Enhancing organic matter productivity in microalgal-bacterial biofilm using novel bio-coating

Research on renewable energy from microalgae has led to a growing interest in porous substrate photobioreactors, but their widespread adoption is currently limited to pure microalgal biofilm cultures. The behavior of microalgal-bacterial biofilms immobilized on microporous substrates remains as a research challenge, particularly in uncovering their mutualistic interactions in environment enriched with dissolved organic matter. Therefore, this study established a novel culture platform by introducing microalgal-derived bio-coating that preconditioned hydrophilic polyvinylidene fluoride membranes for the microalgal-bacterial biofilm growth of freshwater microalgae, Chlorella vulgaris ESP 31 and marine microalgae, Cylindrotheca fusiformis with bacteria, Escherichia coli. In the attached co-culture mode, the bio-coating we proposed demonstrated the ability to enhance microalgal growth for both studied species by a range of 2.5 % to 19 % starting from day 10 onwards. Additionally, when compared to co-culture on uncoated membranes, the bio-coating exhibited a significant bacterial growth promotion effect, increasing bacterial growth by at least 2.35 times for the C. vulgaris-E. coli co-culture after an initial adaptation phase. A significant increase of at least 72 % in intracellular biochemical compounds (including chlorophyll, polysaccharides, proteins, and lipids) was observed within just five days, primarily due to the high concentration of pre-coated organic matter, mainly sourced from the internal organic matter (IOM) of C. fusiformis. Higher accumulation of organic compounds in the bio-coating indirectly triggers a competition between microalgae and bacteria which potentially stimulate the production of additional intra-/extra-organic substances as a defensive response. In short, insight gained from this study may represent a paradigm shift in the ways that symbiotic interactions are promoted to increase the yield of specific bio-compounds with the presence of bio-coating.

Bio-coatings in permeated cultivation systems: Unprecedented impacts on microalgal monoculture growth and organic matter yield

Bio-coating, a recent and promising approach in attached microalgal cultivation systems, has garnered attention due to its efficiency in enhancing immobilized algal growth, particularly in submerged cultivation systems. However, when the cells are cultured on thin solid microporous substrates that physically separate them from the nutrient medium, it remains unclear whether the applied bio-coatings still have a significant impact on algal growth or the subsequent rates of algal organic matter (AOM) release. Therefore, this current work investigated the role of bio-coatings on the microalgal monoculture growth of one freshwater species, Chlorella vulgaris ESP 31, and one marine species, Cylindrotheca fusiformis on a hydrophilic substrate, polyvinylidene fluoride membrane in a permeated cultivation system. Wide range of bio-coating sources were adapted, with the result demonstrating that bacteria-derived coating promoted algal growth by as high as 140% when compared with the control group for both species. Interestingly, two distinct adaptation mechanisms were observed between the species, with only C. fusiformis demonstrating a positive correlation between cell growth and AOM productivity, particularly in its extracellularly bound fractions. It is worth noting that despite this specific fraction exhibiting the lowest content among all; it displayed significant relevance in terms of AOM productivity. High extracellular protein-to-polysaccharide ratio (>5.7 fold) quantified on bacterial intracellular exudate-coated membranes indirectly revealed an underlying symbiotic microalgal-bacterial interaction. This is the first study showing how bio-coating influenced AOM yield without any physical interaction between microalgae and bacteria. It further confirms the practical benefits of bio-coating in attached cultivation systems.

A microscale system for in situ investigation of immobilized microalgal cell resistance against liquid flow in the early inoculation stage

In attached microalgae cultivation systems, cell detachment due to fluid hydrodynamic flow is not a subject matter that is commonly looked into. However, this phenomenon is of great relevance to optimizing the operating parameters of algae cultivation and feasible reactor design. Hence, this current work miniaturizes traditional benchtop assays into a microfluidic platform to study the cell detachment of green microalgae, Chlorella vulgaris, from porous substrates during its early cultivation stage under precisely controlled conditions. As revealed by time lapse microscopy, an increase in bulk flow velocity facilitated nutrient transport but also triggered cell detachment events. At a flow rate of 1000 μL min-1 of growth medium for 120 min, the algal cell coverage was up to 5% lower than those at 5 μL min-1 and 50 μL min-1. In static seeding, the evolution of attached cell resistance toward liquid flows was dependent on hydrodynamic zones. The center zone of the microchannel was shown to be a "comfortable zone" of the attached cells to sequester nutrients effectively at lower medium flow rates but there was a profile transition where outlet zones favored cell attachment the most at higher flow rates (1.13 times higher than the center zone for 1000 μL min-1). Besides, computational fluid dynamics (CFD) simulations illustrated that the focusing band varied between cross-sections and depths, while the streamline was the least concentrated along the side walls and bottom plane of the microfluidic devices. It was intriguing to learn that cell detachment was not primarily happening along the symmetry streamline. Insight gained from this study could be further applied in the optimization of operating conditions of attached cultivation systems whilst preserving laminar flow conditions.

Muscular and Kinematic Responses to Unexpected Translational Balance Perturbation: A Pilot Study in Healthy Young Adults

Falls and fall-related injuries are significant public health problems in older adults. While balance-controlling strategies have been extensively researched, there is still a lack of understanding regarding how fast the lower-limb muscles contract and coordinate in response to a sudden loss of standing balance. Therefore, this pilot study aims to investigate the speed and timing patterns of multiple joint/muscles' activities among the different challenges in standing balance. Twelve healthy young subjects were recruited, and they received unexpected translational balance perturbations with randomized intensities and directions. Electromyographical (EMG) and mechanomyographical (MMG) signals of eight dominant-leg's muscles, dominant-leg's three-dimensional (3D) hip/knee/ankle joint angles, and 3D postural sways were concurrently collected. Two-way ANOVAs were used to examine the difference in timing and speed of the collected signals among muscles/joint motions and among perturbation intensities. This study has found that (1) agonist muscles resisting the induced postural sway tended to activate more rapidly than the antagonist muscles, and ankle muscles contributed the most with the fastest rate of response; (2) voluntary corrective lower-limb joint motions and postural sways could occur as early as the perturbation-induced passive ones; (3) muscles reacted more rapidly under a larger perturbation intensity, while the joint motions or postural sways did not. These findings expand the current knowledge on standing-balance-controlling mechanisms and may potentially provide more insights for developing future fall-prevention strategies in daily life.

A review on microalgal-bacterial co-culture: The multifaceted role of beneficial bacteria towards enhancement of microalgal metabolite production

Mass microalgal-bacterial co-cultures have come to the fore of applied physiological research, in particularly for the optimization of high-value metabolite from microalgae. These co-cultures rely on the existence of a phycosphere which harbors unique cross-kingdom associations that are a prerequisite for the cooperative interactions. However, detailed mechanisms underpinning the beneficial bacterial effects onto microalgal growth and metabolic production are rather limited at the moment. Hence, the main purpose of this review is to shed light on how bacteria fuels microalgal metabolism or vice versa during mutualistic interactions, building upon the phycosphere which is a hotspot for chemical exchange. Nutrients exchange and signal transduction between two not only increase the algal productivity, but also facilitate in the degradation of bio-products and elevate the host defense ability. Main chemical mediators such as photosynthetic oxygen, N-acyl-homoserine lactone, siderophore and vitamin B12 were identified to elucidate beneficial cascading effects from the bacteria towards microalgal metabolites. In terms of applications, the enhancement of soluble microalgal metabolites is often associated with bacteria-mediated cell autolysis while bacterial bio-flocculants can aid in microalgal biomass harvesting. In addition, this review goes in depth into the discussion on enzyme-based communication via metabolic engineering such as gene modification, cellular metabolic pathway fine-tuning, over expression of target enzymes, and diversion of flux toward key metabolites. Furthermore, possible challenges and recommendations aimed at stimulating microalgal metabolite production are outlined. As more evidence emerges regarding the multifaceted role of beneficial bacteria, it will be crucial to incorporate these findings into the development of algal biotechnology.

Bio-coatings as immobilized microalgae cultivation enhancement: A review

Bio-coatings serve as artificial scaffolds for immobilizing microalgae to facilitate cell concentration and harvesting. It has been used as an additional step to enhance the natural microalgal biofilm cultivation and to promote new opportunities in artificially-immobilize cultivation technology of microalgae. This technique is able to enhance biomass productivities, enable energy and cost saving, water volume reduction and ease of biomass harvesting since the cells are physically isolated from the liquid medium. However, scientific discoveries of bio-coatings for process intensification are still lacking and their working principles remained unclear. Therefore, this critical review aims to shed light on the advancement of cell encapsulation systems (hydrogel coating, artificial leaf, bio-catalytic latex coating, and cellular polymeric coating) over the years and aid in the selection of appropriate bio-coating techniques for various applications. Discussion on the different preparation routes of bio-coatings, as well as the exploration towards the potential of bio-based coating materials such as natural/synthetic polymers, latex binders, and algal organic matters are also included, with a focus on sustainable pursuits. This review also presents in-depth investigations into the environmental applications of bio-coatings in wastewater remediation, air purification, carbon bio-fixation, and bio-electricity. The field of bio-coating in microalgae immobilization gives rise to a new ecofriendly strategy with scalable cultivation footprint and a balanced environmental risk aligning with the United Nation's Sustainable Development Goals with potential towards the contribution of Zero Hunger, Clean Water and Sanitation, Affordable and Clean Energy, and Responsible Consumption and Production.

Microalgal extract as bio-coating to enhance biofilm growth of marine microalgae on microporous membranes

Microalgal biofilm is a popular platform for algal production, nutrient removal and carbon capture; however, it suffers from significant biofilm exfoliation under shear force exposure. Hence, a biologically-safe coating made up of algal extracellular polymeric substances (EPS) was utilized to secure the biofilm cell retention and cell loading on commercial microporous membrane (polyvinylidene fluoride), making the surfaces more hydrophobic (contact angle increase up to 12°). Results demonstrated that initial cell adhesion of three marine microalgae (Amphora coffeaeformis, Cylindrotheca fusiformis and Navicula incerta) was enhanced by at least 1.3 times higher than that of pristine control within only seven days with minimized biofilm exfoliation issue due to uniform distribution of sticky transparent exopolymer particles. Bounded extracellular polysaccharide gathered was approximately 23% higher on EPS-coated membranes to improve the biofilm's hydraulic resistance, whereas bounded extracellular protein would only be substantially elevated after the attached cells re-accommodate themselves onto the EPS pre-coating of themselves. In accounting the rises of hydrophobic protein content, biofilm was believed to be more stabilized, presumably via hydrophobic interactions. EPS biocoating would generate a groundswell of interest for bioprocess intensifications though there are lots of inherent technical and molecular challenges to be further investigated in future.

Marine microalgal biofilm development and its adhesion propensities on commercial membrane via XDLVO approach

An emerging biofilm immobilization method has enabled effortless biomass harvesting and promoted economic feasibility. The current limitation towards the adaptation of this technology is the inadequate understanding of the biofilm interaction towards microporous membrane. Cell adhesion is recognized as the most important step towards the immobilized cultivation of microalgae. Cell attachment kinetic was studied in a short-term batch culture of three marine diatoms, Amphora coffeaeformis, Cylindrotheca fusiformis and Navicula incerta over 96 h on submerged commercial polyvinylidene fluoride (PVDF) membrane under swirling motion of culture medium. Both the evolution of cell adhesion intensity and compositional changes of the extracellular polymeric substances (EPS) released were quantified throughout the cultivation period. To delve into the cell-substratum interactions, existing thermodynamics and colloidal extended Derjaguin, Landau, Vervey, and Overbeek (XDLVO) theory were employed. As a result, A. coffeaeformis and N. incerta recorded a higher cell colonization percentage than C. fusiformis being the lowest about 2.16±0.17% cell colonization due to their respective species-dependent EPS variation. Polysaccharide contents were at least two times higher than protein contents for both C. fusiformis and N. incerta except for A. coffeaeformis depicting a lower polysaccharide-to-protein ratio whereby the protein contents were maximized at 1.03 × 103 ± 64.14 pg m^-2 cell^-1 at 6th h. From the surface free energy point of view, both thermodynamics and XDLVO model elucidated that cells adhered reversibly in the secondary energy minimum and ranked C. fusiformis the lowest adhesion tendency among three. These findings establish fundamental knowledge about biofilm formation in porous substrate bioreactors.

Algal extracellular organic matter pre-treatment enhances microalgal biofilm adhesion onto microporous substrate

Adhesive biocoating has microstructure composed of biomolecules to entrap viable cells in a stabilized matrix over exposed surfaces. Although marine benthic diatoms are a common group of algae excreting substantial amount of extracellular polymeric substances (EPS), studies regarding the utilization of these EPS are scarce. Using the soluble EPS derived from Navicula incerta and pre-deposition of it as a thin conditioning layer on microporous polyvinylidene fluoride (PVDF) membranes, the pre-coated surface was used to investigate the cell binding affinity of three marine microalgae, namely Amphora coffeaeformis, Cylindrotheca fusiformis and Navicula incerta. Microalgae actively engaged themselves on the pre-coated membranes which was 10 times greater than the initial cell adhesion degree. Soluble EPS is mainly comprised of polysaccharide while bounded EPS is mainly comprised of protein. On EPS pre-coated membranes, N. incerta released the least amount of bounded polysaccharides (<100 mg m^-2) and vice versa for the other two because EPS production is usually maximized to assist cell adhesion onto unfavorable substrates. In stark contrast, when the adaptation period (first 6 h) ended, cells began to secrete more bounded protein for cell growth, and an increasing trend of protein content found in N. incerta has verified its optimal adaptation onto the biocoating itself. On pristine PVDF membranes, the adhesion degree was ranked in ascending order: C. fusiformis, N. incerta and A. coffeaeformis. Interestingly, after the pre-coating process, the order was reported as: A. coffeaeformis, N. incerta and C. fusiformis, but it should be noted that C. fusiformis demonstrated fluctuating cell colonization degree and bounded EPS production over time. In other words, the biofilm's susceptibility was confirmed since the cells latched loosely on the membranes rather than in a biofilm matrix. Biocoating enables uniform cell distribution and firmer biofilm growth, opening the door to vast future applications in environmental bioremediation and sensing.

Novel Extrapolymeric Substances Biocoating on Polyvinylidene Fluoride Membrane for Enhanced Attached Growth of Navicula incerta

Cell adhesion is always the first step in biofilm development. With the emergence of attached cultivation systems, this study aims to promote a cost-effective approach for sustainable cultivation of microalgae, Navicula incerta, by pre-coating the main substrates, commercial polyvinylidene fluoride (PVDF) membranes with its own washed algal cells and self-produced soluble extracellular polymeric substances (EPS) for strengthened biofilm development. The effects of pH value (6 to 9), cell suspension volume (10 to 30 mL), and EPS volume (10 to 50 mL) were statistically optimized by means of response surface methodology toolkit. Model outputs revealed good agreement with cell adhesion data variation less than 1% at optimized pre-coating conditions (7.20 pH, 30 mL cell suspension volume, and 50 mL EPS volume). Throughout long-term biofilm cultivation, results demonstrated that EPS pre-coating substantially improved the attached microalgae density by as high as 271% than pristine PVDF due to rougher surface and the presence of sticky exopolymer particles. Nutrients absorbed via the available EPS coating from the bulk medium made the immobilized cells to release less polysaccharides on an average of 30% less than uncoated PVDF. This work suggests that adhesive polymer binders derived from organic sources can be effectively integrated into the development of high-performance novel materials as biocoating for immobilized microalgae cultivation.

Membrane surface roughness promotes rapid initial cell adhesion and long term microalgal biofilm stability

In biofilm membrane photobioreactors development, conscientious works revolving around the effect of external environment factors on microalgal biofilm growth were assessed but more comparative research about the role of carrier surfaces properties such as surface roughness is necessary. Thus, commercial polyethersulfone (PES) membranes with two different molecular-weight-cut-offs (1 kDa and 30 kDa) were selected as the main representatives of surface roughness in a 20 days long-term biofilm cultivation experiment under dynamic flow condition for the biofilm evolvement of three benthic diatoms (Amphora coffeaeformis, Cylindrotheca fusiformis and Navicula incerta). Results depicted that rougher 30 kDa PES enable higher cell attachment degree for C. fusiformis (25.85 ± 2.75 × 10⁹ cells m^-2), followed by A. coffeaeformis (11.86 ± 2.76 × 10⁹ cells m^-2) and N. incerta (10.10 ± 0.65 × 10⁹ cells m^-2). Bounded extracellular polymeric substances (bEPS) gathered were relatively higher than soluble EPS (sEPS) while bEPS accumulated at least 10% higher on smooth 1 kDa PES than rough 30 kDa PES for the purpose of enhancing the biofilm disruption resistivity under liquid flow. Moreover, cell adhesion mechanism was proposed via computational fluid dynamics in parallel with EPS analysis. Copious amount of asperities and stagnant zones present on rough 30 kDa surfaces accelerated biofilm development and the consistency of the results have a great valence for interpretation of microalgal biofilm lifestyle on porous surfaces.

[Value of bedside echocardiography in diagnosis and risk assessment of in-hospital death for patients with Stanford type A aortic dissection]

Objective: To investigate the value of bedside echocardiography in diagnosis and risk assessment of in-hospital death of patients with Stanford type A aortic dissection. Methods: The clinical data of 229 patients with Stanford type A aortic dissection diagnosed by CT angiography in Zhongshan Hospital affiliated to Fudan University between January 2009 and January 2016 were retrospectively analyzed. The patients were divided into survival group(191 cases)and non-survival group(38 cases)according to presence or absence of in-hospital death. The bedside echocardiography features were analyzed, and influence factors of in-hospital death were determined by multivariate logistic regression analysis. Results: (1) Compared with the survival group, the non-survival group had lower surgery rate (60.52%(23/38) vs. 85.34%(163/191), P<0.01). Age, gender and Debakey classification were similar between survival group and death group (all P>0.05). (2) The bedside echocardiography results showed that prevalence of aortic valve involvement(65.79%(25/38) vs.34.03%(65/191), P<0.01) and severe aortic regurgitation (44.74%(17/38) vs. 14.14%(27/191), P<0.01) were significantly higher in non-survival group than in survival group. The non-survival group had larger aortic root diameter than the survival group ((55.5±6.4)mm vs. (42.3±7.8)mm, P<0.01). There were no significant differences in pericardial effusion, expansion of aortic sinus, and left ventricular ejection fraction between survival group and non-survival group (all P>0.05). (3) The multivariate logistic regression analysis showed that aortic valve involvement(OR=3.275, 95%CI 1.290-8.313, P<0.05), aortic root diameter(OR=1.202, 95%CI 1.134-1.275, P<0.01), and surgery (OR=0.224, 95%CI 0.079-0.629, P<0.01) were independent risk factors for in-hospital death in patients with Stanford type A aortic dissection. Conclusions: Bedside echocardiography has significant diagnostic value for Stanford type A aortic dissection. Aortic valve involvement, enlargement of aortic root diameter and without surgery are independent risk factors for patients with Stanford type A aortic dissection.

[The situation of social support and its relationship with antenatal depression among 1 075 Zhejiang primiparas in their third trimesters]

Objective: To investigate the situation of social support (SS), and explore its relationship with antenatal depression (AD) among Zhejiang primiparas in their third trimesters. Methods: From March to August 2016, a cross-sectional study was conducted and the questionnaire was used at the outpatient consulting room of one maternity hospital in Hangzhou. Inclusion criteria includes the primiparas over 18 years old, gestation from 30 to 36 weeks, been able to understand and complete the questionnaires independently, no family history and history of mental disorders and no use of psychotropic drugs, without serious illness and so on. Exclusion criteria was that the primiparas were unable to complete all the contents of the questionnaire and of poor compliance. 1 150 questionnaires were actually given out, and 1 075 questionnaires were valid, so the valid rate was 93.48%. AD was evaluated by the Edinburgh Postnatal Depression Scale (EPDS) and SS was evaluated by the Perceived Social Support Scale (PSSS). SS between the non-AD group and the AD group was compared. The correlation between SS and AD was analyzed. Binary logistic regression model was used to assess the relationship between SS and AD. The level of SS was divided by average scores, groups lower than the average score was defined as the low-score group, groups higher than the average score was defined as the high-score group. Results: The prevalence of AD (score≥9) was 27.3% (293/1 075) among Zhejiang primiparas in their third trimesters. The scores of family support, friend support and other support, and the total score of SS among the non-AD group were 24.80±2.83, 23.40±3.00, 21.91±3.54 and 70.11±7.92, respectively, which were higher than those in the AD group (22.71±3.88, 21.45±3.59, 19.95±3.97, 64.10±10.01), (t values were 8.43, 8.29, 7.83 and 9.25, respectively, P<0.001 for all). The scores of family support, friend support and other support, and the total score of SS were negatively correlated with AD (rs values were-0.26,-0.25,-0.22 and-0.28, respectively, P<0.001 for all). Compared with low-score group, the scores of family support, friend support and other support, and the total score of SS among the high-score group had a lower risk of antenata depression among primiparas in their third trimesters, OR(95%CI) values were 0.56 (0.41-0.77), 0.66(0.47-0.92), 0.57(0.41-0.79) and 0.36(0.27-0.48), respectively. Conclusion: The prevalence of AD among Zhejiang primiparas was relatively high, and AD was negatively associated with SS level. We suggest adding SS in community pregnancy health management service in the future.

[Relationship between multi-slice spiral CT angiography imaging features and in-hospital death of patients with aortic dissection]

Objective: To explore the imaging manifestations of multi-slice spiral CT angiography (CTA) and relationship with in-hospital death in patients with aortic dissection (AD). Methods: The clinical data of 429 patients with AD who underwent CTA in Zhongshan Hospital of Fudan University between January 2009 and January 2016 were retrospectively analyzed. AD patients were divided into 2 groups, including operation group who underwent surgery or interventional therapy (370 cases) and non-operation group who underwent medical conservative treatment(59 cases). The multi-slice spiral CTA imaging features of AD were analyzed, and multivariate logistic regression analysis was used to investigate the relationship between imaging manifestations and in-hospital death in AD patients. Results: There were 12 cases (3.24%) of in-hospital death in operation group, and 28 cases (47.46%) of in-hospital death in non-operation group(P<0.001). AD involved different vascular branches. Multi-slice spiral CTA can clearly show the dissection of true and false lumen, and intimal tear was detected in 363 (84.62%) cases, outer wall calcification was revealed in 63 (14.69%) cases, and thrombus formation was present in 227 (52.91%) cases. The multivariate logistic regression analysis showed that the number of branch vessels involved (OR=1.374, 95%CI 1.081-1.745, P=0.009) and tearing false lumen range(OR=2.059, 95%CI 1.252-3.385, P=0.004) were independent risk factors of in-hospital death in AD patients, and the number of branch vessels involved (OR=1.600, 95%CI 1.062-2.411, P=0.025) was independent risk factor of in-hospital death in the operation group, while the tearing false lumen range (OR=2.315, 95%CI 1.019-5.262, P=0.045) was independent risk factor of in-hospital death of non-operation group. Conclusions: Multi-slice spiral CTA can clearly show the entire AD, true and false lumen, intimal tear, wall calcification and thrombosis of AD patients. The number of branch vessels involved and tearing false lumen range are the independent risk factors of in-hospital death in AD patients.

Comparison of urine, first and second endourethral swabs for PCR based detection of genital Chlamydia trachomatis infection in male patients

OBJECTIVES

To compare endourethral swabs and urine as diagnostic specimens for the detection of genital Chlamydia trachomatis infection using the polymerase chain reaction (PCR), in male patients attending a genitourinary clinic and to assess whether the first endourethral swab used solely for diagnosing gonococcal infection could be used for C trachomatis detection as well.

METHODS

Two endourethral swabs were taken from 80 male patients, in whom the likelihood of genital C trachomatis infection was high. The first swab was used for microscopy and culture for Neisseria gonorrhoeae, before being used for C trachomatis detection. First voided urine specimens were collected from 61 of these patients. All three specimens were processed for C trachomatis DNA detection using the Roche Cobas Amplicor PCR. A diagnosis of genital C trachomatis infection was made if any one of the specimens tested reproducibly positive. Samples from 13 patients showing discrepant PCR results between swabs and/or urine were retested by ligase chain reaction (LCR).

RESULTS

Chlamydia trachomatis DNA was detected in 35 (43.8%) of the 80 patients. In 17 of the 35 patients (48.6%), all the genital specimens were positive. However, in 18 (51.4%) patients, one or more of the genital specimens had negative PCR results. Among the 18 patients with discrepant results, urine was found to be a more sensitive diagnostic specimen than the second urethral swab picking up 13 out of 16 positives (81.3%) as opposed to five out of 18 (27.8%). There was no significant difference between the two swabs. Retesting by LCR, of the samples from 13 of the 18 patients with discrepant PCR results confirmed them all as true positives, although as with PCR, not all specimens in the set were concordantly positive. LCR detected all the 13 positives in urine, while there was no difference in the detection rate between the first and the second urethral swabs.

CONCLUSIONS

Urine appeared to be a better diagnostic specimen than the conventional second endourethral swab for C trachomatis detection by PCR in this cohort of male patients. There was no difference between the first swab, intended primarily for N gonorrhoeae testing and the second swab intended for C trachomatis detection. This raises questions over the need for the conventional second swab for detecting C trachomatis.

[A preliminary study of loss of heterozygosity on chromosome 14 in glioblastoma]

OBJECTIVE

In order to locate the deletion areas probably harboring tumor suppressor genes on chromosome 14 and provide clues for discovering novel tumor suppressor genes.

METHODS

Fourteen loci on chromosome 14 were examined to detect loss of heterozygosity(LOH) in 20 cases of glioblastoma(GBM) by PCR based microsatellite polymorphism analyses, in which fluorescence-labeled primers and Perkin Elmer 377 DNA Sequencer were applied.

RESULTS

50% informative cases of GBM displayed LOH on chromosome 14; 38.2% of informative loci showed LOH in our series, in which the most frequent LOH was observed at locus D14S65(57.1%) on 14q31-32.3 and in the chromosomal region from locus D14S63 (46.7%) to D14S74(47.1%) on 14q21-24.1. 32% of informative cases displayed LOH on 14p and 50% on 14q. No microsatellite instability was observed.

CONCLUSION

Loss of genetic material on chromosome 14q may play an important role in molecular genetic pathogenesis of GBM. The chromosomal regions at D14S65 on 14q31-32.3 and from D14S63 to D14S74 on 14q21-24.1 may harbor novel tumor suppressor genes associated with GBM.

Identification of novel regions of allelic loss in ependymomas by high-resolution allelotyping with 384 microsatellite markers

OBJECT

Ependymomas are rare glial neoplasms; little is known about the molecular pathogenesis of this tumor entity. In a previous study the authors found multiple genomic imbalances in ependymomas resected in 20 adults and eight children, including loss of chromosomes 1p, 6, 16, 17, 19q, 20q, and 22q, as well as gain of chromosomes 4q, 5q, 7q, 9q, and 12q on comparative genomic hybridization. The aim of this study was to map in more detail the commonly affected regions in ependymomas.

METHODS

A comprehensive allelotype analysis of 16 ependymomas was conducted using 384 microsatellite markers that span the 22 autosomes. Based on this high-resolution loss of heterozygosity analysis, multiple overlapping deletion regions were identified as follows: 6q25.2-27, 16p12-13.1, 16q22.3-24.1, 17q22-24, 19q12-13.2, 20q13.2-13.3, and 22q13.1-13.3.

CONCLUSIONS

These data confirmed previous reports that loss of chromosomes 17 and 22 were common in ependymomas. Moreover, the authors were able to identify loss of chromosomes 13, 16, 19, and 20 as novel findings in ependymomas. It is believed that potential tumor suppressor genes that reside in these commonly deleted regions may contribute to the molecular tumorigenesis of ependymomas.

Association of tumour necrosis factor alpha and interleukin 6 levels with cytomegalovirus DNA detection and disease after renal transplantation

Cytokines such as tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) are thought to be important in the pathogenesis of post-transplant cytomegalovirus (CMV) disease. CMV infection increases the production of TNF-alpha and IL-6. Conversely, TNF-alpha switches on the replication of CMV. To study the association of these two cytokines with CMV activity and disease, TNF-alpha and IL-6 levels were assayed in plasma samples taken serially from three groups of renal transplant recipients. Group A (n = 12) had CMV disease and syndrome; Group B (n = 11) had detectable CMV DNA in plasma or peripheral blood leucocytes without disease, i.e., presumed asymptomatic CMV infection, and Group C (n = 11) had no detectable CMV DNA nor disease. The median peak TNF-alpha levels in patients with CMV disease (Group A) were significantly higher than that in Group B or Group C (P < 0.02) whereas the median peak IL-6 levels in group C patients were significantly lower than that in group A (P < 0.04) or group B (P < 0.03). A TNF-alpha level of above 100 pg/ml was significantly associated with CMV disease and high plasma CMV load (> 10,000 copies/ml). IL-6 levels above 15 pg/ml were significantly associated with CMV DNA detection, but not with CMV disease or elevated CMV load. High levels of TNF-alpha or IL-6 were not associated with CMV donor/recipient serostatus, HHV-6 or HHV-7 DNA detection, immunosuppressive regimen or rejection episodes. The role of TNF-alpha in the pathogenesis of CMV disease deserves further investigation.

Multicenter comparison trial of DNA extraction methods and PCR assays for detection of Chlamydia pneumoniae in endarterectomy specimens

The reported rate of detection of Chlamydia pneumoniae DNA within atherosclerotic lesions by PCR varies between 0 and 100%. In this study, identical sets of coded experimental atheroma samples (n = 15) and spiked controls (n = 5) were analyzed by 16 test methods in nine centers by means of PCR. The positive controls were correctly identified to levels of 1, 0.1, and 0.01 inclusion bodies of C. pneumoniae/ml of tissue homogenate by 16 (100%), 11 (69%), and 3 (19%) of the test methods, respectively. Three out of 16 negative controls (19%) were rated positive. Positivity rates for atheroma samples varied between 0 and 60% for the different test methods, with the maximum concordant result for positivity being only 25% for one carotid artery sample. There was no consistent pattern of positive results among the various laboratories, and there was no correlation between the detection rates and the sensitivity of the assay used.

Is Mycoplasma hominis a vaginal pathogen?

OBJECTIVE

To evaluate the role of Mycoplasma hominis as a vaginal pathogen.

DESIGN

Prospective study comprising detailed history, clinical examination, sexually transmitted infection (STI) and bacterial vaginosis screen, vaginal swabs for mycoplasmas and other organisms, follow up of bacterial vaginosis patients, and analysis of results using SPSS package.

SETTING

Genitourinary medicine clinic, Royal Liverpool University Hospital.

PARTICIPANTS

1200 consecutive unselected new patients who had not received an antimicrobial in the preceding 3 weeks, and seen by the principal author, between June 1987 and May 1995.

MAIN OUTCOME MEASURES

Relation of M. hominis isolation rate and colony count to: (a) vaginal symptoms and with the number of polymorphonuclear leucocytes (PMN) per high power field in the Gram stained vaginal smear in patients with a single condition--that is, candidiasis, bacterial vaginosis, genital warts, chlamydial infection, or trichomoniasis, as well as in patients with no genital infection; (b) epidemiological characteristics of bacterial vaginosis.

RESULTS

1568 diagnoses were made (the numbers with single condition are in parenthesis). These included 291 (154) cases of candidiasis, 208 (123) cases of bacterial vaginosis, 240 (93) with genital warts, 140 (42) chlamydial infections, 54 (29) cases of trichomoniasis, and 249 women with no condition requiring treatment. M. hominis was found in the vagina in 341 women, but its isolation rates and colony counts among those with symptoms were not significantly different from those without symptoms in the single condition categories. There was no association between M. hominis and the number of PMN in Gram stained vaginal smears whether M. hominis was present alone or in combination with another single condition. M. hominis had no impact on epidemiological characteristics of bacterial vaginosis.

CONCLUSION

This study shows no evidence that M. hominis is a vaginal pathogen in adults.

Central neurocytomas are genetically distinct from oligodendrogliomas and neuroblastomas

AIMS

Central neurocytoma is a rare central nervous system tumour typically found in the lateral ventricles and at the septum pellucidum. Histologically, it resembles oligodendrogliomas and yet ultrastructurally, it shows neuronal differentiation. Its molecular oncogenesis is not known. The aim of this study was to examine whether major genetic events found in oligodendrogliomas and neuronal tumours, namely allelic deletions of chromosomes 1p and 19q and N-myc amplification, can be found in central neurocytomas. As there was one report describing gain of chromosome 7 in central neurocytomas, we also examined epidermal growth factor receptor (EGFR) amplification, as the EGFR gene is located at chromosome 7p.

METHODS AND RESULTS

Nine central neurocytomas and matched blood samples were examined for loss of heterozygosity (LOH) of 1p and 19q13.2-13.4 with 23 finely mapped microsatellite markers. N-myc amplification was studied by fluorescence in-situ hybridization using paraffin-embedded sections. EGFR amplification was tested for by differential PCR. Six of nine (67%) tumours showed LOH at one or more loci at 1p and 5/9 (56%) of cases showed LOH at 19q. However, common regions of deletion cannot be identified. The majority of informative markers are retained at 1p (84%) and 19q (86%). Only one tumour showed amplification of N-myc and none of the cases showed amplification of EGFR.

CONCLUSION

Central neurocytomas are genetically distinct from oligodendrogliomas, and chromosomes 1p and 19q probably do not play an important role in their pathogenesis. N-myc and EGFR amplification are rare.

Association of human herpesvirus 7 with cytomegalovirus disease in renal transplant recipients

BACKGROUND

Recent studies have linked human herpesviruses 6 (HHV-6) and 7 (HHV-7) with posttransplant cytomegalovirus (CMV) disease.

METHODS

Thirty-seven renal transplant recipients were monitored weekly for CMV, HHV-6, and HHV-7 DNA and serological responses for 12 weeks after transplantation. Plasma CMV load and the occurrence of CMV disease was related to HHV-6 and -7 detection.

RESULTS

CMV disease was identified in 12 patients. In a logistic regression analysis, factors significantly associated with CMV disease were the detection of HHV-7 DNA in peripheral blood leucocytes and donorrecipient CMV serostatus. Patients with detectable HHV-7 DNA had significantly higher peak plasma CMV loads (P=0.01).

CONCLUSIONS

An association was found between HHV-7, but not HHV-6, DNA detection and CMV disease, suggesting a possible role of HHV-7 in its pathogenesis.

Prediction and diagnosis of cytomegalovirus disease in renal transplant recipients using qualitative and quantitative polymerase chain reaction

BACKGROUND

Preemptive antiviral therapy against cytomegalovirus (CMV) disease after transplantation requires information from suitable laboratory markers. We examined the use of qualitative and quantitative polymerase chain reaction (PCR) to monitor renal transplant recipients.

METHODS

A cohort of 77 renal transplant recipients was monitored using an in-house and a commercial (Amplicor; Roche Diagnostic, Basel, Switzerland) PCR on leukocytes and plasma. Quantitative plasma viral load was determined using a commercial PCR kit (CMV Monitor; Roche Diagnostic). Patients were analyzed according to their pretransplantation CMV serological status (R- or R+).

RESULTS

Seventeen patients developed CMV disease after transplantation. Qualitative leukocyte PCRs had the best overall sensitivity (54-69%) and specificity (75-87%) in identifying R- recipients with CMV disease before onset. The specificities of qualitative PCRs for R+ recipients were poor and, if used, could result in unnecessary preemptive treatment in up to 50% of patients. Symptomatic and asymptomatic R+, but not R-, recipients could be distinguished using a plasma viral load of 25,000 copies/ml. An increase in viral load of >0.7 log (fivefold) per week also distinguished between symptomatic and asymptomatic R+ recipients with high sensitivity (100%) and specificity (95%).

CONCLUSIONS

Qualitative leukocyte PCRs were the best assays to predict CMV disease for R- recipients who received R+ kidneys. None of the qualitative assays could be used to guide preemptive therapy of R+ recipients, but plasma viral load and its incremental rate could be used as diagnostic tools in R+ recipients.

Comparison of two commercial methods for measurement of cytomegalovirus load in blood samples after renal transplantation

A cohort of 77 renal transplant recipients was prospectively studied for comparison of two commercially available cytomegalovirus (CMV) load assays, i.e., the COBAS AMPLICOR CMV Monitor test (Amplicor), using plasma samples, and the Murex Hybrid Capture System (HCS), using whole blood. The manufacturer of the HCS assay changed the version of the test from 1.0 (HCS-1) to 2.0 (HCS-2) after the first 37 patients had been tested. Despite the differences in principle and type of specimen used, the Amplicor and HCS assays gave comparable results. The regression line correlating the HCS-1 assay to the Amplicor assay was similar to that correlating the HCS-2 assay to the Amplicor assay. The HCS results could be converted to Amplicor-equivalent units by using linear-regression equations [log(10) HCS-1 result = 0.49 (log(10) Amplicor result) + 2.58, and log(10) HCS-2 result = 0.61 (log(10) Amplicor result) + 2.18]. The HCS-2 assay appeared to have the lowest detection limit, followed by the Amplicor assay and then the HCS-1 assay. When a sliding scale of cutoff values in Amplicor-equivalent units (>1,000, >2,500, >6,000, >16,000, >40,000, and >100,000 copies/ml) was applied to diagnose CMV disease, similar patterns of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were observed with the Amplicor and HCS assays. A cutoff value of >40,000 copies/ml has a low sensitivity (Amplicor, 29.4%; HCS, 41.2%) but is specific (Amplicor, 96.7%; HCS, 93.3%) and can be used for the differential diagnosis of CMV disease (PPV, 71.4% [Amplicor] or 63. 6% [HCS]; NPV, 82.9% [Amplicor] or 84.8% [HCS]). A lower cutoff value of >1,000 copies/ml improves the sensitivity (Amplicor, 76.5%; HCS, 82.4%) and has a high NPV (Amplicor, 91.8%; HCS, 94.2%) but, due to the low PPV (Amplicor, 46.2%; HCS, 56%), is useful only for exclusion of CMV disease.

Post-transfusion HIV infection despite donor screening: a report of three cases

In August 1996, a blood donation was collected which subsequently infected three patients post-transfusion with HIV 1. The donation itself was originally screened as negative for anti-HIV 1/2 using a sensitive EIA method, but subsequently was shown to contain p24 Ag and HIV RNA by an amplification technique. The proposed introduction of nucleic acid testing of all blood donations in the UK for hepatitis C, hepatitis B and HIV may further reduce the remote risk of further episodes of post-transfusion infection. The infection in the index recipient was detected on routine pre-transplant virological screening but proved difficult to confirm, at a time when she had recently received myeloablative treatment for a haematological malignancy which impaired the immune response. There is a need for continued vigilance in such patients to exclude post-transfusion infection, at a time when natural immunological responses have been impaired by their disease or treatment.

Multiplex polymerase chain reaction for the simultaneous detection of Mycoplasma pneumoniae, Chlamydia pneumoniae, and Chlamydia psittaci in respiratory samples

AIMS

To develop a multiplex polymerase chain reaction (PCR) for the simultaneous detection of Mycoplasma pneumoniae, Chlamydia pneumoniae, and Chlamydia psittaci in respiratory samples.

METHODS

Oligonucleotide primers for the amplification of the DNA of these three organisms were optimised for use in combination in the same reaction. PCR products were detected by hybridisation with pooled internal probes using an enzyme linked immunosorbent assay. Those with positive signals were further differentiated using species specific probes. Quality of DNA extraction and PCR inhibition were controlled by amplification of a human mitochondrial gene. A panel of 53 respiratory samples with known results was evaluated blindly. This was followed by a retrospective study on sputa collected from 244 patients with suspected community acquired pneumonia.

RESULTS

The multiplex assay had a lower sensitivity than PCR with individual primers by about one log. The resultant sensitivity was considered acceptable for diagnostic use. Of the panel of 53 samples, nine of 11 M pneumoniae, 11 of 11 C pneumoniae, six of seven C psittaci, and 24 of 24 negative samples were correctly identified. Of the 244 patients with pneumonia, seven (2.9%) had detectable M pneumoniae, six (2.5%) had C pneumoniae, and one (0.4%) had C psittaci. The case notes from 11 patients were studied. The PCR finding was of possible significance in at least eight of these patients.

CONCLUSIONS

This multiplex PCR assay has the potential to be used as a diagnostic and epidemiological tool. Further prospective studies are needed to establish its clinical value.

Molecular genetic analysis of non-astrocytic gliomas

AIMS

Oligodendroglial tumours follow genetic pathways different from but overlapping with those of astrocytic tumours. The aim of this study was to examine whether major genetic events such as loss of chromosome 10 and p53 mutation found in astrocytic gliomas are also involved in the development and anaplastic transformation of non-astrocytic gliomas and to correlate the findings with histopathological subtypes of these tumours.

METHODS AND RESULTS

Sixty-one formalin-fixed, paraffin-embedded oligodendroglial and ependymal tumours (16 oligodendrogliomas, 12 anaplastic oligodendrogliomas, seven oligoastrocytomas, 24 ependymomas and two anaplastic ependymomas) were examined for allelic deletions on chromosome 10q23 and 10q25-26 regions, mutations of PTEN/MMAC1 and p53, MDM2 gene amplification and apoptosis. The frequencies of allelic deletions at marker D10S2491 (which mapped within PTEN/MMAC1) and between markers D10S209 and D10S587 (where DMBT1 was located) were found to be < 30% in both types of non-astrocytic gliomas. High frequency of allelic deletions was detected at marker D10S215 (80%) at the proximal 10q23 region in both oligodendroglial and ependymal tumours and between markers D10S216 (42%) and D10S169 (67%) at distal 10q25-26 region in oligodendroglial tumours. No mutations of PTEN/MMAC1 were found. p53 mutations were detected in three oligoastrocytomas and one ependymoma; three out of five mutations were found in exon 4. MDM2 gene amplification was found in one ependymoma harbouring wild-type p53. The apoptotic index was lower in p53-mutated tumours than in tumours with wild-type p53.

CONCLUSION

The telomeric end of chromosome 10q could be involved in the development and anaplastic transformation of oligodendroglial tumours. Mutations of PTEN/MMAC1 and p53, amplification of the MDM2 gene and allelic loss on chromosome 10q do not play a major part in the pathogenesis or anaplastic transformation of oligodendrogliomas and ependymal tumours.

Use of laboratory assays to predict cytomegalovirus disease in renal transplant recipients

Eight laboratory assays, viz., the pp65 direct antigenemia test, a quantitative cytomegalovirus (CMV)-specific immunoglobulin G (IgG) assay (Biomerieux VIDAS), a CMV-specific IgM assay (Biomerieux VIDAS), the Hybrid Capture system (Murex), an in-house PCR with plasma (P-PCR) and leukocytes (L-PCR), and a commercial PCR (Roche AMPLICOR) with plasma (P-AMP) and leukocytes (L-AMP), were compared for their abilities to predict CMV disease before the onset of illness in a prospective study of 37 renal transplant recipients. By using an expanded criterion for active infection (two or more of the markers positive) and a clinical definition of disease, 22 (59%) patients were identified as having active CMV infection and 13 (35%) were identified as having CMV disease. Of the 13 CMV-seronegative recipients who received seropositive kidneys (R- group), 8 had active infection and disease. All assays were 100% specific and 100% predictive of CMV disease in the R- group. The leukocyte PCRs (L-PCR and L-AMP) were the most sensitive assays, had positive results an average of between 8 and 13 days before the onset of illness, and were the assays of choice. The performance of the assays was less satisfactory for the 24 patients who were CMV seropositive before transplantation (R+ group). A negative result was more useful for this group. Overall, P-AMP had the best results, and it could be the assay of choice for monitoring R+ patients. The non-PCR-based methods generally had high specificities but often gave late positive results and were not sensitive enough for use as prediction tools for either group of patients.

Hepatitis G virus infection in drug users in Liverpool

OBJECTIVES

To establish the prevalence of hepatitis G (HGV) in drug users in Liverpool; to explore the risk factors for, and the effects of, HGV infection.

METHODS

Serum samples from 129 drug users who had attended the Infectious Diseases Unit at Fazakerley Hospital, Liverpool, between January 1995 and June 1996 were examined for HGV RNA using PCR, HGV RNA results were collated with demographic data, information on drug-use behaviour, hepatitis B (HBV) and C (HCV) serology, and the results of serum bilirubin and aspartate amino-transferase (AST) measurements.

RESULTS

Overall, 37 (29%) of patients were HGV RNA positive, 89 (69%) were negative, and equivocal results were obtained in three (2%) cases. Direct sequencing of PCR products of the 5' non-translated region for 13 patients showed that these were generally more closely related to the HGV than the GB virus C (GBV-C) sequence. HGV co-infection with HCV and HBV was common: of HGV-positive patients, 28 (76%) and 16 (44%) had antibodies to HCV (anti-HCV) and hepatitis B core protein (anti-HBc), respectively. Increasing duration of injecting drug use was associated with a decreasing seroprevalence of HGV RNA, dropping from 39% for 0-4 years of injecting to 14% for > 12 years injecting. Serum bilirubin and AST values were frequently elevated, but statistical analysis showed no differences between HGV-positive and HGV-negative patient groups.

CONCLUSIONS

HGV infection is common in drug users in Liverpool, but HGV RNA prevalence falls with increasing duration of injecting drug use, probably as a result of viral clearance and the development of protective immunity. HGV infection does not appear to be a significant cause of hepatic dysfunction in Liverpool drug users.

Effect of genotypes on the quantification of hepatitis C virus (HCV) RNA in clinical samples using the Amplicor HCV Monitor Test and the Quantiplex HCV RNA 2.0 assay (bDNA)

The Amplicor HCV Monitor test and the Quantiplex HCV RNA 2.0 (bDNA) assay are two commercially available assays for the quantification of hepatitis C virus (HCV) RNA in clinical samples. A direct comparison of the two assays was carried out using sera frozen previously from patients known to be chronically infected with HCV. Overall, 61 samples from 51 patients were tested simultaneously by the two methods: 67% (28/42) of the patients were infected by HCV genotype/serotype 1, 10% (4/42) with type 2, and 24% (10/42) with type 3. When the absolute value from each assay was examined, the Quantiplex assay gave a consistently higher reading and the mean logarithmic difference between the two assays was 1.4 (1.0 in type 1, 2.0 in type 2, and 2.2 in type 3). When analyzed according to genotype, strong correlation was observed between the two assays for type 1 (r = 0.83, 95% CI 0.63-0.93, P < 0.01), but not for nontype 1 samples. Despite the difference in absolute level reported by the two assays, there was a consistent trend of change in HCV RNA concentration by both assays in patients whose consecutive samples were analyzed and the differences between the two assays in consecutive samples were within 0.4 log of each other. The results suggested that with samples containing genotype 1, the Amplicor assay was more sensitive than the Quantiplex assay by about one log. However, the sensitivities of the two assays with nontype 1 samples were much closer probably due to the failure of the Amplicor assay to quantify nontype 1 genotypes effectively.

Echovirus keratoconjunctivitis

PURPOSE

To investigate an outbreak of echovirus-related keratoconjunctivitis.

METHODS

We undertook a retrospective study of recent cases of echovirus infection with recall and further evaluation of conjunctivitis patients. All patients from whom an echovirus was isolated in Liverpool during 1995 were included. The natural course of ocular echovirus disease was studied, including the likelihood of echovirus keratoconjunctivitis being linked with meningitis and the risk of long-term carriage of the virus in the conjunctiva.

RESULTS

Of 10 unrelated patients with echovirus conjunctivitis, six also had a mild keratitis. None of these patients developed meningitis, and no cases of long-term carriage in the conjunctiva were encountered. There was no link between cases of echovirus meningitis and conjunctivitis. There was no corresponding increase in other ocular viral isolates.

CONCLUSIONS

Echovirus is a relatively unrecognized cause of keratoconjunctivitis. Echoviral keratoconjunctivitis appears to be an independent ocular event unassociated with systemic sequelae. Long-term carriage in the conjunctiva does not appear to occur.

Hepatitis G virus RNA and its relation to hepatitis C infection in adult haemophilic patients

The prevalence of hepatitis C virus (HCV) infection and hepatitis G virus (HGV) RNA were studied in 50 adult haemophilic patients who had received commercial clotting factors prior to 1980. HGV RNA was detectable in 6/ 50 patients (12%); 49/50 (98%) had antibody to HCV and 40/49 (82%) of these were viraemic with detectable HCV RNA; 5/6 patients with detectable HGV RNA had co-existing HCV infection and viraemia. The HGV PCR products from all six patients were directly sequenced and all were shown to be similar to that of HGV but more diverse from that of GB virus C. One patient who had persistent abnormal liver function tests had detectable HGV RNA but no evidence of hepatitis B or C. The presence of HGV RNA in the absence of hepatitis B and C infection indicates that this virus is capable of independent transmission. Independent response to interferon was demonstrated in one patient with co-infection who lost HGV but not HCV after interferon therapy.

Impact of HIV on mortality from acute lower respiratory tract infection in rural Zambia

AIMS

To establish the prevalence and clinical correlates of HIV among children with acute lower respiratory tract infection.

METHODS

Children admitted to a rural Zambian hospital were studied over an eight month period. The diagnosis of acute lower respiratory tract infection was made clinically, according to World Health Organisation (WHO) criteria. Clinicians, who were unaware of the children's HIV status, prescribed antibiotic and supportive treatment according to WHO guidelines. HIV status was established using the polymerase chain reaction (Amplicor HIV1, Roche) applied to dried blood spots.

RESULTS

Acute lower respiratory tract infection was diagnosed in 132 children (median age 8 months, range 1 month to 4 years). The WHO criteria for severe or very severe pneumonia were met by 96/132 patients (73%) and 21 patients (16%) died. HIV dried blood spot PCR was positive in 14 cases (11%), of whom four fulfilled the WHO clinical case definition for paediatric AIDS and five died. The group as a whole were malnourished, but the HIV positive children were more severely malnourished (mean z score for weight = -3.01) than the HIV negative children (mean z score = -1.73, p < 0.001). The relative risk of death was 2.6 in the HIV positive group but this was not significant (p = 0.079).

CONCLUSIONS

An important minority of children with acute lower respiratory tract infection in rural Zambia will be infected with HIV. However, most HIV positive children presenting with respiratory infection will survive given simple antibiotic and supportive treatment.

Lowering the cut off value of an automated chlamydia enzyme immunoassay and confirmation by PCR and direct immunofluorescent antibody test

AIMS

To increase the sensitivity of an automated chlamydia enzyme immunoassay by significantly lowering its cut off value, and to maintain specificity by confirmation with polymerase chain reaction (PCR) and direct immunofluorescent antibody test (DFA).

METHODS

Over five months, the cut off value of the enzyme immunoassay used to screen urogenital samples for chlamydia antigen was reduced from 80 to 10. Samples with a test value of 10 or above were further tested with a commercial PCR assay. All samples during the first three months and discrepant samples during the last two months of the study were also tested with the DFA.

RESULTS

3250 urogenital swabs (1246 urethral, 1335 endocervical, 669 pooled urethral/endocervical) from 1246 males and 2004 females were processed. Using the manufacturer's recommended cut off of 80, the enzyme immunoassay identified chlamydia antigen in 134 samples (4.1%). Using the lower cut off value of 10 and either PCR or DFA as the confirmatory test, Chlamydia trachomatis was identified in 178 samples (5.5%). Thus, 45 additional positive samples were identified and the confirmed detection rate was increased by 33.8% (45/133). Excluding equivocal PCR results, the concordance between DFA and PCR was 91.8%. This strategy increased the detection rate by 2.1% in men and 0.9% in women (significant only in men). In female patients, pooled urethral/endocervical swabs as a specimen gave a significantly higher yield than endocervical swabs regardless of whether the lower cut off strategy was used.

CONCLUSIONS

This strategy of significantly lowering the cut off test value with confirmation on the same specimen by either PCR or DFA is feasible and cost effective. The use of pooled urethral/ endocervical specimens in females should be considered routinely as detection rate was significantly improved.

Evaluation of two simplified methods for genotyping hepatitis C virus

A number of different approaches have been used for genotyping hepatitis C virus (HCV). Two simplified methods were evaluated, both of which used polymerase chain reaction (PCR) to amplify products from the 5' non-coding region of HCV: non-isotopic restriction fragment length polymorphism (RFLP) analysis and type-specific PCR. Sixty-four viraemic patients suffering from chronic HCV infection were studied using these two techniques; 25/64 samples were further tested with a commercial serotyping ELISA based on synthetic NS4 antigen (Murex, U.K.). The results of the three typing methods were generally in agreement with each other. When only the predominant genotype identified by each method was analysed, the 3 methods had 100% agreement. RFLP did not detect any mixed infections and it was unsuccessful in 16/64 (25%) samples. Both type-specific PCR and serotyping ELISA detected mixed infections. However, serotyping ELISA did not give typeable results in 7/25 (28%) samples, whereas type-specific PCR gave typeable results in all 64 samples. Type-specific PCR detected more mixed infections than serotyping ELISA. Direct sequencing of four PCR products with indeterminate RFLP confirmed changes in restriction enzyme recognition sites. The sequences also confirmed the validity of the predominant genotype in cases of apparent mixed infections. It is possible that some of these cases were artefacts as a result of quasispecies.

The occurrence of hepatitis B and C viruses in Pakistani patients with chronic liver disease and hepatocellular carcinoma

To study the occurrence of hepatitis B virus (HBV) and hepatitis C virus (HCV) in patients with chronic liver disease (CLD) and hepatocellular carcinoma (HCC) in Pakistan, blood samples from 105 sequential patients with biopsy-proven CLD (n = 82) and HCC (n = 23) were tested for HBV and HCV markers. Of the 105, 87 (83%) had evidence of hepatitis B exposure, 58 (55%) were positive for hepatitis B surface antigen (HBsAg), 23 (22%) had hepatitis C antibodies and 25 (24%) had detectable HCV RNA. Significantly more patients with HCC had evidence of HBV exposure in the absence of HCV markers (49/82 vs. 20/23, odds ratio 4.49, 95% CI 1.17-25.16). The proportion of patients positive for HBsAg with no HCV markers was also significantly higher in the HCC group (34/82 vs. 18/23, odds ratio 5.08, 95% CI 1.59-18.96). There were more patients with only HCV markers in the CLD group than the HCC group but the difference was not statistically significant (19/82 vs. 1/23, odds ratio 6.63, 95% CI 0.93-288.01). A modified non-isotopic restriction fragment length polymorphism study on PCR products was used to investigate the epidemiology of HCV genotypes in Pakistan. Due to depletion of the initial samples, a second series of specimens collected one year afterwards was used. Fifteen out of 40 samples had amplifiable product and all were identified as type 3. A commercial serological typing method on the same samples also confirmed that type 3 was the predominant HCV genotype in Pakistan.

Comparison of an automated enzyme immunoassay with a direct fluorescent antibody test and polymerase chain reaction for the detection of Chlamydia trachomatis in diagnostic specimens from male patients

Endourethral swabs and first-pass urine (FPU) samples from 148 male patients were tested for Chlamydia trachomatis by an automated enzyme immunoassay (EIA) (Vidas; bioMérieux, France), a direct fluorescent antibody (DFA) test (MicroTrak; Syva, USA) and two polymerase chain reaction (PCR) methods. Chlamydia trachomatis was considered present if a specimen was positive by at least two methods. This expanded criterion identified 27 patients (18%) as truly infected. One of the PCR methods was most sensitive for both types of specimen. When the recommended cut-off value of Vidas was reduced by 50%, its sensitivity on endourethral swabs was comparable to that of the DFA test, but the DFA test performed better with FPU. In general, FPU was suitable only for PCR.

Effect of respiratory virus infections including rhinovirus on clinical status in cystic fibrosis

One hundred and eight patients with cystic fibrosis were investigated over one year to determine whether an association existed between rhinovirus or other respiratory virus infection and clinical status. Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), Shwachman score, Chrispin-Norman chest radiograph score, and percentage weight for height were recorded at the beginning and end of the study; days of intravenous antibiotics were noted. Nasopharyngeal aspirates were taken for viral studies during respiratory exacerbations. Serum was collected at enrollment and 2-6 weeks after each respiratory exacerbation. One hundred and fifty seven exacerbations occurred in 76 patients. Respiratory virus infection was detected in 44 exacerbations and rhinovirus was present in 16% (25/157) of exacerbations. Patients with one or more respiratory virus infections were compared with those who had none. When all respiratory virus infections were considered, patients had a significantly greater deterioration in Shwachman score and received significantly more days of intravenous antibiotics. When rhinovirus was considered separately, patients received significantly more days of intravenous antibiotics, but showed no deterioration in clinical status. However, patients infected with another respiratory virus had a significant decline in FEV1, with trends towards significance for decline in FVC and Shwachman score.

A novel fast T1-mapping method

The authors present a novel fast T1-mapping technique that allows a T1 map to be reconstructed from data acquired in less than 3 seconds. Data were acquired by using two modified TurboFLASH (fast low-angle shot) sequences and were processed with a combination of one-dimensional Fourier transforms and a parameter-fitting routine, instead of a standard two-dimensional Fourier transform. Apparent T1 (T1*) maps were obtained, from which T1 maps were calculated. Comparisons of T1 values obtained in phantoms and the human brain by using this technique with those obtained with multipoint inversion-recovery T1 mapping showed that the new method yielded accurate T1 values. Optimization of the method will further improve speed and accuracy. The general approach of this T1-mapping technique is believed to be also applicable to other problems, such as T2 and T2* mapping.

Measurement of the extraction efficiency and distribution volume for Gd-DTPA in normal and diseased canine myocardium

We have previously shown that the myocardial Gd-DTPA concentration ([Gd-DTPA]t(t)) after a bolus injection of Gd-DTPA can be predicted by the Modified Kety Equation (MKE). If [Gd-DTPA]t(t) can be determined by MRI and the data fit to the MKE, then the distribution volume (lambda) of Gd-DTPA and the myocardial flow (F) times the extraction efficiency (E), i.e., the FE product, can be determined. Therefore F can only be quantified if E is known. We measured the global E in vivo in normal canine myocardium, and measured E and lambda, in vitro, locally in normal, acute ischemic (n = 5; coronary artery occlusion < 4 h), infarcted (n = 4; coronary artery occlusion, 6 days) and reperfused (n = 4; coronary artery occlusion 2 h, and reperfusion 2 h and 6 days) myocardium. Results indicate that E differs with F and with individuals and consequently, F cannot be quantified using the MKE unless the local E is also determined in vivo.

Techniques for the measurement of the local myocardial extraction efficiency for inert diffusible contrast agents such as gadopentate dimeglumine

We have previously shown that the concentration of Gd-DTPA as a function of time ([Gd-DTPA]t(t)) in the myocardium following an intravenous bolus injection of Gd-DTPA can be modeled using the Modified Kety Equation. Fitting this model to measurements of [Gd-DTPA]t(t) in a region of myocardium would allow the determination of myocardial distribution volume (lambda) and the product of flow (F) and extraction efficiency (E), i.e., FE. Thus, to measure F, E must be known. We describe here techniques developed to measure local values of E in normal and diseased myocardium. These techniques are valid for any inert diffusible MR contrast agent.

Detection of Chlamydia pneumoniae and Chlamydia psittaci in sputum samples by PCR

AIMS

To use the polymerase chain reaction (PCR) to detect Chlamydia pneumoniae and Chlamydia psittaci in sputum samples.

METHODS

A nested PCR was developed, the first stage of which amplified DNA from both C pneumoniae and C psittaci while the second stage targeted specifically at C pneumoniae, allowing the two species to be differentiated. The primers were designed not to amplify sequences from C trachomatis. A panel of 26 sputum samples from patients with community acquired pneumonia evaluated previously by enzyme linked immunosorbent assay (ELISA), direct immunofluorescence (DIF), and culture was tested blind by PCR. Most of these specimens also had accompanying serial serum samples which were tested for species specific antibodies using microimmunofluorescence (micro-IF).

RESULTS

PCR detected C pneumoniae DNA in 10 of the 26 samples and C psittaci DNA in four. There was good concordance between ELISA, DIF, micro-IF and PCR in the C pneumoniae group. Two of the C psittaci identified by PCR were labelled C pneumoniae by DIF but the PCR results were supported by serology or a history of bird contact. Of the PCR negative group: six were true negative results; two contained C trachomatis. There were four discrepant results.

CONCLUSIONS

The data suggest that PCR is effective in the detection of C pneumoniae. The sensitivity for C psittaci is inevitably lower due to the strategy taken but specificity seemed to be good.