In this study, we investigated the impact of mastitis infection on the quality of milk composition in small-scale dairy bovine herds. The purpose of this study was to find a milk quality somatic cell count (SCC) standard that could be used as an integral component of a control program. In all, 396 quarter milk samples from lactating cross-bred cows (Holstein & Zebu) were analyzed; 56% of these quarters were experiencing intramammary infection, with an overall mean SCC of 5.46 × 105 ± 2.30 × 104cells/ml. Infected quarters had significantly (p < 0.05) higher mean SCC levels (6.19 × 105± 4.40 × 104cells/ml) compared to healthy quarters (2.65 × 105 ± 2.40 × 104cells/ml). In high SCC milk and infected quarters, the concentrations of non-casein fractions, sodium, chloride, and free fatty acid were higher (p < 0.05), while the casein content, lactose, casein-to-total protein, potassium, and calcium were lower (p < 0.05) compared to normal quarters. These findings suggest a mean SCC threshold limit of 5.46 × 105 cells/ml for the region. It was concluded that the results could be used to propose a milk quality SCC standard that can be used as an integral component of a control program.

The improved Dutch tube diffusion test was used to study the occurrence of inhibitory substances in raw bulk milk samples within the Nakuru District in Kenya. Initially the detection limits of the method were verified using milk standards spiked with selected antibiotics. Addition of penicillinase to inhibitor‐positive samples was used for preliminary identification of penicillin G‐type antibiotics and residue levels were estimated against a standard curve constructed by means of a B. stearothermophilus disc assay. The two‐tube test was used to screen 1109 field samples of which 229 (21%) were suspect positive. The identification procedure confirmed 165 samples (14.9%) to contain penicillin G‐type residues of which 118 contained levels exceeding the established EU MRL for penicillin G (4 μg/kg). This study indicates that antibiotic residues are prevalent in milk within the Nakuru district of Kenya. It suggests that the improved tube diffusion test in combination with a multiplate system could be useful for qualitative and quantitative identification of antimicrobial drug residues in milk.

Phytochemicals have been found to be promising alternatives to conventional antibiotic therapies for the control of bacterial infections, as they may entail less selective pressure and hence reduce the development of resistance. This study involved examining the inhibition of biofilm formation and of quorum sensing (QS), and the cytotoxicity on mammalian cells of two flavonoids, quercetin and baicalein, in free form and associated into chitosan-based nanocapsules. This was done by use of a transformed E. coli Top 10 biosensor strain, while the cytotoxicity was evaluated on MDCK-C7 cells. In free form, application both flavonoids exhibited slight inhibitory activity on the QS response and biofilm formation, a scenario that was improved positively upon encapsulation with chitosan (Mw ∼115,000 g/mol and DA ∼42%). The association efficiency of 99% (quercetin) and 87% (baicalein) was determined, and each formulation had an average diameter of 190 ± 4 and 187 ± 2 nm, and zeta (ζ) potential of +48.1 ± 2.03 and +48.4 ± 3.46 mV, respectively. Both types of systems were stable against aggregation in M9 and MEM media. The in vitro release kinetics data of both flavonoids seemed to be similar with only ∼20% released over the first 5 h, or ∼10% over the first 4 h, respectively, with subsequent sudden release increase up to ∼40% in both cases. The free phytochemicals seemed to be cytotoxic to MDCK-C7 cells at higher doses, however, upon nanoencapsulation, a cytoprotective effect was evidenced. We have gained proof-of-principle of the advantages of encapsulation of two bioactive flavonoids.

Productions of various bacterial traits like production of virulence factors (e.g. toxins, enzymes), biofilm formation, luminescence among others, have been known to be controlled by quorum sensing (QS), a process that is dependent on chemical signals or autoinducers (AIs). Bacteria known to rely on such AIs are known to be virulent and tend to be resistant against various antimicrobial agents. Therefore, strategies aimed at the inhibition of QS pathways, are regarded as potential novel therapies in managing bacterial virulence hence reducing their ability to induce infections in humans. In the present study, a portfolio of 25 medicinal plant extracts (ethanol 50% v/v) used in southwestern Kenya were assayed against a transformed E. coli Top 10 reporter QS strain. This biosensor responds to the exogenous addition of 3-oxo-N-hexanoyl homoserine lactone (3OC6HSL) expressing green fluorescent protein (GFP). The large majority of the screened medicinal plants seemed to exhibit toxic effects and almost none of them induced antiquorum sensing (AQS) activity. This could be the consequence of the presence of mixed compounds in the extracts. Elaeodendron buchananii Loes and Acacia gerrardii Benth extracts that seemed to show AQS activity were further proved found to possess mild AQS but with defined antimicrobial activities, and no antibiofilm formation inhibition. As a control, an E. coli pBCA9145_jtk2828::sfGFP strain that produces constitutively GFP was used and confirmed that none of the two extracts quenched the fluorescence of sfGFP. Cytotoxicity assays with mammalian MDCK cells also did indicate that the selected extracts with putative AQS activity, also reduced the cell viability. Therefore, further studies will be needed to separate and re-test the individual compounds especially from the selected two promising plants.

This study evaluated the prevalence of multidrug resistant Staphylococcus aureus in Kenyan milk and investigated any differences in antimicrobial resistance between large- (>200 L/d) and small- (<50 L/d) scale producers. Susceptibility profiles for penicillin G, tetracycline, erythromycin, trimethoprim/sulfamethazine, and chloramphenicol were determined for Staph. aureus (n=402) isolated from cows with subclinical mastitis. There was a significant difference in the overall mean resistance profile between large- (7.1%) and small-scale farm (14.7%) isolates. The overall prevalence of multidrug resistance (> or =2 antibiotics) differed significantly between isolates from small farms (34.3%) and those from large farms (18.0%). Additionally, the producers were interviewed about their usage of antimicrobial drugs and their attitudes toward education in related fields. There was an evident difference between the producer types in their documentation of the use of antimicrobial drugs. Small-scale farms were less inclined to documentation, and treatment records were available from 22% of small-scale farms, compared with 73% of large-scale farms. Farmers expressed a need for more information in 5 areas, ranking preventive management highest (34.0%); followed by affordable tests to control residues in milk (22.8%); preparation of antimicrobial drugs (20.0%); public health concerns (11.2%); disposal of surplus antimicrobial drugs (7.8%); and antimicrobial drug residue persistence in milk (4.2%). It was concluded that herd size might be an indirect risk factor in the development of antimicrobial resistance in Staph. aureus within the region.