Antibiotic susceptibility of Escherichia coli isolated from a case of neonatal diarrhea in an alpaca cria

Introduzione South American camelids, such as llamas and alpacas, are becoming increasingly common in Italy. Most of them are bred as pets, resulting in high human-animal contact. Diarrhea is a significant disease in newborn camelids, and its aetiology plays a crucial role. This study aimed to investigate the presence of possible antibiotic resistance in an alpaca cria with neonatal diarrhea [1]. Descrizione del caso The cria was admitted to the ruminants unit of the University of Milan Veterinary Teaching Hospital (VTH) with mild dehydration and diarrhea, detected by the owner the previous day. After a complete clinical examination, the cria was stabilized with intravenous fluid therapy, NSAIDs, and supplementation of minerals and vitamins. Two fecal samples were collected and processed in the VTH microbiology and parasitology laboratories. For bacteria isolation, a fecal sample was inoculated onto 5% sheep blood agar plates and MacConkey agar plates and incubated at 37°C for 24-48 h under aerobic and anaerobic conditions. Using the direct transfer method, the identification of species was performed by matrix-assisted laser desorption mass spectrometry (MALDI-TOF MS; Bruker Daltonics, Fremont, CA). The isolate was subjected to antimicrobial susceptibility testing (AST) by the disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines [2]. The following antimicrobials were tested: amoxicillin/clavulanic acid (30µg), ampicillin (10µg), ceftiofur (30µg), enrofloxacin (5µg); oxytetracycline (30µg), penicillin (10iu) marbofloxacin (5µg), florfenicol (30µg), trimethoprim/sulfamethoxazole (25µg). Antibiotic susceptibility of the isolates was classified by measuring the zone of inhibition according to CLSI guidelines [3]. The quantitative coprological examination was performed using FLOTAC Dual Technique; flotation solutions of saturated sodium chloride (specific gravity 1200) and zinc sulfate (specific gravity 1.350), recommended for the detection of nematodes, cestodes, and trematodes eggs, nematodes larvae, and coccidian oocysts, were used [4]. No parasite was detected. Escherichia coli was isolated and found to be resistant to ampicillin, florfenicol, oxytetracycline, and penicillin. The other antibiotics tested were found to be sensitive. According to CSLI guidelines [3], there is no inherent resistance of E. coli, so the resistances detected in this sample were all acquired. Conclusioni These results show that some resistance may already be present in alpacas, and further epidemiological investigation must be performed to assess the antimicrobial resistance in South American camelids in Italy. Bibliografia 1. Whitehead CE, Anderson DE. Neonatal diarrhea in llamas and alpacas. Small Rumin Res. 2006 Feb;61(2):207-215. doi: 10.1016/j.smallrumres.2005.07.012. Epub 2005 Aug 24. PMID: 32288213; PMCID: PMC7134812. 2. Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Disk and Dilution Susceptibility Tests for Bacteria Isolated From Animals—Fourth Edition: Approved Standard VET01-A4. CLSI, Wayne, PA, USA, 2013. 3. CLSI (Clinical and Laboratory Standards Institute) (3rd ed.), Performance standards for antimicrobial disk and dilution susceptibility tests for bacteria collected from animals; Approved standard, 28, Clinical and Laboratory Standards Institute, Wayne, PA (2008) No. 8. 4. Cringoli G, Rinaldi L, Maurelli MP, Utzinger J (2010) FLOTAC: new multivalent techniques for qualitative and quantitative copromicroscopic diagnosis of parasites in animals and humans. Nat Protoc 5:503–515. https://doi.org/10.1038/nprot.2009.235.