14 % for tetracycline, 9 % for streptomycin, 4.4 % for chloramphenicol and 2.5 % for kanamycin. No resistance was observed for gentamycin. It was concluded from the study that healthy food animals form a reservoir of multiple resistant E. coli which may be transmitted to humans through the food chain. Thus, continued surveillance of E. coli obtained from food production continuum is merited to identify emerging antimicrobial-resistant phenotypes. The Kenya Veterinarian Vol. 30 (1) 2006: pp. 23-2

Species Composition, Phenotypic and Genotypic Resistance Levels in Major Malaria Vectors in Teso North and Teso South Subcounties in Busia County, Western Kenya

Introduction. Knockdown resistance (kdr) is strongly linked to pyrethroid insecticide resistance in Anopheles gambiae in Africa, which may have vital significance to the current increased use of pyrethroid-treated bed net programmes. The study is aimed at determining species composition, levels of insecticide resistance, and knockdown patterns in Anopheles gambiae sensu lato in areas with and areas without insecticide resistance in Teso North and Teso South subcounties, Western Kenya. Materials and Methods. For WHO vulnerability tests, mosquito larvae were sampled using a dipper, reared into 3-5-day-old female mosquitoes (4944 at 100 mosquitoes per insecticide) which were exposed to 0.75% permethrin, 0.05% deltamethrin, and 0.1% bendiocarb using the WHO tube assay method. Species identification and kdr East gene PCRs were also performed on randomly selected mosquitoes from the collections; including adult mosquitoes (3448) sampled using standard collection methods. Results. Anopheles gambiae sensu stricto were the majority in terms of species composition at 78.9%. Bendiocarb caused 100% mortality while deltamethrin had higher insecticidal effects (77%) on female mosquitoes than permethrin (71%). Susceptible Kengatunyi cluster had higher proportion of An. arabiensis (20.9%) than resistant Rwatama (10.7%). Kengatunyi mosquitoes exposed to deltamethrin had the highest KDT50 R of 8.2. Both Anopheles gambiae sensu stricto and Anopheles arabiensis had equal S allelic frequency of 0.84. Indoor resting mosquitoes had 100% mortality rate after 24 h since exposure. Overall SS genotypic frequency in Teso North and Teso South subcounties was 79.4% against 13.7% homozygous LL genotype and 6.9% heterozygous LS genotype. There was a significant difference (ρ<0.05) in S allele frequencies between Kengatunyi (0.61) and Rwatama (0.95). Mosquito samples collected in 2013 had the highest S allelic frequency of 0.87. Discussion. Most likely, the higher the selection pressure exerted indoors by insecticidal nets, the higher were the resistance alleles. Use of pyrethroid impregnated nets and agrochemicals may have caused female mosquitoes to select for pyrethroid resistance. Different modes of action and chemical properties in different types of pyrethroids aggravated by a variety of edaphic and climatic factors may have caused different levels of susceptibility in both indoor and outdoor vectors to pyrethroids and carbamate. Species composition and populations in each collection method may have been influenced by insecticide resistance capacity in different species. Conclusions and Recommendations. Both phenotypic and genotypic insecticide resistance levels have been confirmed in Teso North and Teso South subcounties in Western Kenya. Insecticide resistance management practices in Kenya should be fast tracked and harmonized with agricultural sector agrochemical-based activities and legislation, and possibly switch to carbamate use in order to ease selection pressure on pyrethroids which are useable in insecticidal nets and indoor residual spray due to their low human toxicity. The implication of such high resistance levels in mosquitoes collected in Teso subcounties is that resistance is likely to persist and or even increase if monomolecules of permethrin and deltamethrin or both continue to be used in all net- and nonnet-based mosquito control purposes. Usage of mutually reinforcing piperonyl butoxide (PBO) that prohibits particular enzymes vital in metabolic activities inside mosquito systems and has been integrated into pyrethroid-LLINs to create pyrethroid-PBO nets is an extremely viable option

Impact of Insecticide Resistance on P. falciparum Vectors’ Biting, Feeding, and Resting Behaviour in Selected Clusters in Teso North and South Subcounties in Busia County, Western Kenya

Introduction. Behavioural resistance to insecticides restrains the efficacy of vector control tools against mosquito-transmitted diseases. The current study is aimed at determining the impact of insecticide resistance on major malaria vectors’ biting, feeding, and resting behaviour in areas with and areas without insecticide resistance in Teso North and Teso South, Busia County, Western Kenya. Methods. Mosquito larvae were sampled using a dipper, reared into 3-5-day-old female mosquitoes [4944] which were exposed to 0.75% permethrin and 0.05% deltamethrin using World Health Organization tube assay method. Blood meal, species identification, and kdr Eastgene PCRs were also performed on adult mosquitoes sampled using mosquito collection methods [3448]. Biting, feeding, resting, and exiting behaviours of field-collected mosquitoes from five selected clusters were analysed. Results. The lowest Kdr genotypic frequency (SS) proportion was found in female Anophelines collected in Kengatunyi at 58% while Rwatama had the highest genotypic frequency at 93%, thus susceptible and resistant clusters, respectively. The peak hour for mosquito seeking a human bite was between 0300 and 0400 hrs in the resistant cluster and 0400-0500 hrs in the susceptible cluster. The heterozygous mosquitoes maintained the known 2100-2200 hrs peak hour. There was a higher proportion of homozygous susceptible vectors (86.4%) seeking humans indoor than outdoor bitters (78.3%). Mosquito blood meals of human origin were 60% and 87% in susceptible Kengatunyi and resistant Rwatama cluster, respectively. There was significant difference between homozygous-resistant vectors feeding on human blood compared to homozygous susceptible mosquitoes (p≤0.05). The proportion of bovine blood was highest in the susceptible cluster. A higher proportion of homozygous-resistant anophelines were feeding and resting indoors. No heterozygous mosquito was found resting indoor while 4.2% of the mosquitoes were caught while exiting the house through the window. Discussion. A shift in resistant Anopheles gambiae sl highest peak hour of aggressiveness from 2100-2200 hrs to 0300-0400 hrs is a key change in its biting pattern. Due to the development of resistance, mosquitoes no longer have to compete against the time the human host enters into the formerly lethal chemical and or physical barrier in the form of long-lasting insecticide-treated net. No heterozygous LS mosquito rested indoors possibly due to disadvantages of heterozygosity which could have increased their fitness costs as well as energy costs in the presence of the insecticidal agents in the treated nets. Conclusions and recommendations. Out of bed biting by female mosquitoes and partial susceptibility may contribute to residual malaria transmission. Insecticide-resistant vectors have become more endophagic and anthropophillic. Hence, insecticidal nets, zooprophylaxis, and novel repellents are still useful chemical, biological, and physical barriers against human blood questing female mosquitoes. Further studies should be done on genetic changes in mosquitoes and their effects on changing mosquito behaviour