O-142 SARS-CoV-2 vaccination and IVF cycle outcomes

Study question

Does recent mRNA SARS-CoV-2 vaccination effect IVF pregnancy rate?

Summary answer

We observed no influence of mRNA SARS-CoV-2 vaccine on patients’ IVF cycle outcomes; vaccination did not change pregnancy rates.

What is known already

Two recent studies showed that the BNT162b2 mRNA SARS-COV-2 vaccine does not appear to have negative effects on oocytes during controlled ovarian stimulation. Assessment of follicular fluid after vaccination (1) concluded that there was no affect on the follicle quality or function. An additional study of 36 patients that underwent IVF both immediately before and immediately after vaccination found no change in ovarian yield or embryo quality (2).

Study design, size, duration

A retrospective case control study including 385 women from January 1, 2021 to May 31st of the same year.

Participants/materials, setting, methods

The study group included patients that received 2 doses of the Pfizer SARS-COV-2 vaccine between 7-180 days prior to starting IVF and without a history of COVID infection. Controls included unvaccinated patients from the same time period and historical age matched patients from our hospital from the same months in prior years. 385 patients under the age of 40 years met the inclusion criteria, 349 in the control and 36 in the vaccinated group.

Main results and the role of chance

Demographic and clinical characteristics were comparable between groups. The pregnancy rate was 33.3% (n = 12) in the vaccinated group vs 31.8% (n = 111) in the control group (p > 0.1). There were no statistically significant differences between the control and vaccine groups with a small non-significant trend to higher pregnancy rates in vaccinated patients: pregnancy rate OR for vaccination group was 1.17 (95% CI 0.56-2.44). 

Limitations, reasons for caution

Our study size was small and was observational leaving it open to confounding and selection bias regarding who chose to receive the vaccine and those in high risk groups for COVID infection. Additionally, longterm effect of the vaccine and booster were not assessed.

Wider implications of the findings

We did not observe any effect of this vaccine regimen on IVF outcomes or pregnancy rates. This underscores worldwide data and physiologic reasoning that there should not be significant effects of this COVID vaccine on developing gametes quality and function and is a good option for those trying to conceive.

Trial registration number

LND 0031-21

P–448 Clinical outcome of social oocyte cryopreservation at advanced age

Study question

What are the success rates of social oocyte cryopreservation (SOC) at advanced age?

Summary answer

In this study, one in four women who underwent SOC above age 35 had a delivery.

What is known already

While SOC is gaining popularity, reports on delivery rates are limited due to low utilization rates.

Study design, size, duration

Retrospective data collection of all woman who underwent SOC between 2011–2018, and presented for treatment using cryopreserved oocytes until January 2021. Participants/materials, setting, methods: Review of patient records (including both IVF and antenatal/postnatal) and laboratory data in a university affiliated hospital-based IVF unit. Main results and the role of chance: A total of 448 women underwent SOC during 2011–2018. 50 (11.2%) women returned to use these oocytes until the end of January 2021. Women who returned to use their oocytes underwent cryopreservation at mean age of 38.2±2.2. 46 (92%) of participants were above 35 at time of cryopreservation. Number of oocytes cryopreserved was 11.3±9.7. Mean time from cryopreservation to thawing was 5.5±1.8years (range 1–9 years). and age at thawing was 43.4±2.1 (range 40–49). Nearly half of patients initially attempted to conceive before using their cryopreserved oocytes, mostly by ART using fresh oocytes. Mean number of oocytes thawed and oocytes survived per women was 9.7±6.2 and 6.1±4.9 respectively (post thawing survival rate 65.4±35%).

Mean number of embryos transferred, at one or more attempts was 2.6±2.1 per women. Eleven women gave birth or had an ongoing pregnancy > 20 weeks at time of analysis. All deliveries resulted from cryopreservation at age 36 and older (delivery rate 23.9% per women). Limitations, reasons for caution: We report our initial experience of women who underwent SOC at a single center. Most women who returned to use their oocytes had undergone SOC at advanced age, therefore not necessarily reflecting outcome for younger patients attempting to preserve fertility using this technology. Wider implications of the findings: Considering modest success rates of SOC in our cohort, women considering SOC are advised to do so at an earlier age.

Trial registration number

Not applicable

Self-Competitive Inhibition of the Bacteriophage P22 Tailspike Endorhamnosidase by O-Antigen Oligosaccharides

The P22 tailspike endorhamnosidase confers the high specificity of bacteriophage P22 for some serogroups of Salmonella differing only slightly in their O-antigen polysaccharide. We used several biophysical methods to study the binding and hydrolysis of O-antigen fragments of different lengths by P22 tailspike protein. O-Antigen saccharides of defined length labeled with fluorophors could be purified with higher resolution than previously possible. Small amounts of naturally occurring variations of O-antigen fragments missing the nonreducing terminal galactose could be used to determine the contribution of this part to the free energy of binding to be ∼7 kJ/mol. We were able to show via several independent lines of evidence that an unproductive binding mode is highly favored in binding over all other possible binding modes leading to hydrolysis. This is true even under circumstances under which the O-antigen fragment is long enough to be cleaved efficiently by the enzyme. The high-affinity unproductive binding mode results in a strong self-competitive inhibition in addition to product inhibition observed for this system. Self-competitive inhibition is observed for all substrates that have a free reducing end rhamnose. Naturally occurring O-antigen, while still attached to the bacterial outer membrane, does not have a free reducing end and therefore does not perform self-competitive inhibition.

Elucidation of the O-antigen structure of Escherichia coli O63

The structure of the O-antigen polysaccharide (PS) from the Shiga-toxin producing Escherichia coli O63 has been elucidated using a combination of bioinformatics, component analyses and NMR spectroscopy. The O-antigen is comprised of tetrasaccharide repeating units with the following structure: →2)-β-d-Quip3N(d-allo-ThrAc)-(1→2)-β-d-Ribf-(1→4)-β-d-Galp-(1→3)-α-d-GlcpNAc-(1→ in which the N-acetylated d-allo-threonine is amide-linked to position 3 of the 3-amino-3-deoxy-d-Quip sugar residue. The presence of a predicted flippase and polymerase encoded in the O63 gene cluster is consistent with the Wzx/Wzy biosynthetic pathway and consequently the biological repeating unit has likely an N-acetyl-d-glucosamine residue at its reducing end. A bioinformatics approach based on predictive glycosyltransferase function present in ECODAB (E. coli O-antigen database) suggested the structural element β-d-Galp-(1→3)-d-GlcpNAc in the O-antigen. Notably, multiple gene sequence alignment of fdtA and qdtA from E. coli to that in E. coli O63 resulted in discrimination between the two, confirmation of the latter in E. coli O63, and consequently, together with qdtB, biosynthesis of dTDP-d-Quip3N. The E. coli O63 O-antigen polysaccharide differs in two aspects from that of E. coli O114 where the latter carries instead an l-serine residue, and the glycosidic linkage positions to and from the Quip3N residue are both changed. The structural characterization of the O63 antigen repeat supports the predicted functional assignment of the O-antigen cluster genes.

In-vitro activity of solithromycin against anaerobic bacteria from the normal intestinal microbiota

Solithromycin is a novel fluoroketolide with high activity against bacteria associated with community-acquired respiratory tract infections as well as gonorrhea. However, data on the activity of solithromycin against anaerobic bacteria from the normal intestinal microbiota are scarce. In this study, 1024 Gram-positive and Gram-negative anaerobic isolates from the normal intestinal microbiota were analyzed for in-vitro susceptibility against solithromycin and compared to azithromycin, amoxicillin/clavulanic acid, ceftriaxone, metronidazole and levofloxacin by determining the minimum inhibitory concentration (MIC). Solithromycin was active against Bifidobacteria (MIC₅₀, 0.008 mg/L) and Lactobacilli (MIC₅₀, 0.008 mg/L). The MIC₅₀ for Clostridia, Bacteroides, Prevotella and Veillonella were 0.5, 0.5, 0.125 and 0.016 mg/L, respectively. Gram-positive anaerobes were more susceptible to solithromycin as compared to the other antimicrobials tested. The activity of solithromycin against Gram-negative anaerobes was equal or higher as compared to other tested agents.

Complement activation by Proteus mirabilis negatively charged lipopolysaccharides

Proteus mirabilis strains are human pathogens responsible for urinary tract infections and bacteremias and may be involved in rheumatoid arthritis. Lipopolysaccharide (LPS, bacterial endotoxin), the major component of the cell wall, is one of the virulence factors of Proteus. In the presented studies, we have investigated complement activation by LPSs isolated from P. mirabilis O10, O23, O30, and O43 strains, which differ in the number of negative COO— groups on their polysaccharide components. Four P. mirabilis strains studied were sensitive to complement-mediated killing, despite complement binding by their LPSs. The optimal complement binding by LPSs was detected in serum with functional assays for both the classical and alternative pathways.

Complement activation in 80% serum by the smooth, uronic acid, and hexosamine containing P. mirabilis LPSs was not critically determined by the structure of their O-chain polysaccharides. One of four LPSs used as a model, P. mirabilis O10 LPS, fragmented C3 in an LPS dose- and time-dependent manner. It was detected by crossed-immunoelectrophoresis and capture ELISA with anti-C3c antibodies. The lower complement activation by O23 LPS correlates with its reduced C3 fragmentation, compared with three other Proteus LPSs studied. Rabbit anti-O antibodies enhanced the complement binding and factor C3 fragmentation by O10, O23, O30, and O43 P. mirabilis LPSs.

Structural studies of a polysaccharide from Vibrio parahaemolyticus strain AN-16000

The structure of a polysaccharide from Vibrio parahaemolyticus strain AN-16000 has been investigated. The sugar and absolute configuration analysis revealed d-Glc, d-GalN, d-QuiN and l-FucN as major components. The PS was subjected to dephosphorylation with aqueous 40% HF to obtain an oligosaccharide that was analyzed by (1)H and (13)C NMR spectroscopy. The HR-MS spectrum of the oligosaccharide revealed a pentasaccharide composed of two Glc residues, one QuiNAc and one GalNAc, one FucNAc, as well as a glycerol moiety. The structure of the PS was determined using (1)H, (13)C, (15)N and (31)P NMR spectroscopy; inter-residue correlations were identified by (1)H,(13)C-heteronuclear multiple-bond correlation, (1)H,(1)H-NOESY and (1)H,(31)P-hetero-TOCSY experiments. The PS backbone has the following teichoic acid-like structure: →3)-d-Gro-(1-P-6)-β-d-Glcp-(1→4)-α-l-FucpNAc-(1→3)-β-d-QuipNAc-(1→ with a side-chain consisting of α-d-Glcp-(1→6)-α-d-GalpNAc-(1→ linked to the O3 position of the FucNAc residue.

Clostridium difficile recurrences in Stockholm

Sixty-eight hospital-admitted patients with a first episode of Clostridium difficile infection (CDI) were included and followed up during 1 year. Faeces samples were collected at 1, 2, 6 and 12 months after inclusion and analyzed for the presence of C. difficile toxin B, genes for toxin A, toxin B, binary toxin and TcdC deletion by PCR. All strains were also PCR-ribotyped and the MICs of the isolates were determined against eight antimicrobial agents. In 68 patients initially included, antibiotics, clinical signs and co-morbidities were analyzed and 56 were evaluable for recurrences. The mean number of different antibiotics given during 3 months prior to inclusion was 2.6 (range 0-6). Six patients had not received any antibiotics and three of them had diagnosed inflammatory bowel disease. Thirty-two patients (57%) had either a microbiological or clinical recurrence, 16 of whom had clinical recurrences that were confirmed microbiologically (13, 23%) or unconfirmed by culture (3, 5%). Twenty-nine patients were positive in at least one of the follow-up tests, 16 had the same ribotype in follow-up tests, i.e. relapse, and 13 a different ribotype, i.e., reinfection. Most common ribotypes were 078/126, 020, 023, 026, 014/077, 001 and 005. No strain of ribotype 027 was found. Strains ribotype 078/126 and 023 were positive for binary toxin and were the strains most prone to cause recurrence. All strains were sensitive to vancomycin and metronidazole. Patients with recurrences were significantly older (p = 0.02) and all patients had a high burden of comorbidities, which could explain the high fatality rate, 26 (38%) patients died during the 1-year follow-up.

Structure of the O-polysaccharide of Escherichia coli O132

Mild acid degradation of the lipopolysaccharide of Escherichia coli O132 released its O-polysaccharide. Analysis by 1D and 2D (1)H and (13)C NMR spectroscopy prior and subsequent to O-deacetylation, in conjunction with sugar analysis, revealed a linear pentasaccharide repeating unit of the O-polysaccharide having the following structure: →2)-α-d-Galf-(1→3)-α-l-Rhap2Ac-(1→4)-α-d-Glcp-(1→2)-α-l-Rhap-(1→3)-β-d-GlcpNAc-(1→ Putative functions of genes in the O-antigen gene cluster of E. coli O132 are consistent with the O-polysaccharide structure.

A comparison of Clostridium difficile diagnostic methods for identification of local strains in a South African centre

Accurate diagnosis of Clostridium difficile infection is essential for disease management. A clinical and molecular analysis of C. difficile isolated from symptomatic patients at Groote Schuur Hospital, South Africa, was conducted to establish the most suitable clinical test for the diagnosis and characterization of locally prevalent strains. C. difficile was detected in stool samples using enzyme-based immunoassays (EIA) and nucleic acid amplification methods, and their performance was compared with that of C. difficile isolation using direct selective culture combined with specific PCR to detect the C. difficile tpi gene, toxin A and B genes and binary toxin genes. Toxigenic isolates were characterized further by ribotyping. Selective culture isolated 32 C. difficile strains from 145 patients (22 %). Of these, the most prevalent (50 %) were of ribotype 017 (toxin A^-B⁺) while 15.6 % were ribotype 001 (toxin A⁺B⁺). No ribotype 027 strains or binary toxin genes (cdtA and cdtB) were detected. The test sensitivities and specificities, respectively, of four commercial clinical diagnostic methods were as follows: ImmunoCard Toxins A & B (40 % and 99.1 %), VIDAS C. difficile Toxin A & B (50 % and 99.1 %), GenoType CDiff (86.7 % and 88.3 %) and Xpert C. difficile (90 % and 97.3 %). Ribotype 001 and 017 strains had a 100 % detection rate by Xpert C. difficile, 100 % and 93.3 % by GenoType CDiff, 75 % and 53.3 % by ImmunoCard and 75 % and 60 % by VIDAS, respectively. The overall poor performance of EIA suggests that a change to PCR-based testing would assist diagnosis and ensure reliable detection of locally prevalent C. difficile 017 strains.

Molecular characteristics of Clostridium difficile strains from patients with a first recurrence more than 8 weeks after the primary infection

BACKGROUND/PURPOSE

Nearly all published studies of recurrent Clostridium difficile infections (CDI) report recurrent CDI within 8 weeks after the primary infection. This study explored the molecular characteristics of C. difficile isolates from the first recurrent CDI more than 8 weeks after the primary infection.

METHODS

Consecutive hospitalized patients with a recurrent CDI more than 8 weeks after a primary infection were enrolled prospectively from January 2008 to February 2011. All C. difficile isolates of the primary and recurrent infections were collected and subjected to polymerase chain reaction ribotyping and antimicrobial susceptibility testing.

RESULTS

There were 62 cases of CDI in this study, which included 32 cases (51.6%) of recurrence due to the same ribotype of C. difficile, 26 (41.9%) cases due to a different ribotype, and four (6.5%) cases with 2-4 recurrences due to the same or different strains. One hundred and forty C. difficile isolates were obtained, which included 62 primary CDI isolates and 78 recurrent isolates. Ribotype 020 was the most common C. difficile strain in primary and recurrent infections. Ribotype 001 accounted for 15.4% (10/78) of recurrent infections and 3.2% (2/62) of primary infections (p = 0.0447). The minimum inhibitory concentration at 90% (MIC₉₀) values of linezolid, moxifloxacin, and clindamycin against type 001 strains were much higher, compared to the three other common ribotypes.

CONCLUSION

Recurrent CDI more than 8 weeks after a primary infection can be caused by the same or different C. difficile ribotype at similar percentages. Ribotype 001 C. difficile strains, which have a lower susceptibility to antimicrobials, were isolated more frequently in patients with a recurrent CDI.

Structure and gene cluster of the O-antigen of Escherichia coli O165 containing 5-N-acetyl-7-N-[(R)-3-hydroxybutanoyl]pseudaminic acid

Upon mild acid degradation of the lipopolysaccharide of Escherichia coli O165, the O-polysaccharide chain was cleaved at the glycosidic linkage of 5-N-acetyl-7-N-[(R)-3-hydroxybutanoyl]pseudaminic acid (Pse5Hb7Ac). Analysis of the resulting linear tetrasaccharide and alkali-treated lipopolysaccharide by (1)H/(13)C 1D and 2D nuclear magnetic resonance spectroscopy enabled elucidation of the following structure of the O-polysaccharide: →8)-α-Psep5Hb7Ac-(2 → 6)-β-d-Galp-(1 → 4)-β-d-Glсp-(1 → 3)-α-d-GlсpNAc-(1→. The β-d-Galp-(1 → 4)-β-d-Glсp-(1 → 3)-d-GlсpNAc structural element is also present in the O-polysaccharide of E. coli O82. The content of the O-antigen gene cluster of E. coli O165 was found to be consistent with the O-polysaccharide structure established. Functions of proteins encoded in the gene cluster, including enzymes involved in the Pse5Hb7Ac biosynthesis and glycosyltransferases, were putatively assigned by comparison with sequences in available databases.

Ecological Effect of Ceftaroline-Avibactam on the Normal Human Intestinal Microbiota

Ceftaroline-avibactam is a new combination of the antibiotic ceftaroline with a novel non-β-lactam β-lactamase inhibitor, avibactam. The purpose of the present study was to investigate the effect of ceftaroline-avibactam on the human intestinal microbiota. Fourteen healthy volunteers received ceftaroline-avibactam (600 mg ceftaroline fosamil and 600 mg avibactam) intravenously over 2 h every 8 h on days 1 to 6 and as a single dose on day 7. Fecal samples were collected on day -1 (within 24 h of the first infusion on day 1) and on days 2, 5, 7, 9, 14, and 21. Escherichia coli numbers decreased during the study and normalized on day 21. An increased number of Klebsiella bacteria appeared on day 14 and normalized on day 21. The number of other enterobacteria decreased during the study, and the number of enterococci decreased from days 2 to 7 and normalized on day 9. Candida numbers increased from days 5 to 9 and normalized after day 14. The number of lactobacilli decreased during the study and recovered on day 14. The number of bifidobacteria decreased on day 2 and normalized on day 21. The number of Bacteroides bacteria was unchanged. Clostridium difficile numbers decreased on days 7 and 9 and increased on days 14 and 21. A toxigenic C. difficile strain was detected in one volunteer on day 21 with no reported adverse events. Plasma samples were collected on days -1, 2, 5, and 7. Ceftaroline and avibactam concentrations were 0 to 34.5 mg/liter and 0 to 61.6 mg/liter, respectively, in plasma and 0 to 35.4 mg/kg and 0 to 98.5 mg/kg, respectively, in feces. (This study is registered in the European Clinical Trials Database [https://eudract.ema.europa.eu/] under number EudraCT 2012 004921-25.).

Structure and genetics of the O-antigen of Escherichia coli O169 related to the O-antigen of Shigella boydii type 6

The O-polysaccharide (O-antigen) of Escherichia coli O169 was studied by sugar analysis along with 1D and 2D (1)H and (13)C NMR spectroscopy. The following structure of the branched hexasaccharide repeating unit was established: [Formula: see text] The O-polysaccharide of E. coli O169 differs from that of Shigella boydii type 6 only in the presence of a side-chain glucose residue. A comparison of the O-antigen biosynthesis gene clusters between the galF to gnd genes in the genomes of the two bacteria revealed their close relationship. The glycosyltransferase gene responsible for the formation of the β-D-Glcp-(1 → 6)-α-D-Galp linkage in the O-antigen was identified in the gene cluster.

Analysis of effects of MCB3681, the antibacterially active substance of prodrug MCB3837, on human resident microflora as proof of principle

The water-soluble prodrug MCB3837 is rapidly converted to MCB3681, active against Gram-positive bacterial species, after intravenous infusion. The aim of this study was to prove the principle that MCB3681 is efficacious in vivo by demonstrating its effect on the resident microflora or colonizers of the human skin, nose, oropharynx and intestine. MCB3837 was infused at a daily dose of 6 mg/kg for 5 days. MCB3681 was active against clostridia, bifidobacteria, lactobacilli, enterococci and Staphylococcus aureus, thus proving the principle that MCB3681 is antibacterially efficacious in vivo without affecting the Gram-negative microflora.

The origin of endodontic Enterococcus faecalis explored by comparison of virulence factor patterns and antibiotic resistance to that of isolates from stool samples, blood cultures and food

AIM

To elucidate the origin of Enterococcus faecalis isolated from secondary root canal infections and the possibility for a foodborne transmission by comparing them to strains recovered from food, blood and stool regarding putative virulence factors and antibiotic susceptibility profiles, where strains from common origin were hypothesized to harbour similar characteristics.

METHODOLOGY

A total of 108 E. faecalis strains recovered in the county of Stockholm, Sweden, were screened using PCR for putative virulence factors esp, cylA, gelE/gelatinase-negative phenotype (ef1841/fsrC), efaA, ace and asa1. The minimum inhibitory concentration (MIC) for ampicillin, piperacillin-tazobactam, imipenem, gentamicin, vancomycin, ciprofloxacin and linezolid was determined using the agar dilution method.

RESULTS

Next to strains from blood, the food isolates presented the highest average number of virulence determinants and were frequently enriched with asa1 coding for aggregation substance. None of the endodontic strains carried cylA, and the gelatinase-negative phenotype caused by a deletion dominated the group. Altogether, the most prevalent genes were gelE, efaA and ace, and a combination of them was equally present in approximately 80% of the strains from food, stool and root canals in comparison with 43.3% of the blood isolates. High-level resistance to ciprofloxacin and gentamicin was observed in 30% of the blood isolates, whereas the isolates from other origins, with single exceptions, were susceptible to all tested antibiotics.

CONCLUSIONS

Evidence for a foodborne transmission, explaining the high reported prevalence of E. faecalis in root filled teeth, could not be determined based on the similarities in virulence factor patterns and antibiotic susceptibility. The only linkage between isolates from food and root canals consisted of a shared common combination of the genes gelE, efaA and ace. The high occurrence of putative virulence traits in food isolates questions the safety of E. faecalis in food products.

Ecological effect of ceftazidime/avibactam on the normal human intestinal microbiota

Ceftazidime/avibactam is a new combination of the antibiotic ceftazidime with the novel, non-β-lactam β-lactamase inhibitor avibactam. The purpose of the present study was to investigate the effect of ceftazidime/avibactam on the human intestinal microbiota following intravenous (i.v.) administration. Twelve healthy volunteers received ceftazidime/avibactam by i.v. infusion (2000mg ceftazidime and 500mg avibactam) given over 2h every 8h on Days 1-6 (inclusive) and a single dose on Day 7. Faecal samples were collected on Day-1 (pre-dose), during administration on Days 2, 5 and 7 and post-dose on Days 9, 14 and 21. Samples were cultured on non-selective and selective media. The number of Escherichia coli and other enterobacteria decreased significantly during administration of ceftazidime/avibactam, whereas the number of enterococci increased. Lactobacilli, bifidobacteria, clostridia and Bacteroides decreased significantly during ceftazidime/avibactam administration. The effects on lactobacilli, bifidobacteria and Bacteroides were similar in the 12 volunteers, whilst clostridia showed different ecological patterns among the volunteers. Toxigenic Clostridium difficile strains were detected in five volunteers during the study. In four of the volunteers, loose stools were reported as adverse events. Plasma samples were collected on Days -1, 2, 5 and 7. Ceftazidime and avibactam concentrations in plasma (ceftazidime 0-224.2mg/L of plasma and avibactam 0-70.5mg/L of plasma) and faeces (ceftazidime 0-468.2mg/kg of faeces and avibactam 0-146.0mg/kg of faeces) were found by bioassay. New colonising resistant clostridia were found in five volunteers and lactobacilli were found in three volunteers.

Structures and gene clusters of the closely related O-antigens of Escherichia coli O46 and O134, both containing D-glucuronoyl-D-allothreonine

The O-polysaccharides (O-antigens) were isolated by mild acid degradation of the lipopolysaccharide (LPS) of Escherichia coli O46 and O134. The structures of their linear tetrasaccharide repeating units were established by sugar analysis along with 1D and 2D (1)H and (13)C NMR spectroscopy: [Formula: see text], where D-aThr indicates D-allothreonine and R indicates O-acetyl substitution (∼ 70% on aThr and ∼ 15% on GalNAc) in E. coli O46 whereas the O-acetylation is absent in E. coli O134. Functions of genes in the essentially identical O-antigen gene clusters of E. coli O46 and O134 were tentatively assigned by a comparison with sequences in available databases and found to be in agreement with the O-polysaccharide structures established.

Structural Elucidation of the O-Antigen Polysaccharide from Escherichia coli O181

Shiga-toxin-producing Escherichia coli (STEC) is an important pathogen associated to food-borne infection in humans; strains of E. coli O181, isolated from human cases of diarrhea, have been classified as belonging to this pathotype. Herein, the structure of the O-antigen polysaccharide (PS) from E. coli O181 has been investigated. The sugar analysis showed quinovosamine (QuiN), glucosamine (GlcN), galactosamine (GalN), and glucose (Glc) as major components. Analysis of the high-resolution mass spectrum of the oligosaccharide (OS), obtained by dephosphorylation of the O-deacetylated PS with aqueous 48 % hydrofluoric acid, revealed a pentasaccharide composed of two QuiNAc, one GlcNAc, one GalNAc, and one Glc residue. The ¹H and ¹³C NMR chemical shift assignments of the OS were carried out using 1 D and 2 D NMR experiments, and the OS was sequenced using a combination of tandem mass spectrometry (MS/MS) data and NMR ¹³C NMR glycosylation shifts. The structure of the native PS was determined using NMR spectroscopy, and it consists of branched pentasaccharide repeating units joined by phosphodiester linkages: →4)[α-l-QuipNAc-(1→3)]-α-d-GalpNAc6Ac-(1→6)-α-d-Glcp-(1→P-4)-α-l-QuipNAc-(1→3)-β-d-GlcpNAc-(1→; the O-acetyl groups represent 0.4 equivalents per repeating unit. Both the OS and PSs exhibit rare conformational behavior since two of the five anomeric proton resonances could only be observed at an elevated temperature.

Ecological impact of MCB3837 on the normal human microbiota

MCB3837 is a novel, water-soluble, injectable prodrug that is rapidly converted to the active substance MCB3681 in vivo following intravenous (i.v.) administration. Both MCB3837 and MCB3681 are oxazolidinone-quinolone hybrid molecules. The purpose of the present study was to investigate the effect of MCB3681 on the human skin, nose, oropharyngeal and intestinal microbiota following administration of MCB3837. Twelve healthy male subjects received i.v. MCB3837 (6 mg/kg body weight) once daily for 5 days. Skin, nose, saliva and faecal samples were collected on Day -1 (pre dose), during administration on Days 2 and 5, and post dose on Days 8, 12 and 19. Micro-organisms were identified to genus level. No measurable concentrations of MCB3681 were found in any saliva samples or in the faecal samples on Day -1. On Day 2, 10 volunteers had faecal MCB3681 concentrations between 16.5 mg/kg faeces and 275.1mg/kg faeces; no MCB3681 in faeces could be detected in two of the volunteers. On Day 5, all volunteers had faecal concentrations of MCB3681 ranging from 98.9 to 226.3 mg/kg. MCB3681 caused no ecological changes in the skin, nasal and oropharyngeal microbiota. The numbers of enterococci, bifidobacteria, lactobacilli and clostridia decreased in the intestinal microbiota during administration of the drug. Numbers of Escherichia coli, other enterobacteria and Candida were not affected during the study. There was no impact on the number of Bacteroides. The faecal microbiota was normalised on Day 19. No new colonising aerobic or anaerobic Gram-positive bacteria with MCB3681 minimum inhibitory concentrations of ≥4 mg/L were found.

Rapid structural elucidation of polysaccharides employing predicted functions of glycosyltransferases and NMR data: application to the O-antigen of Escherichia coli O59

A computerized method that uses predicted functions of glycosyltransferases (GTs) in conjunction with unassigned NMR data has been developed for the structural elucidation of bacterial polysaccharides (PSs). In this approach, information about the action of GTs (consisting of possible sugar residues used as donors and/or acceptors, as well as the anomeric configuration and/or substitution position in the respective glycosidic linkages) is extracted from the Escherichia coli O-antigen database and is submitted, together with the unassigned NMR data, to the CASPER program. This time saving methodology, which alleviates the need for chemical analysis, was successfully implemented in the structural elucidation of the O-antigen PS of E. coli O59. The repeating unit of the O-specific chain was determined using the O-deacylated PS and has a branched structure, namely, →6)[α-d-GalpA3Ac/4Ac-(1 → 3)]-α-d-Manp-(1 → 3)-α-d-Manp-(1 → 3)-β-d-Manp-(1 → 3)-α-d-GlcpNAc-(1→. The identification of the O-acetylation positions was efficiently performed by comparison of the (1)H,(13)C HSQC NMR spectra of the O-deacylated lipopolysaccharide and the lipid-free PS in conjunction with chemical shift predictions made by the CASPER program. The side-chain d-GalpA residue carries one equivalent of O-acetyl groups at the O-3 and O-4 positions distributed in the LPS in a 3:7 ratio, respectively. The presence of O-acetyl groups in the repeating unit of the E. coli O59 PS is consistent with the previously proposed acetyltransferase WclD in the O-antigen gene cluster.

Characterization of enterotoxigenic Escherichia coli strains isolated from Nicaraguan children in hospital, primary care and community settings

Enterotoxigenic Escherichia coli (ETEC) is one of the most common causes of diarrhoea among young children in developing countries. ETEC vaccines offer promise in reducing the burden of ETEC disease, but the development of these vaccines relies on the characterization of ETEC isolates from a variety of settings. To best reflect the full spectrum of ETEC disease in León, Nicaragua, the aim of this study was to characterize ETEC strains isolated from children with diarrhoea attending different settings (hospital, primary care clinics and in the community) and children from different age groups. We characterized ETEC isolates in terms of their colonization factors (CFs) and enterotoxins, and determined whether these factors varied with setting and age group. Diarrhoeal stool samples were obtained from children under the age of 60 months from: (1) the regional public hospital, (2) four public primary care clinics, and (3) a population-based cohort. In total, 58 ETEC-positive isolates were analysed by multiplex-PCR assays for the identification of CFs (CS1, CS2, CS3, CS4, CS5, CS6, CS7, CS8, CS12, CS13, CS14, CS15, CS17, CS18, CS19, CS20, CS21, CS22 and CFA/I), and enterotoxins [heat-labile toxin (LT) and heat-stable variants STh and STp]. The frequency of CFs and enterotoxins was compared among the three settings and for different age groups, using Fisher's exact test or a χ(2) test. At least one CF was detected among one-half of samples; CS19 was detected among all strains in which a CF was identified, either alone or in combination with another CF. Among all CFs detected, 91.7 % were identified as members of the class 5 fimbrial family. CFs were detected more commonly among samples from infants captured in the health facility setting compared with the community setting. Overall, LT was detected among 67.2 % of samples, STh was detected among 20.7 % and both enterotoxins were detected among 12.1 %. The enterotoxin STh was detected more commonly among cases in the community, whilst a combination of STh and LT was detected more commonly among cases treated in health facilities. Our results suggest that, to protect against diarrhoeal cases associated with this E. coli pathotype in León, Nicaragua, an ETEC vaccine that effectively targets the archeotype CFA/I of the class 5 fimbrial family would be the most effective in this setting.

Facile Structural Elucidation of Glycans Using NMR Spectroscopy Data and the Program CASPER: Application to the O-Antigen Polysaccharide of Escherichia coli O155

Time saver: The program CASPER was successfully employed to rapidly elucidate a new O-antigen polysaccharide structure (obtained from a strain of Escherichia coli serogroup O155), using solely unassigned NMR spectroscopy data as input information. Thus, what is considered the most tedious and time-consuming part of the structural elucidation process has been reduced from several hours (or even days) of manual interpretation to about four minutes of automated analysis.

In vitro activity of cadazolid against Clostridium difficile strains isolated from primary and recurrent infections in Stockholm, Sweden

One hundred thirty-three Clostridium difficile strains were collected from 71 patients and analyzed for the presence of C. difficile toxin B by the cell cytotoxicity neutralization assay, genes for toxin A, toxin B, binary toxin and TcdC deletion by PCR. All strains were also PCR-ribotyped and analyzed for sporulation frequency. The MICs of the isolates were determined against cadazolid and seven other antimicrobial agents by the agar dilution method. All isolates were positive for toxin B by the cell cytotoxicity neutralization assay. One hundred fourteen isolates were positive for toxin A and B and 16 isolates were positive for toxin A, toxin B and binary toxin by PCR. Three isolates were negative for toxin A but positive for toxin B. Thirty-three different ribotypes were identified. No strain of ribotype 027 was found. No differences in sporulation were noticed between the primary and recurrent isolates. All 133 isolates were sensitive to cadazolid (0.064-0.5 mg/l), fidaxomicin (0.008-0.125 mg/l), metronidazole (0.125-2 mg/l), vancomycin (0.125-1 mg/l) and tigecycline (0.032-0.25 mg/l). Three isolates were resistant to linezolid (8 mg/l), 15 isolates were resistant to moxifloxacin (8-32 mg/l) and 103 isolates were resistant to clindamycin (8-256 mg/l). No association between toxins A, B and binary toxin, ribotypes or the sporulation and the sensitivity to cadazolid could be found. Cadazolid has a potent in vitro activity against C. difficile.

Ecological impact of doxycycline at low dose on normal oropharyngeal and intestinal microflora

This study included 34 healthy volunteers (16 male and 18 female) aged 19-37 years, of whom 17 received doxycycline 40 mg capsules orally once daily (o.d.) and 17 received placebo 40 mg capsules orally o.d. for 16 weeks. Plasma, saliva and faecal samples were collected before drug administration and at 4, 8, 16 and 20 weeks. Plasma samples were assayed for doxycycline concentrations, and saliva and faecal samples were investigated for doxycycline concentrations and microbiological analyses. Plasma concentrations of doxycycline in the doxycycline group were as follows: baseline visit (2 h), 0.20-0.61 mg/L; 4-week visit, 0.30-1.04 mg/L; 8-week visit, 0.43-1.49 mg/L; 16-week visit, 0.32-1.12 mg/L; and 20-week visit 0 mg/L. No doxycycline was detected in plasma in the placebo group. No doxycycline concentrations in the saliva samples were found in the doxycycline or placebo groups at the five visits. Faecal concentrations of doxycycline in the doxycycline group were as follows: baseline visit, 0 mg/kg; 4-week visit, 0-3.71 mg/kg; 8-week visit, 0-1.85 mg/kg; 16-week visit, 0-4.10 mg/kg; and 20-week visit, 0 mg/kg. No doxycycline faecal concentrations were detected in the placebo group. Minor effects on the aerobic and anaerobic oropharyngeal microflora were observed both in the doxycycline and placebo groups. There were minor changes in the number of enterococci and Escherichia coli in the doxycycline and placebo groups. The anaerobic intestinal microflora in the doxycycline and placebo groups was not changed, and no Clostridium difficile strains were isolated.

Structural studies of the O-antigen polysaccharide from Escherichia coli O115 and biosynthetic aspects thereof

The structure of the O-antigen polysaccharide (PS) of Escherichia coli O115 has been investigated using a combination of component analysis and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy experiments. The repeating unit of the O-antigen was elucidated using the O-deacetylated PS and has the following branched pentasaccharide structure: →3)[β-L-Rhap-(1 → 4)]-β-D-GlcpNAc-(1 → 4)-α-D-GalpA-(1 → 3)-α-D-Manp-(1 → 3)-β-D-GlcpNAc-(1→. Cross-peaks of low intensity, corresponding to a β-L-Rhap-(1 → 4)-β-D-GlcpNAc-(1→ structural element, were present in the NMR spectra and attributed to the terminal part of the PS; this information defines the biological repeating unit of the O-antigen by having a 3-substituted N-acetyl-D-glucosamine (GlcNAc) residue at its reducing end. Analysis of the NMR spectra of the native PS revealed O-acetyl groups distributed over different positions of the l-Rhap residue (∼0.70 per repeating unit) as well as at O-2 and O-3 of the D-GalpA residue (∼0.03 and ∼0.25 per repeating unit, respectively), which is in agreement with the presence of two acetyltransferases previously identified in the O-antigen gene cluster (Wang Q, Ruan X, Wei D, Hu Z, Wu L, Yu T, Feng L, Wang L. 2010. Mol Cell Probes. 24:286-290.). In addition, the four glycosyltransferases initially identified in the O-antigen gene cluster of E. coli O115 were analyzed using BLAST, and the function of two of them predicted on the basis of similarities with glycosyltransferases from Shigella dysenteriae type 5 and 12, as well as E. coli O58 and O152.

Antibiotic resistance patterns of Escherichia coli isolates from different aquatic environmental sources in León, Nicaragua

Antibiotic-resistant bacteria have emerged due to the selective pressure of antimicrobial use in humans and animals. Water plays an important role in dissemination of these organisms among humans, animals and the environment. We studied the antibiotic resistance patterns among 493 Escherichia coli isolates from different aquatic environmental sources collected from October 2008 to May 2009 in León, Nicaragua. High levels of antibiotic resistance were found in E. coli isolates in hospital sewage water and in eight of 87 well-water samples. Among the resistant isolates from the hospital sewage, ampicillin, chloramphenicol, ciprofloxacin, nalidixic acid, trimethoprim-sulphamethoxazole was the most common multi-resistance profile. Among the resistant isolates from the wells, 19% were resistant to ampicillin, ceftazidime, ceftriaxone, cefotaxime, chloramphenicol, ciprofloxacin, gentamicin, nalidixic acid and trimethoprim-sulphamethoxazole. E. coli producing ESBL and harbouring bla(CTX-M) genes were detected in one of the hospital sewage samples and in 26% of the resistant isolates from the well-water samples. The bla(CTX-M-9) group was more prevalent in E. coli isolates from the hospital sewage samples and the bla(CTX-M-1) group was more prevalent in the well-water samples.

Structural studies and biosynthetic aspects of the O-antigen polysaccharide from Escherichia coli O174

The structure of the repeating unit of the O-antigenic polysaccharide (PS) from Escherichia coli O174 has been determined. Component analysis together with (1)H and (13)C NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by (1)H,(13)C-heteronuclear multiple-bond correlation and (1)H,(1)H-NOESY experiments. The PS is composed of tetrasaccharide repeating units with the following structure: [formula see text] Cross-peaks of low intensity were present in the NMR spectra consistent with a β-D-GlcpNAc-(1→2)-β-D-GlcpA(1→ structural element at the terminal part of the polysaccharide, which on average is composed of ∼15 repeating units. Consequently the biological repeating unit has a 3-substituted N-acetyl-D-galactosamine residue at its reducing end.

Effect of new antimicrobial agents on the ecological balance of human microflora

The human normal microflora is relatively stable at each ecological habitat under normal circumstances and acts as a barrier against colonization by potentially pathogenic microorganisms and against overgrowth of already present opportunistic microorganisms. Administration of antimicrobial agents causes disturbances in the ecological balance between the host and the normal microflora. The risk of emergence and spread of resistant strains between patients and dissemination of resistant determinants between microorganisms is reduced if colonization resistance is not disturbed by antimicrobial agents. In this article, the potential ecological effects of administration of new antimicrobial agents on the intestinal and oropharyngeal microflora are summarized. The review is based on clinical studies published during the past 10 years.

Structural studies of the O-antigenic polysaccharide from Plesiomonas shigelloides strain AM36565

The structure of the repeating unit of the O-antigenic polysaccharide from Plesiomonas shigelloides strain AM36565 has been determined. Component analysis and (1)H and (13)C NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by (1)H,(13)C heteronuclear multiple-bond correlation, (1)H,(1)H-NOESY, and (1)H,(13)C-HSQC-(1)H,(1)H-NOESY experiments. The O-antigen polysaccharide is composed of repeating units with the following structure: →3)-α-L-Rhap-(1→2)-α-L-Rhap-(1→4)[β-D-GalpNAc-(1→3)]-α-D-GlcpNAc-(1→, in which the monosaccharide side-chain substitutes the backbone in half of the repeating units. A matrix-assisted laser desorption/ionization mass spectrometry experiment suggested that the polysaccharide consists of two regions, one with tetrasaccharide repeating units and one with trisaccharide repeating units.

Antibiotic resistance patterns of intestinal Escherichia coli isolates from Nicaraguan children

In developing countries, diarrhoeal diseases are one of the major causes of death in children under 5 years of age. It is known that diarrhoeagenic Escherichia coli (DEC) is an important aetiological agent of infantile diarrhoea in Nicaragua. However, there are no recent studies on antimicrobial resistance among intestinal E. coli isolates in Nicaraguan children. The aim of the present study was to determine the antimicrobial resistance pattern in a collection of 727 intestinal E. coli isolates from the faeces of children in León, Nicaragua, between March 2005 and September 2006. All samples had been screened previously for the presence of DEC by multiplex PCR. Three hundred and ninety-five non-DEC isolates (270 from children with diarrhoea and 125 from children without diarrhoea) and 332 DEC isolates (241 from children with diarrhoea and 91 from children without diarrhoea) were analysed in this study. In general, antimicrobial resistance among the 727 intestinal E. coli isolates was high for ampicillin (60 %), trimethoprim–sulfamethoxazole (64 %) and chloramphenicol (11 %). Among individual E. coli categories, enteroaggregative E. coli isolates from children with and without diarrhoea exhibited significantly higher levels of resistance (P<0.05) to ampicillin and trimethoprim–sulfamethoxazole compared to the other E. coli categories. Resistance to ceftazidime and/or ceftriaxone and a pattern of multi-resistance was related to CTX-M-5- or CTX-M-15-producing E. coli isolates. The results suggest that E. coli isolates from Nicaraguan children have not reached the high levels of resistance to the most common antibiotics used for diarrhoea treatment as in other countries.

Effect of ceftaroline on normal human intestinal microflora

Ceftaroline is a new broad-spectrum cephalosporin being developed for the treatment of serious bacterial infections, including those caused by aerobic Gram-positive and Gram-negative bacteria. The purpose of the present study was to investigate the effect of administration of ceftaroline on the intestinal flora of healthy subjects. Twelve healthy subjects (6 males and 6 females), 20 to 41 years of age, received ceftaroline (600 mg) by intravenous infusion every 12 h (q12h) for 7 days. Plasma and feces were collected for determination of ceftaroline concentration and analysis of fecal flora. Fecal specimens were cultured on nonselective and selective media. Different colony types were counted, isolated in pure culture, and identified to the genus level. All new strains of colonizing bacteria were tested for susceptibility to ceftaroline. The concentrations of ceftaroline in plasma were as follows: on day 2, 17.5 to 34.8 mg/liter; on day 5, 19.7 to 33.2 mg/liter; and on day 7, 18.0 to 29.8 mg/liter. No ceftaroline concentrations were found on day -1, 9, 14, or 21. No measurable concentrations in feces were found on day -1, 2, 5, 7, 9, 14, or 21. There was a minor impact on the numbers of Escherichia coli strains, while the numbers of enterococci and Candida albicans strains were not affected. There were moderate decreases in the numbers of bifidobacteria and lactobacilli during the first 7 days, while the numbers of clostridia increased during the same period. No impact on the numbers of Bacteroides bacteria was noticed. No new colonizing aerobic or anaerobic bacteria resistant to ceftaroline (MIC >or= 4 mg/liter) were found. Ceftaroline had no significant ecological impact on the human intestinal microflora.

Genetic and structural relationships of Salmonella O55 and Escherichia coli O103 O-antigens and identification of a 3-hydroxybutanoyltransferase gene involved in the synthesis of a Fuc3N derivative

O-antigen (O-polysaccharide), a part of the outer membrane of Gram-negative bacteria, is one of the most variable cell constituents and is related to bacterial virulence. O-antigen diversity is almost entirely due to genetic variations in O-antigen gene clusters. In this study, the O-polysaccharide structures of Salmonella O55 and Escherichia coli O103 were elucidated by chemical analysis and nuclear magnetic resonance spectroscopy. It was found that the O-polysaccharides have similar pentasaccharide O-units, which differ only in one sugar (glucose versus N-acetylglucosamine) and in the N-acyl group (acetyl versus 3-hydroxybutanoyl) on 3-amino-3,6-dideoxy-d-galactose (d-Fuc3N). The Salmonella O55 antigen gene cluster was sequenced and compared with the E. coli O103 antigen gene cluster reported previously. The two gene clusters were found to share high-level similarity (DNA identity ranges from 53% to 76%), except for two putative acyl transferase genes (fdtC in Salmonella O55 and fdhC in E. coli O103) which show no similarity. Replacement of the fdtC gene in Salmonella O55 with the fdhC gene from E. coli O103 resulted in production of a modified O-antigen, which contains a 3-hydroxybutanoyl derivative of Fuc3N in place of 3-acetamido-3,6-dideoxygalactose. This finding strongly suggests that fdhC is a 3-hydroxybutanoyltransferase gene. The sequence similarity level suggested that the O-antigen gene clusters of Salmonella O55 and E. coli O103 originate from a common ancestor, and this evolutionary relationship is discussed.

Antibiotic resistance patterns in gram-negative and gram-positive bacteria causing septicemia in newborns in León, Nicaragua: correlation with environmental samples

The aim of this study was to identify the bacteria causing neonatal septicemia in a neonatal intensive care unit (NICU) in León, Nicaragua and its relation with bacteria isolated from the environment at the NICU. Our data showed that 74% (34/46) of the bacteria related to newborns with septicemia were Gram-negative and highly resistant to beta-lactams (>85%) and aminoglycosides (80%), leading to treatment failure in 10 neonates with fatal outcome. Although, the prevalence of Gram-positive bacteria (26%) was lower than Gram-negative bacteria, Staphylococcus epidermidis was related to the death of three newborns. No clonal similarity was found among Enterobacter cloacae , Escherichia coli and Serratia liquefaciens isolated from the neonates with septicemia and the NICU environment. However, in order to improve the outcome for neonates with septicemia, infection control practices and appropriate empirical therapy should be considered to reduce the high prevalence of extended-spectrum beta-lactamase (ESBL)-producing Gram-negative bacteria isolated from neonates with septicemia (80%) and from the NICU environment (34%).

Diversity of intestinal Escherichia coli populations in Nicaraguan children with and without diarrhoea

Escherichia coli remains an important aetiological agent of infantile diarrhoea in Nicaragua. However, little is known about whether there is a high prevalence of endemic strains or whether infection is due to the epidemic spread of virulent clones. This study was undertaken to determine the diversity and distribution of clonal groups in a population of intestinal E. coli isolated from the faeces of children from León, Nicaragua, with (n=381) and without (n=145) diarrhoea, between March 2005 and September 2006. All samples had been screened previously for the presence of diarrhoeagenic E. coli (DEC) markers by multiplex PCR. From each sample, 8 E. coli colonies (where available) were analysed by biochemical fingerprinting (PhP-RE system), yielding a total of 4009 tested isolates. On average, three different biochemical phenotypes (BPTs) were found among the eight colonies analysed from each sample. The total diversity, measured as Simpson's diversity index (Di), was 0.97 among all 4009 isolates studied. Cluster analysis of data from all 4009 isolates revealed 24 common BPTs (identified in at least 1 % of the isolates) and 234 less common BPTs. Similar Di values were obtained among isolates from infants with and without diarrhoea, indicating that no widespread outbreak of DEC had occurred. Moreover, among samples that were positive for the DEC types enteroaggregative E. coli, enteropathogenic E. coli and enterotoxigenic E. coli (ETEC) carrying the eltB gene, the diversities were almost as high as among non-DEC samples, whereas samples positive for ETEC carrying estA, enteroinvasive E. coli and enterohaemorrhagic E. coli showed lower diversities, indicating the prevalence of virulent clonal groups among these samples. The PhenePlate patterns of the 24 common BPTs identified here were compared with those obtained from E. coli isolated in a cohort infant study performed in 1991–1992 in the same area. Only 4 % of the isolates from the 1990s were similar to any of the common BPTs found in the present study.

Antimicrobial resistance in Clostridium difficile

Clostridium difficile is the leading cause of hospital-acquired diarrhoea and the number of outbreaks has risen markedly since 2003. The emergence and spread of resistance in C. difficile is complicating treatment and prevention. Most isolates are still susceptible to vancomycin and metronidazole (MTZ), however transient and heteroresistance to MTZ have been reported. The prevalence of resistance to other antimicrobial agents is highly variable in different populations and in different countries, ranging from 0% to 100%. Isolates of common polymerase chain reaction (PCR) ribotypes are more resistant than uncommon ribotypes. Most of the resistance mechanisms that have been identified in C. difficile are similar to those in other Gram-positive bacteria, including mutation, selection and acquisition of the genetic information that encodes resistance. Better antibiotic stewardship and infection control are needed to prevent further spread of resistance in C. difficile.

Structural studies of the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 94/D4 and the international type strain Escherichia coli O82

The structure of the O-antigen polysaccharides (PS) from the enteroaggregative Escherichia coli strain 94/D4 and the international type strain E. coli O82 have been determined. Component analysis and (1)H, (13)C, and (31)P NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by (1)H, (13)C-heteronuclear multiple-bond correlation, and (1)H, (1)H-NOESY experiments. D-GroA as a substituent is linked via its O-2 in a phosphodiester-linkage to O-6 of the alpha-D-Glcp residue. The PS is composed of tetrasaccharide repeating units with the following structure: -->4)-alpha-D-Glcp6-(P-2-D-GroA)-(1-->4)-beta-D-Galp-(1-->4)-beta-D-Glcp-(1-->3)-beta-D-GlcpNAc-(1--> Cross-peaks of low intensity from an alpha-D-Glcp residue were present in the NMR spectra and spectral analysis indicates that they originate from the terminal residue of the polysaccharide. Consequently, the biological repeating unit has a 3-substituted N-acetyl-D-glucosamine residue at its reducing end. Enzyme immunoassay using specific anti-E. coli O82 rabbit sera showed identical reactivity to the LPS of the two strains, in agreement with the structural analysis of their O-antigen polysaccharides.