Clustered cases of infections due to an uncommon methicillin-resistant Staphylococcus aureus originating in a maternity ward

OBJECTIVE

We aimed to report a community outbreak of an uncommon methicillin-resistant Staphylococcus aureus (MRSA) originating in a maternity ward.

PATIENTS AND METHODS

Cases were defined by epidemiological, clinical, and microbiological investigations. Microbiological investigations included phenotypic analysis, molecular typing, and whole-genome sequencing. To control the outbreak, we applied both national recommendations to prevent in-hospital transmission and the French High Council for Public Health guidelines on the management of community-acquired MRSA infections.

RESULTS

Between March and July 2016, seven patients with MRSA infections were identified: six skin and soft tissue infections and one pulmonary infection, including six microbiologically confirmed infections. Infections occurred in community settings, but a link with the same maternity ward was found for all patients. All MRSA strains had a t690 spa type, were tetracycline-resistant, and produced Panton-Valentine leukocidin. All isolates belonged to the sequence type 88 (ST88).

CONCLUSION

This outbreak highlights the largely underestimated risk of healthcare-associated infections in maternity wards. Healthcare workers should be aware of the importance of standard hygiene precautions and use of alcohol-based hand sanitizers for neonates and mothers.

Charge-Induced Force Noise on Free-Falling Test Masses: Results from LISA Pathfinder

We report on electrostatic measurements made on board the European Space Agency mission LISA Pathfinder. Detailed measurements of the charge-induced electrostatic forces exerted on free-falling test masses (TMs) inside the capacitive gravitational reference sensor are the first made in a relevant environment for a space-based gravitational wave detector. Employing a combination of charge control and electric-field compensation, we show that the level of charge-induced acceleration noise on a single TM can be maintained at a level close to 1.0  fm s^{-2} Hz^{-1/2} across the 0.1-100 mHz frequency band that is crucial to an observatory such as the Laser Interferometer Space Antenna (LISA). Using dedicated measurements that detect these effects in the differential acceleration between the two test masses, we resolve the stochastic nature of the TM charge buildup due to interplanetary cosmic rays and the TM charge-to-force coupling through stray electric fields in the sensor. All our measurements are in good agreement with predictions based on a relatively simple electrostatic model of the LISA Pathfinder instrument.

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1  fm s^{-2}/sqrt[Hz], or (0.54±0.01)×10^{-15}  g/sqrt[Hz], with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3)  fm/sqrt[Hz], about 2 orders of magnitude better than requirements. At f≤0.5  mHz we observe a low-frequency tail that stays below 12  fm s^{-2}/sqrt[Hz] down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

Synthesis of tritiated tuftsin and macrophage inhibitory tripeptide via acetylenic intermediates

Acetylenic analogues of tuftsin (Thr-Dah-Pro-Arg) and of a macrophage inhibitory tripeptide (Thr-Dah-Pro) have been synthesized by conventional procedures in solution (Dah = 2,6-diamino-4-hexynoic acid). These acetylenic derivatives are intermediates for the preparation of structurally unmodified, tritiated peptides. Catalytic tritiation of Thr-Dah-Pro-Arg and of Thr-Dah-Pro has afforded the radioactive tetra- and tripeptides with specific activities of 11.4 Ci/mmol and 37 Ci/mmol, respectively.

[Retrospective study of serological tests for syphilis diagnosis at Nantes University hospital, between 1999 and 2006]

Since 2000, a resurgence of syphilis cases was observed in France and, particularly, in Paris area. The aim of this study was to evaluate the evolution of syphilis prevalence in Nantes area and its impact on our laboratory activity. Between 1999 and 2006, serological tests for syphilis performed at the laboratory were analysed according to the results of these tests, the age and patient sex and the wards. We treated about 32,000 serological tests, over an eight-year period. The number of tests increased by 7.5% per year and patients with a positive result were multiplied by three. These patients were men for 78%, with an average age of 43.4 years. The serological tests providing positive results were in general from two sectors, the anonymous and free detection center and the internal medicine ward and infectious diseases unit. Our study highlighted a strong increase in the number of positive tests, since 2001, with a clear orientation towards a sex male ratio in our area. This inclination currently did not show any decrease, at the opposite to what was observed by the InVS in Paris area.

Isotopic scaling and the symmetry energy in spectator fragmentation

Isotopic effects in the fragmentation of excited target residues following collisions of 12C on (112,124)Sn at incident energies of 300 and 600 MeV per nucleon were studied with the INDRA 4pi detector. The measured yield ratios for light particles and fragments with atomic number Z < or = 5 obey the exponential law of isotopic scaling. The deduced scaling parameters decrease strongly with increasing centrality to values smaller than 50% of those obtained for the peripheral event groups. Symmetry-term coefficients, deduced from these data within the statistical description of isotopic scaling, are near gamma = 25 MeV for peripheral and gamma < 15 MeV for central collisions.

Evidence of a functional requirement for a carbamoylated lysine residue in MurD, MurE and MurF synthetases as established by chemical rescue experiments

Enzymes MurD, MurE, MurF, folylpolyglutamate synthetase and cyanophycin synthetase, which belong to the Mur synthetase superfamily, possess an invariant lysine residue (K198 in the Escherichia coli MurD numbering). Crystallographic analysis of MurD and MurE has recently shown that this residue is present as a carbamate derivative, a modification presumably essential for Mg(2+) binding and acyl phosphate formation. In the present work, the importance of the carbamoylated residue was investigated in MurD, MurE and MurF by site-directed mutagenesis and chemical rescue experiments. Mutant proteins MurD K198A/F, MurE K224A and MurF K202A, which displayed low enzymatic activity, were rescued by incubation with short-chain carboxylic acids, but not amines. The best rescuing agent was acetate for MurD K198A, formate for K198F, and propionate for MurE K224A and MurF K202A. In the last of these, wild-type levels of activity were recovered. A complementarity between the volume of the residue replacing lysine and the length of the carbon chain of the acid was noted. These observations support a functional role for the carbamate in the three Mur synthetases. Experiments aimed at recovering an active enzyme by introducing an acidic residue in place of the invariant lysine residue were also undertaken. Mutant protein MurD K198E was weakly active and was rescued by formate, indicating the necessity of correct positioning of the acidic function with respect to the peptide backbone. Attempts at covalent rescue of mutant protein MurD K198C failed because of its lack of reactivity towards haloacids.

Interaction of bacterial lipopolysaccharide with mouse surfactant protein C inserted into lipid vesicles

Infection of the respiratory tract is a frequent cause of lung pathologies, morbidity, and death. When bacterial endotoxin [lipopolysaccharide (LPS)] reaches the alveolar spaces, it encounters the lipid-rich surfactant that covers the epithelium. Although binding of hydrophilic surfactant protein (SP) A and SP-D with LPS has been established, nothing has been reported to date on possible cross talks between LPS and hydrophobic SP-B and SP-C. We designed a new binding technique based on the incorporation of surfactant components to lipid vesicles and the separation of unbound from vesicle-bound LPS on a density gradient. We found that among the different hydrophobic components of mouse surfactant separated by gel filtration or reverse-phase HPLC, only SP-C exhibited the capacity to bind to a tritium-labeled LPS. The binding of LPS to vesicles containing SP-C was saturable, temperature dependent, related to the concentrations of SP-C and LPS, and inhibitable by distinct unlabeled LPSs. Unlike SP-A and SP-D, the binding of SP-C to LPS did not require calcium ions. This LPS binding capacity of SP-C may represent another antibacterial defense mechanism of the lung.

Evidence for spinodal decomposition in nuclear multifragmentation

Multifragmentation of a "fused system" was observed for central collisions between 32 MeV/nucleon 129Xe and (nat)Sn. Most of the resulting charged products were well identified due to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but nonambiguous enhancement of events with nearly equal-sized fragments. Supported by dynamical calculations in which spinodal decomposition is simulated, this observed enhancement is interpreted as a "fossil" signal of spinodal instabilities in finite nuclear systems.

Synthesis and biochemical evaluation of some novel N-acyl phosphono- and phosphinoalanine derivatives as potential inhibitors of the D-glutamic acid-adding enzyme

A series of N-(5-phthalimidopentanoyl)-, N-[2-(2-ethoxy)acetyl]-, and N-(7-oxooctanoyl)-phosphono and phosphinoalanine derivatives has been synthesized and evaluated for inhibition of the D-glutamic acid-adding enzyme (MurD) of peptidoglycan biosynthesis.

"Open" structures of MurD: domain movements and structural similarities with folylpolyglutamate synthetase

UDP-N-acetylmuramoyl-l-alanine:d-glutamate (MurD) ligase catalyses the addition of d-glutamate to the nucleotide precursor UDP-N-acetylmuramoyl-l-alanine (UMA). The crystal structures of Escherichia coli in the substrate-free form and MurD complexed with UMA have been determined at 2.4 A and 1.88 A resolution, respectively. The MurD structure comprises three domains each of a topology reminiscent of nucleotide-binding folds. In the two structures the C-terminal domain undergoes a large rigid-body rotation away from the N-terminal and central domains. These two "open" structures were compared with the four published "closed" structures of MurD. In addition the comparison reveals which regions are affected by the binding of UMA, ATP and d-Glu. Also we compare and discuss two structurally characterized enzymes which belong to the same ligase superfamily: MurD and folylpolyglutamate synthetase (FGS). The analysis allows the identification of key residues involved in the reaction mechanism of FGS. The determination of the two "open" conformation structures represents a new step towards the complete elucidation of the enzymatic mechanism of the MurD ligase.

Shape coexistence and the N = 28 shell closure far from stability

The masses of 31 neutron-rich nuclei in the range A = 29-47 have been measured. The precision of 19 masses has been significantly improved and 12 masses were measured for the first time. The neutron-rich Cl, S, and P isotopes are seen to exhibit a change in shell structure around N = 28. Comparison with shell model and relativistic mean field calculations demonstrate that the observed effects arise from deformed prolate ground state configurations associated with shape coexistence. Evidence for shape coexistence is provided by the observation of an isomer in 43S.

Determination of the MurD mechanism through crystallographic analysis of enzyme complexes

UDP -N- acetylmuramoyl- L -alanine: D -glutamate (MurD) ligase catalyses the addition of d -glutamate to the nucleotide precursor UDP -N- acetylmuramoyl- L -alanine (UMA). The crystal structures of three complexes of Escherichia coli MurD with a variety of substrates and products have been determined to high resolution. These include (1) the quaternary complex of MurD, the substrate UMA, the product ADP, and Mg2+, (2) the quaternary complex of MurD, the substrate UMA, the product ADP, and Mn2+, and (3) the binary complex of MurD with the product UDP - N- acetylmuramoyl- L -alanine- D -glutamate (UMAG). The reaction mechanism supported by these structures proceeds by the phosphorylation of the C-terminal carboxylate group of UMA by the gamma-phosphate group of ATP to form an acyl-phosphate intermediate, followed by the nucleophilic attack by the amino group of D-glutamate to produce UMAG. A key feature in the reaction intermediate is the presence of two magnesium ions bridging negatively charged groups.

A comparative analysis of arranging in-flight oxygen aboard commercial air carriers

INTRODUCTION

As air travel has become more commonplace in today's society, so too has air travel by oxygen-using individuals. Because there is little oversight or standardization of in-flight oxygen by the Federal Aviation Administration, individual airlines' policies and practices may vary greatly. On the premise that such variation may cause confusion by prospective air travelers, we undertook the current study to describe individual air carriers' policies and practices and to provide guidance to future air travelers.

METHODS

Data were collected by a series of telephone calls placed by the study investigators to all commercial air carriers listed in the 1997 Cleveland Metropolitan Yellow Pages. The callers were registered respiratory therapists who identified themselves as inexperienced oxygen-requiring travelers wishing to arrange in-flight oxygen for an upcoming trip. Standard questions were asked of each carrier that included the following: Did the carrier have a special "help desk" to assist with oxygen arrangements? What oxygen systems, liter flow options, and interface devices were available? What was the charge for oxygen? How was the charged determined? What documentation from the physician was required? How much notification was required by the airline before the actual flight? In addition to recording these responses, the total amount of time spent on the telephone by the caller was logged along with the number of telephone calls and number of people spoken to in arranging in-flight oxygen. To compare oxygen charges between airlines, we calculated charges based on a "standard trip," which was defined as a nonstop, round-trip lasting 6 h in which the traveler used a flow rate of 2 L/min.

RESULTS

Of the 33 commercial air carriers listed in the directory, 11 were US-based carriers and 22 were international-based carriers. Seventy-six percent of the airlines offered in-flight oxygen. For the 25 carriers offering in-flight oxygen, mean phone time required to make the arrangements was 9.96+/-4.8 min (range, 3 to 20 min). No more than two telephone calls were required to make oxygen arrangements. Most carriers required 48- to 72-h advance notice, with a single carrier requiring 1-month advance notice. Most carriers required some notification of oxygen needs by the traveler's physician. There was a great variation in oxygen device and liter flow availability. Liter flow options ranged from only two flow rates (36% of carriers) to a range of 1 to 15 L/min (one carrier). All carriers offered nasal cannula, which was the only device available for 21 carriers (84%). Actual charges for in-flight oxygen also varied greatly. Six carriers supplied oxygen free and 18 carriers charged a fee (range, $64 to $1,500). One airline allowed the traveler to bring one "E" cylinder with no fee assessed. For 14 of the 18 carriers that charged, the charge for the standard trip ranged from $100 to $250.

CONCLUSIONS

(1) As expected from the lack of standard regulations, the availability, costs, and ease of implementing in-flight oxygen vary greatly among commercial air carriers. (2) Because the expense of in-flight oxygen is usually borne by the traveler (rather than by insurers), prospective travelers should consider charges for oxygen use when choosing an airline. (3) In the context that the current study shows substantial variation in oxygen policies, costs, and services among commercial air carriers and that such policies may change over time, our findings encourage the prospective air traveler needing in-flight oxygen to "shop around."

Large-scale preparation, purification, and crystallization of UDP-N-acetylmuramoyl-L-alanine: D-glutamate ligase from Escherichia coli

The UDP-N-acetylmuramoyl-L-alanine:D-glutamate ligase from Escherichia coli, an enzyme involved in the biosynthesis of the bacterial peptidoglycan monomer unit, was overproduced and purified to homogeneity on a large scale, yielding 4 mg of protein per liter of bacterial culture. Crystals of the complex with the substrate UDP-MurNAc-L-Ala were grown by the hanging drop method using ammonium sulfate as the precipitant. They are tetragonal with cell dimensions a = b = 65.5 A and c = 134.59 A, space group P4(1) or P4(3), and contain one monomer of 46,842 Da in the asymmetric unit. In order to use the multiple-wavelength anomalous diffraction method for phasing, a selenomethionine derivative of the protein has also been overproduced, purified, and crystallized.

Crystal structure of UDP-N-acetylmuramoyl-L-alanine:D-glutamate ligase from Escherichia coli

UDP-N-acetylmuramoyl-L-alanine:D-glutamate ligase (MurD) is a cytoplasmic enzyme involved in the biosynthesis of peptidoglycan which catalyzes the addition of D-glutamate to the nucleotide precursor UDP-N-acetylmuramoyl-L-alanine (UMA). The crystal structure of MurD in the presence of its substrate UMA has been solved to 1.9 A resolution. Phase information was obtained from multiple anomalous dispersion using the K-shell edge of selenium in combination with multiple isomorphous replacement. The structure comprises three domains of topology each reminiscent of nucleotide-binding folds: the N- and C-terminal domains are consistent with the dinucleotide-binding fold called the Rossmann fold, and the central domain with the mononucleotide-binding fold also observed in the GTPase family. The structure reveals the binding site of the substrate UMA, and comparison with known NTP complexes allows the identification of residues interacting with ATP. The study describes the first structure of the UDP-N-acetylmuramoyl-peptide ligase family.

Effect of analogues of diaminopimelic acid on the meso-diaminopimelate-adding enzyme from Escherichia coli

Several analogues of diaminopimelic acid (A2pm) were tested as substrates or inhibitors of the meso-diaminopimelate-adding enzyme from Escherichia coli. They included lanthionine derivatives, a phosphonic analogue, heterocyclic compounds, 3-fluoro-A2pm, 4-methylene-A2pm and N-hydroxy-A2pm. The best substrates were, in decreasing order of specific enzyme activity, (2S,3R,6S)-3-fluoro-A2pm, meso-lanthionine sulfoxide and N-hydroxy-A2pm (mixture of stereoisomers). In those cases where all the stereoisomers were available, the specificity could be described as meso > > DD approximately to LL. N-Hydroxy-A2pm (mixture of stereoisomers) strongly inhibited the addition of radioactive meso-A2pm to UDP-N-acetylmuramoyl-dipeptide.

Purification and partial characterization of a hepatocyte antiproliferative glycopeptide

A low molecular weight compound, which inhibits the G1-S transition in rat hepatocytes, was obtained by tryptic hydrolysis of human alpha 2-macroglobulin followed by ultrafiltration at pH 10. It was purified by high-performance liquid chromatography on mu Bondapak C18 and mu Bondapak NH2 with a practically quantitative yield; from 5.1 g of alpha 2-macroglobulin, 2.8 micrograms of purified compound were recovered. Inactivation by specific enzymes and chemical analyses showed that the inhibitor is a sialylated glycopeptide whose peptide moiety contains a pyroglutamyl residue. Its molecular mass, estimated by gel permeation chromatography, would be in the interval 3,500-4,600. However, amino acid analyses indicated that it is not yet pure. All these data suggest that alpha 2-macroglobulin could be the carrier of the precursor form of the glycopeptide.

Synthesis and biological activity of eight thymulin analogues

Eight analogues of thymulin, a thymic nonapeptide involved in several aspects of T-cell differentiation, were synthesized by the conventional method in solution. Four were modified in residue 7 (Ala, D-Ala, D-Leu or Sar instead of Gly) and two in residue 8 (D-Ser or Thr instead of Ser); in the others, the Gly6-Gly7 sequence was replaced either by a single glycyl residue or by a triglycyl sequence. The biological activity of the analogues was determined in the rosette assay: five exhibited a prolonged activity in vivo with respect to thymulin. All the analogues inhibited the binding of tritiated thymulin to thymulin receptors on three human lymphoblastoid T-cell lines (HSB2, 1301 and CEM) with the same order of magnitude as non-labelled thymulin.

Partial purification of rat and human serum factors inhibiting the G1-S transition in rat hepatocytes

A low molecular weight compound, which inhibits the G1-S transition in rat hepatocytes, was purified from rat trypsin-treated serum by DEAE-cellulose chromatography and high-performance liquid chromatography on three different stationary phases. This procedure led to a 34500-fold purification with a 29% yield. Inactivation of the purified material by specific enzymes showed that the inhibitor is a glycopeptide containing a peptide moiety, N-acetylneuraminic acid and galactose residues. Amino acid analyses indicated the possible existence of a pentapeptide structure. The same purification procedure was applied to the corresponding human inhibitor. Inactivation by specific enzymes showed that it is also a glycopeptide.

Synthesis of an immunogenic conjugate and of two 125I-labelled derivatives of the "facteur thymique sérique"

[4-Aminobenzoyl-Gln1]FTS was synthesized from a suitably-protected derivative of the "facteur thymique sérique" (FTS). It was diazotized and coupled to bovine serum albumin, yielding an immunogenic conjugate in which all the functional groups of the peptide remained intact. [4-Aminobenzoyl-Gln1]FTS and another synthetic ćompound, [3-(4-hydroxyphenyl)propionyl-Gln1]FTS, were 125I-labelled. The binding of these radioactive peptides of the anti-FTS antibodies obtained with our immunogenic conjugate was inhibited by unlabelled FTS.

Synthesis of analogs of the serum thymic nonapeptide, "facteur thymique serique" (FTS). Part II

New analogs of FTS (Facteur Thymique Sérique), less than (Formula: see text), a circulating thymic factor, were prepared by replacing the amino acid residues in positions, 1, 3, 4, 5, 6 and 3 and 6 together. Five other analogs of C-terminal heptapeptide were prepared by replacing the amino acid residues in position 3 or 6. These peptides were synthesized using conventional synthesis in solution.

Synthesis of analogs of the serum thymic nonapeptide, "facteur thymique serique" (FTS). Part I

Analogs of FTS (Facteur Thymique Sérique), less than :formula: (see text), a circulating thymic factor, were prepared by replacing the amino acid residues in positions 1, 2, 8 and 9, or by shortening the nonapeptide chain at the N- or C-terminal end. These peptides were synthesized by two different schemes using the conventional synthesis in solution.