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Staphyloccous aureus belonging to sequence type 5477 have recently been identified as a predominant clone causing bovine mastitis in Rwanda and Tanzania. We compared nine S. aureus ST5477 to 17 isolates belonging to other sequence types by their biochemical profile and ability to acidify milk and grow in minimum media containing lactose. We found that ST5477 isolates all were positive in ONPG (o-nitrophenyl-β-D-galactopyranoside) test and negative for mannitol fermentation potentially challenging the correct identification of this sequence type as S. aureus. In addition, ST5477 isolates were all much faster in acidifying milk and grew faster in minimal media with lactose compared to other strains suggesting an increased lactose utilization and thereby adaptation to the bovine udder environment as a possible reason for the recent successful emergence. Comparison of the lac gene region of the genome of a recently sequenced ST5477 and that of S. aureus reference genome showed that both strains contained the known lacABCD genes involved in the lactose degradation, but that ST5477 had a 12 amino-acid deletion and two amino-acid differences in the lac gene transcription regulator, suggesting that increased transcription might play a role. In conclusion, these preliminary data suggests that improved lactose utilization and the ability to grow faster in milk may have been a key feature for the recent success of ST5477 as a bovine adapted clone.

Abstract Background Data on the prevalence, genotypes and antibiotic resistance patterns of colonizing and infection-associated Staphylococcus aureus (S. aureus) strains both in humans and animals in Tanzania are scarce. Given the wide range of infections caused by S. aureus and the rise of methicillin-resistant S. aureus (MRSA) globally, this review aims at collecting published data on S. aureus bacterium to improve our understanding of its epidemiology in Tanzania. Main body We carried out a systematic review of scientific studies reporting on prevalence, antibiotic resistance and genotyping data pertaining to S. aureus in human and animal infection and colonization. The literature extracted from electronic databases such as PubMed and Google Scholar was screened for eligibility and relevant articles were included. The review is limited to manuscripts published in English language between the years 2010 and 2020. A total of 45 studies conducted in 7 of the 9 administrative zones in Tanzania were reviewed to gather data on S. aureus prevalence in humans and animals. Prevalence in humans ranged from 1 to 60%. Antibiotic resistance patterns of S. aureus isolated from colonized humans showed high resistance rates against co-trimoxazole (46%) and erythromycin (41%) as compared to reports from studies conducted outside Africa. The review suggests an increased MRSA prevalence of up to 26% as compared to 6–16% reported in previous years. Genotypic data reviewed suggested that MRSA predominantly belonged to ST88. The prevalence of S. aureus in animal studies ranged from 33 to 49%, with 4 to 35% of MRSA isolates. Most studies reported low antibiotic resistance levels, with the exception of penicillin (85%) and ampicillin (73%). Conclusion The prevalence of S. aureus and MRSA in Tanzania is rising, although clear variations between different geographic areas could be observed. Non-susceptibility to commonly prescribed antibiotics in community-associated S. aureus is of concern. Research strategies to ameliorate our knowledge on S. aureus epidemiology should employ regular antibiotic resistance surveillance, antimicrobial stewardship as well as genotypic characterization.

Staphylococcus aureus is a common cause of infection in humans and animals, including bovine mastitis, globally. The objective of this study was to genetically characterize a collection of S. aureus isolates recovered from milk and nasal swabs from humans with and without animal contact (bovine = 43, human = 12). Using whole genome sequencing (NextSeq550), isolates were sequence typed, screened for antimicrobial resistance and virulence genes and examined for possible inter-species host transmission. Multi locus sequence typing (MLST) and single nucleotide polymorphism (SNP)-based phylogeny revealed 14 different sequence types, including the following six novel sequence types: ST7840, 7841, 7845, 7846, 7847, and 7848. The SNP tree confirmed that MLST clustering occurred most commonly within CC97, CC5477, and CC152. ResFinder analysis revealed five common antibiotic resistance genes, namely tet(K), blaZ, dfrG, erm©, and str, encoding for different antibiotics. mecA was discovered in one human isolate only. Multidrug resistance was observed in 25% of the isolates, predominantly in CC152 (7/8) and CC121 (3/4). Known bovine S. aureus (CC97) were collected in humans and known human S. aureus lineages (CC152) were collected in cattle; additionally, when these were compared to bovine-isolated CC97 and human-isolated CC152, respectively, no genetic distinction could be observed. This is suggestive of inter-host transmission and supports the need for surveillance of the human–animal interface.

Urinary tract infections (UTIs) are among the most common infections in sub-Saharan Africa, but microbiological data to guide treatment decisions are limited. Hence, we investigated the bacterial aetiology and corresponding antimicrobial susceptibility patterns in outpatients with UTIs in Bagamoyo, Tanzania. Urine samples from symptomatic individuals were subjected to microbiological examinations for bacterial species identification using conventional methods and disc diffusion-based resistance testing. Subsequently, urine samples were transferred to Germany for confirmatory diagnostics using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and automated resistance testing. Overall, 104 out of 270 (38.5%) individuals had a positive urine culture and 119 putative pathogens were identified. The most frequently detected bacteria were Escherichia coli (23%), Klebsiella spp. (7%), Enterobacter cloacae complex (3%) and Staphylococcus aureus (2%). E. coli isolates showed high resistance against cotrimoxazole (76%), ampicillin (74%), piperacillin (74%) and fluoroquinolones (37%), but widespread susceptibility to meropenem (100%), fosfomycin (98%), piperacillin/tazobactam (97%) and amoxicillin/clavulanic acid (82%). The agreement between E. coli susceptibility testing results in Tanzania and Germany was ≥95%, except for piperacillin/tazobactam (89%) and ciprofloxacin (84%). Given the considerable resistance to frequently prescribed antibiotics, such as cotrimoxazole and fluoroquinolones, future research should explore the potential of oral alternatives (e.g., fosfomycin) for the treatment of UTIs in Tanzania.