Characterization of cytotoxic necrotizing factor 1-producing Escherichia coli strains from faeces of healthy macaques

Abstract

Twenty-five (27 %) of 92 clinically normal macaques were found to have b-haemolytic Escherichia coli isolated from their faeces. Five of six isolates chosen for further characterization had multiple antibiotic resistance and were PCR-positive for cytotoxic necrotizing factor 1 (cnf1) with a demonstrated cytopathic effect in vitro. By repetitive element sequence-based PCR genotyping, genetic similarity was established for selected isolates. We believe this to be the first report of E. coli strains producing CNF1 in non-human primates. INTRODUCTIONEscherichia coli strains that produce cytotoxic necrotizing factors (CNFs) belong to the pathotype necrotoxigenic E. coli (NTEC) and are associated with intestinal and extraintestinal infections in both humans and animals (Kaper et al., 2004). The majority of toxin-producing isolates produce either the chromosomally encoded CNF1 (Falbo et al., 1993) or the plasmid-encoded CNF2 (Oswald et al., 1989); more recently, a third type has been isolated from sheep and goats and named CNF3 (Orden et al., 2007). CNF1 is a 115 kDa protein with lethal and necrotizing activity in vivo. In vitro, affected cells undergo multinucleation and membrane ruffling and form focal adhesions and actin stress fibres. The mechanism involves activation of Rho GTPases, a family of molecular switches with multiple cellular functions, resulting in reorganization of the actin cytoskeleton. CNF1 shares a pathogenicity island with a-haemolysin and P fimbriae . CNF1-producing strains most notably cause urinary tract infections in humans. These strains have also been isolated from healthy and diseased animal species. The list includes weaned pigs (Tó th et al., 2000) and dogs (Starcic et al., 2002) with diarrhoea; cats (Féria et al., 2001) and dogs (Johnson et al., 2003;Siqueira et al., 2009;Yuri et al., 1998) with urinary tract infections; ferrets with diarrhoea and extra-intestinal infections (Marini et al., 2004); and birds and mink with suspected colibacillosis (RodriguezSiek et al., 2005) and colisepticaemia (Tibbetts et al., 2003). NTEC-2 strains, although commonly reported in ruminants , have also been reported in a very small percentage of human faecal E. coli isolates (Kadhum et al., 2008). The objective of this study was to evaluate the presence of specific virulence genes and toxin activity in several b-haemolytic E. coli isolates cultured from a macaque colony used for neurobiology research. METHODSAnimals. Macaques (Macaca mulatta and Macaca fascicularis) received from three US-based vendors in 2005-2006 received physical examinations and routine diagnostic evaluations during quarantine and at quarterly intervals. Animals were routinely pair-housed and maintained in an animal facility accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International. They were fed specified amounts of primate chow (Purina Lab Diet 5038) twice a day and provided with water ad libitum. Housing conditions were maintained at 20-22 uC, 30-70 % humidity, 10-15 non-recirculated ai...

Cytotoxic Escherichia coli strains encoding colibactin and cytotoxic necrotizing factor (CNF) colonize laboratory macaques

“…The 20.9% prevalence of cnf1 + E. coli in this study was consistent with our previous findings [ 21 ]. Close correlation was observed between the cnf1 gene and β-hemolysis in E. coli isolates.…”

“…Close correlation was observed between the cnf1 gene and β-hemolysis in E. coli isolates. This association was reported in our previous studies [ 20 , 21 ] and by other authors [ 19 , 38 ]. In the E. coli J96 strain and other strains, the cnf1 gene is located downstream of hemolysin ( hlyCABD ) in pathogenicity island II (PAI II), and the expression of cnf1 is regulated by the hemolysin promoter [ 39 – 41 ].…”

“…These strains are also isolated from healthy and diseased animals. In our laboratory, cnf1 + E. coli strains were isolated from ferrets with diarrhea and extra-intestinal infections [ 20 ] and from healthy macaques [ 21 ]. cnf1 -encoding E. coli strains have also been isolated from cats [ 22 ], dogs [ 23 , 24 ], pigs [ 25 ], and birds [ 26 ].…”

Bacterial Diseases

“…Their clinical relevance in marmosets requires further investigation. CNF-positive E. coli also have been isolated from macaques [42]. In a recent study, the prevalence of cytotoxins encoded by pks and cnf in E. coli cultured from rectal swabs of marmosets housed in three separate colonies was documented.…”

Genomic diversity ofEscherichia coliisolates from non-human primates in the Gambia

“…E. coli is also capable of colonising the gut in non-human primates (3–5), where data from captive animals suggest that gut isolates are dominated by phylogroups B1 and A, which, in humans, encompass commensals as well as strains associated with intestinal pathology (6–9). E. coli strains encoding colibactin, or cytotoxic necrotising factor 1 have been isolated from healthy laboratory rhesus macaques (4, 10), while enteropathogenic E. coli strains can—in the laboratory—cause colitis in marmosets (11), rhesus macaques infected with simian immunodeficiency virus (12) and cotton-top tamarins (13).…”