Antimicrobial Usage and Detection of Multidrug-Resistant Staphylococcus aureus, Including Methicillin-Resistant Strains in Raw Milk of Livestock from Northern Kenya.

The association of antimicrobial usage (AMU) with prevalence of antimicrobial-resistant (AMR) Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) in livestock raw milk consumed by pastoralists in Kenya remains unclear. We investigated the relationship between AMU and emergence of multidrug-resistant (MDR) S. aureus, including MRSA in raw milk of livestock. AMU data were obtained using sales records from veterinary pharmacies. S. aureus was isolated from 603 milk samples from various livestock species, including sheep, goat, cow, and camel reared in Isiolo and Marsabit counties in Kenya. Resistant phenotypes and genotypes were determined by disc diffusion and molecular methods, respectively. Correlation between AMU and occurrence of resistance was determined by Pearson's correlation coefficient (r) method. The consumption of various antimicrobial classes were as follows; 4,168 kg of oxytetracycline, 70 kg of sulfonamides, 49.7 kg of aminoglycosides, 46 kg of beta-lactams, 39.4 kg of macrolides, and 0.52 kg for trimethoprim. The S. aureus isolates were mainly resistant to tetracycline (79%), ampicillin (58%), and oxacillin (33%), respectively. A few isolates (5-18%) were resistant to clindamycin, cephalexin, erythromycin, kanamycin, and ciprofloxacin. Most of the MDR-S. aureus isolates were MRSA (94%). The genetic determinants found in the AMR isolates included tetK/tetM (96.5%/19%) for tetracycline, blaZ (79%) for penicillin, aac (6')/aph (2'')/aph (3')-IIIa (53%) for aminoglycosides, mecA (41%) for oxacillin, and msrA/ermA (24%/7%) for macrolides. Oxytetracycline usage was correlated to tetK/tetM (r = 0.62/1) detection, penicillins to mecA/blaZ (r = 0.86/0.98), aminoglycoside to aac (6')/aph (2'')/aph (3')-IIIa (r = 0.76/-13), and macrolide usages for detection of ermA/msrA (r = 0.94/0.77). AMU appeared to be associated with occurrence of MDR-SA and the tetM detection. Consumption of raw milk contaminated with MRSA could pose a serious public health risk in pastoral communities in northern Kenya.

Serotypes and antimicrobial resistance profiles of Salmonella isolates from pigs at slaughter in Kenya.

BACKGROUND: Salmonellosis is considered one of the most widespread food-borne zoonoses in industrialized as well as developing countries. The presence of Salmonella in food animals at slaughter and the consequent cross-contamination of edible carcass tissues present a significant food safety hazard. METHODOLOGY: Samples were collected from randomly selected pigs at the Ndumbuini abattoir in Nairobi. Isolates were confirmed to be Salmonella by biochemical tests and characterised by serotyping, phage typing and plasmid analysis. Minimum inhibitory concentrations (MICs) of eight antimicrobials were determined and the resistant isolates were screened for resistance genes by PCR. RESULTS: Sixteen (13.8%) of 116 samples were positive for Salmonella. Three Salmonella enterica subsp. enterica serovars, namely Saintpaul, Braenderup, and Heidelberg were identified, S. Saintpaul being predominant. Antimicrobial resistance was found in 35.7% of the isolates. The S. Heidelberg isolates were susceptible to all the antimicrobials tested. Multidrug resistance was found in 7.1% of the Salmonella isolates. Plasmids were only detected in S. Heidelberg. Ampicillin resistance was based on expression of a blaTEM gene, while chloramphenicol, streptomycin, and tetracycline resistances were encoded by the genes catA1, strA, and tet(A), respectively. CONCLUSIONS: Pigs may serve as reservoirs of antimicrobial resistant Salmonella and slaughterhouse cross-contamination of pork may be a food safety risk.

Establishment and comparative analyses of different culture conditions of primary hepatocytes from Nile tilapia (oreochromis niloticus) as a model to study stress induction in vitro.

We established an in vitro hepatocyte primary culture system from Oreochromis niloticus, a tropical fish species of great economical importance, and evaluated its ability to express albumin, a liver-specific protein, consistently for a period of 3 wk. Serum requirements for fish hepatocyte cultures were assessed. A one-step in situ perfusion of tilapia liver retrogradely followed by collagenase liver dissociation and subsequent washing produced nearly 90% homogenous viable hepatocytes, as shown by trypan blue exclusion test. Mixed primary monolayer and aggregate hepatocyte cultures achieved by 10% fetal calf serum medium supplements expressed consistent levels of albumin. The results of light and electron microscopy showed that the hepatocytes did not significantly proliferate (P<0.05) but remained viable for at least 3 wk. The results of this study show that in vitro cultures of mixed primary hepatocyte monolayers and aggregates established from Nile tilapia may be useful models for studying transient cellular stress induction.

Cross-reactive studies in visceral leishmaniasis: comparison of antigens of some Leishmania species in Kenya.

Little is known about the common antigens of the various strains of Leishmania in Kenya, and their possible role in immunity to disease. Kenyan isolates of Leishmania donovani, L. Major and L. tropica were cultured, crude antigens prepared and electrophoresced in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Immunoblots by pooled sera from cutaneous and visceral leishmaniasis patients revealed common antigens within the 110-116kD, 70kD and the 63kD ranges. Only the 112-116kD antigens from L. major strains were reacted to by both cutaneous and visceral leishmaniasis patient sera. Sera from normal individuals living in an endemic area for leishmaniasis also showed reactivity to the 116kD antigen. We suggest that these common antigens may be of value in future vaccine studies