Neuropathogenic Escherichia coli K1 does not exhibit proteolytic activities to exert its pathogenicity

Abstract

BackgroundProteases are well-known virulence factors that promote survival, pathogenesis and immune evasion of many pathogens. Several lines of evidence suggest that the blood–brain barrier permeability is a prerequisite in microbial invasion of the central nervous system. Because proteases are frequently associated with vascular permeability by targeting junctional proteins, here it is hypothesized that neuropathogenic Escherichia coli K1 exhibit proteolytic activities to exert its pathogenicity.MethodsZymographic assays were performed using collagen and gelatin as substrates. The lysates of whole E. coli K1 strain E44, or E. coli K-12 strain HB101 were tested for proteolytic activities. The conditioned media were prepared by incubating bacteria in RPMI-1640 in the presence or absence of serum. The cell-free supernatants were collected and tested for proteases in zymography as mentioned above. Additionally, proteolytic degradation of host immune factors was determined by co-incubating conditioned media with albumin/immunoglobulins using protease assays.ResultsWhen collagen or gelatin were used as substrates in zymographic assays, neither whole bacteria nor conditioned media exhibited proteolytic activities. The conditioned media of neuropathogenic E. coli K1 strain E44, or E. coli K-12 strain HB101 did not affect degradation of albumin and immunoglobulins using protease assays.ConclusionsNeither zymographic assays nor protease assays detected proteolytic activities in either the whole bacteria or conditioned media of E. coli K1 strain E44 and E. coli K-12 strain HB101. These findings suggest that host cell monolayer disruptions and immune evasion strategies are likely independent of proteolytic activities of neuropathogenic E. coli K1.

Acanthamoeba and bacteria produce antimicrobials to target their counterpart

“…Bacterial isolates used in the present study were Acinetobacter sp., Aeromonas hydrophila, Enterobacter aerogenes, Enterobacter sp., Escherichia coli K1, Klebsiella pneumoniae, Methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa , Shigella flexneri, and Vancomycin-resistant Enterococcus faecalis (VRE). Escherichia coli K1 strain RS218 (O18:K1:H7) and MRSA have been described previously [ 20 , 21 ]. They were isolated from the cerebrospinal fluid of a meningitis patient [ 20 ] and blood culture of septicemia patient [ 21 ], respectively.…”

“…Escherichia coli K1 strain RS218 (O18:K1:H7) and MRSA have been described previously [ 20 , 21 ]. They were isolated from the cerebrospinal fluid of a meningitis patient [ 20 ] and blood culture of septicemia patient [ 21 ], respectively. Enterobacter sp.…”

“…Cytotoxicity assays were performed as previously described [ 20 ]. Briefly, assays were performed in 24 well plates containing confluent human brain microvascular endothelial cells (HBMEC) monolayers.…”

Virulence factors and drug resistance of gastrointestinal Escherichia coli isolated from different animals

“…Proteases play a crucial role in virulence which helps in the survival and immune evasion of the pathogen (Iqbal et al, 2013). Several researchers have demonstrated the proteolytic activity of E. coli (Haddadi et al, 2005;Budiarti and Mubarik, 2007;Abed et al, 2016).…”

Black cobra (Naja naja karachiensis) lysates exhibit broad-spectrum antimicrobial activities

“…E. coli K1 strains RS218 20 and MRSA 21 were isolated earlier from CSF and blood samples of neonatal meningitis and sepsis patients, respectively. Streptococcus pneumoniae was isolated from the blood culture of a pneumonia patient and P. aeruginosa was isolated from pus sample.…”