Other food borne infections

This article presents an update of several emerging or reemerging pathogens: Yersinia, Cryptosporidia, Cyclospora, Brucella, and Mycobacterium. All of these zoonotic pathogens show evidence of food borne transmission. Yersiniosis is presented as an emerging pathogen that has as its major route of transmission preparation and consumption of pork products. New evidence is presented that supports the transmission of brucellosis via the food chain, especially through contaminated raw milk and cheese. While TB has limited transmission via raw milk, it is highlighted as a reemerging infection due to the development of multiple drug resistance. Public health veterinarians stand in an excellent position to recognize these emerging diseases and apply intervention strategies to prevent and control these infections in the future. This article is intended to raise their consciousness as to the management and medical practices that can diminish food borne transmission.

[Occurrence of Mycobacterium genavense in birds]

A total of 253 birds were investigated to determine the presence of mycobacteria. Scrapings from various internal organs were stained according to Ziehl-Neelsen, and acid-fast bacilli were found in 26 birds (10.2%). Cultivation of mycobacteria was attempted from 22 livers, 12 spleens, 14 kidneys, 12 lungs, and 9 intestines from these 26 birds. Each sample was first decontaminated using a modified sodium dodecyl sulfate method, and three media were inoculated (Bactec 12 B; Löwenstein-Jensen, Herrold). Using a Polymerase-Chain-Reaction-Restriction-Enzyme-Analysis (PRA), M. genavense could be identified in 19 of 26 birds (73%). M. avium could be isolated from three birds and M. fortuitum from one bird. In total, mycobacteriosis was the primary diagnosis made in 24 of 26 birds (92%). A presumptive diagnosis of mycobacteriosis was already made macroscopically in 14 of these birds. In the remaining 10 cases, bacteriological and histological investigations with specific staining methods were necessary for diagnosis. Several different histological changes were found. We observed individual macrophages as well as epitheloid cell proliferation, with variable, relatively mild inflammatory and fibrous reactions. We could not find any correlation between infection with a mycobacterium species and a specific tissue reaction pattern. This report demonstrates that M. genavense is an important cause of avian mycobacteriosis especially in pet birds.

Randomly amplified polymorphic DNA PCR for comparison of Mycobacterium abscessus strains from nosocomial outbreaks

Mycobacterium abscessus is an important cause of water-related nosocomial outbreaks or pseudo-outbreaks. Strain comparison has relied on pulsed-field gel electrophoresis (PFGE). Unfortunately, almost 50% of strains cannot be assessed by this method. We studied 118 strains of M. abscessus previously studied by PFGE by randomly amplified polymorphic DNA (RAPD) PCR, including isolates from eight nosocomial outbreaks. Ten random primers were evaluated by using DNA prepared by boiling or phenol-chloroform extraction. Both DNA preparations gave the same grouping of isolates for three outbreaks compared to the groupings obtained by PFGE. Five outbreaks due to M. abscessus which gave broken DNA by PFGE gave evaluable patterns when studied by RAPD-PCR, with isolate clustering being consistent with that from other laboratory and epidemiologic data. The patterns were highly method dependent, strain comparison required the use of multiple primers, and the method worked best with purified DNA and by using strains for comparison on the same gel. We propose categories of indistinguishable, different, and inconclusive when comparing strains by RAPD-PCR. This study demonstrates that RAPD-PCR can be used for genetic comparison of M. abscessus strains, including strains which cannot be compared by PFGE, but the potential for misinterpretation is greater than that by PFGE.

[An observation on tuberculosis associated with HIV infection in Japan]

OBJECTIVE

To observe the reported cases of tuberculosis (TB) with HIV infection in Japan, in terms of their main clinical features and related factors.

METHODS

A voluntary reporting network has been organized by the authors who are specialists of TB or respiratory medicine in tuberculosis institutions located roughly all over the country. The members have been encouraged to report not only their own cases but cases seen by their friends or in other institutions.

RESULTS

By the end of 1996, a total of 71 cases have been reported of which 59 were TB and 12 NTM cases. Nationality of the cases were; Japan 48, Other Asian countries 16, Others 7. All of the NTM cases were Japanese. 30% of the cases were aged less than 30 years, 24% were thirties, 24% forties, 17% fifties and 6% were those aged 60 years or older. The cases were clearly younger than the TB cases in the national TB registry, and older than HIV-infected persons as known from the HIV surveillance system. 97% of the TB cases were bacteriologically confirmed cases. Eight of NTM cases were positive for MAC, others for M.kansasii. 42% of the cases had extra-pulmonary disease, including disseminated infections seen among 19%. Of TB cases 25% were excreting bacilli resistant to any of the anti-TB drugs which was higher than in the case of general TB population (10-15%). 11% of TB cases had past history of TB treatment. The cases had severe immunological impairment, 79% of the cases having CD4+ cell count less than 100. The route of HIV infection were; 51% heterosexual, 13% homosexual, 13% through blood preparations, etc.

DISCUSSION

Although there may be many cases not included in this observation, it is considered to well reflect the real situation of the problem of Japan. More attention should be paid to HIV infection of the patients in the clinical practice of TB in Japan.

Regional differences in use of antiretroviral agents and primary prophylaxis in 3122 European HIV-infected patients. EuroSIDA Study Group

Little is known about how widely HIV-related drugs are used outside controlled clinical trials. We therefore assessed factors associated with use of antiretroviral (ARV) therapy and primary prophylactic regimens to prevent HIV-associated opportunistic infections. Baseline data from a prospective study from May to August 1994, on 3122 consecutive HIV infected patients with a CD4 count <500 cells/microl, followed in 37 centers from 16 European countries, were analyzed. Two thousand and twenty patients (65%) were receiving at least 1 ARV drug at the time of the study. ARV therapy was more frequently used among patients from southern and central Europe as compared with patients from northern Europe, especially among patients with CD4 counts >200 cells/microl (73%, 57%, and 42%, respectively, p < 0.0001). Of patients on ARV therapy, 34% received open-label combination therapy. This proportion was higher in central Europe compared with other regions (27%, 50%, and 31% for southern, central, and northern Europe, respectively, p < 0.0001). Primary prophylaxis against Pneumocystis carinii pneumonia (PCP) was used by 85% of patients with a CD4 count <200 cells/microl, without marked regional differences. In patients without esophageal candidiasis or other invasive fungal infections, antifungal drugs were far less frequently used in patients from southern and central Europe compared with patients from northern Europe (10%, 10%, and 25%, respectively, p < 0.0001). Only 5% of patients with a CD4 count <100 cells/microl received rifabutine as primary prophylaxis against nontuberculous mycobacterioses. ARV and antifungal therapies are used differently in different parts of Europe, whereas primary PCP prophylaxis is uniformly administered to most at-risk patients. U.S. recommendations on the use of antimycobacterial prophylaxis have not been implemented in Europe.

[Pulmonary mycobacteriosis--diagnostic problem and prevalence in Poland (a retrospective study)]

The diagnosis of pulmonary mycobacteriosis was verified in 267 patients in Poland, classified in the years 1991-1995 to group VI M. Among 267 patients, 213 were men in age 28-83 years (median 43 years) and 54 women in age 24-81 years (median 50 years). The verification of the diagnosis was based on the authors own criteria of pulmonary mycobacteriosis and colonisation. These criteria included at least two positive sputum cultures and presence or absence of the respiratory tract inflammation. Pulmonary mycobacteriosis was recognised in 199 patients (168 men and 31 women). Colonisation was diagnosed in 41 patients (23 men and 18 women). Non-tuberculous mycobacteria most often responsible for pulmonary mycobacteriosis were identified as M. kansasii, M. avium--intracellulare and M. xenopi. Majority of patients with pulmonary mycobacteriosis or with colonisation had pulmonary lesions caused by tuberculosis in the past or suffered from chronic obstructive pulmonary disease. In 63 cases, data concerning previous diseases of the respiratory tract were not available.

[Characterization of fatty acids and mycolic acid degradation products in mycobacterial species of major incidence in Argentina]

The human immunodeficiency virus (HIV) epidemic has altered the epidemiological profile of tuberculosis in both industrialized and developing countries. Serious diseases caused by mycobacteria other that M. tuberculosis, mostly belonging to the M. avium-intracellulare complex (MAC), have become very common in association with severe immunosuppression. The increase in mycobacterial disease complexity has stimulated the development of more rapid and efficient methods of diagnosis. In the present study we characterized the cellular fatty acids and the mycolic acid cleavage product from most frequent mycobacteria species in Argentina using gas chromatography in order to develop a rapid technique for their identification. Fatty acids and mycolic acids extracted from saponified mycobacterial cells were examined as methyl esters by capillary has chromatography. The major constituent fatty acids in all species, with the exception of M. smegmatis, were octadecenoic (18:1) and hexadecanoic (16:1) acids. The fatty acids and mycolic acid cleavage product profiles from the studied species were quantitatively but not qualitatively different. Tuberculostearic acid was found in all species. Significantly different amounts of some fatty acids (p < 0.01) were observed among clinical isolates of M. tuberculosis, M. bovis and MAC. Traces of 2-eicosanol were detected in the M. tuberculosis H37Rv strain. Although a limited number of strains and species were tested, preliminary results indicate that this method could be used to characterize mycobacterial cultures.

Pseudo-outbreak of septicemia due to rapidly growing mycobacteria associated with extrinsic contamination of culture supplement

Between April and December 1994, 23 blood cultures from human immunodeficiency virus-infected patients grew rapidly growing mycobacteria suspected to be Mycobacterium chelonae at a hospital in New Jersey. The isolates were later identified as M. abscessus. Several bacterial species, including M. abscessus, were cultured from an opened multidose supplement vial (BBL Septi-Chek AFB Supplement) that had been used for mycobacterial blood cultures. The M. abscessus isolates from case patients and the supplement vial had identical multilocus enzyme electrophoresis and antimicrobial susceptibility patterns. Finding a contaminated vial of supplement, together with the lack of a distinct syndrome in case patients, was consistent with a pseudo-outbreak.

Report on an outbreak of postinjection abscesses due to Mycobacterium abscessus, including management with surgery and clarithromycin therapy and comparison of strains by random amplified polymorphic DNA polymerase chain reaction

An outbreak of postinjection abscesses occurred in Barranquilla, Colombia, and was associated with local injections of lidocaine given in a single physician's office. Over a 5-month period, 350 (18%) of approximately 2,000 injected patients developed localized cutaneous abscesses or cellulitis; of 210 abscess specimens that were cultured, 205 were positive for rapidly growing mycobacteria, subsequently identified as Mycobacterium abscessus. The source of the outbreak was not identified. M. abscessus could not be characterized by pulsed-field gel electrophoresis, but all isolates were identical in terms of drug and heavy metal resistance patterns and random amplified polymorphic DNA PCR profiles. We believe this is the first report of the use of this latter technique for investigation of an outbreak due to M. abscessus. Therapy with a combination of surgical excision and 3-6 months' administration of clarithromycin was successful for 95% of 148 patients treated in this manner; in contrast, therapy was successful for less than one-third of patients treated with surgery alone or clarithromycin alone. This is the largest of the nine known outbreaks of postinjection abscesses that have occurred due to rapidly growing mycobacteria and is the first in which an effective method of therapy was demonstrated.

Oligonucleotide (GTG)5 as an epidemiological tool in the study of nontuberculous mycobacteria

Analysis of restriction fragment length polymorphisms in the genome of Mycobacterium tuberculosis (DNA fingerprinting) has proved to be a useful epidemiological tool in the study of tuberculosis within populations or communities. However, to date, no similar method has been developed to study the epidemiology of nontuberculous mycobacteria (NTM). In this communication, we report that a simple oligonucleotide repeat, (GTG)5, can be used to accurately genotype all species and strains of NTM tested. We suggest that this technology is an easily applied and accurate tool which can be used for the study of the epidemiology of NTM.

Impact of the human immunodeficiency virus epidemic on detection of Mycobacterium isolates in a general hospital

The number of human samples processed in our mycobacteriology laboratory ranged from 148 per 1,000 admissions in 1988 to 263 per 1,000 admissions in 1995 (5.2% were positive). The human immunodeficiency virus (HIV)-positive population contributed 33.3% of all samples, 43.3% of all isolates, and 36% of all new patients. Given that the ratios of the total number of samples to the number of Mycobacterium-positive samples were 18.3:1 in HIV-positive patients and 28:1 in HIV-negative patients, efforts to reduce the laboratory workload should begin with the HIV-negative population.

Mycobacterial lung disease in cystic fibrosis: a prospective study

BACKGROUND

Patients with cystic fibrosis (CF) may be predisposed to airway infections with unusual organisms, such as mycobacteria. The aim of the study was to determine the incidence and clinical picture of mycobacterial infection in CF children.

METHODS

At least 2 acid-fast bacillus (AFB) smears and mycobacterial cultures were performed on a prospective basis on 682 sputum specimens from 106 patients during a 1-year period.

RESULTS

Thirty-three percent of the cultures were contaminated with other bacteria. Seven children had at least one sputum culture positive for one mycobacterium. Five children had only one positive AFB culture. Their clinical status and lung function remained stable during follow-up. Two teenagers with severe lung disease had several positive AFB smears and cultures for Mycobacterium chelonae and Mycobacterium abscessus. The isolation of M. chelonae and M. abscessus was associated with a clinical and functional decline. Clarithromycin treatment resulted in temporary improvement with the disappearance of the mycobacteria after 6 months of treatment. This prospective study shows an incidence of 2.3% for positive cultures. The prevalence was 6.6% for mycobacterial colonization but only 1.9% for mycobacterial lung disease in our pediatric population.

CONCLUSIONS

We recommend performing AFB smears and cultures in CF children with severe lung disease and/or during a lung exacerbation. In these patients persistence of M. chelonae or M. abscessus in sputum should lead to consideration of treatment with clarithromycin.

Use of multilocus enzyme electrophoresis to examine genetic relationships amongst isolates of Mycobacterium intracellulare and related species

As part of a larger study investigating diversity and distribution of Mycobacterium spp. in Australia, multilocus enzyme electrophoresis was used to assess genetic relationships at 17 enzyme loci amongst a collection of reference strains and isolates initially identified on biochemical and other grounds as M. intracellulare (70), "X' mycobacteria (10), M. scrofulaceum (7), M. avium (8) and M. avium subsp. paratuberculosis (2). Two of the isolates initially identified as M. intracellulare were shown to be quite distinct from the others. Both gave negative results in a species-specific DNA probe test, whilst one was positive by PCR. These results emphasize the uncertainties involved in identifying members of this group. The other M. intracellulare isolates formed a cohesive but diverse group, being divided into 48 electrophoretic types (ETs), with a mean genetic diversity of 0.38. Forty-three of these ETs contained only single isolates. There was no clear relationship between the serovar and ET designation. The index of association calculated for M. intracellulare was significantly different from zero, suggesting that it is a clonal species. PFGE was also applied to selected isolates from the ETs containing multiple isolates, and some of these could be differentiated further. The strains of M. scrofulaceum and "X' mycobacteria were distinct from M. intracellulare, but themselves were highly heterogeneous, with mean genetic diversities of 0.66 and 0.65, respectively. Each of these groups may represent more than one species. M. avium strains were distinct from the two M. avium subsp. paratuberculosis strains, as well as from the other mycobacteria studied.

Nonspecific resistance to Mycobacteria: the role of the Nramp1 gene

The genus Mycobacteria consists of over 50 species that include two of the best-known human pathogens, M. tuberculosis and M. leprae, the causes of tuberculosis (TB) and leprosy, respectively. Whereas the spread of leprosy currently appears to be under control, there are presently about 30 million active cases of TB worldwide, with an alarming increase in the number of multidrug resistant case of M. tuberculosis. As strategies for antibiotic intervention against TB become more limited, it is imperative to develop new therapeutic approaches against this oppressive disease. One promising avenue is to characterize the host genes and gene products which regulate resistance to mycobacterial infections. In the mouse, resistance and susceptibility to intracellular growth of Mycobacteria in macrophages is controlled by the Bcg (Nramp1) gene, which has now been cloned and shown to encode a macrophage transmembrane protein with a putative transporter function. Sequencing of Nramp1 revealed that susceptibility to infection is associates with a single, nonconservative glycine to aspartic acid substitution at position 169 (G169D). Although the intracellular location of the Nramp1 protein in macrophages has not yet been determined, a phagosomal site has been postulated. Consistent with the proposed role of Nramp1 in macrophage activation, recent studies of the Nramp1 promoter region have revealed consensus sequences associated with responsiveness to IFN-gamma and LPS. Finally, a total of 11 polymorphisms have been identified within the human NRAMP1 gene which are being used to test for linkage of NRAMP1 alleles with human susceptibility to TB and leprosy.

Mycobacterial infections following bone marrow transplantation: a 20 year retrospective review

Mycobacterial infections are common in people with impaired cell-mediated immunity. Bone marrow transplant recipients have this defect and might be expected to have a high incidence of mycobacterial infections. We reviewed mycobacterial infections in 2241 BMT recipients at the University of Minnesota Hospital. Mycobacterial infections were diagnosed in 11 (0.49%), including nine of 1486 allograft recipients (0.6%) and two of 755 (0.26%) autograft recipients. Two patients had M. tuberculosis infection, two, M. avium-intracellulare infection and seven, infection with rapid growing atypical mycobacteria (M. fortuitum or M. chelonae). The manifestations included unexplained fever, pulmonary infiltrates, osteomyelitis or central venous catheter tunnel inflammation. Six of the seven infections with rapid growing atypical mycobacteria were related to central venous catheters. Appropriate local measures and therapy with antimycobacterial medications resulted in complete resolution of infection in the nine patients treated. The low incidence of mycobacterial infection observed in BMT recipients contrasts with that observed in people with impaired cell-mediated immunity.

Comparison of DNA fingerprint patterns of isolates of Mycobacterium africanum from east and west Africa

Mycobacterium africanum is a pathogen found in tuberculosis patients in certain parts of Africa and is a member of the Mycobacterium tuberculosis complex. Biochemically, strains of M. africanum exhibit a high degree of variability, with some tendency to cluster according to their geographical origin. To investigate whether this phenotypic variability is reflected at the genetic level, we performed DNA fingerprint analysis of strains isolated from patients with pulmonary tuberculosis in Uganda and Sierra Leone. IS6110 DNA fingerprinting was carried out by the mixed-linker PCR method. A total of 138 strains of M. africanum were analyzed: 42 isolates from Uganda and 96 isolates from Sierra Leone. With few exceptions, the resulting DNA fingerprint patterns grouped together according to their country of origin. A striking lack of variability of DNA fingerprints was found for strains from Sierra Leone, where 70 of 96 isolates (61.5%) fell into clusters. The two largest clusters accounted for 41.7% of all isolates and differed by only one band, as confirmed by standard DNA fingerprinting. In contrast, only two clusters (7.1%) with two and three isolates, respectively, were found for M. africanum isolates collected in Uganda, and three of the DNA fingerprints contained fewer than seven bands. Strains of M. tuberculosis collected and processed during the same time period were highly variable in both countries. Our results support the concept of geographically defined subtypes of M. africanum. In addition, they demonstrate that natural geographic differences in the variability of IS6110 DNA fingerprints within the M. tuberculosis complex must be considered if this technique is used for epidemiologic studies.

Epidemiological and clinical aspects of mycobacterial infections

The incidence of tuberculosis in the developed countries has recently started to rise again due to increased migration, a higher rate of direct transmission of Mycobacterium tuberculosis, and co-infection with HIV. The impact of the latter on the pathogenesis and presentation of tuberculosis is summarised. Important measures to prevent the further spread of tuberculosis include rapid diagnosis, prompt isolation of infectious patients, adequate control of treatment compliance, as well as surveillance of local resistance patterns. Disease due to the Mycobacterium avium complex is more frequent among HIV-infected patients in Central Europe than tuberculosis, and its development in the presence of immune deficiency seems to be mainly the result of a new infection with this ubiquitous microorganism rather than the reactivation of a previously acquired infection. It has a significant impact on mortality. The diagnosis of Mycobacterium avium complex infection requires a high degree of conjecture because most of the symptoms are non-specific, such as fever, night sweats, weight loss and anaemia. Promptly initiated treatment significantly prolongs the survival time of those affected by comparison with untreated patients.

Genotypic characterization of five subspecies of Mycobacterium kansasii

Different molecular typing methods including restriction fragment length polymorphism (RFLP) analysis with the major polymorphic tandem repeat (MPTR) probe and the IS1652 probe, pulsed-field gel electrophoresis (PFGE), amplified fragment length polymorphism (AFLP) analysis, and PCR restriction analysis of the hsp-65 gene (PRA) were applied to clinical and water isolates of Mycobacterium kansasii. RFLP with the MPTR probe, PRA, PFGE, and AFLP analysis revealed five homogeneous clusters which appeared to be subspecies. RFLP with the MPTR probe and PRA gave patterns specific for each cluster, whereas PFGE and AFLP analysis gave polymorphic patterns. IS1652 was present in two of the five clusters and provided polymorphic patterns for one cluster only. The two IS1652-positive clusters were Accuprobe negative (Accuprobe test; Gen-Probe Inc.), and only two other clusters were Accuprobe positive. A PCR test based on the detection of a species-specific fragment (M. Yang, B.C. Ross, and B. Dwyer, J. Clin. Microbiol. 31:2769-2772, 1993) was positive for all M. kansasii strains. This PCR test is an accurate, rapid, and specific M. kansasii identification test. No subspecies was particularly more virulent, because all clusters contained clinical strains, from AIDS patients and non-AIDS patients, and environmental strains.

Characterization of an SAV organism and proposal of Mycobacterium triplex sp. nov

Polyphasic taxonomic methods were employed to characterize a new species of slowly growing, nonpigmented mycobacteria. We propose the name Mycobacterium triplex sp. nov. for this new taxon. Conventional identification testing demonstrated a group of similar organisms that were geographically widespread in the United States. Commercially available nucleic-acid probes specific for the Mycobacterium avium complex were unreactive for these strains. High-performance liquid chromatography analysis of the mycolic acids revealed mycolate profiles that closely resembled Mycobacterium simiae. Comparative 16S rRNA sequence data confirmed the phylogenetic relationship of the strains with the slowly growing mycobacteria. Representative-type strains have been deposited in the American Type Culture Collection as strain ATCC 700071 [corrected].

Nontuberculous mycobacterial disease in children

In most developed countries infections with nontuberculous mycobacteria are causing an increasing proportion of all mycobacterial infections in children. The major clinical syndromes caused by these ubiquitous organisms include pulmonary infections, lymphadenitis, otologic infections, skin and soft tissue infections, indwelling catheter infection, and disseminated infections. Of these, cervical lymphadenitis is the most frequently encountered entity in children, whereas pulmonary infection is rare in this age group. Chronic otorrhea caused by nontuberculous mycobacteria has recently been described. Because many of these infections are similar in presentation to tuberculosis, it is imperative to exclude this diagnosis. The clinical manifestations and management of these infections in children are discussed in this article.