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Biomedical subjects

M V Chadwick

Publications and source records attributed to M V Chadwick.

At least 19 recordsLinked to original sources
PubMed2005

An audit into the efficacy of single use bacterial/viral filters for the prevention of equipment contamination during lung function assessment.

Lung function testing has been suggested to provide a potential risk regarding cross-infection between patients. About 155 patients (86 infectious, 69 non-infectious) used a single use bacterial/viral filter when performing routine lung function tests. Swabs from the patient side of the filter (Proximal) and the equipment side (Distal), and two sections of the filter itself were cultured. About 33/155 samples showed bacterial growth on the Proximal compared with 2/155 on the Distal side (P<0.01). Growth was obtained from the filter in 125/155 (80.6%) of cases. Pathogenic micro-organisms such as Pseudomonas aeruginosa (4 cases) and Staphylococcus aureus (5 cases) were isolated. Appropriate infection control measures should be used when performing lung function tests.

Bacterial Infections↗
PubMed2005

Non-tuberculous mycobacteria in patients with bronchiectasis.

BACKGROUND: Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms. Patients with pre-existing lung damage are susceptible to NTM, but their prevalence in bronchiectasis is unknown. Distinguishing between lung colonisation and disease can be difficult. METHODS: A prospective study of 100 patients with bronchiectasis was undertaken to evaluate the prevalence of NTM in sputum, and a retrospective analysis of clinical, microbiological, lung function and radiology data of our clinic patients with NTM sputum isolates over 11 years was performed. RESULTS: The prevalence of NTM in this population of patients with bronchiectasis was 2%. Patients in the retrospective study were divided into three groups: bronchiectasis+multiple NTM isolates (n=25), bronchiectasis+single isolates (n=23), and non-bronchiectasis+multiple isolates (n=22). Mycobacterium avium complex (MAC) species predominated in patients with bronchiectasis compared with non-bronchiectasis lung disease (72% v 9%, p<0.0001). Single isolates were also frequently MAC (45.5%). Multiple isolates in bronchiectasis were more often smear positive on first sample than single isolates (p<0.0001). NTM were identified on routine screening samples or because of suggestive radiology. No particular bronchiectasis aetiology was associated with an NTM. Pseudomonas aeruginosa and Staphylococcus aureus were frequently co-cultured. Six (25%) of multiple NTM patients had cavities of which five were due to MAC. Half the patients with multiple isolates were treated, mostly due to progressive radiology. CONCLUSIONS: NTM are uncommon in non-cystic fibrosis bronchiectasis. Routine screening identifies otherwise unsuspected patients. MAC is the most frequent NTM isolated.

Adult↗
PubMed2004

Inhibition of adherence of Mycobacterium avium complex and Mycobacterium tuberculosis to fibronectin on the respiratory mucosa.

Mycobacterium species adhere to the respiratory mucosa via mucus and fibronectin of extracellular matrix exposed by damaged epithelium. We have investigated whether inhibiting adherence to fibronectin influences subsequent infection of human respiratory tissue by Mycobacterium avium complex and Mycobacterium tuberculosis. Human respiratory tissue was pretreated with mycobacterial fibronectin attachment proteins prior to infection with M. avium complex and M. tuberculosis and the number of recoverable bacteria over time was compared to untreated controls. Inhibition significantly reduced recovery of M. avium complex at 15min (P= 0.02), 7days (P = 0.04), and 14 days (P= 0.03); whereas recovery of M. tuberculosis was only reduced at 15 min (P = 0.01) and not at later timepoints. We conclude that M. avium complex and M. tuberculosis infection of the mucosa proceeds by different mechanisms, since M. tuberculosis infection is independent of fibronectin adherence.

Adhesins, Bacterial↗
PubMed2003

Investigation of mycobacterial colonisation and invasion of the respiratory mucosa.

BACKGROUND: The pathogenesis of Mycobacterium avium complex and Mycobacterium tuberculosis in the respiratory tract is poorly understood, as are the reasons for their differing virulence. We have previously shown that their initial adherence to the mucosa is identical. METHODS: The interaction of M avium complex, M tuberculosis, and M smegmatis with human respiratory tissue was investigated in an organ culture model with an air interface. Tissue was infected for intervals up to 14 days and assessed by scanning electron microscopy for adherent bacteria or cultured for recoverable bacteria. RESULTS: The mean number of adherent bacteria/mm(2) (and the viable count of macerated tissue, cfu/ml) at 15 minutes, 3 and 24 hours, 7 and 14 days were: M avium complex 168 (153), 209 (136), 289 (344), 193 (313), 14140 (16544); M tuberculosis 30 (37), 39 (23), 48 (53), 1 (760), 76 (2186); M smegmatis 108 (176), 49 (133), 97 (81), 114 (427), 34 (58), (n=6). There was no significant change in morphology between infected and uninfected tissue or tissue infected with the different species over 14 days. The number of M avium complex on the mucosa and recovered from tissue increased over time (p=0.03). M tuberculosis decreased on the surface, but recoverable bacteria increased (p=0.01). M smegmatis numbers on the mucosa and recovered from tissue decreased. Sectioned tissue showed M avium complex and M tuberculosis in submucosal mucus glands and M tuberculosis penetrating epithelial cells in one experiment. CONCLUSIONS: The initial adherence to the mucosa of the three species was similar, but after 14 days they varied in their interaction with the tissue in a manner compatible with their pathogenicity.

Bacterial Adhesion↗
PubMed2002

Interaction of Mycobacterium tuberculosis with human respiratory mucosa.

OBJECTIVE: Endobronchial infection is associated with pulmonary tuberculosis in the majority of cases. We have investigated the adherence of Mycobacterium tuberculosis to the human respiratory mucosa. DESIGN: Organ cultures constructed with human tissue were infected with M. tuberculosis in the presence or absence of mycobacterial fibronectin attachment cell surface proteins and examined by scanning electron microscopy. RESULTS: M. tuberculosis adhered mainly to extracellular matrix (ECM) in areas of mucosal damage, but not to ciliated mucosa, intact extruded cells, basement membrane or collagen fibres. Bacteria also adhered to fibrous but not globular mucus and occasionally to healthy unciliated mucosa, open tight junctions and to extruded cells that had degenerated, exposing their contents. There was a significant reduction (p<0.05) in the number of bacteria adhering to ECM after pre-incubation of bacteria with fibronectin and after pre-incubation of the tissue with M. avium fibronectin attachment protein (FAP) and M. bovis antigen 85B protein, in a concentration dependent manner. The combined effect of FAP and antigen 85B protein was significantly greater than either protein alone. Bacterial adherence to fibrous mucus was not influenced by fibronectin. CONCLUSION: We conclude that M. tuberculosis adheres to ECM in areas of mucosal damage at least in part via FAP and antigen 85B protein.

Acyltransferases↗
PubMed2002

Antibiotic resistant tuberculosis in the United Kingdom: 1993-1999.

BACKGROUND: The re-emergence of tuberculosis as a global health problem over the past two decades, accompanied by an increase in tuberculosis drug resistance, prompted the development of a comprehensive national surveillance system for tuberculosis drug resistance in 1993. METHODS: The UK Mycobacterial Resistance Network (Mycobnet), which includes all mycobacterial reference and regional laboratories in the UK, collects a minimum dataset on all individuals from whom an initial isolate of Mycobacterium tuberculosis complex has been isolated and submitted by source hospital laboratories. Data sought include susceptibility to first line antibiotics, demographic, geographical, and risk factor information. RESULTS: There were 25 217 reports of initial isolates of M tuberculosis complex in the UK between 1993 and 1999. All were tested for sensitivity to isoniazid, rifampicin, and ethambutol and 12 692 of the isolates were also tested for sensitivity to pyrazinamide and streptomycin. A total of 1523 (6.1%) isolates were resistant to one or more drugs, 1397 isolates (5.6%) were resistant to isoniazid with or without resistance to other drugs, and 299 (1.2%) were multidrug resistant. Although the numbers of drug resistant isolates increased over the period, the proportions remained little changed. Certain groups of people were at a higher risk of acquiring drug resistant tuberculosis including younger men, residents of London, foreign born subjects, patients with a previous history of tuberculosis and those infected with HIV. CONCLUSION: Although the proportion of drug resistant tuberculosis cases appears to be stable in the UK at present, more than one in 20 patients has drug resistant disease at diagnosis and more than one in 100 has multidrug resistant disease. Tuberculosis control measures should be strengthened to minimise the emergence of drug resistance through rapid diagnosis, rapid identification of drug resistance, supervised treatment, and maintenance of comprehensive surveillance.

AIDS-Related Opportunistic Infections↗
PubMed2000

The role of Mycobacterium avium complex fibronectin attachment protein in adherence to the human respiratory mucosa.

Mycobacterium avium complex (MAC) are opportunistic respiratory pathogens that infect non-immunocompromised patients with established lung disease, although they can also cause primary infections. The ability to bind fibronectin is conserved among many mycobacterial species. We have investigated the adherence of a sputum isolate of MAC to the mucosa of organ cultures constructed with human tissue and the contribution of M. avium fibronectin attachment protein (FAP) to the process. MAC adhered to fibrous, but not globular mucus, and to extracellular matrix (ECM) in areas of epithelial damage, but not to intact extruded cells and collagen fibres. Bacteria occasionally adhered to healthy unciliated epithelium and to cells that had degenerated exposing their contents, but never to ciliated cells. The results obtained with different respiratory tissues were similar. Two ATCC strains of MAC gave similar results. There was a significant reduction (P < 0.05) in the number of bacteria adhering to ECM after preincubation of bacteria with fibronectin and after preincubation of the tissue with M. avium FAP in a concentration-dependant manner. The number of bacteria adhering to fibrous mucus was unchanged. Immunogold labelling demonstrated fibronectin in ECM as well as in other areas of epithelial damage, but only ECM bound FAP. A Mycobacterium smegmatis strain had the same pattern of adherence to the mucosa as MAC. When the FAP gene was deleted, the strain demonstrated reduced adherence to ECM, and adherence was restored when the strain was transfected with an M. avium FAP expression construct. We conclude that MAC adheres to ECM in areas of epithelial damage via FAP and to mucus with a fibrous appearance via another adhesin. Epithelial damage exposing ECM and poor mucus clearance will predispose to MAC airway infection.

Adenoids↗
PubMed2000

Comparison of a solution of super-oxidized water (Sterilox) with glutaraldehyde for the disinfection of bronchoscopes, contaminated.

The efficacy of Sterilox, a super-oxidized water holding a reduction/oxidation potential of greater than 950 mV was compared with the efficacy of glutaraldehyde against clinical isolates of Mycobacterium tuberculosis and Mycobacterium avium-intracellulare. An in use method using an automated bronchoscope washing machine demonstrated that over five cycles, Sterilox with a contact time of 5 min gave log10 reduction factors for M. tuberculosis and M. avium-intracellulare of >6 and >5, respectively. Glutaraldehyde with a contact time of 10 min gave log10 reduction factors for both M. tuberculosis and M. avium-intracellulare of >4, and at a contact time of 20 min >5 each. The non-toxic nature of Sterilox, together with the reduction in viable counts demonstrated in this study, suggest that the solution is an effective alternative mycobactericidal agent to the established disinfectants for the disinfection of bronchoscopes and, therefore, justifies further investigation.

Bronchoscopes↗
PubMed1997

Evaluation of a commercial radiometric system for primary isolation of mycobacteria over a fifteen-year period.

The rate of recovery and time to detection of mycobacteria from clinical specimens were analysed for specimens inoculated into both radiometric Middlebrook 7H12 (Bactec 12B, originally 12A) medium and Lowenstein-Jensen egg-based medium (with and without sodium pyruvate) over the 15-year period from 1980 to 1994. A total of 19,679 Bactec vials were inoculated together with Lowenstein-Jensen slopes, with 2198 mycobacterial isolates detected. The mean times to detection for Bactec and Lowenstein-Jensen were 11.7 days and 23.9 days, respectively. In 195 cases mycobacteria were isolated from Bactec and not from Lowenstein-Jensen, whereas the reverse was true in 42 cases. The number of contaminated Bactec vials was 488 and the number of contaminated Lowenstein-Jensen slopes 448.

Bacteriological Techniques↗
PubMed1997

Disinfection of bronchoscopes, contaminated in vitro with Mycobacterium tuberculosis, Mycobacterium avium-intracellulare and Mycobacterium chelonae in sputum, using stabilized, buffered peracetic acid solution ('Nu-Cidex').

The efficacy of 0.35% stabilized buffered peracetic acid solution ('Nu-Cidex') against clinical isolates of Mycobacterium tuberculosis, Mycobacterium avium-intracellulare and Mycobacterium chelonae in homogenized sputum was tested. An in-use method, using an automated bronchoscope washing machine, showed that over 10 cycles, at a disinfectant contact time of 5 min, M. tuberculosis and M. chelonae were effectively eradicated from the bronchoscope, even in the absence of detergent and pre-cleaning. M. avium-intracellulare was not eradicated in only one of 10 cycles with contact times of 5 and 10 min, but numbers were reduced by > 7 log10 and > 5 log10, respectively. With detergent present, M. avium-intracellulare was successfully eradicated in all cycles at a contact time of 5 min or greater. The results demonstrate that peracetic acid is an effective mycobactericidal agent for use in the disinfection of bronchoscopes.

Bronchoscopes↗
PubMed1995

The efficacy of the disinfection of bronchoscopes contaminated in vitro with Mycobacterium tuberculosis and Mycobacterium avium-intracellulare in sputum: a comparison of Sactimed-I-Sinald and glutaraldehyde.

The efficacy of Sactimed-I-Sinald and glutaraldehyde was tested against clinical isolates of Mycobacterium tuberculosis (MTB) and Mycobacterium avium-intracellulare (MAI). An in-use method demonstrated that over 10 disinfection cycles, using an auto-disinfector and a contact time of 60 min, MTB was eradicated in 10 out of 10 cycles with Sactimed-I-Sinald and five out of 10 cycles for glutaraldehyde. For MAI, Sactimed-I-Sinald showed a 5 log reduction at a 60 min contact time, which was not seen with glutaraldehyde. Although further evaluation is necessary, Sactimed-I-Sinald appears a promising alternative to glutaraldehyde.

Bronchoscopes↗
PubMed1992

A study of glutaraldehyde disinfection of fibreoptic bronchoscopes experimentally contaminated with Mycobacterium tuberculosis.

Mycobacteria are difficult to inactivate, and concern about the spread of tuberculosis at bronchoscopy has a major influence on infection control practices. Recommendations from the UK Department of Health are based largely on in-vitro mycobactericidal assays which do not take into account the particular conditions encountered in endoscopy units. In this applied study cleaning and disinfection methods were examined using five bronchoscopes that were heavily contaminated with a recent isolate of Mycobacterium tuberculosis in sputum. Cleaning reduced contamination by a mean 3.5 log(10) colony forming units (cfu) per ml; all bronchoscopes were free of detectable mycobacteria after 10 min in 2% alkaline glutaraldehyde (AG). It is recommended that all bronchoscopes be thoroughly pre-cleaned and disinfected in 2% AG for 20 min as part of a uniform policy of infection control.

Bronchoscopes↗
PubMed1991

Recovery of the human immunodeficiency virus from fibreoptic bronchoscopes.

Ten bronchoscopes that had been used on patients with the acquired immunodeficiency syndrome were sampled to determine the nature and extent of microbial contamination. Samples were taken by irrigating the suction biopsy channel with modified viral transport medium and by swabbing the insertion tube. Sampling was repeated after they had been cleaned in detergent and after two minutes' disinfection in 2% alkaline glutaraldehyde. Before being cleaned the seven bronchoscopes tested by polymerase chain reaction were contaminated with the human immunodeficiency virus, though infectivity and antigen assays gave negative results. Other organisms identified were hepatitis B virus (1), commensal bacteria (9), and Pneumocystis carinii (4). Mean bacterial contamination was 2.27 log colony forming organisms per millilitre. Cleaning the bronchoscope before disinfection removed all detectable contaminants with a reduction in bacterial growth of up to 8 log colony forming units/ml.

Bronchoscopes↗
PubMed1990

Double-blind randomized study of prolonged higher-dose oral amoxycillin in purulent bronchiectasis.

Thirty-eight patients with bronchiectasis and daily expectoration of purulent sputum despite conventional antibiotic courses were randomly allocated to receive a sachet of amoxycillin (3 g) or matched placebo twice daily for 32 weeks in a double-blind study. Nine patients (four amoxycillin, five placebo) were withdrawn from the study treatment; the response of the two patients (both on amoxycillin) withdrawn within the first six weeks was not assessed. The pretreatment characteristics of the two groups were similar. Independent assessment of overall response based on patients' diary cards showed that a higher proportion improved in the amoxycillin group (11 of 17) than in the placebo group (four of 19; p = 0.02). Patients in the amoxycillin group spent significantly less time confined to bed and away from work during treatment. The frequency of exacerbations during the study treatment phase was similar in the two groups but they were less severe than before study treatment in the amoxycillin group. There was a greater reduction in purulent sputum volume between exacerbations during the study treatment in the amoxycillin group to 20 per cent of pretreatment volume than in the placebo group (88 per cent of pretreatment volume, p = 0.008), although the concentrations of Haemophilus spp. in sputum between exacerbations was similar in the two groups. Adverse effects experienced were minor except in one patient (amoxycillin) withdrawn after developing a rash and in six patients (three amoxycillin, three placebo) who had diarrhoea lasting more than one week necessitating withdrawal of two patients (one amoxycillin, one placebo) from study treatment. Sputum and stool cultures collected regularly during the study showed no important changes in the bacterial flora in either group. Prolonged higher-dose antibiotic therapy in these patients with severe purulent bronchiectasis significantly reduced the host (patient) inflammatory response to colonizing microorganisms and reduced morbidity.

Adult↗
PubMed1989

Contamination of endoscopes used in AIDS patients.

Contamination of twenty endoscopes used in patients with AIDS was assessed. The suction-biopsy, air, and water channels and the insertion tube were sampled after use, after washing in detergent, and after disinfection for 2 min in 2% alkaline glutaraldehyde. The polymerase chain reaction with Southern blotting, cell cultures, and antigen immunoassay were used to detect human immunodeficiency virus (HIV). Samples were also examined for cytomegalovirus, adenoviruses, enteroviruses, herpes simplex virus, myxoviruses, hepatitis B surface antigen, fungi, and bacteria. Seven of twenty unwashed endoscopes were contaminated by HIV. Commensal bacteria were found in all endoscopes, Candida albicans in six, Staphylococcus aureus in five, and Pseudomonas aeruginosa in five. Washing alone removed all detectable organisms from 66 of 68 contaminated sites; Neisseria spp were recovered from two air channels after washing but not after disinfection. Washing achieved a mean reduction of 4.93 (95% confidence interval 3.69-6.17) colony forming units per ml.

Acquired Immunodeficiency Syndrome↗