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Streptococcus suis infection: 12 of 18 drugs failed
Two finishing pigs on one commercial farm carried a streptococcus suis infection that resisted 12 of the 18 antimicrobials tested. Gentamicin was the only drug that stayed fully susceptible in both isolates. Tetracycline resistance was part of the same pattern, so the panel and not the farm’s history has to decide which drug is still usable. Why a streptococcus suis infection that resists drugs matters Streptococcus suis is a Gram-positive coccus, and 29 serotypes have been described. It sits in the tonsils and the upper respiratory tract of healthy pigs, so its presence alone tells a herd owner very little. Where it goes and what it brings along are the…
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Plasmid mediated antibiotic resistance in aquaculture: pRAS2
Plasmid mediated antibiotic resistance in aquaculture travels through conjugation between bacteria, not through fish that move. pRAS2, a conjugative plasmid found in Aeromonas salmonicida, encodes a complete type IV secretion system and uses it to mobilize a second, non conjugative plasmid, pRAS3, into new host cells, while pRAS2 itself stays behind in the donor. The event is too rare to emerge in routine culture, and it needs no antibiotic exposure at all to occur. Why a single 1992 fish isolate still matters Antibiotics are used at scale in aquaculture to treat bacterial infection, and that use is one of the strongest forces pushing antimicrobial resistance (AMR) upward in farmed aquatic…
