Air-stable Perylene Diimide Trimer Material for n-type Organic Electrochemical Transistors

We report a new method to make air-stable n-type organic mixed ionic-electronic conductor (OMIEC) films for organic electrochemical transistors (OECTs) using a solution-processable small molecule helical perylene diimide trimer, hPDI[3]-C11. Alkyl side chains were attached to the conjugated core for processability and film making, which were then cleaved via thermal annealing. After the sidechains were removed, the hPDI[3] film becomes less hydrophobic, more ordered, and has a deeper lowest unoccupied molecular orbital (LUMO). These features provide improved ionic transport, greater electronic mobility, and increased stability in air and in aqueous solution. Subsequently, we use hPDI[3]-H as the active material in OECTs and demonstrate a device with a transconductance of 44 mS, volumetric capacitance of ∼250 F/cm3, µC* value of 1 F/cmVs, and excellent stability (> 5 weeks). As proof of their practical applications, we utilize a hPDI[3]-H-based OECTs as a glucose sensor and electrochemical inverter. The approach of side chain removal after film formation charts a path to a wide range of molecular semiconductors to be used as stable, mixed ionic-electronic conductors. This article is protected by copyright. All rights reserved.

High-Performance Wearable Organic Photodetectors by Molecular Design and Green Solvent Processing for Pulse Oximetry and Photoplethysmography

White-light detection from the visible to the near-infrared region is central to many applications such as high-speed cameras, autonomous vehicles, and wearable electronics. While organic photodetectors (OPDs) are being developed for such applications, several challenges must be overcome to produce scalable high-detectivity OPDs. This includes issues associated with low responsivity, narrow absorption range, and environmentally friendly device fabrication. Here, an OPD system processed from 2-methyltetrahydrofuran (2-MeTHF) sets a record in light detectivity, which is also comparable with commercially available silicon-based photodiodes is reported. The newly designed OPD is employed in wearable devices to monitor heart rate and blood oxygen saturation using a flexible OPD-based finger pulse oximeter. In achieving this, a framework for a detailed understanding of the structure-processing-property relationship in these OPDs is also developed. The bulk heterojunction (BHJ) thin films processed from 2-MeTHF are characterized at different length scales with advanced techniques. The BHJ morphology exhibits optimal intermixing and phase separation of donor and acceptor moieties, which facilitates the charge generation and collection process. Benefitting from high charge carrier mobilities and a low shunt leakage current, the newly developed OPD exhibits a specific detectivity of above 1012  Jones over 400-900 nm, which is higher than those of reference devices processed from chlorobenzene and ortho-xylene.

Additive-free molecular acceptor organic solar cells processed from a biorenewable solvent approaching 15% efficiency

We report on the use of molecular acceptors (MAs) and donor polymers processed with a biomass-derived solvent (2-methyltetrahydrofuran, 2-MeTHF) to facilitate bulk heterojunction (BHJ) organic photovoltaics (OPVs) with power conversion efficiency (PCE) approaching 15%. Our approach makes use of two newly designed donor polymers with an opened ring unit in their structures along with three molecular acceptors (MAs) where the backbone and sidechain were engineered to enhance the processability of BHJ OPVs using 2-MeTHF, as evaluated by an analysis of donor-acceptor (D-A) miscibility and interaction parameters. To understand the differences in the PCE values that ranged from 9-15% as a function of composition, the surface, bulk, and interfacial BHJ morphologies were characterized at different length scales using atomic force microscopy, grazing-incidence wide-angle X-ray scattering, resonant soft X-ray scattering, X-ray photoelectron spectroscopy, and 2D solid-state nuclear magnetic resonance spectroscopy. Our results indicate that the favorable D-A intermixing that occurs in the best performing BHJ film with an average domain size of ∼25 nm, high domain purity, uniform distribution and enhanced local packing interactions - facilitates charge generation and extraction while limiting the trap-assisted recombination process in the device, leading to high effective mobility and good performance.

Green-Solvent-Processed High-Performance Broadband Organic Photodetectors

Solution-processed organic photodetectors with broadband activity have been demonstrated with an environmentally benign solvent, ortho-xylene (o-xylene), as the processing solvent. The organic photodetectors employ a wide band gap polymer donor PBDB-T and a narrow band gap small-molecule non-fullerene acceptor CO1-4F, both dissolvable in o-xylene at a controlled temperature. The o-xylene-processed devices have shown external quantum efficiency of up to 70%, surpassing the counterpart processed with chlorobenzene. With a well-suppressed dark current, the device can also present a high specific detectivity of over 1012 Jones at -2 V within practical operation frequencies and is applicable for photoplethysmography with its fast response. These results further highlight the potential of green-solvent-processed organic photodetectors as a high-performing alternative to their counterparts processed in toxic chlorinated solvents without compromising the excellent photosensing performance.

Observing the onset of pressure-driven K-shell delocalization

The gravitational pressure in many astrophysical objects exceeds one gigabar (one billion atmospheres)^1-3, creating extreme conditions where the distance between nuclei approaches the size of the K shell. This close proximity modifies these tightly bound states and, above a certain pressure, drives them into a delocalized state⁴. Both processes substantially affect the equation of state and radiation transport and, therefore, the structure and evolution of these objects. Still, our understanding of this transition is far from satisfactory and experimental data are sparse. Here we report on experiments that create and diagnose matter at pressures exceeding three gigabars at the National Ignition Facility⁵ where 184 laser beams imploded a beryllium shell. Bright X-ray flashes enable precision radiography and X-ray Thomson scattering that reveal both the macroscopic conditions and the microscopic states. The data show clear signs of quantum-degenerate electrons in states reaching 30 times compression, and a temperature of around two million kelvins. At the most extreme conditions, we observe strongly reduced elastic scattering, which mainly originates from K-shell electrons. We attribute this reduction to the onset of delocalization of the remaining K-shell electron. With this interpretation, the ion charge inferred from the scattering data agrees well with ab initio simulations, but it is significantly higher than widely used analytical models predict⁶.

Unraveling Device Physics of Dilute-Donor Narrow-Bandgap Organic Solar Cells with Highly Transparent Active Layers

The charge generation-recombination dynamics in three narrow-bandgap near-IR absorbing nonfullerene (NFA) based organic photovoltaic (OPV) systems with varied donor concentrations of 40%, 30%, and 20% are investigated. The dilution of the polymer donor with visible-range absorption leads to highly transparent active layers with blend average visible transmittance (AVT) values of 64%, 70%, and 77%, respectively. Opaque devices in the optimized highly reproducible device configuration comprising these transparent active layers lead to photoconversion efficiencies (PCEs) of 7.0%, 6.5%, and 4.1%. The investigation of these structures yields quantitative insights into changes in the charge generation, non-geminate charge recombination, and extraction dynamics upon dilution of the donor. Lastly, this study gives an outlook for employing the highly transparent active layers in semitransparent organic photovoltaics (ST-OPVs).

Efficient Fabrication of Organic Electrochemical Transistors via Wet Chemical Processing

A wet processing method to fabricate high-performance organic electrochemical transistors (OECTs) is reported. Wet chemical processing enables a simple and reliable patterning step, substituting several complex and expensive cleanroom procedures in the fabrication of OECTs. We fabricate depletion-mode OECTs based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and enhancement-mode OECTs based on a conjugated polyelectrolyte PCPDTBT-SO₃K on rigid and flexible substrates using this wet processing method. We show that the wet chemical processing step can also serve as a chemical treatment to enhance the electrical properties of the active material in OECTs. To highlight the potential of the fabrication process in applications, a transistor-based chemical sensor is demonstrated, capable of detecting methylene blue, a popular redox reporter in biodetection and immunoassays, with good detectivity. Given the tremendous potential of OECTs in emerging technologies such as biosensing and neuromorphic computing, this simple fabrication process established herein will render the OECT platform more accessible for research and applications.

Resolving Atomic-Scale Interactions in Nonfullerene Acceptor Organic Solar Cells with Solid-State NMR Spectroscopy, Crystallographic Modelling, and Molecular Dynamics Simulations

Fused-ring core nonfullerene acceptors (NFAs), designated "Y-series," have enabled high-performance organic solar cells (OSCs) achieving over 18% power conversion efficiency (PCE). Since the introduction of these NFAs, much effort has been expended to understand the reasons for their exceptional performance. While several studies have identified key optoelectronic properties that govern high PCEs, little is known about the molecular level origins of large variations in performance, spanning from 5% to 18% PCE, for example, in the case of PM6:Y6 OSCs. Here, a combined solid-state NMR, crystallography, and molecular modeling approach to elucidate the atomic-scale interactions in Y6 crystals, thin films, and PM6:Y6 bulk heterojunction (BHJ) blends is introduced. It is shown that the Y6 morphologies in BHJ blends are not governed by the morphology in neat films or single crystals. Notably, PM6:Y6 blends processed from different solvents self-assemble into different structures and morphologies, whereby the relative orientations of the sidechains and end groups of the Y6 molecules to their fused-ring cores play a crucial role in determining the resulting morphology and overall performance of the solar cells. The molecular-level understanding of BHJs enabled by this approach will guide the engineering of next-generation NFAs for stable and efficient OSCs.

Insights into the Structural and Morphological Properties of Layer-by-Layer Processed Organic Photovoltaics

Recently, with the development of figure-of-merit non-fullerene acceptor materials combined with a ternary strategy and layer-by-layer (LbL) processing, the efficiency of single-junction organic solar cells has exceeded 18%. However, the structural properties of LbL-processed films have not been sufficiently elucidated. Herein, we systematically investigate films fabricated via LbL processing of three different systems, including a ternary system. In particular, we focus on the structural and morphological transitions associated with the diffusion process controlled by thermal annealing and an additive solvent. Different diffusion and crystal formation mechanisms were clearly identified, which were observed to be dependent on the characteristics of the upper layer formed during the LbL process. Based on this insight, the photovoltaic properties associated with various LbL conditions are elucidated, and an ideal path toward a better device is suggested.

Alkyl Conformation and π-π Interaction Dependent on Polymorphism in the 1,8-Naphthalimide (NI) Derivative

The 1,8-naphthalimide (NI) derivative Lumogen F Violet 570 exhibits different photoluminescence (PL) and aggregation-caused quenching properties due to its crystal polymorphism, which depends on the solvent evaporation process in tetrahydrofuran solution. In the slow drying process, molecules aggregated into an energetically more stable form (time-dependent density functional theory calculation), of which the PL peak maximum was 453 nm, corresponding to blue emission at the 365 nm excitation. However, the fast evaporation process induces an energetically less stable form, with a PL peak maximum of 508 nm, corresponding to green emission. The main difference between the two crystal structures is the alkyl conformation, as confirmed by X-ray single-crystal analysis. Due to the different alkyl conformations, NI groups aggregated into more obliquely aligned structures that emit blue PL, which plays a role in weakening the π-π interactions between molecules relative to green PL crystals. We found that the conformational stable molecular stacking induced instability in the electronic energy levels of the blue crystal compared to the green crystal.

Manipulating the crystal structure of a conjugated polymer for efficient sequentially processed organic solar cells

Recently, the sequential (Sq) process, which forms nanoscale network structures from quasi-solid-state inter-diffusion through swelling and annealing, is considered to be one of the most efficient methods for fabricating organic solar cells and blend films. Here, we examined the effect of the crystallinity and orientation of poly(3-hexylthiophene) (P3HT) molecules on the formation of the nanostructure by carrying out a Sq process using various solvents with different boiling points. We showed that the moderate crystallinity promoted suitable inter-diffusion between the donor (P3HT) and acceptor ([6,6]-pentadeuterophenyl C61 butyric acid methyl ester, PC₆₀BM), and hence was important for achieving high-performance solar cells using Sq processing. Nanostructure formation by inter-diffusion was investigated and visualized by taking a combination of grazing-incidence wide-angle X-ray scattering (GIWAXS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements. In addition, our Sq-processed solar cell yielded a device efficiency as high as 3.25%, and was also impressive because it was made with an eco-friendly solvent and using a short-duration annealing process, in contrast to the conventional BHJ process. The present findings provided advanced insight into the Sq process, and we anticipate this efficacious sequential process to contribute not only to the development of higher-efficiency organic solar cells but also to the fabrication of functional blend films.

Using time-resolved penumbral imaging to measure low hot spot x-ray emission signals from capsule implosions at the National Ignition Facility

We have developed and fielded a new x-ray pinhole-imaging snout that exploits time-resolved penumbral imaging of low-emission hot spots in capsule implosion experiments at the National Ignition Facility. We report results for a series of indirectly driven Be capsule implosions that aim at measuring x-ray Thomson scattering (XRTS) spectra at extreme density conditions near stagnation. In these implosions, x-ray emission at stagnation is reduced by 100-1000× compared to standard inertial confinement fusion (ICF) implosions to mitigate undesired continuum background in the XRTS spectra. Our snout design not only enables measurements of peak x-ray emission times, t _o , where standard ICF diagnostics would not record any signal, but also allows for inference of hot spot shapes. Measurement of t _o is crucial to account for shot-to-shot variations in implosion velocity and therefore to benchmark the achieved plasma conditions between shots and against radiation hydrodynamic simulations. Additionally, we used differential filtering to infer a hot spot temperature of 520 ± 80 eV, which is in good agreement with predictions from radiation hydrodynamic simulations. We find that, despite fluctuations of the x-ray flash intensity of up to 5×, the emission time history is similar from shot to shot and slightly asymmetric with respect to peak x-ray emission.

Using Femtosecond Laser Irradiation to Enhance the Vertical Electrical Properties and Tailor the Morphology of a Conducting Polymer Blend Film

We report femtosecond infrared laser-induced selective tailoring of carrier transport as well as surface morphology on a conducting polymer blend thin film. Maximal 2.4 times enhancement on vertical current transport in poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester, was achieved by this irradiation. The laser irradiation induced a photo expansion without deteriorating its molecular structure and the film morphology could be customized in the micron scale by adjusting the laser writing parameters. In the photoexpanded region, the face-on populations were about 2.2 times larger in comparison with the pristine region, which was a major contributor to the enhanced carrier transport.

P2-09-13: The Value of FDG PET/CT in Screening Detected Breast Cancer Patients

Background. To evaluate the diagnostic value of FDG PET/CT for initial staging of screening detected breast cancer.

Methods. Between January 2008 and June 2010, a total of 77 women (mean age 54 years, range 31–77 years) with screening detected primary breast cancer (mean invasive tumor size 1.65cm, range 1–70mm) underwent whole body fluorine-18 fluorodeoxyglucose (FDG) PET/CT for initial staging and were included in this retrospective study. Two patients had bilateral breast cancer. The sensitivity of FDG PET/CT for the detection of primary tumor and the sensitivity, specificity, PPV and NPV for the detection of axillary lymph node metastases were determined. Systemic staging with whole body FDG PET/CT was also performed. For analysis of diagnostic performance of FDG PET/CT, quantitative measurement of the maximum standardized uptake value (SUVmax) criteria 1.0 was used. The final histopathology following surgery served as the gold standard.

Results. The primary tumor was FDG PET/CT positive in 65 of 79 lesions (82%). Depending on the tumor size, there was a variation in diagnostic sensitivity (63% in ≤ 1cm tumor, n=19 vs. 88% in > 1cm tumor, n=60) and the uptake of FDG was significantly higher in > 1cm tumor than in ≤ 1cm tumor (mean SUVmax 2.85 vs. 1.11, p<0.05). The uptake of FDG was significantly higher in ductal carcinomas compared to lobular carcinomas (median SUVmax 2.0, n=72 vs. 1.3, n=7, p<0.05). Of the 77 patients included in this study, 16 patients were found to have axillary node metastasis. The sensitivity, specificity, PPV and NPV of FDG PET/CT for detection of LN metastasis were 63% (10/16), 89% (54/61), 59% (10/17) and 90% (54/60), respectively. FDG PET/CT showed distant uptake in 9 patients and 8 of 9 were false positive results. 4 lesions were confirmed histopathologically as benign and 4 lesions were evaluated with radiologic methods. One of nine was true positive result. Distant involvement was skeletal and visible on the conventional bone scintigraphy. The patient staged as cT1N3M1.

Conclusion. FDG PET/CT has limited value for the initial staging of screening detected breast cancer patients. Considering high costs, radiation exposure and false positivity, FDG PET-CT is not recommended for the preoperative evaluation of screening detected breast cancer patients.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-09-13.

Correlation between mammographic and sonographic findings and prognostic factors in patients with node-negative invasive breast cancer

OBJECTIVES

The purpose of this study was to correlate sonographic and mammographic findings with prognostic factors in patients with node-negative invasive breast cancer.

METHODS

Sonographic and mammographic findings in 710 consecutive patients (age range 21-81 years; mean age 49 years) with 715 node-negative invasive breast cancers were retrospectively evaluated. Pathology reports relating to tumour size, histological grade, lymphovascular invasion (LVI), extensive intraductal component (EIC), oestrogen receptor (ER) status and HER-2/neu status were reviewed and correlated with the imaging findings. Statistical analysis was performed using logistic regression analysis and intraclass correlation coefficient (ICC).

RESULTS

On mammography, non-spiculated masses with calcifications were associated with all poor prognostic factors: high histological grade, positive LVI, EIC, HER-2/neu status and negative ER. Other lesions were associated with none of these poor prognostic factors. Hyperdense masses on mammography, the presence of mixed echogenicity, posterior enhancement, calcifications in-or-out of masses and diffusely increased vascularity on sonography were associated with high histological grade and negative ER. Associated calcifications on both mammograms and sonograms were correlated with EIC and HER-2/neu overexpression. The ICC value for the disease extent was 0.60 on mammography and 0.70 on sonography.

CONCLUSION

Several sonographic and mammographic features can have a prognostic value in the subsequent treatment of patients with node-negative invasive breast cancer. Radiologists should pay more attention to masses that are associated with calcifications because on both mammography and sonography associated calcifications were predictors of positive EIC and HER-2/neu overexpression.

Distortionless large-ratio stretcher for ultra-short pulses using photonic crystal fiber

A large-ratio stretcher for ultra-short pulses is proposed based on photonic crystal fiber (PCF). Through proper design of the PCF structure, we obtain over 300-nm wavelength range with flattened dispersion characteristics. Analysis indicates that 1-km of such fiber can broaden over 10,000 times for ultra-short pulses with <100-fs pulse-width. Distortion due to dispersion and nonlinearity is negligible.

Sexual practices and prevalence of HIV, HTLV-I/II, and Treponema pallidum among clandestine female sex workers in Lima, Peru

BACKGROUND AND OBJECTIVES

A survey was conducted to determine the sexual behavior practices and prevalence of HIV-1, HTLV-I/II, and T. pallidum infections among unlicensed female sex workers (FSWs) in Lima, Peru.

GOAL OF THIS STUDY

To assess the role of unlicensed FSWs as a potential source of retroviral and T. pallidum infection.

STUDY DESIGN

Female sex workers from 15 brothels were enrolled. Sera samples were obtained and tested for antibodies to HIV-1, HTLV-I, and Treponema pallidum.

RESULTS

Of 158 FSWs studied, all were negative for HIV-1, 6 were positive for HTLV-I, and 5 were positive for Treponema pallidum. Of their male clients, 75% used condoms, whereas only 3% reported condom use with their steady partners. When condoms were always used by clients, the history of a sexually transmitted disease was significantly reduced (p < 0.01), and the prevalence of HTLV-I (p < 0.05) and syphilis was lower among these workers.

CONCLUSION

Data suggested that the low rate of sexually transmitted diseases among FSWs reflected the high rate of condom use by their male clients.

Topographical distribution of [125I]-glial cell line-derived neurotrophic factor in unlesioned and MPTP-lesioned rhesus monkey brain following a bolus intraventricular injection

The present study determined the topographical distribution profile for [125I]-glial cell line-derived neurotrophic factor in unlesioned and MPTP-lesioned (unilateral intracarotid injection) rhesus monkeys following an intraventricular injection. Autoradiographic analysis showed that following a bolus intraventricular injection, there was widespread distribution of [125I]-glial cell line-derived neurotrophic factor throughout the ventricular system (walls of lateral, third, and fourth ventricles and aqueduct), with some accumulation at the lateral ventricle injection site, possibly associated with the ependymal cell layer. In both unlesioned and MPTP-lesioned monkeys, there was labelling of the cerebral cortex, substantia nigra/ventral tegmental area and sequestration of [125I]-glial cell line-derived neurotrophic factor adjacent to the hippocampal formation, globus pallidus, ventral to and in the substantia nigra. However, [125I]-glial cell line-derived neurotrophic factor did not appear to diffuse readily or accumulate in the caudate-putamen even though there was some penetration away from the ventricular walls. Throughout the brain, there was also substantial non-parenchymal labelling of [125I]-glial cell line-derived neurotrophic factor, possibly associated with extracellular matrix components, meninges and vasculature due to the heparin binding properties of glial cell line-derived neurotrophic factor. In addition to the extensive loss of tyrosine hydroxylase immunoreactivity within the substantia nigra, there was also decreased accumulation of [125I]-glial cell line-derived neurotrophic factor and reduced glial cell line-derived neurotrophic factor immunoreactivity ipsilateral to the lesion. Microscopic analysis showed that glial cell line-derived neurotrophic factor immunoreactivity was associated with upper cortical layers including a high density of immunoreactivity at the surface of the cortex (meningeal, pial layer, vasculature) and around the ventricular walls (with some cellular labelling and labelling of vasculature). Moderate staining was observed in nigral cells contralateral to the MPTP-lesion, whereas only minimal levels of that glial cell line-derived neurotrophic factor immunoreactivity were detected ipsilateral to the lesion. This study shows that intraventricularly injected glial cell line-derived neurotrophic factor accumulates not only around the ventricular walls, but also in specific brain regions in which sub-populations of cells are more readily accessible than others. The presence of cells labelled with [125I] and immunopositive for glial cell line-derived neurotrophic factor in the substantia nigra indicates that these cells are a target for the trophic factor following intraventricular administration. Thus, the behavioral improvement observed in MPTP-lesioned monkeys following an intraventricular injection of glial cell line-derived neurotrophic factor is likely the result of activation of nigral cells.

Functional recovery in parkinsonian monkeys treated with GDNF

Parkinson's disease results from the progressive degeneration of dopamine neurons that innervate the striatum. In rodents, glial-cell-line-derived neurotrophic factor (GDNF) stimulates an increase in midbrain dopamine levels, protects dopamine neurons from some neurotoxins, and maintains injured dopamine neurons. Here we extend the rodent studies to an animal closer to the human in brain organization and function, by evaluating the effects of GDNF injected intracerebrally in rhesus monkeys that have had the symptomatology and pathophysiological features of Parkinson's disease induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The recipients of GDNF displayed significant improvements in three of the cardinal symptoms of parkinsonism: bradykinesia, rigidity and postural instability. GDNF administered every four weeks maintained functional recovery. On the lesioned side of GDNF-treated animals, dopamine levels in the midbrain and globus pallidus were twice as high, and nigral dopamine neurons were, on average, 20% larger, with an increased fibre density. The results indicate that GDNF may be of benefit in the treatment of Parkinson's disease.

Clinical characteristics and risk factors for Vibrio cholerae infection in children

Surveillance was conducted during February and March 1991 in the pediatric emergency department of Cayetano Heredia Hospital, Lima, Peru, to contrast the characteristics of children with epidemic cholera with those of children with noncholera-associated diarrhea. Among 626 patients 14 years of age or younger, Vibrio cholerae O1 was isolated from stool specimens of 310 patients (49%), more commonly from children older than 24 months of age (66%; p < 0.0001) than from younger children. Cholera was clinically characterized by a more sudden onset; watery diarrhea; and associated abdominal pain, muscle cramps, and vomiting, which led to more severe dehydration and hospitalization more often than in noncholera cases. Only one patient with cholera died, for a case-fatality rate of 3.2 deaths per 1000 persons. Nonpotable water and uncooked foods were identified as probable vehicles for V. cholerae. The frequency of diarrhea among relatives of patients with cholera suggested intrafamily transmission. This study of epidemic cholera describes the clinical features and the risk factors for acquisition of the infection, and points out the low case-fatality rate with prompt and appropriate treatment.

Clindamycin plus amikacin versus clindamycin plus aztreonam in established intraabdominal infections

BACKGROUND

A prospective, randomized, single-blind study evaluated the efficacy and safety of clindamycin plus amikacin versus clindamycin plus aztreonam (Cl-Az) in treating intraabdominal infections in adults.

METHODS

Patients were treated intravenously for 7 to 10 days, clindamycin 900 mg plus amikacin 5.0 mg/kg three times a day or clindamycin 900 mg plus aztreonam 2.0 gm three times a day. All 67 patients enrolled were evaluated for safety and 31 in each group for clinical and microbiologic response. Both groups were similar in initial diagnosis, perforated appendicitis or intraabdominal abscess. In each group 24 patients (77%) were admitted in serious condition and three (10%) in critical condition. Twenty-five patients (80.6%) in each group had aerobic and anaerobic pathogens; the remainder had either aerobic or anaerobic pathogens.

RESULTS

On therapy completion, clinical and bacteriologic responses were as follows: clindamycin plus amikacin group, 26 (84%) cured, 3 (9.7%) improved, and 2 (6.3%) failed; Cl-Az group, 25 (80.7%) cured, 6 (19.3%) improved, and 0 failed. Rapid temperature decrease occurred in Cl-Az group (p = 0.007). Forty-one mild adverse medical events reported were evenly distributed, but no patients were removed as a result.

CONCLUSIONS

Both combinations were highly effective in managing intraabdominal sepsis. Clindamycin aztreonam showed a slight advantage because of absence of renal toxicity and shorter time to apyrexia.

Evaluation of alkaline phosphatase-labelled ipaH probe for diagnosis of Shigella infections

The presence of many enteropathogens which are not easily detectable by routine stool culture has led to the development of alternative diagnostic methods. One of these techniques, nucleic acid probe hybridization, has been used to identify Shigella spp. and enteroinvasive Escherichia coli (EIEC) in stool specimens through the detection of genetic material encoded by a specific large approximately 200-kbp virulence-related plasmid. In the present study, an alkaline phosphatase-labelled oligonucleotide probe developed to detect the gene for ipaH, a repetitive genetic sequence thought to be present on both the virulence-related plasmid and the chromosomes of all strains of Shigella and EIEC, was tested in a developing-country setting through a prospective clinical trial. In a group of 219 Peruvian adults and children with acute gastroenteritis, the ipaH probe detected 85% of cases of shigellosis and demonstrated a specificity of 95% when compared with simultaneous detection by several stool culture techniques. Additionally, three cases of EIEC infection which could not be diagnosed by culture methods alone were detected with the ipaH probe and were confirmed by plasmid analysis and Sereny testing. These preliminary results suggest that, with further research, the ipaH probe should prove to be a useful and rapid adjunct in the diagnosis of acute gastroenteritis in developing countries.

Comparison of three methods to obtain upper small bowel contents for culture

In this study of 27 patients with dyspepsia, we compared three methods for obtaining upper small bowel contents for culture: 1) the Enterotest or string capsule method, 2) duodenal intubation using a closed polyethylene tube filled with water that had been boiled for sterilization and removal of dissolved oxygen, and 3) brushing of duodenal mucosa with a cytology brush protected by a sheath (the last two done during endoscopy). In 12 of the 27 patients, duplicate intubations and brushings were performed. The samples obtained were cultured aerobically. Parameters used to compare the three methods were: the contribution of each method to the diagnosis of upper small bowel bacterial overgrowth (USBBO), agreement between the methods in diagnosis of USBBO and in detailed microbiological findings, and the reproducibility of diagnosis of USBBO and of microbiological findings in duplicate intubation and brushing. Intubation and brushing were highly reproducible and superior to the Enterotest in all of the tested parameters. Intubation and brushing are equally efficacious, but intubation is preferred because of the slight cost advantage, ease of specimen processing, and the ability to obtain anaerobic specimens.

Etiologic agents in acute vs persistent diarrhea in children under three years of age in peri-urban Lima, Perú

In a longitudinal study of acute and persistent diarrhea in 677 children less than three years old in a peri-urban community of Lima, Perú, during 27 months of surveillance, stools were cultured at the beginning of each diarrheal episode and on each subsequent week of illness. Analyzing stool cultures only from children who had not received antibiotic treatment in the 48 h prior to the culture, no association was found between any enteropathogen and persistent diarrhea. We did not find any increase in mixed infections in persistent diarrhea episodes as compared with acute diarrhea, controlling for age, season and anthropometric status. The isolation rate for any given enteropathogen was similar during the first, second, third or later week of illness, but when the presence of a specific enteropathogen was sought in sequential stools within a single episode, no evidence of persistent infection was found. This study shows that in developing countries with a high incidence of diarrheal diseases frequent re-infections with enteropathogens prevalent in the population are one reason for prolonged illnesses. Host factors that increase susceptibility to infection or decrease recovery from illness may also play a role. Further studies of these factors, such as micronutrient deficiencies, are needed to identify a public health intervention to control persistent diarrhea, a condition associated with mortality in many developing countries.

Serological responses to various Coccidioides antigen preparations in a new enzyme immunoassay

A new enzyme immunoassay (EIA) was used to investigate immunoglobulin M (IgM) and IgG responses to various coccidioidal antigen preparations. Direct binding and inhibition assays both revealed that the IgG responses of many serum specimens were directed largely to the tube precipitin (TP) antigen even when the microwells were coated with a combination of coccidioidal antigens (CCAs). From a panel of 28 serum specimens containing antibodies to CCAs, 4 serum specimens yielded high IgG signals (absorbance, greater than 1.0) and were negative for IgM (absorbance, less than 0.2), yet all four IgG responses were inhibited by at least 90% with partially purified TP antigens (2.4 micrograms/ml). The IgM and IgG fractions of several serum specimens were separated by ion-exchange chromatography and assayed by using different antigen preparations adsorbed to the microwells. The binding of both IgM and IgG peaks to the microwells coated with the CCA preparation was inhibited significantly by preincubation with TP antigens. One serum specimen (specimen 26) yielded a large IgG response (absorbance, greater than 2.0) with the CCA preparation and also bound directly to microwells coated only with TP antigens. The IgG signal (absorbance) of serum specimen 26 was reduced by 98% when it was preincubated with TP antigens prior to the assay. Significant IgG signals from several other serum specimens were observed when microwells were coated with TP antigen preparations, but they were absent when periodate-treated preparations were used. Two cerebrospinal fluid specimens yielded IgG signals with CCA-coated microwells, which were not inhibited by TP antigens, and yielded no signal with microwells coated only with TP antigens. The results are consistent with the concept that the typical serologic response to TP antigens occurs early in disease progression, but they suggest that TP antigens stimulate both IgM and IgG responses.

Prospective study of systemic and mucosal immune responses in dysenteric patients to specific Shigella invasion plasmid antigens and lipopolysaccharides

Shigellosis is a major cause of infant morbidity and mortality in developing countries. To find immunological correlates of specific protection against shigellosis, we examined chronological samples of sera, stool extracts, duodenal aspirates, and saliva samples from 39 adults and 22 children with shigellosis from Peru for the presence of specific antibody to invasion plasmid antigens (Ipa) common to all virulent Shigella strains, by using both a whole-organism enzyme-linked immunosorbent assay (ELISA) and a Western blot (immunoblot) assay. Antibody responses to lipopolysaccharide (LPS) from Shigella serotypes both homologous and heterologous to the infecting strain were also determined by ELISA. ELISAs showed that the highest serum immunoglobulin G (IgG) antibody titers to Shigella whole organisms both with and without surface Ipa were found in adults and malnourished children, the two groups with the shortest and longest durations of disease, respectively. Mucosal IgA antibody titers to Shigella strains decreased over time to a much greater extent than serum IgG titers, and IgA to Ipa in mucosal secretions was found in adults and well-nourished children but not in malnourished children. The presence of mucosal antibody to Ipa may limit the spread and severity of the infection, as indicated by the prolonged illness observed in malnourished children who have no significant mucosal antibody to Shigella Ipa. Serum antibody titers to the Ipa antigens were high relative to anti-Shigella LPS antibody titers, especially in pediatric patients. In contrast to the anti-Ipa responses observed, no differences in antibody responses to LPS in children compared by nutritional status were found. High levels of serum and mucosal cross-reacting antibody to heterologous serotype LPS were found between Shigella flexneri serotypes 1a and 2a. Different patterns of immune response to Ipa proteins and LPS that may aid in the definition of Shigella antigens important in host protection were observed in adults, well-nourished children, and malnourished children.

High frequency of coinfecting enteropathogens in Aeromonas-associated diarrhea of hospitalized Peruvian infants

Rectal swabs from 391 infants less than 18 months of age who were hospitalized with acute diarrhea and from 138 similarly aged healthy infants were examined for the etiologic agents of diarrhea. Aeromonas spp. were recovered from 205 of 391 (52.4%) diarrheic patients, whereas they were recovered from 12 of 138 (8.7%) controls (P less than 10(-11). Among the 205 Aeromonas-positive diarrheic patients, 118 (57.6%) were found to be coinfected with other common enteropathogens. Of the 164 Aeromonas-positive initial diarrheic specimens, 82 (50.0%) had one or more other enteropathogens present; 30 patients were coinfected with rotavirus, 20 with enterotoxigenic Escherichia coli, 16 with Campylobacter spp., 14 with Shigella spp., 13 with enteropathogenic E. coli, 4 with Vibrio spp., 1 with Salmonella spp., and 1 with Plesiomonas spp. of Aeromonas strains from cases compared with that from controls supports an etiologic role for this organism. However, frequent concomitant infections with other well-recognized enteropathogens and a lack of disease correlation with common Aeromonas phenotypes suggest that only a subset of Aeromonas strains may be diarrhea causing and that such strains may be common to several of the existing species.

Measles-associated diarrhea in hospitalized children in Lima, Peru: pathogenic agents and impact on growth

Because the causes of measles-associated diarrhea are not well known, 0- to 5-year-old children presenting to the hospital with measles-associated diarrhea (cases, n = 77) or acute diarrhea only (controls, n = 77) were compared. Growth and diarrheal morbidity were evaluated for 1 month after acute illness. Campylobacter jejuni was more frequently isolated from cases (31%) than controls (16%; P = .03). Rotavirus was absent in all cases versus 28% of controls (P less than .001). Incidence density for new episodes of diarrhea was significantly greater in cases (6.5 vs. 4.1; odds ratio, 1.6; confidence intervals, 1.09-2.34; P = .01), as was duration of episodes (3 vs. 2 days, P = .02). Both groups showed similar positive cumulative percentage weight gains throughout follow-up. These data support the theory of measles as a risk factor for developing diarrhea. The bacteriologic and virologic findings may reflect the immunologic response of the host to measles infection.

Laboratory observations on Plesiomonas shigelloides strains isolated from children with diarrhea in Peru

Eleven strains of Plesiomonas shigelloides isolated from 10 Peruvian children with diarrhea were examined. All the strains were resistant to two or more antibiotics, most commonly ampicillin, gentamicin, erythromycin, kanamycin, and streptomycin. The strains were all negative in the Sereny and cell culture assays used to test for enteroinvasiveness. One strain showed cytotoxic activity on Vero cells. The strains showed no antigenic relationship with Shigella organisms. Both bioassays and enzyme-linked immunosorbent assays used for detection of Escherichia coli enterotoxins were negative. Nucleic acid probes for such toxins likewise gave negative results. The strains all possessed a large (approximately 200-megadalton) plasmid in addition to one or more other plasmids. Several different plasmid profiles were observed among these 11 P. shigelloides strains, indicating that the isolates were not acquired from a common source or from a single bacterial clone.

Comparison of single-dose treatment with norfloxacin and standard 5-day treatment with trimethoprim-sulfamethoxazole for acute shigellosis in adults

Shigellae have been shown to be highly susceptible to new quinolone agents, with average MICs for 90% of isolates of less than 0.1 microgram/ml. Because these agents also reach high concentrations in the stool after a single dose, the effectiveness of a single 800-mg dose of norfloxacin and of 5-day treatment with trimethoprim-sulfamethoxazole (TMP-SMX) were compared in a randomized trial. Patients with clinical dysentery received one of these treatment regimens, and clinical data and follow-up culture results were analyzed for patients whose stool culture on presentation grew shigellae. When 55 patients with shigellosis (26 treated with TMP-SMX, 29 treated with norfloxacin) whose bacterial isolates were susceptible to the antibiotic given were compared by treatment group, no significant differences were seen in days of illness (mean, 2.5 +/- 0.65 days with TMP-SMX and 2.0 +/- 0.47 days with norfloxacin; P = 0.200) or number of unformed stools after starting treatment (mean, 9.7 +/- 2.37 stools with TMP-SMX and 7.6 +/- 3.19 stools with norfloxacin; P = 0.312). Resistance in vitro to TMP-SMX was seen in 15% of Shigella isolates, whereas none was resistant to norfloxacin. Bacteriologic failure was found in 1 patient among 24 receiving TMP-SMX and in none of 25 patients receiving norfloxacin. One single dose of norfloxacin was as effective as 5 days of treatment with TMP-SMX in these adults with shigellosis.

Assessment of HIV-1 screening test sensitivities using serially diluted positive sera can give misleading results

Three FDA licensed HIV-1 viral lysate and two nonlicensed recombinant antigen assays were used to evaluate six serially diluted plasma samples and 2 highly characterized seroconversion series. The sensitivity as measured by serial dilution did not necessarily correlate with the sensitivity as measured by seroconversion performance with the lysate and the recombinant assays. It is concluded that national licensing agencies should arrange to share seroconversion panels to evaluate accurately the sensitivity of new HIV-1 screening tests.

Furazolidone and chloramphenicol for treatment of typhoid fever

Seventy-one adults who were hospitalized between March 1985 and March 1987 were entered into a randomized, double-blind study to compare the efficacy and safety of furazolidone and chloramphenicol in therapy for typhoid fever. Patients received chloramphenicol capsules (total daily dosage, 2 g) plus placebo tablets for furazolidone tablets (total daily dosage, 800 mg) plus placebo capsules for 14 days. Seven patients were excluded from the analysis of efficacy because blood, bile, or bone marrow cultures at admission failed to demonstrate the presence of Salmonella typhi. Four additional patients were excluded because of intercurrent illness or failure to return for follow-up visits. Cure was achieved in 31 (97%) of 32 chloramphenicol recipients and 24 (86%) of 28 furazolidone recipients. In the chloramphenicol group, one patient experienced moderate sideroblastic anemia, and another experienced moderate neutropenia. Both adverse reactions resolved spontaneously within 7 days. Mild gastritis was reported by two patients who received furazolidone and one who received chloramphenicol. This study has demonstrated that furazolidone is an effective and safe alternative to chloramphenicol for the treatment of typhoid fever in adults.

Early treatment with erythromycin of Campylobacter jejuni-associated dysentery in children

To evaluate the efficacy of early treatment with erythromycin on the duration of fecal excretion and of diarrhea associated with Campylobacter jejuni, 170 patients, age 3 to 60 months, were randomly assigned in a double-blind fashion to receive either erythromycin ethyl succinate or placebo immediately after being seen at Cayetano Heredia Hospital because of acute dysentery. The groups' pretreatment characteristics were comparable. Of the 30 patients with stools positive for C. jejuni, 12 were in the placebo group and 16 in the treatment group. After 2 days of treatment, none of the patients in the placebo group and 36% of those in the erythromycin group had normal stools (P less than 0.05). After 5 days of treatment, 50% of the patients in the placebo group and 93% of those in the erythromycin group had normal stools (P less than 0.02). Fecal excretion of the organism continued significantly longer in the placebo group (P less than 0.01). There were no treatment failures in the treatment group compared with five (42%) in the placebo group (P less than 0.01). Thus, early administration of erythromycin significantly reduced the duration of both diarrhea and fecal excretion of the organism in infants and children with acute dysentery associated with C. jejuni.

Bicarbonate versus citrate in oral rehydration therapy in infants with watery diarrhea: a controlled clinical trial

In a double-blind, randomized trial, we compared the efficacy of bicarbonate-containing oral rehydration solution vs citrate-containing solution in the treatment of infantile diarrheal dehydration and acidosis. Ninety-seven infants 3 to 24 months of age were entered in the study; 49 received bicarbonate-containing solution and 48 citrate-containing solution. The two groups were similar in all respects at the beginning of the study. Oral rehydration was successful (i.e., no intravenously administered fluids were required) in 85% of study patients; the success rate was similar in both treatment groups. Serum total CO2 concentration increased in a similar fashion in both groups, reaching near normal values at 48 hours after admission. We conclude that sodium citrate can be substituted for sodium bicarbonate in the formulation of the orally administered rehydration solution recommended by the World Health Organization for treatment of diarrheal dehydration in infants.