CsiR-mediated signal transduction pathway in response to low iron conditions promotes Escherichia coli K1 invasion and penetration of the blood-brain barrier.

Escherichia coli K1 is the leading cause of neonatal Gram-negative bacterial meningitis, but the pathogenesis of E. coli K1 meningitis remains unclear. Blood-brain barrier (BBB) penetration is a crucial step in E. coli meningitis development. Here, we uncovered the crucial role of CsiR, a GntR family regulator, in E. coli K1 virulence. During infection, csiR expression was induced due to the derepression by Fur in the blood and human brain microvascular endothelial cells (HBMECs). CsiR positively regulated ilvB expression, which is associated with branched chain amino acid synthesis. Furthermore, we revealed that IlvB activated the FAK/PI3 K pathway of HBMECs to induce actin cytoskeleton rearrangements, thereby promoting the bacterial invasion and penetration of the BBB. Overall, this study reveals a CsiR-mediated virulence regulation pathway in E. coli K1, which may provide a useful target for the prevention or therapy of E. coli meningitis.

K1 capsule-dependent phage-driven evolution in Escherichia coli leading to phage resistance and biofilm production.

AIMS: Understanding bacterial phage resistance mechanisms has implications for developing phage-based therapies. This study aimed to explore the development of phage resistance in Escherichia coli K1 isolates' to K1-ULINTec4, a K1-dependent bacteriophage. METHODS AND RESULTS: Resistant colonies were isolated from two different strains (APEC 45 and C5), both previously exposed to K1-ULINTec4. Genome analysis and several parameters were assessed, including growth capacity, phage adsorption, phenotypic impact at capsular level, biofilm production, and virulence in the in vivo Galleria mellonella larvae model. One out of the six resistant isolates exhibited a significantly slower growth rate, suggesting the presence of a resistance mechanism altering its fitness. Comparative genomic analysis revealed insertion sequences in the region 2 of the kps gene cluster involved in the capsule biosynthesis. In addition, an immunoassay targeting the K1 capsule showed a very low positive reaction compared to the control. Nevertheless, microscopic images of resistant strains revealed the presence of capsules with a clustered organization of bacterial cells and biofilm assessment showed an increased biofilm production compared to the sensitive strains. In the G. mellonella model, larvae infected with phage-resistant isolates showed better survival rates than larvae infected with phage-sensitive strains. CONCLUSIONS: A phage resistance mechanism was identified at the genomic level and had a negative impact on the K1 capsule production. The resistant isolates showed an increased biofilm production and a decreased virulence in vivo.

Phage Targeting Neonatal Meningitis E. coli K1 In Vitro in the Intestinal Microbiota of Pregnant Donors and Impact on Bacterial Populations.

Escherichia coli K1 is a leading cause of neonatal meningitis. The asymptomatic carriage of these strains in the maternal intestinal microbiota constitutes a risk of vertical transmission to the infant at birth. The aim of this work was to evaluate the efficacy of phage therapy against E. coli K1 in an intestinal environment and its impact on the intestinal microbiota. For this purpose, three independent experiments were conducted on the SHIME® system, the first one with only the phage vB_EcoP_K1_ULINTec4, the second experiment with only E. coli K1 and the last experiment with both E. coli K1 and the phage. Microbiota monitoring was performed using metagenetics, qPCR, SCFA analysis and the induction of AhR. The results showed that phage vB_EcoP_K1_ULINTec4, inoculated alone, was progressively cleared by the system and replicates in the presence of its host. E. coli K1 persisted in the microbiota but decreased in the presence of the phage. The impact on the microbiota was revealed to be donor dependent, and the bacterial populations were not dramatically affected by vB_K1_ULINTec4, either alone or with its host. In conclusion, these experiments showed that the phage was able to infect the E. coli K1 in the system but did not completely eliminate the bacterial load.

Paired Siglec receptors generate opposite inflammatory responses to a human-specific pathogen.

Paired immune receptors display near-identical extracellular ligand-binding regions but have intracellular sequences with opposing signaling functions. While inhibitory receptors dampen cellular activation by recognizing self-associated molecules, the functions of activating counterparts are less clear. Here, we studied the inhibitory receptor Siglec-11 that shows uniquely human expression in brain microglia and engages endogenous polysialic acid to suppress inflammation. We demonstrated that the human-specific pathogen Escherichia coli K1 uses its polysialic acid capsule as a molecular mimic to engage Siglec-11 and escape killing. In contrast, engagement of the activating counterpart Siglec-16 increases elimination of bacteria. Since mice do not have paired Siglec receptors, we generated a model by replacing the inhibitory domain of mouse Siglec-E with the activating module of Siglec-16. Siglec-E16 enhanced proinflammatory cytokine expression and bacterial killing in macrophages and boosted protection against intravenous bacterial challenge. These data elucidate uniquely human interactions of a pathogen with Siglecs and support the long-standing hypothesis that activating counterparts of paired immune receptors evolved as a response to pathogen molecular mimicry of host ligands for inhibitory receptors.

Development of a chitosan-modified PLGA nanoparticle vaccine for protection against Escherichia coli K1 caused meningitis in mice.

BACKGROUND: Escherichia coli K1 (E. coli K1) caused neonatal meningitis remains a problem, which rises the urgent need for an effective vaccine. Previously, we rationally designed and produced the recombinant protein OmpAVac (Vo), which elicited protective immunity against E. coli K1 infection. However, Vo has limited stability, which hinders its future industrial application. METHOD: Chitosan-modified poly (lactic-co-glycolic acid) (PLGA) nanoparticles were prepared and used as carried for the recombinant Vo. And the safety, stability and immunogenicity of Vo delivered by chitosan-modified PLGA nanoparticles were tested in vitro and in a mouse model of bacteremia. RESULTS: We successfully generated chitosan-modified PLGA nanoparticles for the delivery of recombinant Vo (VoNP). In addition, we found that a freeze-drying procedure increases the stability of the VoNPs without changing the shape, size distribution and encapsulation of the Vo protein. Unlike aluminum adjuvant, the nanoparticles that delivered Vo were immunoprotective in mice even after storage for as long as 180 days. CONCLUSIONS: We identified an effective strategy to improve the stability of Vo to maintain its immunogenicity, which will contribute to the future development of vaccines against E. coli K1.

Inhibition of enteropathogenic Escherichia coli biofilm formation by DNA aptamer.

Enteropathogenic Escherichia coli (EPEC) is a bioagent that causes diarrhea through the formation of biofilm. The recalcitrant of EPEC to the current conventional antibiotic treatment has grown a big concern in a way to find effective alternative inhibitors. Aptamers have been demonstrated to show the ability to kill the pathogenic bacteria through inhibition of biofilm formation. Therefore, this study aimed to investigate antibiofilm activities of six types of aptamers against EPEC K1.1 which was isolated from patients with diarrhea. Environmental conditions such as temperatures and pH which impacted on biofilm formation of EPEC K1.1 and also biofilm inhibition of aptamer on EPEC K1.1 were performed by counting the crystal violet formation in 96-well polystyrene microplates at OD570. The motility examination combined with qPCR were applied to prove the mechanism of aptamers inhibition on biofilm by targeting essential genes that involve biofilm formation. The result showed that by applying cut off value at 0.399, aptamer SELEX 10 Colony 5 exhibited the highest biofilm inhibition against EPEC K1.1 with an absorbance value of 0.126. Further analysis showed that this aptamer also was able to reduce the motility diameter of EPEC K1.1. The effect of this aptamer on EPEC K1.1 motility was confirmed by qPCR where the mRNA level of motB, csgA and lsrA gene reduced significantly compared to the untreated group. Aptamer SELEX 10 Colony 5 was able to inhibit biofilm formation through interfering the motility ability of EPEC K1.1 and also by reducing the mRNA level of biofilm formation-related genes. This study provides evidences that aptamer is effective and promising for both antibiofilm of EPEC K1.1 and alternative treatment of diarrhea.

Activation of brain endothelium by Escherichia coli K1 virulence factor cglD promotes polymorphonuclear leukocyte transendothelial migration.

Escherichia coli K1 is the most common Gram-negative bacteria causing neonatal meningitis. Polymorphonuclear leukocyte (PMN) transmigration across the blood-brain barrier (BBB) is the hallmark of bacterial meningitis. Reportedly, the deletion of virulence factor cglD (E44:ΔcglD) from E44 is responsible for a less efficient PMN transendothelial migration ability. In the present study, we found that complementation of the cglD gene into E44:ΔcglD mutant strain might restore the PMN count and myeloperoxidase level in a neonatal mouse meningitis. Using human brain microvascular endothelial cells (HBMECs), the main model of the BBB in vitro, we found that E44:ΔcglD mutant strain induced a less efficient PMN adhesion to HBMECs and down-regulated chemokines CXCL1, CXCL6 and CXCL8 and adhesion molecule E-selectin, compared with the E44 strain. Complementation of cglD restored the PMN adhesion to HBMECs and the level of these proteins. E44:ΔcglD mutant strain also induced a less efficient NF-κB pathway activation in HBMECs and reduced the soluble p65 (sp65) level in the cerebral spinal fluid of newborn mice, compared with the E44 strain. Complementation of cglD restored the NF-κB pathway activation and increased the sp65 levels. This suggests that cglD in E44 contributes to NF-κB pathway activation in the brain endothelium to promote PMN adhesion to HBMECs and transendothelial migration. Our identified novel requirement of cglD for immune activation and subsequent PMN entry into the central nervous system suggests that therapies directed at neutralising this molecule will be beneficial in preventing bacterial meningitis progression.

Construction, heterologous expression, partial purification, and in vitro cytotoxicity of the recombinant plantaricin E produced by Lactococcus lactis against Enteropathogenic Escherichia coli K.1.1 and human cervical carcinoma (HeLa) cells.

Lactobacillus plantarum produces bacteriocin called plantaricin that can kill or inhibit other bacteria. Plantaricin E (Pln E), a recombinant bacteriocin, has been successfully constructed and produced by a GRAS host, Lactococcus lactis. A polymerase chain reaction (PCR) overlapping technique has been used to construct a ligation of signal peptide gene, Pln A and bacteriocin encoding gene, Pln E. Furthermore, the fusion fragment were cloned into pNZ8148 vector and transformed into L. lactis NZ3900. Molecular expression study shows that recombinant L. lactis NZ3900 is able to express the mature pln E at transcription level with size of 168 bp. Plantaricin E is purified by ammonium sulphate precipitation followed by gel filtration chromatography. Purified fractions were proven to be active against Enteropathogenic Escherichia coli K.1.1. The other fractions of Pln E also have antibacterial activity against several Gram positive and Gram negative bacteria. Purified recombinant plantaricin E is 3.7 kDa in size. The cytotoxicity assay shows purified Pln E inhibits 46.949 ± 3.338% of HeLa cell lines on 10 ppm dose whilst the metabolite inhibits 53.487 ± 2.957% of HeLa cell line on 100 ppm dose. The IC50 calculation of Pln E metabolite is 107.453 ppm, while the purified protein is 11.613 ppm.

Non-invasive three-dimensional imaging of Escherichia coli K1 infection using diffuse light imaging tomography combined with micro-computed tomography.

In contrast to two-dimensional bioluminescence imaging, three dimensional diffuse light imaging tomography with integrated micro-computed tomography (DLIT-µCT) has the potential to realise spatial variations in infection patterns when imaging experimental animals dosed with derivatives of virulent bacteria carrying bioluminescent reporter genes such as the lux operon from the bacterium Photorhabdus luminescens. The method provides an opportunity to precisely localise the bacterial infection sites within the animal and enables the generation of four-dimensional movies of the infection cycle. Here, we describe the use of the PerkinElmer IVIS SpectrumCT in vivo imaging system to investigate progression of lethal systemic infection in neonatal rats following colonisation of the gastrointestinal tract with the neonatal pathogen Escherichia coli K1. We confirm previous observations that these bacteria stably colonize the colon and small intestine following feeding of the infectious dose from a micropipette; invading bacteria migrate across the gut epithelium into the blood circulation and establish foci of infection in major organs, including the brain. DLIT-µCT revealed novel multiple sites of colonisation within the alimentary canal, including the tongue, oesophagus and stomach, with penetration of the non-keratinised oesophageal epithelial surface, providing strong evidence of a further major site for bacterial dissemination. We highlight technical issues associated with imaging of infections in new born rat pups and show that the whole-body and organ bioburden correlates with disease severity.

Escherichia coli K1 Modulates Peroxisome Proliferator-Activated Receptor γ and Glucose Transporter 1 at the Blood-Brain Barrier in Neonatal Meningitis.

Escherichia coli K1 meningitis continues to be a major threat to neonatal health. Previous studies demonstrated that outer membrane protein A (OmpA) of E. coli K1 interacts with endothelial cell glycoprotein 96 (Ecgp96) in the blood-brain barrier to enter the central nervous system. Here we show that the interaction between OmpA and Ecgp96 downregulates peroxisome proliferator-activated receptor γ (PPAR-γ) and glucose transporter 1 (GLUT-1) levels in human brain microvascular endothelial cells, causing disruption of barrier integrity and inhibition of glucose uptake. The suppression of PPAR-γ and GLUT-1 by the bacteria in the brain microvessels of newborn mice causes extensive pathophysiology owing to interleukin 6 production. Pretreatment with partial or selective PPAR-γ agonists ameliorate the pathological outcomes of infection by suppressing interleukin 6 production in the brain. Thus, inhibition of PPAR-γ and GLUT-1 by E. coli K1 is a novel pathogenic mechanism in meningitis, and pharmacological upregulation of PPAR-γ and GLUT-1 levels may provide novel therapeutic avenues.

Host-pathogen interactions in bacterial meningitis.

Bacterial meningitis is a devastating disease occurring worldwide with up to half of the survivors left with permanent neurological sequelae. Due to intrinsic properties of the meningeal pathogens and the host responses they induce, infection can cause relatively specific lesions and clinical syndromes that result from interference with the function of the affected nervous system tissue. Pathogenesis is based on complex host-pathogen interactions, some of which are specific for certain bacteria, whereas others are shared among different pathogens. In this review, we summarize the recent progress made in understanding the molecular and cellular events involved in these interactions. We focus on selected major pathogens, Streptococcus pneumonia, S. agalactiae (Group B Streptococcus), Neisseria meningitidis, and Escherichia coli K1, and also include a neglected zoonotic pathogen, Streptococcus suis. These neuroinvasive pathogens represent common themes of host-pathogen interactions, such as colonization and invasion of mucosal barriers, survival in the blood stream, entry into the central nervous system by translocation of the blood-brain and blood-cerebrospinal fluid barrier, and induction of meningeal inflammation, affecting pia mater, the arachnoid and subarachnoid spaces.

Livedo Reticularis: A Presenting Sign of Escherichia Coli Sepsis in a Newborn.

UNLABELLED: Livedo reticularis is a red cutaneous netlike pattern that is caused by abnormalities of the microvascularization and can be associated with many other potential systemic etiologies. We describe a case of a newborn that presented with livedo reticularis on his first day of life without any obvious systemic signs. The livedo reticularis was associated with Escherichia Coli K1 meningitis as revealed by laboratory tests. Clinical infectious signs developed a few hours later. Despite appropriate antibiotics therapy, he died on his second day because of sepsis and disseminated intravascular coagulation. Cerebrospinal fluid culture, blood culture, and culture of samples from trachea showed the presence of Escherichia Coli serotype K1 with many virulence determinants. CONCLUSION: In newborn, livedo reticularis must not be considered as physiological, but as a potential sign of unknown severe bacterial infection. Thus, the presence of livedo reticularis must require urgent laboratory tests.

Angiotensin II receptor type 1--a novel target for preventing neonatal meningitis in mice by Escherichia coli K1.

The increasing incidence of Escherichia coli K1 meningitis due to escalating antibiotic resistance warrants alternate treatment options to prevent this deadly disease. We screened a library of small molecules from the National Institutes of Health clinical collection and identified telmisartan, an angiotensin II receptor type 1 (AT1R) blocker, as a potent inhibitor of E. coli invasion into human brain microvascular endothelial cells (HBMECs). Immunoprecipitation studies revealed that AT1R associates with endothelial cell gp96, the receptor in HBMECs for E. coli outer membrane protein A. HBMECs pretreated with telmisartan or transfected with AT1R small interfering RNA were resistant to E. coli invasion because of downregulation of protein kinase C-α phosphorylation. Administration of a soluble derivative of telmisartan to newborn mice before infection with E. coli prevented the onset of meningitis and suppressed neutrophil infiltration and glial cell migration in the brain. Therefore, telmisartan has potential as an alternate treatment option for preventing E. coli meningitis.

Lpp of Escherichia coli K1 inhibits host ROS production to counteract neutrophil-mediated elimination.

Escherichia coli (E. coli) is the most common Gram-negative bacterial organism causing neonatal meningitis. The pathogenesis of E. coli meningitis, especially how E. coli escape the host immune defenses, remains to be clarified. Here we show that deletion of bacterial Lpp encoding lipoprotein significantly reduces the pathogenicity of E. coli K1 to induce high-degree of bacteremia necessary for meningitis. The Lpp-deleted E. coli K1 is found to be susceptible to the intracellular bactericidal activity of neutrophils, without affecting the release of neutrophil extracellular traps. The production of reactive oxygen species (ROS), representing the primary antimicrobial mechanism in neutrophils, is significantly increased in response to Lpp-deleted E. coli. We find this enhanced ROS response is associated with the membrane translocation of NADPH oxidase p47phox and p67phox in neutrophils. Then we constructed p47phox knockout mice and we found the incidence of bacteremia and meningitis in neonatal mice induced by Lpp-deleted E. coli is significantly recovered by p47phox knockout. Proteomic profile analysis show that Lpp deficiency induces upregulation of flagellar protein FliC in E. coli. We further demonstrate that FliC is required for the ROS induction in neutrophils by Lpp-deleted E. coli. Taken together, these data uncover the novel role of Lpp in facilitating intracellular survival of E. coli K1 within neutrophils. It can be inferred that Lpp of E. coli K1 is able to suppress FliC expression to restrain the activation of NADPH oxidase in neutrophils resulting in diminished bactericidal activity, thus protecting E. coli K1 from the elimination by neutrophils.

Meningitis Relapse in a Neonate: From Extended-Spectrum Beta-Lactamases-Producing Escherichia coli to Escherichia coli K1.

We report the case of a 10-day-old preterm neonate with extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli meningitis that was treated appropriately and yet relapsed with E. coli K1 meningitis at the age of one month. Although the patient had multiple risk factors for ESBL-producing E. coli, the patient did not follow the reported pattern of the risk of E. coli K1 infection in relapse.

Interaction of Escherichia coli K1 and K5 with Acanthamoeba castellanii trophozoites and cysts.

The existence of symbiotic relationships between Acanthamoeba and a variety of bacteria is well-documented. However, the ability of Acanthamoeba interacting with host bacterial pathogens has gained particular attention. Here, to understand the interactions of Escherichia coli K1 and E. coli K5 strains with Acanthamoeba castellanii trophozoites and cysts, association assay, invasion assay, survival assay, and the measurement of bacterial numbers from cysts were performed, and nonpathogenic E. coli K12 was also applied. The association ratio of E. coli K1 with A. castellanii was 4.3 cfu per amoeba for 1 hr but E. coli K5 with A. castellanii was 1 cfu per amoeba for 1 hr. By invasion and survival assays, E. coli K5 was recovered less than E. coli K1 but still alive inside A. castellanii. E. coli K1 and K5 survived and multiplied intracellularly in A. castellanii. The survival assay was performed under a favourable condition for 22 hr and 43 hr with the encystment of A. castellanii. Under the favourable condition for the transformation of trophozoites into cysts, E. coli K5 multiplied significantly. Moreover, the pathogenic potential of E. coli K1 from A. castellanii cysts exhibited no changes as compared with E. coli K1 from A. castellanii trophozoites. E. coli K5 was multiplied in A. castellanii trophozoites and survived in A. castellanii cysts. Therefore, this study suggests that E. coli K5 can use A. castellanii as a reservoir host or a vector for the bacterial transmission.

In Vitro Characterization and In Vivo Efficacy Assessment in Galleria mellonella Larvae of Newly Isolated Bacteriophages against Escherichia coli K1.

Extra-intestinal Escherichia coli express several virulence factors that increase their ability to colonize and survive in different localizations. The K1 capsular type is involved in several infections, including meningitis, urinary tract, and bloodstream infections. The aims of this work were to isolate, characterize, and assess the in vivo efficacy of phages targeting avian pathogenic E. coli (APEC) O18:K1, which shares many similarities with the human strains responsible for neonatal meningitis. Eleven phages were isolated against APEC O18:K1, and four of them presenting a narrow spectrum targeting E. coli K1 strains were further studied. The newly isolated phages vB_EcoS_K1-ULINTec2 were similar to the Siphoviridae family, and vB_EcoP_K1-ULINTec4, vB_EcoP_K1-ULINTec6, and vB_EcoP_K1-ULINTec7 to the Autographiviridae family. They are capsular type (K1) dependent and present several advantages characteristic of lytic phages, such as a short adsorption time and latent period. vB_EcoP_K1-ULINTec7 is able to target both K1 and K5 strains. This study shows that these phages replicate efficiently, both in vitro and in vivo in the Galleria mellonella model. Phage treatment increases the larvae survival rates, even though none of the phages were able to eliminate the bacterial load.

O-Acetylation of Capsular Polysialic Acid Enables Escherichia coli K1 Escaping from Siglec-Mediated Innate Immunity and Lysosomal Degradation of E. coli-Containing Vacuoles in Macrophage-Like Cells.

Escherichia coli K1 causes bacteremia and meningitis in human neonates. The K1 capsule, an α2,8-linked polysialic acid (PSA) homopolymer, is its essential virulence factor. PSA is usually partially modified by O-acetyl groups. It is known that O-acetylation alters the antigenicity of PSA, but its impact on the interactions between E. coli K1 and host cells is unclear. In this study, a phase variant was obtained by passage of E. coli K1 parent strain, which expressed a capsule with 44% O-acetylation whereas the capsule of the parent strain has only 3%. The variant strain showed significantly reduced adherence and invasion to macrophage-like cells in comparison to the parent strain. Furthermore, we found that O-acetylation of PSA enhanced the modulation of trafficking of E. coli-containing vacuoles (ECV), enabling them to avoid fusing with lysosomes in these cells. Intriguingly, by using quartz crystal microbalance, we demonstrated that the PSA purified from the parent strain interacted with human sialic acid-binding immunoglobulin-like lectins (Siglecs), including Siglec-5, Siglec-7, Siglec-11, and Siglec-14. However, O-acetylated PSA from the variant interacted much less and also suppressed the production of Siglec-mediated proinflammatory cytokines. The adherence of the parent strain to human macrophage-like cells was significantly blocked by monoclonal antibodies against Siglec-11 and Siglec-14. Furthermore, the variant strain caused increased bacteremia and higher lethality in neonatal mice compared to the parent strain. These data elucidate that O-acetylation of K1 capsule enables E. coli to escape from Siglec-mediated innate immunity and lysosomal degradation; therefore, it is a strategy used by E. coli K1 to regulate its virulence. IMPORTANCE Escherichia coli K1 is a leading cause of neonatal meningitis. The mortality and morbidity of this disease remain significantly high despite antibiotic therapy. One major limitation on advances in prevention and therapy for meningitis is an incomplete understanding of its pathogenesis. E. coli K1 is surrounded by PSA, which is observed to have high-frequency variation of O-acetyl modification. Here, we present an in-depth study of the function of O-acetylation in PSA at each stage of host-pathogen interaction. We found that a high level of O-acetylation significantly interfered with Siglec-mediated bacterial adherence to macrophage-like cells, and blunted the proinflammatory response. Furthermore, the O-acetylation of PSA modulated the trafficking of ECVs to prevent them from fusing with lysosomes, enabling them to escape degradation by lysozymes within these cells. Elucidating how subtle modification of the capsule enhances bacterial defenses against host innate immunity will enable the future development of effective drugs or vaccines against infection by E. coli K1.

An ArcA-Modulated Small RNA in Pathogenic Escherichia coli K1.

Escherichia coli K1 is the leading cause of meningitis in newborns. Understanding the molecular basis of E. coli K1 pathogenicity will help develop treatment of meningitis and prevent neurological sequelae. E. coli K1 replicates in host blood and forms a high level of bacteremia to cause meningitis in human. However, the mechanisms that E. coli K1 employs to sense niche signals for survival in host blood are poorly understood. We identified one intergenic region in E. coli K1 genome that encodes a novel small RNA, sRNA-17. The expression of sRNA-17 was downregulated by ArcA in microaerophilic blood. The ΔsRNA-17 strain grew better in blood than did the wild-type strain and enhanced invasion frequency in human brain microvascular endothelial cells. Transcriptome analyses revealed that sRNA-17 regulates tens of differentially expressed genes. These data indicate that ArcA downregulates the sRNA-17 expression to benefit bacterial survival in blood and penetration of the blood-brain barrier. Our findings reveal a signaling mechanism in E. coli K1 for host adaptation.

Prevalence of Escherichia coli K1 Rectovaginal Colonization Among Pregnant Women in Iran: Virulence Factors and Antibiotic Resistance Properties.

Neonatal invasive infections caused by Escherichia coli K1 are still major health problems and effective preventive strategies at the maternal level can be a concern. The aim of this study was to determine the prevalence of rectovaginal colonization, related risk factors, virulence factors, and antibiotic resistance properties of E. coli K1 among pregnant women. In this cross-sectional study, vaginal and rectal swabs were collected from 400 pregnant women. The identification of E. coli isolates was performed by microbiological tests. A polymerase chain reaction (PCR) assay was used to identify the E. coli K1 strains. The antimicrobial susceptibility patterns were determined by the Kirby-Bauer disk diffusion. Two duplex PCR assays were developed separately to detect genes encoding virulence determinants (fimH, hlyF, ibeA, and iucC) in the E. coli strains. The vaginal and rectal maternal E. coli K1 colonization rates were 3.7% and 19.25%, respectively. There is no significant association between demographic-obstetric factors and vaginal E. coli colonization in pregnant women. The most effective antibiotics against E. coli K1 strains were imipenem, gentamycin, ciprofloxacin, and ceftazidime. In our study, the E. coli K1 strains were significantly more likely to possess the fimH (90.9% vs. 60.7%) and iucC (90.9% vs. 53.6%) than the E. coli non-K1 strains. This study demonstrates that E. coli K1 seems to be more virulent than non-K1 strains. Our findings highlight the importance of screening pregnant women for vaginal colonization by E. coli K1 and of the appropriate antibiotic prophylaxis for the prevention of early-onset E. coli neonatal infection and comorbidity.