Antimicrobial Resistance Patterns and Bovine Sub-Clinical Mastitis Burden in Low and High Tick Acaricide Resistance Regions of Uganda

Mastitis, antimicrobial resistance and acaricide resistance pose significant threats to the development of the dairy industry in sub-Saharan Africa. This study aimed to determine the prevalence of antimicrobial resistance in bacteria isolated from CMT positive cows on farms located in high (HARA) and low (LARA) acaricide resistance challenge regions of Uganda. Among selected herds in both regions, subclinical mastitis (SCM) screening was performed using CMT. CMT positive samples were collected, cultured, bacteria isolated and antibiotic sensitivity tests conducted. Overall, the prevalence of SCM in cows was 71.5% and 27.7% for HARA and LARA respectively. A SCM herd prevalence of 66.3% and 28.2% was recorded for HARA and LARA respectively. Furthermore, 67.5% and 20.8% of the cows in the HARA and LARA groups, respectively, had three out of four udder quarters infected with SCM. Staphylococcus aureus (44.2%) and coagulase-negative Staphylococcus (CNS) (47.6%) were the most prevalent causative agents of SCM isolated from cows from HARA and LARA, respectively. Most isolates from both regions were highly resistant to penicillin (HARA, 84.3%;LARA, 95.6%) and colistin (HARA, 100%;LARA, 97.8%). Tetracycline (77.1%) and oxacillin (76.1%) resistance was high in isolates from HARA and LARA, respectively. Intermediate responses (neither susceptible nor resistant) to antibiotics were more common in isolates from HARA than in those from LARA. With this level of antibiotic resistance, there is a potential risk of failure to control mastitis in dairy cattle using antibiotics, especially in the HARA region, which may possibly jeopardize the growth of the dairy industry in Uganda.

Molecular Epidemiology of Klebsiella pneumoniae from Clinical Bovine Mastitis in Northern Area of China,2018–2019

Klebsiella pneumoniae(K.pneumonia,KpⅠ)is a predominate inducement of bovine mastitis,which is associated with high mortality and milk yield reduction.However,data is lacking on the molecular characteristics of bovine K.pneumoniae,limiting the risk assessment of its transmission through the food chain.Herein,we investigated the prevalence of K.pneumoniae in 6301 clinical mastitis(CM)milk samples from dairy cattle in northern area of China.In total,183 K.pneumoniae isolates were recovered,with detection rates of 3.0% and 2.8% in 2018 and 2019,respectively.Like human clinical K.pneumoniae,all CM K.pneumoniae isolates belonged to one of three phylogroups:KpⅠ(n=143),Klebsiella.quasipneumoniae subsp.similipneumoniae(KpⅡ-B)(n=37),and Klebsiella variicola(KpⅢ)(n=3).We detected the extendedspectrum β-lactamase-encoding genes bla_(SHV-2a),blac_(CTX-M-14),and bla_(CTX-M-15),as well as clpC,lpfA,lacI,lacZ,lacY,and the fecABDEIR operon in the KpⅠ isolates,which may contribute to their pathogenicity and host adaptability in cows.The high prevalence of KpⅠ in dairy farms may be problematic,as it showed relatively higher rates of antibiotic resistance and virulence gene carriage than the KpⅡ-B and KpⅢ isolates.Furthermore,we observed distinct differences in population structure between CM-and human infection-associated KpⅠ isolates,with the genes associated with invasive infection in humans rarely being observed in bovine isolates,indicating that few CM-associated K.pneumoniae isolates pose a threat to human health.Nevertheless,bovine KpⅡ-B isolates shared a high level of nucleotide sequence identity with isolates from human infections and frequently carried the nitrogen-fixation gene nif,suggesting an association between KpⅡ-B isolates from cattle and humans,and plant-derived bacteria.

Comparative Proteomic Analysis of Plasma from Clinical Healthy Cows and Mastitic Cows

The current research presents the protein changes in plasma from healthy dairy cows and clinical mastitic cows using two- dimensional gel electrophoresis （2-DE）. After staining with silver nitrate and Coomassie Blue, differential expression proteins were detected by PDQuest 7.4 software, and then subjected to ion trap mass spectrometer equipped with a Surveyor HPLC System, differential spots of protein were identified. Three protein spots that originated from preparation gels were identified to be two proteins. Overall, haptoglobin precursor was up-regulated in cows infected with clinical mastitis and could be a mastitis-associated diagnostic marker, whereas SCGB 2A1 （secretoglobin, family 2A, member 1） was down-regulated protein. Plasma protein expression patterns were changed when cows were infected with mammary gland inflammation; it suggests that analysis of differential expression protein might be useful to clarify the mechanisms involved in the pathophysiology, and find new diagnostic markers of mastitis and potential protein targets for treatment.