Acanthamoeba sp. promotes the survival and growth of Acinetobacter baumanii

Laboratoire de parasitologie et mycologie médicale, Faculté de médecine et de pharmacie, Poitiers, France.
FEMS Microbiology Letters (Impact Factor: 2.72). 03/2011; 319(1):19-25. DOI: 10.1111/j.1574-6968.2011.02261.x
Source: PubMed

ABSTRACT Acinetobacter baumanii, which may be found in water, is an important emerging hospital-acquired pathogen. Free-living amoebae can be recovered from the same water networks, and it has been shown that these protozoa may support the growth of other bacteria. In this paper, we have studied potential relationships between A. baumanii and Acanthamoeba species. Two strains of A. baumanii isolated from hospital water were co-cultivated with the trophozoites or supernatants of two free-living amoebae strains: Acanthamoeba castellanii or Acanthamoeba culbertsoni. Firstly, the presence of the amoebae or their supernatants induced a major increase in A. baumanii growth, compared with controls. Secondly, A. baumanii affected only the viability of A. culbertsonii, with no effect on A. castellanii. Electron microscopy observations of the cultures investigating the bacterial location in the protozoa showed persistence of the bacteria within cyst wall even after 60 days of incubation. In our study, the survival and growth of A. baumanii could be favored by Acanthamoeba strains. Special attention should consequently be paid to the presence of free-living amoebae in hospital water systems, which can promote A. baumanii persistence.

Download full-text


Available from: Yann Hechard, Nov 12, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Enterohemorrhagic Escherichia coli (EHEC) are involved in outbreaks of food-borne illness and transmitted to humans through bovine products or water contaminated by cattle feces. Microbial interaction is one of the strategies used by pathogenic bacteria to survive in the environment. Among protozoa, the free-living amoebae are known to host and protect several water-borne pathogens. In this study, the interaction between EHEC and the predacious protozoa Acanthamoeba castellanii was investigated. Using monoculture and cocultures, growth of both organisms was estimated for 3 weeks by total and viable cell counts. The numbers of EHEC were significantly higher when cultured with amoebae than without, and less EHEC shifted into a viable but nonculturable state in the presence of amoebae. Using several mutants, we observed that the Pho regulon is required for EHEC growth when cocultured with amoebae. In contrast, the Shiga toxins (Stx) were not involved in this association phenotype. Cocultures monitored by electron microscopy revealed a loss of the regular rod shape of EHEC and the secretion of multilamellar vesicles by the amoebae, which did not contain bacteria. As the interaction between A. castellanii and EHEC appears beneficial for bacterial growth, this supports a potential role for protozoa in promoting the persistence of EHEC in the environment.
    12/2012; 1(4). DOI:10.1002/mbo3.40
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Free-living amoebae (FLA) are ubiquitous protozoa that do not require a host organism for survival. They are found in natural environments such as water or soil, and man-made environments including tap water or swimming pools, where they may interact with other micro-organisms, including bacteria, fungi and viruses. FLA can harbour micro-organisms including those found in hospital water systems, offering them protection against hostile conditions, providing a vehicle of dissemination, and enabling them to prepare for subsequent survival in macrophages. The interaction between Legionella pneumophila and FLA has been studied extensively; subsequent investigations have shown that FLA may serve as a reservoir for other bacteria including mycobacteria, Pseudomonas aeruginosa, Acinetobacter baumannii, or even fungi and viruses. Amoebae found in hospital water systems can serve as a reservoir of potential pathogens and thus be indirectly related to healthcare-associated infections.
    Journal of Hospital Infection 07/2014; DOI:10.1016/j.jhin.2014.05.001 · 2.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Acinetobacter baumannii is a multidrug resistant pathogen capable of causing a wide spectrum of clinical conditions in humans. Acinetobacter spp. is ubiquitously found in different water sources. Chlorine being the most commonly used disinfectant in water, the study investigated the effect of chlorine on the survival of A. baumannii in water and transcription of genes conferring antibiotic resistance. Eight clinical isolates of A. baumannii, including a fatal meningitis isolate (ATCC 17978) (~108 CFU/mL) were separately exposed to free chlorine concentrations (0.2, 1, 2, 3 and 4 ppm) with a contact time of 30, 60, 90 and 120 second. The surviving pathogen counts at each specified contact time were determined using broth dilution assay. In addition, real-time quantitative PCR (RT-qPCR) analysis of the antibiotic resistance genes (efflux pump genes and those encoding resistance to specific antibiotics) of three selected A. baumannii strains following exposure to chlorine was performed. Results revealed that all eight A. baumannii isolates survived the tested chlorine levels during all exposure times (p > 0.05). Additionally, there was an up-regulation of all or some of the antibiotic resistance genes in A. baumannii, indicating a chlorine-associated induction of antibiotic resistance in the pathogen.
    International Journal of Environmental Research and Public Health 02/2014; 11(2):1844-54. DOI:10.3390/ijerph110201844 · 1.99 Impact Factor