Cephalosporinases associated with outer membrane vesicles released by Bacteroides spp. protect gut pathogens and commensals against β-lactam antibiotics

Abstract

ObjectivesTo identify β-lactamase genes in gut commensal Bacteroides species and to assess the impact of these enzymes, when carried by outer membrane vesicles (OMVs), in protecting enteric pathogens and commensals.MethodsA deletion mutant of the putative class A β-lactamase gene (locus tag BT_4507) found in the genome of the human commensal Bacteroides thetaiotaomicron was constructed and a phenotypic analysis performed. A phylogenetic tree was built from an alignment of nine Bacteroides cephalosporinase protein sequences, using the maximum likelihood method. The rate of cefotaxime degradation after incubation with OMVs produced by different Bacteroides species was quantified using a disc susceptibility test. The resistance of Salmonella Typhimurium and Bifidobacterium breve to cefotaxime in liquid culture in the presence of B. thetaiotaomicron OMVs was evaluated by measuring bacterial growth.ResultsThe B. thetaiotaomicron BT_4507 gene encodes a β-lactamase related to the CepA cephalosporinase of Bacteroides fragilis. OMVs produced by B. thetaiotaomicron and several other Bacteroides species, except Bacteroides ovatus, carried surface-associated β-lactamases that could degrade cefotaxime. β-Lactamase-harbouring OMVs from B. thetaiotaomicron protected Salmonella Typhimurium and B. breve from an otherwise lethal dose of cefotaxime.ConclusionsThe production of membrane vesicles carrying surface-associated β-lactamases by Bacteroides species, which constitute a major part of the human colonic microbiota, may protect commensal bacteria and enteric pathogens, such as Salmonella Typhimurium, against β-lactam antibiotics.

Membrane vesicle secretion and prophage induction in multidrug‐resistant Stenotrophomonas maltophilia in response to ciprofloxacin stress

“…Previous studies on the multidrug-resistant species S. maltophilia showed a clear vesiculation response to b-lactam antibiotics (Devos et al, 2015), and the secreted OMVs were proven to degrade b-lactams in the extracellular environment . Indeed, several other studies showed that OMV biogenesis can be induced in response to b-lactam stress, linking this phenomenon to b-lactam resistance (Ciofu et al, 2000;Schaar et al, 2011;Lee et al, 2013;Stentz et al, 2015). However, vesicle formation has also been observed for antibiotics that do not directly interfere with cell wall synthesis, for example the DNA damaging fluoroquinolone ciprofloxacin.…”

Exploiting host immunity: the Salmonella paradigm

“…Salmonella , however, can catabolize this liberated monosaccharide, and access to it supports the pathogen’s proliferation in the gut [78]. B. thetaiotaomicron also produces a beta-lactamase that protects the bacteria from beta-lactam antibiotics, including Salmonella [79]. Another microbe that helps Salmonella to degrade mucin is Akkermansia muciniphila , which exacerbates Salmonella -induced intestinal inflammation by disturbing host mucus homeostasis [80].…”

Acinetobacter baumannii Extracellular OXA-58 Is Primarily and Selectively Released via Outer Membrane Vesicles after Sec-Dependent Periplasmic Translocation

“…The partial degradation of OMV-associated OXA-58 by proteinase K indicated that some of the OXA-58 is attached to the outer surface of the OMVs. Although Moraxella catarrhalis ␤-lactamase was found within OMVs, a Bacteroides cephalosporinase was found on the outer surface of OMVs (29). This proteinase K-susceptible OXA-58 may also arise from the breakdown of OMVs.…”

“…OMV-associated ␤-lactamase release has been observed in Pseudomonas aeruginosa (34), M. catarrhalis (10), and Bacteroides species (29). Previously, an Acinetobacter-derived cephalosporinase was identified in A. baumannii OMVs, but its function was not characterized (11).…”