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. 2023 Jun 5;11(6):1505.
doi: 10.3390/microorganisms11061505.

Molecular Characterization of Staphylococcus aureus Isolated from Raw Milk and Humans in Eastern Tanzania: Genetic Diversity and Inter-Host Transmission

Tutu Mzee  1   2 , Happiness Kumburu  3 , Theckla Kazimoto  1 , Pimlapas Leekitcharoenphon  4 , Marco van Zwetselaar  3 , Rose Masalu  2 , Tarsis Mlaganile  1 , Tolbert Sonda  3 , Boaz Wadugu  3 , Ignass Mushi  3 , Frank M Aarestrup  4 , Mecky Matee  5
Affiliations

Molecular Characterization of Staphylococcus aureus Isolated from Raw Milk and Humans in Eastern Tanzania: Genetic Diversity and Inter-Host Transmission

Tutu Mzee et al. Microorganisms. .

Abstract

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.

Keywords: Staphylococcus aureus; Tanzania; antibiotic resistance; asymptomatic mastitis; genotyping; virulence factors; whole genome sequencing.

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Conflict of interest statement

The authors declare no conflict of interest in this work.

Figures

Figure 1
Figure 1
SNP tree of 55 S. aureus genomes constructed using CSI phylogeny. AN: Isolates collected from cows, HU: Isolates collected from humans. Clustering STs are colour-coded. The colour-coded bar represents the regions in which the isolates were collected from.
Figure 2
Figure 2
(a) ST diversity and distribution within the study area; (b) Spa type diversity and distribution within the study area.
See this image and copyright information in PMC

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