Isolation, identification, and antimicrobial susceptibility of Brucella spp. cultured from cows and goats manure in Mexico

Abstract

espanolLa brucelosis es una zoonosis distribuida mundialmente que afecta varias especies animales. Los humanos se infectan por el contacto con animales infectados, sus excreciones o por la ingesta de derivados lacteos no pasteurizados. Las heces excretadas por el ganado se usan como fertilizante en paises no desarrollados. Estudios microbiologicos han alertado sobre el riesgo de las heces o estiercol como vector de diseminacion de microorganismos patogenos. El objetivo de este trabajo fue aislar Brucella de heces de vacas y cabras y evaluar la sensibilidad contra antimicrobianos mediante el metodo de E-test. Se analizaron heces de vacas y cabras serologicamente positivas a brucelosis de una region endemica de Mexico. El aislamiento de Brucella se llevo a cabo en un medio de preenriquecimiento y posteriormente se aislo en medio selectivo. La identificacion se realizo mediante pruebas microbiologicas y por PCR. Se obtuvieron 10 aislados de Brucella spp., que fueron positivos a la amplificacion del gen especifico de genero que codifica para la proteina BCSP31 y mediante multiplex Bruce-Ladder se identifico la especie. Se demostro la presencia de B. melitensis, B. abortus y B. suis en las heces de las vacas, mientras que B. abortus solo se aislo de las cabras. Ninguna cepa vacunal se encontro en el estudio. Algunos aislados fueron resistentes a ciprofloxacina, levofloxacina, trimetoprim-sulfametoxazol, y rifampicina. Las heces de animales infectados representan un riesgo de exposicion a Brucella. Se requieren estudios mas detallados para evaluar el factor de riesgo asociado a la materia fecal contaminada con Brucella en regiones endemicas. EnglishBrucellosis is a zoonosis that affects many animal species worldwide. Humans are often infected through direct animal contact, through contact with animal excretions, or through ingestion of unpasteurized dairy products. Livestock manure is extensively used as a pasture fertilizer in many production systems, especially in non-developed countries. Some microbiological studies warn of the risk of manure being a disseminator vector of pathogenic microorganisms. The present study aimed to isolate Brucella in manure from cows and goats that were serologically positive for brucellosis in an endemic region of Mexico. We then used E-test methods to evaluate the isolated microorganisms' susceptibility to antimicrobial agents in vitro. Brucella isolation was performed via a pre-enriched selective culture, and subcultures using selective agar plates. Isolates were identified using microbiological tests as well as BCSP31 PCR and Bruce-Ladder multiplex PCR. We isolated 10 Brucella spp. strains, all of which amplified the genus-specific gene that encodes the BCSP31 protein. The species were identified using multiplex PCR. Interestingly, B. melitensis, B. abortus, and B. suis were isolated from cow manure, while B. abortus was just isolated from goat manure. The isolates did not include any strains that are routinely vaccinated against. Some isolates were resistant to ciprofloxacin, levofloxacin, trimethoprim-sulfamethoxazole, and rifampicin. Manure from infected animals could represent a vehicle for human exposure to Brucella. More detailed studies are needed to evaluate Brucella-contaminated manure as a risk factor in endemic regions.