Surveillance of infection status of drug resistant Staphylococcus aureus in an Indian teaching hospital

Objective

To access nosocomial and community accounts of multidrug resistant strains of Staphylococcus aureus (S. aureus) isolated by surveillance in a teaching hospital, over a period of 30 months.

Methods

Clinical samples from nosocomial sources, i.e., wards and cabins, intensive care unit (ICU) and neonatal intensive care unit (NICU) sources, as well as community or outpatient department (OPD) sources of a hospital were used for isolating strains of S. aureus resistant to methicillin/oxacillin and vancomycin, over a period, November 2009-April 2012.

Results

Of a total of 1 507 S. aureus isolates, 485 strains from community and 1 022 isolates were from nosocomial sources; Out of 485 (100%) OPD S. aureus isolates, 390 (80.41%) were MRSA strains. Similarly, from wards and cabins of 564 (100%) isolates, 461 (81.73%) strains were MRSA; whereas of 458 (100%) isolates obtained from ICU and NICU, 363 (79.25%) strains were MRSA. It was ascertained with χ²-tests of independence that MRSA strains were equally distributed in “community” or “wards and cabins” or “ICU and NICU” sources, alike rest other drug-resistant S. aureus strains. Antibiotic sensitivity patterns of isolated strains with 16 antibiotics were ascertained. Out of 390 (100%) MRSA strains isolated from OPD, 80 (20.51%) were vancomycin resistant (VRSA) and 173 (44.35%) strains were moderately sensitive to vancomycin or called, vancomycin intermediate strains (VISA). Similarly, from nosocomial sources, out of 461 (100%) MRSA isolates obtained from wards and cabins, 110 (23.86%) strains were VRSA and 208 (45.11%) were VISA strains, whereas out of 363 MRSA isolates obtained from ICU and NICU, 61 (16.8%) VRSA strains and 164 (45.17%) VISA strains were found. A progressive increase of percent values of drug resistance to 16 antibiotics used for antibiotic profiling revealed its subtle infection dynamics.

Conclusions

This study revealed the appalling state of occurrence of MRSA and VRSA in a resource-limited setting. A progressive increase of percent values of drug resistance to 16 antibiotics used revealed its subtle infection dynamics.     

Genomic epidemiology of the Escherichia coli O104:H4 outbreaks in Europe, 2011

The degree to which molecular epidemiology reveals information about the sources and transmission patterns of an outbreak depends on the resolution of the technology used and the samples studied. Isolates of Escherichia coli O104:H4 from the outbreak centered in Germany in May-July 2011, and the much smaller outbreak in southwest France in June 2011, were indistinguishable by standard tests. We report a molecular epidemiological analysis using multiplatform whole-genome sequencing and analysis of multiple isolates from the German and French outbreaks. Isolates from the German outbreak showed remarkably little diversity, with only two single nucleotide polymorphisms (SNPs) found in isolates from four individuals. Surprisingly, we found much greater diversity (19 SNPs) in isolates from seven individuals infected in the French outbreak. The German isolates form a clade within the more diverse French outbreak strains. Moreover, five isolates derived from a single infected individual from the French outbreak had extremely limited diversity. The striking difference in diversity between the German and French outbreak samples is consistent with several hypotheses, including a bottleneck that purged diversity in the German isolates, variation in mutation rates in the two E. coli outbreak populations, or uneven distribution of diversity in the seed populations that led to each outbreak.     

ANTIMICROBIAL DRUG RESISTANCE IN STRAINS OF Escherichia coli ISOLATED FROM FOOD SOURCES

A variety of foods and environmental sources harbor bacteria that areresistant to one or more antimicrobial drugs used in medicine and agriculture.Antibiotic resistance in Escherichia coli is of particular concernbecause it is the most common Gram-negative pathogen in humans. Hence this study wasconducted to determine the antibiotic sensitivity pattern of E. coliisolated from different types of food items collected randomly from twelve localitiesof Hyderabad, India. A total of 150 samples comprising; vegetable salad, rawegg-surface, raw chicken, unpasteurized milk, and raw meat were processedmicrobiologically to isolate E. coli and to study their antibioticsusceptibility pattern by the Kirby-Bauer method. The highest percentages of drugresistance in isolates of E. coli were detected from raw chicken(23.3%) followed by vegetable salad (20%), raw meat (13.3%), raw egg-surface (10%)and unpasteurized milk (6.7%). The overall incidence of drug resistant E.coli was 14.7%. A total of six (4%) Extended Spectrum β-Lactamase (ESBL)producers were detected, two each from vegetable salads and raw chicken, and one eachfrom raw egg-surface and raw meat. Multidrug resistant strains of E.coli are a matter of concern as resistance genes are easily transferableto other strains. Pathogen cycling through food is very common and might pose apotential health risk to the consumer. Therefore, in order to avoid this, goodhygienic practices are necessary in the abattoirs to prevent contamination of cattleand poultry products with intestinal content as well as forbidding the use ofuntreated sewage in irrigating vegetables.     

Cotrimoxazole-resistant Escherichia coli bacteremia in neutropenic patients at a regional oncology hospital

In a regional oncology hospital using cotrimoxazole (trimethoprim-sulphamethoxazole) prophylaxis during chemotherapy-induced neutropenia, a single strain of Escherichia coli (indole negative) caused 15 of 27 episodes of Gram-negative rod bacteremia in 1987, and four of 32 such episodes in 1988. This biotype had not been recovered in 1986. Investigations during this ‘outbreak’ of bacteremias revealed enteric colonization with this strain of E coli in 37% of patients on leukemia or bone marrow transplant wards and in several staff members in July 1987. In 1988, 11 of 32 Gram-negative rod bacteremias were secondary to other strains of indole positive E coli of several different biotypes and plasmid profiles. Indole negative strains all exhibited low level trimethoprim resistance, whereas indole positive strains which subsequently appeared exhibited high level trimethoprim resistance. Failure of cotrimoxazole prophylaxis was initially due to the clonal dissemination of a single strain of E coli within the institution, with the subsequent appearance of multiple E coli strains with probable differing genetic bases for their resistance.     

A precise reconstruction of the emergence and constrained radiations of Escherichia coli O157 portrayed by backbone concatenomic analysis

Single nucleotide polymorphisms (SNPs) in stable genome regions provide durable measurements of species evolution. We systematically identified each SNP in concatenations of all backbone ORFs in 7 newly or previously sequenced evolutionarily instructive pathogenic Escherichia coli O157:H7, O157:H⁻, and O55:H7. The 1,113 synonymous SNPs demonstrate emergence of the largest cluster of this pathogen only in the last millennium. Unexpectedly, shared SNPs within circumscribed clusters of organisms suggest severely restricted survival and limited effective population sizes of pathogenic O157:H7, tenuous survival of these organisms in nature, source-sink evolutionary dynamics, or, possibly, a limited number of mutations that confer selective advantage. A single large segment spanning the rfb-gnd gene cluster is the only backbone region convincingly acquired by recombination as O157 emerged from O55. This concatenomic analysis also supports using SNPs to differentiate closely related pathogens for infection control and forensic purposes. However, constrained radiations raise the possibility of making false associations between isolates.     

Antibiotic-resistant Escherichia coli in women with acute cystitis in Canada

BACKGROUND:

Trimethoprim-sulfamethoxazole (TMP-SMX) has been a traditional first-line antibiotic treatment for acute cystitis; however, guidelines do not recommend TMP-SMX in regions where Escherichia coli resistance exceeds 20%. While resistance is increasing, there are no recent Canadian estimates from a primary care setting to guide prescribing decisions.

METHODS:

A total of 330 family physicians assessed 752 women with suspected acute cystitis between 2009 and 2011. Physicians documented clinical features and collected urine for cultures for 430 (57.2%) women. The proportion of resistant isolates of E coli and exact binomial 95% CIs were estimated nationally, and compared regionally and demographically. These estimates were compared with those from a 2002 national study.

RESULTS:

The proportion of TMP-SMX-resistant E coli was 16.0% nationally (95% CI 11.3% to 21.8%). This was not statistically higher than 2002 (10.9% [P=0.14]). TMP-SMX resistance was increased in women ≤50 years of age (21.4%) compared with older women (10.7% [P=0.037]). In women with no antibiotic exposure in the previous three months, TMP-SMX-resistant E coli remained more prevalent in younger women (21.8%) compared with older women (4.4% [P=0.003]). The proportion of ciprofloxacin-resistant E coli was 5.5% nationally (95% CI 2.7% to 9.9%), and was increased compared with 2002 (1.1% [P=0.036]). Ciprofloxacin resistance was highest in British Columbia (17.7%) compared with other regions (2.7% [P=0.003]), and was increased compared with 2002 levels in this province (0.0% [P=0.025]). Nitrofurantoin-resistant E coli levels were low (0.5% [95% CI 0.01% to 2.7%).

DISCUSSION:

The proportion of TMP-SMX-resistant E coli causing acute cystitis in women in Canada remains below 20% nationally, but may exceed this level in premenopausal women. Ciprofloxacin resistance has increased, notably in British Columbia. Nitrofurantoin resistance levels are low across the country. These observations indicate that TMP-SMX and nitrofurantoin remain appropriate empirical antibiotic agents for treating cystitis in primary care settings in Canada.     

Recombinant transfer in the basic genome of Escherichia coli

An approximation to the ∼4-Mbp basic genome shared by 32 strains of Escherichia coli representing six evolutionary groups has been derived and analyzed computationally. A multiple alignment of the 32 complete genome sequences was filtered to remove mobile elements and identify the most reliable ∼90% of the aligned length of each of the resulting 496 basic-genome pairs. Patterns of single base-pair mutations (SNPs) in aligned pairs distinguish clonally inherited regions from regions where either genome has acquired DNA fragments from diverged genomes by homologous recombination since their last common ancestor. Such recombinant transfer is pervasive across the basic genome, mostly between genomes in the same evolutionary group, and generates many unique mosaic patterns. The six least-diverged genome pairs have one or two recombinant transfers of length ∼40–115 kbp (and few if any other transfers), each containing one or more gene clusters known to confer strong selective advantage in some environments. Moderately diverged genome pairs (0.4–1% SNPs) show mosaic patterns of interspersed clonal and recombinant regions of varying lengths throughout the basic genome, whereas more highly diverged pairs within an evolutionary group or pairs between evolutionary groups having >1.3% SNPs have few clonal matches longer than a few kilobase pairs. Many recombinant transfers appear to incorporate fragments of the entering DNA produced by restriction systems of the recipient cell. A simple computational model can closely fit the data. Most recombinant transfers seem likely to be due to generalized transduction by coevolving populations of phages, which could efficiently distribute variability throughout bacterial genomes.The increasing availability of complete genome sequences of many different bacterial and archaeal species, as well as metagenomic sequencing of mixed populations from natural environments, has stimulated theoretical and computational approaches to understand mechanisms of speciation and how prokaryotic species should be defined (1–8). Much genome analysis and comparison has been at the level of gene content, identifying core genomes (the set of genes found in most or all genomes in a group) and the continually expanding pan-genome. Population genomics of Escherichia coli has been particularly well studied because of its long history in laboratory research and because many pathogenic strains have been isolated and completely sequenced (9–14). Proposed models of how related groups or species form and evolve include isolation by ecological niche (7–9, 11, 15), decreased homologous recombination as divergence between isolated populations increases (2–4, 8, 14, 16), and coevolving phage and bacterial populations (6).E. coli genomes are highly variable, containing an array of phage-related mobile elements integrated at many different sites (17), random insertions of multiple transposable elements (18), and idiosyncratic genome rearrangements that include inversions, translocations, duplications, and deletions. Although E. coli grows by binary cell division, genetic exchange by homologous recombination has come to be recognized as a significant factor in adaptation and genome evolution (9, 10, 19). Of particular interest has been the relative contribution to genome variability of random mutations (single base-pair differences referred to as SNPs) and replacement of genome regions by homologous recombination with fragments imported from other genomes (here referred to as recombinant transfers or transferred regions). Estimates of the rate, extent, and average lengths of recombinant transfers in the core genome vary widely, as do methods for detecting transferred regions and assessing their impact on phylogenetic relationships (12–14, 20, 21).In a previous comparison of complete genome sequences of the K-12 reference strain MG1655 and the reconstructed genome of the B strain of Delbrück and Luria referred to here as B-DL, we observed that SNPs are not randomly distributed among 3,620 perfectly matched pairs of coding sequences but rather have two distinct regimes: sharply decreasing numbers of genes having 0, 1, 2, or 3 SNPs, and an abrupt transition to a much broader exponential distribution in which decreasing numbers of genes contain increasing numbers of SNPs from 4 to 102 SNPs per gene (22). Genes in the two regimes of the distribution are interspersed in clusters of variable lengths throughout what we referred to as the basic genome, namely, the ∼4 Mbp shared by the two genomes after eliminating mobile elements. We speculated that genes having 0 to 3 SNPs may primarily have been inherited clonally from the last common ancestor, whereas genes comprising the exponential tail may primarily have been acquired by horizontal transfer from diverged members of the population.The current study was undertaken to extend these observations to a diverse set of 32 completely sequenced E. coli genomes and to analyze how SNP distributions in the basic genome change as a function of evolutionary divergence between the 496 pairs of strains in this set. We have taken a simpler approach than those of Touchon et al. (13), Didelot et al. (14), and McNally et al. (21), who previously analyzed multiple alignments of complete genomes of E. coli strains. The appreciably larger basic genome derived here is not restricted to protein-coding sequences and retains positional information.     

Antimicrobial-resistant Escherichia coli in public beach waters in Quebec

INTRODUCTION:

Human exposure to antimicrobial-resistant bacteria may result in the transfer of resistance to commensal or pathogenic microbes present in the gastrointestinal tract, which may lead to severe health consequences and difficulties in treatment of future bacterial infections. It was hypothesized that the recreational waters from beaches represent a source of antimicrobial-resistant Escherichia coli for people engaging in water activities.

OBJECTIVE:

To describe the occurrence of antimicrobial-resistant E coli in the recreational waters of beaches in southern Quebec.

METHODS:

Sampling occurred over two summers; in 2004, 674 water samples were taken from 201 beaches, and in 2005, 628 water samples were taken from 177 beaches. The minimum inhibitory concentrations of the antimicrobial-resistant E coli isolates against a panel of 16 antimicrobials were determined using microbroth dilution.

RESULTS:

For 2004 and 2005, respectively, 28% and 38% of beaches sampled had at least one water sample contaminated by E coli resistant to one or more antimicrobials, and more than 10% of the resistant isolates were resistant to at least one antimicrobial of clinical importance for human medicine. The three antimicrobials with the highest frequency of resistance were tetracycline, ampicillin and sulfamethoxazole.

DISCUSSION:

The recreational waters of these beaches represent a potential source of antimicrobial-resistant bacteria for people engaging in water activities. Investigations relating the significance of these findings to public health should be pursued.     

High frequency of hotspot mutations in core genes of Escherichia coli due to short-term positive selection

Core genes comprising the ubiquitous backbone of bacterial genomes are not subject to frequent horizontal transfer and generally are not thought to contribute to the adaptive evolution of bacterial pathogens. We determined, however, that at least one-third and possibly more than one-half of the core genes in Escherichia coli genomes are targeted by repeated replacement substitutions in the same amino acid positions—hotspot mutations. Occurrence of hotspot mutations is driven by positive selection, as their rate is significantly higher than expected by random chance alone, and neither intragenic recombination nor increased mutability can explain the observed patterns. Also, commensal E. coli strains have a significantly lower frequency of mutated genes and mutations per genome than pathogenic strains. E. coli strains causing extra-intestinal infections accumulate hotspot mutations at the highest rate, whereas the highest total number of mutated genes has been found among Shigella isolates, suggesting the pathoadaptive nature of such mutations. The vast majority of hotspot mutations are of recent evolutionary origin, implying short-term positive selection, where adaptive mutations emerge repeatedly but are not sustained in natural circulation for long. Such pattern of dynamics is consistent with source-sink model of virulence evolution.     

A surprising sweetener from enteropathogenic Escherichia coli

Infections with enteropathogenic Escherichia coli (EPEC) are remarkably devoid of gut inflammation and necrotic damage compared to infections caused by invasive pathogens such as Salmonella and Shigella. Recently, we observed that EPEC blocks cell death using the type III secretion system (T3SS) effector NleB. NleB mediated post-translational modification of death domain containing adaptor proteins by the covalent attachment of N-acetylglucosamine (GlcNAc) to a conserved arginine in the death domain.  N-linked glycosylation of arginine has not previously been reported in mammalian cell biology and the precise biochemistry of this modification is not yet defined. Although the addition of a single GlcNAc to arginine is a seemingly slight alteration, the impact of NleB is considerable as arginine in this location is critical for death domain interactions and death receptor induced apoptosis. Hence, by blocking cell death, NleB promotes enterocyte survival and thereby prolongs EPEC attachment to the gut epithelium.     

Escherichia coli sister chromosome separation includes an abrupt global transition with concomitant release of late-splitting intersister snaps

The basis for segregation of sister chromosomes in bacteria is not established. We show here that two discrete ~150-kb regions, both located early in the right replichore, exhibit prolonged juxtaposition of sister loci, for 20 and 30 min, respectively, after replication. Flanking regions, meanwhile, separate. Thus, the two identified regions comprise specialized late-splitting intersister connections or snaps. Sister snap loci separate simultaneously in both snap regions, concomitant with a major global nucleoid reorganization that results in emergence of a bilobed nucleoid morphology. Split snap loci move rapidly apart to a separation distance comparable with one-half the length of the nucleoid. Concomitantly, at already split positions, sister loci undergo further separation to a comparable distance. The overall consequence of these and other effects is that thus far replicated sister chromosomes become spatially separated (individualized) into the two nucleoid lobes, while the terminus region (and likely, all unreplicated portions of the chromosome) moves to midcell. These and other findings imply that segregation of Escherichia coli sister chromosomes is not a smooth continuous process but involves at least one and likely, two major global transition(s). The presented patterns further suggest that accumulation of internal intranucleoid forces and constraining of these forces by snaps play central roles in global chromosome dynamics. They are consistent with and supportive of our previous proposals that individualization of sisters in E. coli is driven primarily by internally generated pushing forces and is directly analogous to sister individualization at the prophase to prometaphase transition of the eukaryotic cell cycle.     

Endemically acquired foodborne outbreak of enterotoxin-producing Escherichia coli serotype O169:H41

Purpose

Enterotoxigenic Escherichia coli (ETEC) is traditionally recognized as a common cause of traveler’s diarrhea, but is becoming a more frequent cause of foodborne disease outbreaks in the United States. It is important for public health practitioners and clinicians to be aware of ETEC as a domestic cause of gastroenteritis. We investigated a foodborne disease outbreak to understand the epidemiology of ETEC in this setting.

Methods

We conducted a cohort study of 63 employees of Company A. A case was defined as an employee who experienced diarrhea or vomiting or fever and cramps after eating a catered meal at Company A from August 14th-15th. A standardized questionnaire was administered to cases and controls.

Results

Of 63 employees, 36 met the case definition (Attack Rate = 57.1%). Diarrhea (94%) and cramps (74%) were common, whereas vomiting was not (3%). Mean duration of illness was 2.7 days. Coleslaw at the August 15th lunch was significantly associated with illness (Odds ratio = 4.4, 95% CI = 1.1-17). Stool specimens were positive for heat-stable enterotoxin-producing E. coli O169:H41. Contamination likely occurred at the point of service.

Conclusions

This outbreak illustrates the changing epidemiology of enterotoxigenic E. coli and the importance for healthcare practitioners to consider ETEC as a potential cause of domestically acquired gastroenteritis.     

Infection strategies of enteric pathogenic Escherichia coli

Enteric Escherichia coli (E. coli) are both natural flora of humans and important pathogens causing significant morbidity and mortality worldwide. Traditionally enteric E. coli have been divided into 6 pathotypes, with further pathotypes often proposed. In this review we suggest expansion of the enteric E. coli into 8 pathotypes to include the emerging pathotypes of adherent invasive E. coli (AIEC) and Shiga-toxin producing enteroaggregative E. coli (STEAEC). The molecular mechanisms that allow enteric E. coli to colonize and cause disease in the human host are examined and for two of the pathotypes that express a type 3 secretion system (T3SS) we discuss the complex interplay between translocated effectors and manipulation of host cell signaling pathways that occurs during infection.     

Single-cell,real-time detection of oxidative stress induced in Escherichia coli by the antimicrobial peptide CM15

Antibiotics target specific biochemical mechanisms in bacteria. In response to new drugs, pathogenic bacteria rapidly develop resistance. In contrast, antimicrobial peptides (AMPs) have retained broad spectrum antibacterial potency over millions of years. We present single-cell fluorescence assays that detect reactive oxygen species (ROS) in the Escherichia coli cytoplasm in real time. Within 30 s of permeabilization of the cytoplasmic membrane by the cationic AMP CM15 [combining residues 1–7 of cecropin A (from moth) with residues 2–9 of melittin (bee venom)], three fluorescence signals report oxidative stress in the cytoplasm, apparently involving O₂⁻, H₂O₂, and •OH. Mechanistic studies indicate that active respiration is a prerequisite to the CM15-induced oxidative damage. In anaerobic conditions, signals from ROS are greatly diminished and the minimum inhibitory concentration increases 20-fold. Evidently the natural human AMP LL-37 also induces a burst of ROS. Oxidative stress may prove a significant bacteriostatic mechanism for a variety of cationic AMPs. If so, host organisms may use the local oxygen level to modulate AMP potency.In nature, multicellular organisms produce antimicrobial peptides (AMPs) that participate in the first line of defense against bacterial infection (1). These are ancient molecules that kill a broad, phylogenetically diverse spectrum of bacteria. The selective bacteriostatic (growth halting) properties of cationic AMPs are most often attributed to their ability to compromise bacterial membranes, while leaving eukaryotic cell membranes relatively unharmed. On entry into the periplasm or cytoplasm, various AMPs are known to interfere with cell wall growth, cause loss of osmotic pressure, and degrade the transmembrane potential (2, 3). It is increasingly clear that AMPs launch a multipronged attack on bacterial cells (4).The hybrid antimicrobial peptide CM15 (KWKLFKKIGAVLKVL-NH₂) combines residues 1–7 of cecropin A (from moth) with residues 2–9 of melittin (bee venom). CM15 retains the potency of cecropin A against multiple species of bacteria without the hemolytic activity of melittin (5). Using widefield fluorescence microscopy of plated Escherichia coli cells with excitation at 457 nm, we inadvertently discovered that addition of CM15 caused abrupt enhancement of cellular autofluorescence from the oxidized form of flavins. This led us to explore the possibility that CM15 induces harmful levels of reactive oxygen species (ROS) in the bacterial cytoplasm.Our single-cell, real-time, fluorescence assays demonstrate that CM15 translocates across the outer membrane (OM) without permeabilization to periplasmic GFP, then permeabilizes the cytoplasmic membrane (CM) to GFP and causes abrupt cell shrinkage. Three different intracellular fluorescence signals indicate the onset of oxidative stress within 30 s of cell shrinkage: enhanced cytoplasmic autofluorescence from oxidized flavins, a burst of fluorescence from the permeable dye CellROX Green (CellROX product data sheet available on request) (known to detect O₂^– and •OH), and a burst of fluorescence from resorufin (the product of the Amplex Red assay, known to specifically detect H₂O₂). Additional tests suggest that components of the aerobic respiratory chain contribute to the CM15-induced ROS signals. Importantly, in anaerobic growth conditions the CellROX* (oxidized, fluorescent form of CellROX Green) and resorufin signals decrease significantly and the minimum inhibitory concentration (MIC) increases 20-fold. Oxidative stress is a key aspect of the growth-halting capability of CM15. This may prove true of many natural cationic AMPs, as suggested by our observation of a strong, abrupt CellROX* signal on attack of E. coli by the human cathelicidin LL-37.Recent reports indicate that in addition to their target-specific action, bactericidal drugs such as norfloxacin, ampicillin, and kanamycin A induce oxidative stress in E. coli and Staphylococcus aureus (6, 7). Oxidative damage was evidently essential for complete killing of cells. The initial results have been challenged (8–10), and very recently these challenges have been refuted (11). Evidently, oxidative stress contributes to the lethality of a variety of antimicrobial agents (12, 13), including at least some antimicrobial peptides. The methods presented here enable detection of ROS within the cytoplasm of single cells with 12-s time resolution, a capability that should prove useful in many different contexts.     

NleH effectors interact with Bax inhibitor-1 to block apoptosis during enteropathogenic Escherichia coli infection

The human pathogens enteropathogenic (EPEC) and enterohemorrhagic Escherichia coli and the related mouse pathogen Citrobacter rodentium subvert a variety of host cell signaling pathways via their plethora of type III secreted effectors, including triggering of an early apoptotic response. EPEC-infected cells do not develop late apoptotic symptoms, however. In this study we demonstrate that the NleH family effectors, homologs of the Shigella effector kinase OspG, blocks apoptosis. During EPEC infection, NleH effectors inhibit elevation of cytosolic Ca²⁺ concentrations, nuclear condensation, caspase-3 activation, and membrane blebbing and promote cell survival. NleH1 alone is sufficient to prevent procaspase-3 cleavage induced by the proapoptotic compounds staurosporine, brefeldin A, and tunicamycin. Using C. rodentium, we found that NleH inhibits procaspase-3 cleavage at the bacterial attachment sites in vivo. A yeast two-hybrid screen identified the endoplasmic reticulum six-transmembrane protein Bax inhibitor-1 (BI-1) as an NleH-interacting partner. We mapped the NleH-binding site to the N-terminal 40 amino acids of BI-1. Knockdown of BI-1 resulted in the loss of NleH’s antiapoptotic activity. These results indicate that NleH effectors are inhibitors of apoptosis that may act through BI-1 to carry out their cytoprotective function.     

Cancerous patients and outbreak of Escherichia coli: an important issue in oncology

The widespread of the Escherichia coli outbreak in Europe becomes an important public concern at global level. The infection can be serious and might result in death. The retrospective literature review on this specific topic is performed. In this specific brief article, the author presented and discussed on the problem of Escherichia coli infection in the cancerous patients. This is an actual important issue in medical oncology for the scenario of Escherichia coli epidemic.     

High prevalence of adherent-invasive Escherichia coli associated with ileal mucosa in Crohn's disease

BACKGROUND & AIMS: Adherent-invasive Escherichia coli (AIEC) pathovar has been identified in the intestinal mucosa of patients with Crohn's disease (CD). AIEC reference strain LF82 is able to adhere to intestinal epithelial cells, to invade epithelial cells via a mechanism involving actin polymerization and microtubules, and to survive and replicate within macrophages. This study was performed to assess the prevalence of AIEC associated with intestinal mucosa of patients with CD, ulcerative colitis (UC), and of controls. METHODS: A search for E. coli strains was performed with ileal specimens of 63 patients with CD and 16 controls without inflammatory bowel disease (IBD), and with colonic specimens of 27 patients with CD, 8 patients with UC, and 102 controls. The abilities of E. coli strains to invade epithelial cells and to survive and replicate within macrophages were assessed using the gentamicin protection assay. Bacterial uptake by epithelial cells was analyzed using cytoskeletal inhibitors. Bacterial adhesion was quantified with Caco-2 and Intestine-407 cells. The presence of known E. coli virulence genes was assessed by polymerase chain reaction and DNA hybridization. RESULTS: In ileal specimens, AIEC strains were found in 21.7% of CD chronic lesions vs. in 6.2% of controls. In neoterminal ileal specimens, AIEC strains were found in 36.4% of CD early lesions (P = 0.034 vs. controls) and 22.2% of healthy mucosa of CD patients. In colonic specimens, AIEC strains were found in 3.7% of CD patients, 0% of UC patients, and 1.9% of controls. CONCLUSIONS: AIEC strains are associated specifically with ileal mucosa in CD.