Biology subjects

Guardabassi, L.

Publications and source records attributed to Guardabassi, L..

3 recordsLinked to original sources

bioRxiv2026

In vitro antimicrobial resistance in clinical isolates of bacterial pathogens causing bovine respiratory disease: a systematic review and meta-analysis

Background: Bovine respiratory disease (BRD) is a major cause of antimicrobial use in cattle, raising concerns about antimicrobial resistance (AMR). This systematic review estimated pooled AMR proportions in BRD pathogens: Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni, and assessed temporal and geographic trends in resistance. Methods: Five antimicrobials commonly used for BRD treatment were evaluated: penicillin G (PEN), tetracycline (TET), florfenicol (FLO), tulathromycin (TUL), and enrofloxacin (ENR). Following PRISMA guidelines, 1,097 records were screened and 24 studies met inclusion criteria. Study quality and risk of bias were assessed, and random-effects meta-analyses estimated pooled proportions of resistant isolates by antimicrobial, continent and period. Results: A total of 13,949 bacterial isolates were analysed including P. multocida (5,615), M. haemolytica (5,585), and H. somni (2,749). TET resistance was highest across all pathogens (12-30%), followed by TUL (6-11%), PEN (4-12%), FLO (0.5-1.6%) and ENR (0.2-1.1%). TET resistance in M. haemolytica and P. multocida, and FLO resistance in P. multocida were significantly more frequent in North America than in Europe (p[≤]0.05). TUL resistance increased significantly in P. multocida after 2013 (p=0.038), with similar non significant trends in M. haemolytica and H. somni. FLO resistance decreased significantly in H. somni after 2013 (p=0.013). Egger's test identified significant funnel plot asymmetry for ENR resistance in H. somni and PEN resistance in M. haemolytica, suggesting possible small study effects. Conclusion: These results offer insights into distribution of phenotypic resistance across pathogens and regions, informing BRD antimicrobial treatment guidelines and One-Health antimicrobial stewardship aimed at preserving the effectiveness of medically important antimicrobials.

microbiology↗

bioRxiv2026

Comparative chemical characterisation of chitosans and their impact on growth, faecal consistency and microbiota composition in weaned piglets

Managing post-weaning diarrhoea (PWD) in piglets is difficult due to limits on antibiotics and zinc. Chitosan is emerging as a potential feed additive. We analysed a chito-oligosaccharide hydrochloride (COS-HCl), a low molecular weight (LMW) chitosan, and a medium molecular weight (MMW) chitosan, and assessed their effects on growth, faecal consistency, microbiota, and potential interference with enterotoxigenic Escherichia coli (ETEC). The three chitosans were characterised using {superscript 1}H-NMR, SEC-RI-MS, and SEC-RI-MALLS. COS-HCl had an Mw of 0.824 kDa; LMW and MMW showed Mw ranges of 14.4 kDa (0.3-30 kDa) and 116 kDa (15-600 kDa). Degrees of acetylation were 9.5%, 6.5%, and 15%. Two 42-day field studies evaluated average daily gain (ADG), faecal consistency, and microbiota. In the first trial, COS-HCl at 0.025-0.1% did not significantly affect ADG (-33 to - 12 g/d). In the second, LMW and MMW at 0.01% did not significantly change ADG (-7 and +3 g/d). Faecal consistency, ETEC shedding, and microbiota composition were similar to controls. An enzymatic HPLC-MS method enabled quantification of MMW chitosan in premix. Our results highlight the importance of advanced chitosan characterisation for precision nutrition and suggest that a threshold dosemay be needed to benefit growth and gut health in PWD management. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/714014v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@ffce80org.highwire.dtl.DTLVardef@4e3603org.highwire.dtl.DTLVardef@bc0c73org.highwire.dtl.DTLVardef@1d55472_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2018

Dogs as reservoirs of Escherichia coli strains causing urinary tract infection in their owners

It is known that humans and pets living together can share the same Escherichia coli strain. In this study we assessed the role played by household pets as reservoirs of E. coli strains causing urinary tract infection (UTI) in their owners. Fecal swabs from 15 dogs and six cats living with 19 patients with community-acquired E. coli UTI were screened by antimicrobial selective plating to detect E. coli displaying the same susceptibility profile of the UTI-causing strain. Pet/patient pairs sharing strains with indistinguishable susceptibility and pulsed-field gel electrophoresis (PFGE) profiles were quantitatively screened for fecal carriage of the UTI-causing strain approximately 10 months later using bacterial counts on selective agar supplemented with the relevant antibiotics. Isolates from both time points were characterized by whole-genome single nucleotide polymorphism (SNP) analysis. PFGE revealed indistinguishable E. coli within two (11%) pet/patient pairs. In pair A, the UTI-causing strain was detected 10 months later in both the patient (108 CFU/g) and her dog (104 CFU/g). In pair B, only the dog was colonized with the UTI-causing strain upon re-sampling (105 CFU/g), indicating dog-to-man transmission. For both pairs, less than 70 SNPs distinguished any isolate from the first and second sampling. The study shows regular co-carriership of UTI-causing E. coli strains between humans and their pets, and indicates that dogs can be a source of human infection. Although final evidence for transmission is lacking, hygiene precautions should be considered by people fraternizing pets. This may be particularly relevant for persons with a compromised immune system.

microbiology↗