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Biomedical subjects

H McKenzie

Publications and source records attributed to H McKenzie.

At least 19 recordsLinked to original sources

Prophylactic administration of ponazuril reduces clinical signs and delays seroconversion in horses challenged with Sarcocystis neurona.

The ability of ponazuril to prevent or limit clinical signs of equine protozoal myeloencephalitis (EPM) after infection with Sarcocystis neurona was evaluated. Eighteen horses were assigned to 1 of 3 groups: no treatment, 2.5 mg/kg ponazuril, or 5.0 mg/kg ponazuril. Horses were administered ponazuril, once per day, beginning 7 days before infection (study day 0) and continuing for 28 days postinfection. On day 0, horses were stressed by transport and challenged with 1 million S. neurona sporocysts per horse. Sequential neurologic examinations were performed, and serum and cerebrospinal fluid were collected and assayed for antibodies to S. neurona. All horses in the control group developed neurologic signs, whereas only 71 and 40% of horses in the 2.5 and 5.0 mg/kg ponazuril groups, respectively, developed neurologic abnormalities. This was significant at P = 0.034 by using Fisher exact test. In addition, seroconversion was decreased in the 5.0 mg/kg group compared with the control horses (100 vs. 40%; P = 0.028). Horses with neurologic signs were killed, and a post-mortem examination was performed. Mild-to-moderate, multifocal signs of neuroinflammation were observed. These results confirm that treatment with ponazuril at 5.0 mg/kg minimizes, but does not eliminate, infection and clinical signs of EPM in horses.

Animals↗

Evaluation of endocervical, first-void urine and self-administered vulval swabs for the detection of Chlamydia trachomatis in a miscarriage population.

OBJECTIVE: To compare, in parallel, different approaches of opportunistically screening women with bleeding in early pregnancy for Chlamydia trachomatis. DESIGN: Prospective observational [corrected] study. SETTING: Early pregnancy assessment unit, University hospital, Scotland, UK. POPULATION: Over 200 consecutive women admitted to an early pregnancy assessment unit were recruited. All had a positive pregnancy test, a history of vaginal bleeding and were less than 24 weeks of gestation. Women with recent antibiotic use, heavy vaginal bleeding and cervical shock excluded. METHODS: Each women provided two or more of the following specimens: a self-administered vulval swab, first-void urine and/or endocervical swab. Following screening, each completed a semi-structured questionnaire assessing the acceptability of each method undertaken. MAIN OUTCOME MEASURE: Subjective rating of the screening methods; prevalence; method performance, including proportion requiring repeat testing. RESULTS: The majority accepted screening, with moderate prevalence rates (95% CI) 3.9% (2.0-7.4%) identified. All positive women were less than 30 years of age. Parallel screening exposed the potential of reduced test performance with urine. Non-invasive sampling was more acceptable, but more likely to require repeat testing. CONCLUSION: Both acceptability and the effect of bleeding on test performance need further assessment before a particular specimen can be recommended for screening this population of women for C. trachomatis.

Abortion, Spontaneous↗

Which women should be tested for Chlamydia trachomatis?

OBJECTIVE: To assess the prevalence of genitourinary Chlamydia trachomatis infection among women in different clinical settings, with a view to making decisions about who should be tested routinely. DESIGN: Cross sectional study. SETTING: One regional hospital and family planning clinic serving an urban centre. Population Two thousand thirty-five sexually active women attending various outpatient settings. MAIN OUTCOME MEASURES: Prevalence of positivity by clinical setting, stratified by age. RESULTS: Overall, prevalence of lower genital tract chlamydial infection was similar in a variety of clinical settings. Infertile women were the only exception, demonstrating a much lower prevalence. Stratifying the study population by age found a clear trend towards high prevalence in teenagers and virtually no infection in women over the age of 30 years. CONCLUSIONS: The prevalence of chlamydial infection in women is related to age, regardless of clinical presentation. In practice, opportunistic screening should target sexually active women under 30 years of age.

Adolescent↗

Feasibility of patient-collected vulval swabs for the diagnosis of Chlamydia trachomatis in a family planning clinic: a pilot study.

This pilot study set out to determine the feasibility of using patient-collected vulval swabs, instead of urine, for the diagnosis of female Chlamydia trachomatis infection. Main outcome measures included prevalence of infection and sensitivity, specificity, and acceptability of both test methods. An assessment was also made of those who declined to be tested. Consecutive women under 25 years of age attending a single urban family planning clinic were invited to participate. Sixty-eight percent (103/152) agreed to undergo testing. Overall prevalence was 11.7%. The sensitivity/specificity for the ligase chain reaction (LCR) assayed patient-collected vulval swabs and urine was 100%/100% and 92%/100%, respectively. The acceptability of self-collection was high with 93% characterising the test as 'not bad', 79% recommending it to a friend, and 79% choosing the test next time. Significantly more women, however, would choose urine for testing on a subsequent occasion (p < 0.001). Less than 1/5 of the patients who declined did not take part because of concerns regarding the vulval swab. Patient-collected vulval swabs assayed by LCR represent a non-invasive, sensitive, and acceptable way to detect genital C. trachomatis infection in women attending a family planning clinic. Compared with urine testing, benefits in terms of transport and processing should encourage more widespread use of this approach.

Adolescent↗

Heterogeneity of metabotropic glutamate receptors in autonomic cell groups of the medulla oblongata of the rat.

Metabotropic glutamate receptors (mGluRs) in the medulla oblongata have been suggested to be involved in the regulation of autonomic function. The aim of the present study was to examine the localization and expression of four types of mGluRs: mGluRla, mGluR2/3, mGluR5, and mGluR7 in the dorsal and ventral autonomic nuclei of the medulla of the rat. The four mGluR subtypes studied were differentially distributed in distinct subnuclei in the nucleus of the solitary tract (NTS). mGluRla immunoreactivity was identified in cell bodies, dendrites, and axonal processes in the intermediate, dorsal lateral, and interstitial subnuclei of the NTS. No mGluRla immunoreactivity was observed in the commissural or medial NTS subnuclei. Immunoreactivity for mGluR2/3 and mGluR5 as observed in fibers and putative axonal processes in the interstitial, intermediate, and dorsolateral subnuclei of the NTS. In contrast, mGluR7 was expressed primarily in fibers and terminals in the central and commissural NTS subnuclei. Expression of mGluR2/3 was clearly evident in cell bodies, dendrites, and axonal processes within the area postrema. The vagal outflow nuclei were also studied. The dorsal motor nucleus of the vagus (DMN) contained mGluRla cell bodies, dendrites, and axonal fibers and light mGluR2/3 processes. Throughout the rostral-caudal extent of the compact and semicompact formation nucleus ambiguus, mGluRla was found in cell bodies and fibers. Within the caudal and rostral regions of the ventral lateral medulla, mGluRla was observed in cell bodies and fibers. Cell bodies containing mGluRla were found adjacent to cells staining positive for tyrosine hydroxylase (TH) in these regions but were not colocalized with the TH staining. However, mGluRla-expressing neurons in the ventral lateral medulla did appear to receive innervation from TH-containing fibers. These results suggest that the mGluRla-expressing neurons within the ventral lateral medulla are predominantly not catecholaminergic but may be innervated by catecholamine-containing fibers. These data are the first to provide a mapping of the different mGluR subtypes within the medulla and may facilitate predictions regarding the function of L-glutamate neurotransmission in these regions.

Animals↗

A proteomic analysis of erythromycin resistance in Streptococcus pneumoniae.

Streptococcus pneumoniae is a significant human pathogen which is an important cause of pneumonia and bacteraemia. Over the past few years the incidence of antibiotic resistance among clinical isolates of S. pneumoniae has increased. Penicillin resistance is now widespread and the frequency of isolates that are resistant to erythromycin has risen. Erythromycin resistance in S. pneumoniae follows two basic patterns. The MLS erythromycin-resistant phenotype is due to the enzymatic methylation of ribosomal RNA that blocks erythromycin binding to the ribosome. Alternatively, in isolates of the M phenotype, a more recently documented mechanism, resistance is associated with an active efflux process that reduces intracellular levels of erythromycin. We used two-dimensional electrophoresis to examine the proteins synthesised by erythromycin-susceptible and -resistant S. pneumoniae. Erythromycin-resistant S. pneumoniae with the M phenotype showed a significantly increased synthesis of a 38,500 Dalton (pI 6.27) protein compared to susceptible isolates. Peptide mass mapping was used to identify the 38,500 Dalton protein as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). It was demonstrated that S. pneumoniae synthesised at least three forms of GAPDH that differed in their isoelectric points. The form of GAPDH possessing the most basic pI showed the increased synthesis in the erythromycin-resistant S. pneumoniae isolates. Alterations in the synthesis of GAPDH were only found for those erythromycin-resistant isolates possessing the M phenotype. S. pneumoniae isolates with the MLS phenotype were indistinguishable from the susceptible strains using the analytical conditions employed for the current study. The possible role of GAPDH in erythromycin resistance of S. pneumoniae is considered.

Anti-Bacterial Agents↗

A randomised comparison of strategies for reducing infective complications of induced abortion.

OBJECTIVES: To determine lower genital tract carriage rates of C. trachomatis, N. gonorrhoeae and bacterial vaginosis among women seeking termination of pregnancy. To compare two clinical management strategies for minimising the risks of infective morbidity after induced abortion. DESIGN: Prevalence of infections was assessed by screening women undergoing abortion. Clinical management strategies were compared by a randomised trial. SETTING: The gynaecology departments of four hospitals in Scotland. PARTICIPANTS: 1672 women undergoing induced abortion. INTERVENTIONS: Women randomised to prophylaxis received metronidazole 1 g rectally before abortion plus doxycycline 100 mg twice daily for seven days. Women randomised to screen-and-treat received appropriate antibiotics only if screening proved positive for one or more infection. MAIN OUTCOME MEASURES: Prevalences of infections; morbidity in the eight weeks following abortion as assessed by reported symptoms, general practitioner consultation and prescription rates and hospital re-attendances; costs to the NHS of alternative managements. RESULTS: Prevalence rates: C. trachomatis 5.6%; N gonorrhoeae 0.19%; bacterial vaginosis 17.5%. Overall, women allocated to receive prophylaxis had lower rates of measures of short term infective morbidity than those allocated to screen-and-treat. These differences only reached statistical significance for women who were reported negative on screening. The direct costs to the NHS of prophylaxis and screen-and-treat were calculated to be 8.17 and 18.34 per woman, respectively. CONCLUSIONS: Prevalences of lower genital tract infections which have been implicated in increased rates of infective morbidity after abortion are similar to those reported elsewhere. Universal antibiotic prophylaxis is at least as effective as a policy of screen-and-treat in minimising the risk of short term infective morbidity and is far more cost efficient.

Abortion, Induced↗

Helicobacter pylori is killed by nitrite under acidic conditions.

BACKGROUND: Due to the expression of urease, Helicobacter pylori is able to establish itself in the human stomach under acidic conditions. A novel host defence mechanism was recently proposed, suggesting that the formation of salivary nitrite in symbiosis with facultative anaerobic bacteria in the oropharynx, is aimed at enhancing the antimicrobial activity of gastric juice. AIMS: To investigate whether the addition of nitrite in physiological concentrations influences the resistance of H pylori to acid. METHODS: H pylori cultured from fresh gastric Biopsy specimens was exposed for 30 minutes to normal saline and to HCl/KCl buffer (0.2M) at pH 2 with urea (5 mM) added. The influence of potassium nitrite (50-1000 mumol/l) on bacterial survival was determined. RESULTS: Addition of nitrite (1 mM) to acidic solutions (pH 2) resulted in complete kill of H pylori within 30 minutes exposure time whereas acid alone allowed the organism to survive (p < 0.001). The antimicrobial effect of nitrite at pH 2 against H pylori was dose dependent and complete kill of organisms occurred at concentrations > or = 500 mumol/l. CONCLUSION: Acidified nitrite has anti-bacterial activity against H pylori. This should prompt further research into the effect of salivary nitrite on the survival of H pylori in the human stomach.

Anti-Bacterial Agents↗

Protection against oral and gastrointestinal diseases: importance of dietary nitrate intake, oral nitrate reduction and enterosalivary nitrate circulation.

Over the last 20 years, dietary nitrate has been implicated in the formation of methemoglobin and carcinogenic nitrosamines in humans. This has led to restrictions of nitrate and nitrite levels in food and drinking water. However, there is no epidemiological evidence for an increased risk of gastric and intestinal cancer in population groups with high dietary vegetable or nitrate intake. A reevaluation of our currently very negative perception of dietary nitrates comes from recent research into the metabolism and enterosalivary circulation of nitrate in mammals. These studies showed that nitrate is converted to nitrite in the oral cavity that then "fuels" an important mammalian resistance mechanism against infectious diseases. Moreover, there is now evidence that the conversion of nitrate into oxides of nitrogen prevents the formation carcinogenic nitrosamines.

Animals↗

Moraxella (Branhamella) catarrhalis--clinical and molecular aspects of a rediscovered pathogen.

Since its discovery at the end of the nineteenth century, Moraxella (Branhamella) catarrhalis has undergone several changes of nomenclature and periodic changes in its perceived status as either a commensal or a pathogen. Molecular analysis based on DNA hybridisation or 16S rDNA sequence comparisons has established its phylogenetic position as a member of the Moraxellaceae and shown that it is related more closely to Acinetobacter spp. than to the genus Neisseria in which it was placed formerly. However, confusion with phenotypically similar Neisseria spp. can occur in the routine diagnostic laboratory if appropriate identification tests are not performed. M. catarrhalis is now accepted as the third commonest pathogen of the respiratory tract after Streptococcus pneumoniae and Haemophilus influenzae. It is a significant cause of otitis media and sinusitis in children and of lower respiratory tract infections in adults, especially those with underlying chest disease. Nosocomial spread of infection, especially within respiratory wards, has been reported. Invasive infection is uncommon, but analysis of reports for England and Wales between 1992 and 1995 revealed 89 cases of M. catarrhalis bacteraemia, with the peak incidence in children aged 1-2 years. Carriage rates of M. catarrhalis are high in children and in the elderly, but its role as a commensal organism has probably been overstated in the past. Approximately 90% of strains are now beta-lactamase positive and, given that the first such strain was reported in 1976, this represents a dramatic increase in frequency over the last 20 years which has not been paralleled in any other species. The BRO-1 and BRO-2 beta-lactamase enzymes of M. catarrhalis are found in other Moraxellaceae, but are not related to beta-lactamases of any other species and their origin is therefore unknown. Molecular and typing studies have shown that the M. catarrhalis species is genetically heterogeneous and these methods have aided epidemiological investigation. Studies of factors that may be related to pathogenicity have shown the existence of three serotypes of lipooligosaccharide and the presence of fimbriae and a possible capsule. Some strains are serum-resistant, probably by virtue of interference with complement action, whilst transferrin- and lactoferrin-binding proteins enable the organism to obtain iron from its environment. An antibody response in humans to various M. catarrhalis antigens, including highly conserved outer-membrane proteins, has been demonstrated. Increased understanding of the organism's pathogenic properties and the host response to it may help to identify suitable vaccine targets or lead to other strategies to prevent infection. Whilst it remains, at present, the third most important respiratory pathogen, the impact of immunisation strategies for other organisms may change this position. The speed with which M. catarrhalis acquired beta-lactamase demonstrates the capacity of this organism to surprise us.

Adolescent↗

Familial Klippel-Feil syndrome and paracentric inversion inv(8)(q22.2q23.3).

Klippel-Feil Syndrome (KFS) is characterized by congenital vertebral fusion believed to result from faulty segmentation along the embryo's developing axis. KFS appears to be a heterogeneous disease often associated with craniofacial malformation. Here we provide the first evidence of a familial KFS gene locus on 8q, where an inv(8)(q22.2q23.3) has been found segregating with congenital vertebral fusion. The four-generation KF2-01 family present with dominant form of the KFS where the sequence of vertebral fusion was confined to the cervical spine (always including the C2-3 fusion and reduced expression of the C4-5 and C6-7 fusions) in association with malformation of laryngeal cartilages and mild-to-severe vocal impairment.

Chromosome Inversion↗

Phylogenetic relationships between some members of the genera Neisseria, Acinetobacter, Moraxella, and Kingella based on partial 16S ribosomal DNA sequence analysis.

We obtained 16S ribosomal DNA (rDNA) sequence data for strains belonging to 11 species of Proteobacteria, including the type strains of Kingella kingae, Neisseria lactamica, Neisseria meningitidis, Moraxella lacunata subsp. lacunata, [Neisseria] ovis, Moraxella catarrhalis, Moraxella osloensis, [Moraxella] phenylpyruvica, and Acinetobacter lwoffii, as well as strains of Neisseria subflava and Acinetobacter calcoaceticus. The data in a distance matrix constructed by comparing the sequences supported the proposal that the genera Acinetobacter and Moraxella and [N.] ovis should be excluded from the family Neisseriaceae. Our results are consistent with hybridization data which suggest that these excluded taxa should be part of a new family, the Moraxellaceae. The strains that we studied can be divided into the following five groups: (i) M. lacunata subsp. lacunata, [N.] ovis, and M. catarrhalis; (ii) M. osloensis; (iii) [M.] phenylpyruvica; (iv) A. calcoaceticus and A. lwoffii; and (v) N. meningitidis, N. subflava, N. lactamica, and K. kingae. We agree with the previous proposal that [N.] ovis should be renamed Moraxella ovis, as this organism is closely related to Moraxella species and not to Neisseria species. The generically misnamed taxon [M.] phenylpyruvica belongs to the proposed family Moraxellaceae, but it is sufficiently different to warrant exclusion from the genus Moraxella. Further work needs to be done to investigate genetically similar species, such as Psychrobacter immobilis, before the true generic position of this organism can be determined. Automated 16S rDNA sequencing with the PCR allows workers to accurately determine phylogenetic relationships between groups of organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Acinetobacter↗

Risk of preterm delivery in pregnant women with group B streptococcal urinary infections or urinary antibodies to group B streptococcal and E. coli antigens.

OBJECTIVE: To establish whether there is an association between preterm delivery and either group B streptococcal urinary infection or the presence of urinary antibodies to group B streptococcal or E. coli antigens. DESIGN: A prospective study with urine culture and antibody measurement performed at the first antenatal visit and at 28 weeks gestation. SETTING: Ninewells Hospital, Dundee. SUBJECTS: Two thousand and forty-three women registering consecutively at an antenatal clinic. MAIN OUTCOME MEASURE: Delivery at less than 37 weeks gestation. RESULTS: No increase in preterm delivery was observed in women with positive urine cultures for group B streptococci either at booking or at 28 weeks, even when confirmed by positive repeat cultures. Preterm delivery was more common in women with elevated urinary antibodies to E. coli antigens at booking (relative risk 1.81, 95% CI 1.22-2.68, P = 0.005) and at 28 weeks (relative risk 2.36, 95% CI 1.60-3.48, P < 0.0001) and to group B streptococcal antigens at 28 weeks (relative risk 2.24, 95% CI 1.46-3.43, P = 0.0003). CONCLUSIONS: These data do not support previous reports that positive urine cultures for group B streptococci are associated with an increased risk of preterm delivery. Our report of an association between elevated levels of urinary antibodies and preterm delivery is a new finding consistent with the possibility that a local inflammatory response to uro-genital infection may be important in stimulating the onset of preterm labour. The results suggest that screening for urinary antibodies at 28 weeks gestation might help to identify a group of women at increased risk of prematurity.

Adult↗

Controversies in the laboratory diagnosis of community-acquired urinary tract infection.

Urine samples constitute the largest single category of specimens examined in most medical microbiology laboratories. The everyday nature and apparent simplicity of urinary tract infection belies the intense debate and controversy regarding the optimal methods of collection, transport and processing of urine specimens and reporting of results. There is considerable variation in the interpretation of quantitative culture results between laboratories and the etiology of abacterial cystitis remains unclear. Microscopy to detect pyuria provides information on an important indicator of inflammation and it has been proposed that detection of urinary antibody may provide similar information. Neither of these indices of host response is suitable for use in a screening test for urinary infection however, although they may usefully contribute to the interpretation of significance of culture results. The development of screening tests and automated systems continues, but at present microscopy and culture remain the most important techniques for laboratory diagnosis. However, these techniques have so far failed to provide an etiological diagnosis for abacterial cystitis and this remains a major area for research.

Adult↗