Biomedical subjects
Publications and source records attributed to C A Hart.
Antibiotics have been considered to be safe and effective 'magic bullets', with no disadvantages to their widespread use. This has been proven to be a complacent attitude, with ever-increasing prevalences of resistance now evident. The present review covers aspects of the development, mechanisms and genetics of antimicrobial resistance in enteric commensals and pathogens.
Among 606 children who were treated for acute gastroenteritis at the Queen Elizabeth Central Hospital in Blantyre, Malawi, Group C rotavirus (Gp C RV) was detected by enzyme-linked immunosorbent assay in fecal specimens from 16 (3.9%) of 408 inpatients and in 4 (2.0%) of 198 outpatients. Thirteen (65%) children excreting Gp C RV were coinfected with Group A rotavirus.
This review examines the role of cytokines and chemokines in the pathogenesis of meningococcal disease (MCD) and draws comparisons with studies of other forms of sepsis in adults and in animal models. There are many similarities but also discrepancies between these data. MCD is a well-defined clinical syndrome with identifiable onset and time of presentation. It is a reliable model in which to study cytokine and chemokine responses in bacterial sepsis. Such studies may lead to new adjunctive treatments, which can be tested to ameliorate severe MCD.
A novel spirochaete was isolated from a case of severe virulent ovine foot rot (SVOFR) by immunomagnetic separation with beads coated with polyclonal anti-treponemal antisera and prolonged anaerobic broth culture. The as yet unnamed treponeme differs considerably from the only other spirochaete isolated from ovine foot rot as regards morphology, enzymic profile and 16S rDNA sequence. On the basis of 16S rDNA, it was most closely related to another unnamed spirochaete isolated from cases of bovine digital dermatitis in the USA, raising the possibility of cross-species transmission. Further information is required to establish this novel ovine spirochaete as the cause of SVOFR.
A genotyping method based on PCR-RFLP analysis of the flagellin gene (flaA) was applied to 30 mainly feline isolates of Bordetella bronchiseptica. These isolates were separated into three PCR-RFLP groups with the restriction endonucleases HaeIII, MspI, MboI and RsaI. flaA nucleotide sequences representing each of the three groups differed from each other by 11-13%. One of the groups exhibited far greater flaA sequence identity with the cryptic flagellin gene sequence of B. pertussis (>97%) than with flaA sequences from representatives of the other B. bronchiseptica PCR-RFLP groups. Amongst the 30 isolates were at least 10 representing each of the two major genotypes (A and B) identified in a previous study by macro-restriction analysis and pulsed-field gel electrophoresis (PFGE), as well as representatives of other less common genotypes. Each of the major PFGE genotypes contained strains representing more than one flagellin genotype. Indeed, there was no correlation between the two molecular typing methods. PFGE analysis may identify differences due to genomic re-arrangements rather than genuine variations in gene content. If so, relationships inferred on the basis of PFGE or other molecular methods for whole genome comparison should be treated with caution.
Intracellular phosphorylation of stavudine (d4T) and zidovudine (ZDV) was investigated in peripheral blood mononuclear cells (PBMCs) isolated from ZDV-naive and ZDV-experienced human immunodeficiency virus (HIV)-positive patients. An in vivo study measured the amount of d4T triphosphate (d4TTP), while an ex vivo study assessed the capacity of cells to phosphorylate added d4T. Endogenous dTTP was also measured. d4TTP and dTTP were determined in vivo using a reverse transcriptase chain termination assay. In ex vivo studies, d4T (1 microM) was incubated in resting and phytohemagglutinin-stimulated (10 microg ml(-1); 72 h) PBMCs for 24 h. After washing and methanol extraction, radiolabeled anabolites were detected by high-performance liquid chromatography. d4TTP reached its highest level 2 to 4 h after dosing (0.21 +/- 0.14 pmol/10(6) cells; n = 27 [mean +/- standard deviation]). Comparison of ZDV-naive and ZDV-experienced individuals showed no significant difference in levels of d4TTP (ZDV naive, 0.23 +/- 0.17 pmol/10(6) cells [n = 7] versus ZDV experienced, 0.20 +/- 0.14 pmol/10(6) cells [n = 20]; P = 0.473) or the d4TTP/dTTP ratio (0.14 +/- 0.12 [n = 7] and 0.10 +/- 0.08 [n = 20], respectively; p = 0.391). Ex vivo data demonstrated no significant difference in the formation of d4TTP or total d4T phosphates in naive and experienced patients (0.086 +/- 0.055 pmol/10(6) cells in ZDV-naive patients [n = 17] versus 0.081 +/- 0.038 pmol/10(6) cells in ZDV-experienced patients [n = 22]; P = 0.767). The ability of HIV-infected patients to phosphorylate d4T in vivo and ex vivo was unchanged with increasing exposure to ZDV.
Nine Klebsiella pneumoniae isolates, six from blood and three from cerebrospinal fluid of newborn babies at Kenyatta National Hospital, Nairobi, Kenya, were analyzed for the mechanism of cephalosporin resistance. By using pulsed-field gel electrophoresis of XbaI-digested chromosomal DNA, all the nine isolates were found to be clonal. PCR and direct sequencing revealed a novel extended-spectrum beta-lactamase, which we designated CTX-M-12. It has a more potent hydrolytic activity against cefotaxime than against ceftazidime and a pI of 9.0 and is encoded on a large self-transferable ca. 160-kbp plasmid.
A panel of 30 previously characterized strains representing five genomovars from the Burkholderia cepacia complex (E. Mahenthiralingam, T. Coenye, J. W. Chung, D. P. Speert, J. R. W. Govan, P. Taylor, and P. Vandamme, J. Clin. Microbiol. 38:910--913, 2000) were examined for their iron protoporphyrin IX-binding ability. These included B. cepacia genomovars I and III and B. stabilis (formerly B. cepacia genomovar IV), B. multivorans (formerly B. cepacia genomovar II), and B. vietnamiensis (formerly B. cepacia genomovar V). Cells were exposed to micro-oxo bisheme of iron protoporphyrin IX (micro-oxo dimers) and examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing, nondenaturing conditions for the presence of heme-binding proteins using tetramethylbenzidine-H(2)O(2) staining. Seven of the 30 strains, each belonging to B. cepacia genomovar III and designated epidemic (in possessing the B. cepacia epidemic strain marker), expressed a 96- to 100-kDa heme-binding protein which was located in the outer membrane. The heme-binding protein of B. cepacia genomovar III epidemic strain C5424 bound iron(III) protoporphyrin IX in both the monomeric and micro-oxo bisheme forms. Cells of all strains grown on Columbia agar bound iron protoporphyrin IX in the micro-oxo bisheme (dimeric) form. There were no statistical differences between the five genomovars, or those possessing the heme-binding protein, in their micro-oxo bisheme-binding ability. Possession of the outer membrane heme-binding protein may be a pathogenicity trait in enabling the bacterium to withstand oxidative stresses in inflammatory exudates in the lung and may aid identification of invasive epidemic strains of B. cepacia.
In a 2-year study of viral gastroenteritis in children in Blantyre, Malawi, the diversity of rotavirus strains was investigated by using electropherotyping, reverse transcription-PCR amplification of the VP7 and VP4 genes (G and P genotyping), and nucleotide sequencing. Of 414 rotavirus strains characterized, the following strain types were identified: P[8], G1 (n = 111; 26.8%); P[6], G8 (n = 110; 26.6%); P[8], G3 (n = 93; 22.5%); P[4], G8 (n = 31; 7.5%); P[8], G4 (n = 21; 5.1%); P[6], G3 (n = 12; 2.9%); P[6], G1 (n = 7; 1.7%); P[6], G9 (n = 3; 0.7%); P[6], G4 (n = 3; 0.7%); P[4], G3 (n = 1; 0.2%); and mixed (n = 15; 3.6%). While all strains could be assigned a G type, seven strains (1.7%) remained P nontypeable. The majority of serotype G8 strains and all serotype G9 strains had short electropherotype profiles. All remaining typeable strains had long electropherotypes. Divergent serotype G1 rotaviruses, which contained multiple base substitutions in the 9T-1 primer binding site, were commonly identified in the second year of surveillance. Serotype G2 was not identified. Overall, G8 was the most frequently identified VP7 serotype (n = 144; 34.8%) and P[8] was the most frequently detected VP4 genotype (n = 227; 54.8%). Partial sequence analysis of the VP4 gene of genotype P[8] rotaviruses identified three distinct clusters, which predominantly (but not exclusively) comprised strains belonging to a distinct VP7 serotype (G1, G3, or G4). As a result of mutations in the 1T-1 primer binding site, strains belonging to each cluster required a separate primer for efficient typing. One cluster, represented by P[8], G4 strain OP354, was highly divergent from the established Wa and F45 VP4 P[8] lineages. As is the case for some other countries, the diversity of rotaviruses in Malawi implies that rotavirus vaccines in development will need to protect against a wider panel of serotypes than originally envisioned.
AIMS: To determine long term neurodevelopmental outcome following the spectrum of meningococcal infection. METHODS: Between 1988 and 1990, 152 cases of meningococcal disease were recruited; 139 survived. Between 1998 and 1999, 115 survivors (83%) were evaluated, together with 115 sex and age matched controls. Standard measures of neurological function, coordination, cognition, behaviour, and hearing were used to assess neurodevelopmental status. RESULTS: One case has spastic quadriplegia. Gross neurological examination was normal in all other cases and all controls. Five cases and no controls have significant hearing loss. Cases performed at a lower level than controls on measures of coordination, cognition, and behaviour. Four cases and no controls had major impairments. The adjusted odds ratios for moderate and minor impairments were 3.6 (95% CI 1.3 to 10.3) and 1.6 (95% CI 0.8 to 3.4) respectively. CONCLUSION: The majority of survivors from this cohort do not have gross neurological deficits. However, when objective measures of motor function, cognitive ability, and behaviour were applied significant detriments were found in meningococcal survivors.
AIMS: (1) To examine the relation between neurological soft signs and measures of cognition, coordination, and behaviour in mainstream schoolchildren. (2) To determine whether high soft sign scores may predict children with significant problems in other areas. METHODS: A total of 169 children aged between 8 and 13 years from mainstream schools were assessed. They form part of a larger study into the outcome of meningococcal disease in childhood. Half had previous meningococcal disease and half were controls. Assessment involved measurement of six soft signs followed by assessment of motor skills (movement ABC), cognitive function (WISC-III), and behaviour (Conners' Rating Scales). RESULTS: Children having an age corrected soft sign score above the 90th centile were considered to have an excess of soft signs. When compared to the other children they had significantly worse scores on the other three measures. Median movement ABC score was 15.3 v 7. Mean total IQ scores were lower by 10.3 points. Median behaviour scores were significantly higher on both parental and teacher questionnaires. A soft sign score above the 90th centile had a sensitivity of 38% for detecting cognitive impairment, 42% for detecting coordination problems, and 25% for detecting possible attention deficit hyperactivity disorder. CONCLUSION: In this group of children higher scores on the soft sign battery were related to significantly worse performance on measures of cognition, coordination, and behaviour. However, although soft sign assessment may be of interest it cannot accurately predict which children are likely to have impairment in other areas.
AIM: To evaluate mortality of critically ill children admitted with meningococcal disease. METHODS: Prospective study of all children admitted to a regional paediatric intensive care unit (PICU) between January 1995 and March 1998 with meningococcal disease. Outcome measures were actual overall mortality, predicted mortality (by PRISM), and standardised mortality ratio. RESULTS: A total of 123 children were admitted with meningococcal disease. There was an overall PICU mortality of 11 children (8.9%). The total mortality predicted by PRISM was 24.9. The standardised mortality ratio (SMR) was 0.44. Results were compared with those from four previously published meningococcal PICU studies (USA, Australia, UK, Netherlands) in which PRISM scores were calculated. The overall PICU mortality and SMR were lower than those in the previously published studies. CONCLUSION: Compared with older studies and calibrating for disease severity, this study found a decrease in the mortality of critically ill children with meningococcal disease.
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.
Viscous negatively charged cystic fibrosis (CF) sputum allows colonization by pathogens, inducing a chronic inflammatory response. Heparin thins sputum by decreasing the mucin molecule amino group negative charge, altering its intermolecular hydrogen bonding, and ionically shielding its polyionic moieties. It also has an anti-inflammatory effect within the lung. It may, therefore, be useful in the treatment of CF patients. In order to test this, six fully informed Burkholderia cepacia colonized stable adult CF patients, received 25,000 IU nebulized heparin sulphate daily for 7 days. Subjective sputum parameters, spirometry, platelets, coagulation parameters, and serum and sputum interleukin (IL)-6 and -8 were measured before and after treatment. All patients tolerated the heparin with no evidence of bleeding, thrombocytopenia or change in coagulation parameters. There was no change in spirometry, but a reduction in interleukins (sputum IL-6, p=0.01; sputum IL-8, p=0.002; serum IL-6, p=0.02; serum IL-8, p=0.02). Sputum was easier to expectorate (p < 0.04), with a trend towards thinner sputum (p=0.07) but no change in sputum volume. Heparin therapy was well tolerated and had an anti-inflammatory effect, with subjective sputum mucolysis. Further studies are necessary to define the role of heparin in the treatment of cystic fibrosis patients.
A case history is described of an HIV-seropositive man who presented with a swelling on the right cheek and a history of disseminated molluscum contagiosum. Electron microscopy of the abscess aspirate showed pox virions indicative of molluscum contagiosum. This is an unusual presentation of molluscum contagiosum and the authors review the literature of other presentations.
Meningococcal disease (MCD) is an important cause of morbidity and mortality. The pathophysiology consists of a complex interaction of bacterial and host factors, triggered by the release of endotoxin which initiates the inflammatory cascade, resulting in multi-organ failure, coagulopathy, capillary leak, metabolic derangement and eventually death. Prompt recognition and aggressive management are essential in reducing mortality. Over the past decade, there has been intense research into novel therapies and vaccines, with largely disappointing results. Therapies have been broadly divided into anti-endotoxin and anti-TNF-alpha therapies, treatment aimed at correcting coagulopathy and at blood purification and anti-inflammatory cytokine therapy. The reasons for the disappointing results in the search for new therapeutic strategies are difficult to identify. The disordered physiology in MCD results from a complex interaction of several mediators; therefore attempts to correct this by altering just one step represents a gross oversimplification of the process. In addition, the experimental model of endotoxaemia, which is often used, is a poor representation of an acutely ill patient with rapidly progressive shock. There have been several small or poorly designed trials, which have failed to reach definite conclusions. In order to yield conclusive results any future trials must be multicentre, randomised, controlled trials, but these are expensive and, in practice, difficult to conduct. The BPI trial (vide infra) was a significant step forward in this regard and demonstrated the ability to organise a large multicentred trial which can act as a template for future trials. Although the results were not significant there was an overall trend towards improved outcome in the treatment arm. Whilst the development of effective therapies and vaccines are awaited, the priorities at present must be the prompt recognition and aggressive management of disease.
The fluoroquinolones have become widely used antibacterial agents in the treatment of ocular infections, with topical, intravitreal and systemic routes of administration being used. In general, fluoroquinolones (such as ciprofloxacin, ofloxacin, lomefloxacin and norfloxacin) have good activity against gram-negative and gram-positive bacteria. Therapeutic concentrations are achieved in the cornea after topical administration so that the fluoroqinolones have largely replaced combination therapy for the treatment of bacterial keratitis. However, a second line agent is needed when resistance is likely, such as in disease caused by streptococcal species. Reversal of resistance to quinolones may not occur with withdrawal of the antibacterial. This stresses the importance of prudent prescribing to reduce the occurrence of resistance to quinolones. When used in therapeutic topical dosages, corneal toxicity does not occur. Similarly, retinal toxicity is not seen when fluoroquinolones are used at therapeutic dosages, systemically or topically. Corneal precipitation occurs, particularly with ciprofloxacin and to a lesser extent norfloxacin, but does not appear to interfere with healing. In the treatment of endophthalmitis there is reasonable penetration of systemic fluoroquinolones into the vitreous but sufficiently high concentrations to reach the minimum inhibitory concentration for 90% of isolates (MIC90) of all important micro-organisms may not be guaranteed. Systemic administration may be useful for prophylaxis after ocular trauma.
The diagnosis of pulmonary tuberculosis (PTB) in young children is particularly complex in resource-poor regions where HIV infection is common. This study examines the impact of HIV infection on diagnosis in children with suspected PTB attending Queen Elizabeth Central Hospital, Blantyre. A total of 110 children (4 months-14 years) were studied over a 4-month period. Clinical data were recorded and investigations included Mantoux test, chest X-ray, HIV status (HIV-PCR when younger than 18 months) and sputum, if available. Laryngeal swabs were compared with sputa or gastric aspirates in a subgroup of 60 children. All children were commenced on anti-TB therapy and followed for treatment response. Aware of the clinical overlap between HIV and TB infection, we used more limited criteria than recommended to allocate a final diagnosis following review of all data except HIV status. Final diagnosis included confirmed PTB (n = 8), probable PTB (n = 41), lymphocytic interstitial pneumonitis (n = 10), pulmonary Kaposi sarcoma (n = 3) and bronchiectasis (n = 5). Culture rates of M. tuberculosis were: five (27.8%) of 18 sputa, three (7.1%) of 42 gastric aspirates and four (6.6%) of 60 laryngeal swabs. The HIV infection rate was 70.6% overall and 57.8% in 45 children with confirmed or probable PTB. Although a positive contact history was more common in HIV-infected children, a final diagnosis of confirmed or probable PTB was less common than in HIV-uninfected children (36% vs 63%; p = 0.02). The Mantoux test was positive in 14 (19%) of 72 HIV-infected compared with 15 (50%) of 30 HIV-uninfected children (p < 0.01). A final diagnosis could not be made in 43 (39%) of the study children with suspected PTB, the majority of whom were HIV-infected. HIV-infected children had a significantly poorer response to TB treatment and higher lost-to-follow-up rates.