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Biomedical subjects

J O Falkinham

Publications and source records attributed to J O Falkinham.

At least 19 recordsLinked to original sources
PubMed2004

Effect of different cell fractions of Mycobacterium avium and vaccination regimens on Mycobacterium avium infection.

Because of the availability of uniform genetic stocks and the ability to modulate stress levels, chickens were investigated as a host for the development of an antimycobacterial vaccine. The imposition and the timing of stress significantly influenced the outcome of Mycobacterium avium infection in chickens. Simple, whole cell or lysate vaccines and combinations of vaccine preparations were identified that led to high levels of protection. In addition, short-term stress at the time of vaccination significantly increased the protective efficacy of M. avium vaccine preparations. Post-infection vaccination of M. avium-infected chickens was also shown to significantly reduce the number of lesions and colony counts.

Animals↗
PubMed2001

Rapid coliphage detection assay.

A rapid coliphage detection assay was developed, based on the phage-induced release of beta-galactosidase from cells of Escherichia coli. The assay could detect as few as five coliphage per sample without an overnight incubation period. The range of acceptable assay parameters was identified.

Coliphages↗
PubMed2001

A luciferase-based method for assessing chlorine-susceptibility of Mycobacterium avium.

A rapid and quantitative assay for the disinfection of the water-borne pathogen, Mycobacterium avium, was developed using firefly luciferase as a reporter gene. There was a correlation between the quantity of light produced and the number of colony-forming units. In chlorine-disinfection studies of a luciferase-carrying derivative of M. avium, there was a strong correlation (r2=0.96) between colony forming units and relative light units. It was discovered that chlorine was rapidly lost from suspensions containing 10(6) M. avium cells/ml. The luciferase-based test can be used to rapidly measure susceptibility of M. avium to different disinfectants used in water treatment.

Chlorine↗
PubMed2001

Fluorescent acid-fast microscopy for measuring phagocytosis of Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum by Tetrahymena pyriformis and their intracellular growth.

Fluorescent acid-fast microscopy (FAM) was used to enumerate intracellular Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum in the ciliated phagocytic protozoan Tetrahymena pyriformis. There was a linear relationship between FAM and colony counts of M. avium cells both from cultures and within protozoa. The Ziehl-Neelsen acid-fast stain could not be used to enumerate intracellular mycobacteria because uninfected protozoa contained acid-fast, bacterium-like particles. Starved, 7-day-old cultures of T. pyriformis transferred into fresh medium readily phagocytized M. avium, M. intracellulare, and M. scrofulaceum. Phagocytosis was rapid and reached a maximum in 30 min. M. avium, M. intracellulare, and M. scrofulaceum grew within T. pyriformis, increasing by factors of 4- to 40-fold after 5 days at 30 degrees C. Intracellular M. avium numbers remained constant over a 25-day period of growth (by transfer) of T. pyriformis. Intracellular M. avium cells also survived protozoan encystment and germination. The growth and viability of T. pyriformis were not affected by mycobacterial infection. The results suggest that free-living phagocytic protozoa may be natural hosts and reservoirs for M. avium, M. intracellulare, and M. scrofulaceum.

Animals↗
PubMed2001

Factors influencing numbers of Mycobacterium avium, Mycobacterium intracellulare, and other Mycobacteria in drinking water distribution systems.

Eight water distribution systems were sampled over an 18-month period (528 water and 55 biofilm samples) to measure the frequency of recovery and number of mycobacteria, particularly Mycobacterium avium and Mycobacterium intracellulare, in raw source waters before and after treatment and within the distribution system. The systems were chosen to assess the influence of source water, treatment, and assimilable organic carbon levels on mycobacterial numbers. Overall, mycobacterial recovery from the systems was low (15% of samples). Numbers of mycobacteria ranged from 10 to 700,000 CFU liter(-1). The number of M. avium in raw waters was correlated with turbidity. Water treatment substantially reduced the number of mycobacteria in raw waters by 2 to 4 log units. Mycobacterial numbers were substantially higher in the distribution system samples (average, 25,000-fold) than in those collected immediately downstream from the treatment facilities, indicating that mycobacteria grow in the distribution system. The increase in mycobacterial numbers was correlated with assimilable organic carbon and biodegradable organic carbon levels (r(2) = 0.65, P = 0.03). Although M. intracellulare was seldom recovered from water samples, it was frequently recovered (six of eight systems) in high numbers from biofilms (average, 600 CFU/cm(2)). Evidently, the ecological niches of M. avium and M. intracellulare are distinct.

Biofilms↗
PubMed2000

Chlorine, chloramine, chlorine dioxide, and ozone susceptibility of Mycobacterium avium.

Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.

AIDS-Related Opportunistic Infections↗
PubMed1999

High rates of disseminated infection due to non-tuberculous mycobacteria among AIDS patients in Finland.

OBJECTIVE: to determine the rate of disseminated infection due to non-tuberculous mycobacteria (NTM) among Finnish AIDS patients, and to analyse the epidemiology of these infections. METHODS: in a prospective cohort study HIV-infected patients with CD4 counts < 200 x 10(6)/l were interviewed, and had mycobacterial blood cultures performed at baseline and at 6 months, then subsequently for clinical indications; autopsies were performed on patients who died. The cohort was followed at least for 24 months or to death. Water samples were collected from the homes of patients and from the environment and cultured for organisms of the Myobacterium avium complex (MAC). Environmental and clinical isolates were compared using pulsed field gel electrophoresis (PFGE). RESULTS: NTM infection occurred in 22 (43%) of 51, 19 isolates were Mycobacterium avium, two M. genavense and one M. intracellulare. Multivariate analysis identified urban residence (P=0.04) and eating raw fish (P=0.04) as independent risk factors. Molecular analysis revealed two clusters of related isolates (three M. avium, two M. genavense) among urban residents. CONCLUSION: AIDS patients in Finland have high rates of disseminated infection due to NTM. Clusters of identical organisms and association with urban residence suggests that these are newly acquired infections in advanced AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1996

The international epidemiology of disseminated Mycobacterium avium complex infection in AIDS. International MAC Study Group.

OBJECTIVE: To determine rates of disseminated Mycobacterium avium complex (MAC) infection among AIDS patients in developed and developing countries, and to determine whether different rates reflect differences in exposure or immunity, or both. DESIGN: Prospective cohort study. SETTING: University hospitals and outpatient AIDS programs. METHODS: HIV-infected subjects with CD4 counts < 200 x 10(6)/l were interviewed and had CD4 lymphocyte counts, blood cultures for mycobacteria (baseline and at 6 months), and skin tests with purified protein derivative (PPD) and M. avium sensitin. RESULTS: Among 566 study patients rates of disseminated MAC were 10.5-21.6% in New Hampshire, Boston and Finland compared to 2.4-2.6% in Trinidad and Kenya (P < 0.001). PPD skin test reactions > or = 5 mm were present in 20% of patients from Kenya compared to 1% at other sites (P < 0.001). Among patients from the United States and Finland, multiple logistic regression indicated that occupational exposure to soil and water was associated with a decreased risk of disseminated MAC, whereas the following were associated with an increased risk of disseminated MAC: low CD4 count, swimming in an indoor pool, history of bronchoscopy, regular consumption of raw or partially cooked fish/shellfish and treatment with granulocyte colony-stimulating factor. CONCLUSIONS: Rates of disseminated MAC in AIDS are higher in developed than developing countries and are due to both differences in exposure and differences in immunity. These data provide a rationale for prevention of MAC through both active immunization and reduction in exposure to the organism.

AIDS-Related Opportunistic Infections↗
PubMed1995

Isolation and characteristics of Mycobacterium avium complex from water and soil samples in Uganda.

SETTING: Mycobacterium avium complex organisms have not been isolated from late stage AIDS patients in Uganda. This could possibly be due to the absence of M. avium complex in the Uganda environment. OBJECTIVE AND DESIGN: Determine whether M. avium complex organisms could be isolated from water and soils collected in the living environment of Ugandan AIDS patients. RESULTS: Representatives of the M avium complex were isolated from 3 of 7 (43%) water and 3 of 7 (43%) soil samples collected in Kampala, Uganda. The average number of colony-forming units per ml water was 3.3 and average colony-forming units per gram of soil was 7825. In terms of growth characteristics, antimicrobial susceptibility patterns, and the presence or absence of plasmids and IS901, Ugandan M. avium complex isolates were similar to those isolated from the US and European AIDS patients and their environment. CONCLUSIONS: M. avium complex organisms sharing genetic and physiological characteristics of M. avium complex isolates recovered from patients with AIDS can be isolated from water and soil samples in Uganda.

Colony Count, Microbial↗
PubMed1995

Recovery of Mycobacterium avium from cigarettes.

Mycobacterium avium was recovered from tobacco, cigarette paper, and cigarette filters. M. avium could also be recovered from cigarette filters after the cigarettes had been smoked.

Mycobacterium avium↗
PubMed1994

Persistent colonisation of potable water as a source of Mycobacterium avium infection in AIDS.

The source of Mycobacterium avium infection in AIDS has not been identified and it is not known whether most patients with AIDS acquire the organism from recent infection or by reactivation of previous infection. As part of a prospective epidemiological study, we isolated multiple colonies of M avium from patients with AIDS and from potable water to which they had been exposed. All isolates were analysed with pulsed field gel electrophoresis (PFGE). As judged by PFGE, 29 (81%) of 36 patients were infected with one or more unique clinical strains of M avium. 7 patients (19%) were infected with three groups of common strains. Group 1 included 3 patients who lived in separate rural areas and had no common exposures apart from treatment at hospital A. The same strain was isolated repeatedly during 41 months from a recirculating hot water system at hospital A; residential water cultures were negative. Group 2 included 2 patients with no common exposures apart from treatment at hospital B; the same strain was isolated repeatedly over a period of 24 months from a recirculating hot water system at hospital B. Patients in groups 1 and 2 had numerous possible exposures to hospital hot water. Group 3 included 2 patients treated at the same methadone treatment facility. In an institution the hot water system may be persistently colonised with a particular strain of M avium. HIV-infected patients exposed to these water sources can develop disseminated M avium infection.

AIDS-Related Opportunistic Infections↗
PubMed1994

Comparison of virulence of Mycobacterium avium complex (MAC) strains isolated from AIDS and non-AIDS patients.

Mycobacterium avium complex (MAC) strains from AIDS and non-AIDS patients and from the environment were studied for their colony morphology and virulence in beige mice. The majority of the MAC isolates from AIDS patients, in contrast to those from non-AIDS patients and the environment, showed increased virulence. Similarly, the majority of the MAC isolates from AIDS patients formed smooth transparent (ST) colonies, whereas most of the non-AIDS isolates formed smooth opaque (SO) or intermediate (IM) type of colonies. MAC isolates from the same AIDS patient obtained at different times were found to be heterogenic with respect to serotype, RFLP and glycolipid patterns, suggesting that these patients might be infected with more than one strain of MAC.

AIDS-Related Opportunistic Infections↗
PubMed1994

Field evaluation of two colorimetric coliphage detection methods.

Two new methods for coliphage detection, a colorimetric agar-based (CAB) method and a liquid colorimetric presence-absence (LCPA) method, were compared to the coliphage method proposed by the American Public Health Association (APHA; Standard Methods for the Examination of Water and Wastewater, 18th ed., American Public Health Association, Washington, D.C., 1992). Both new methods are based on the induction of beta-galactosidase in Escherichia coli and the release of the enzyme through a lytic cell infection. The released enzyme then cleaves a chromogenic substrate which produces a colored reaction product. Ninety split water samples from four different sources were tested. A total of 52 samples were positive by the CAB method, 52 were positive by the LCPA method, and 53 were positive by the APHA method. Results indicated that (i) the CAB and LCPA methods were as sensitive in coliphage detection as the APHA method, (ii) both the CAB and LCPA methods were easier to read and interpret than the APHA method, and (iii) the CAB method detected more coliphages in a positive sample than the APHA method in two of the four types of water sources. Importantly, the rapid and simple LCPA method was as reliable and sensitive as either of the two agar-based methods in coliphage detection.

Journal Article↗
PubMed1993

A liquid, colorimetric presence-absence coliphage detection method.

A liquid, colorimetric presence-absence coliphage detection method based on the induction of beta-galactosidase by Escherichia coli is described. The release of beta-galactosidase in the medium due to lytic cell infections by coliphages permits the hydrolysis of a yellow chromogenic substrate that develops into a distinct red coliphage positive sample, while a coliphage negative sample remains yellow. This method has proven to be rapid, simpler to perform than an agar medium assay, easy to read and interpret, inexpensive, and highly sensitive.

Chlorophenols↗
PubMed1993

Genetic diversity among strains of Mycobacterium avium causing monoclonal and polyclonal bacteremia in patients with AIDS.

To define the genetic diversity among Mycobacterium avium isolates from human immunodeficiency virus-infected patients, specimens were cultured prospectively, and isolates obtained from 14 patients (4 with positive blood, stool, and sputum; 6 with positive blood and stool; 3 with positive blood only; and 1 with positive stool only) were studied. Both serotyping and ribotyping had limited ability to discriminate among isolates from different patients, whereas the distinctive restriction fragment profiles resolved by pulsed-field gel electrophoresis indicated that each patient was infected by a unique strain. Of the 13 bacteremic patients, 2 were bacteremic concurrently with 2 distinct strains. The fact that M. avium isolates from AIDS patients exhibit considerable genetic diversity supports the hypothesis that the infection is acquired from various environmental sources. Further, individual patients are not infrequently bacteremic with > 1 strain simultaneously, which may need to be considered in protocols for the diagnosis and management of M. avium disease.

AIDS-Related Opportunistic Infections↗
PubMed1992

Epidemiology of infection by nontuberculous mycobacteria. Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum in acid, brown-water swamps of the southeastern United States and their association with environmental variables.

Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum (MAIS) organisms were isolated and identified from waters, soils, aerosols, and droplets ejected from water collected from four geographically separate aquatic environments (Okefenokee Swamp, GA; Dismal Swamp, VA; Claytor Lake, VA; and Cranberry Glades, WV) during several seasons. Recovery of MAIS was significantly higher from waters, soils, and aerosols collected from the two acid, brown-water swamps located in the southeastern coastal plain. High MAIS numbers correlated with warmer temperature, low pH, low dissolved oxygen, high soluble zinc, high humic acid, and high fulvic acid. This research, in relation to previous findings for the geographic distribution and physiologic ecology of MAIS, supports the conclusion that waters, soils, and aerosols of the acid, brown-water swamps of the southeastern United States coastal plain represent major environmental sources likely connected with the higher incidence of human infection in this region.

Georgia↗