Survival of viruses on fresh produce, using MS2 as a surrogate for norovirus.

AIMS: To study the survival and removal of viruses from fresh fruit and vegetables using the bacteriophage MS2 as a potential surrogate for noroviruses. METHOD AND RESULTS: Survival of MS2 in buffer and on fresh produce was studied at 4, 8 and 22 degrees C. At 4 and 8 degrees C a reduction of <1 log10 was observed after 50 days in buffer; however a reduction in excess of 1 log10 occurred within 9 days at 22 degrees C. Similar results were obtained with fresh produce with virus survival times exceeding the shelf life of the produce. In washing experiments, using a chlorine wash (100 ppm), in all but one case <1.5 log10 MS2 bacteriophage was removed from fruit and vegetables. The mean across all produce types was 0.89 log10. With potable water, reduction was lower (0.3 log mean across all produce types). CONCLUSIONS: MS2 survived for prolonged periods, both in buffer and on fresh produce, at temperatures relevant to chilled foods. It was not removed effectively by chlorine washing. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacteriophage MS2 has been evaluated as a potential surrogate for noroviruses on fresh produce. Experimental results together with current knowledge of norovirus resistance and survival indicate that MS2 could be used as an effective surrogate in future evaluations.

Survival of Cryptosporidium species in environments relevant to foods and beverages.

AIMS: To provide data on the survival of Cryptosporidium oocysts in a range of conditions relevant to foods and beverages. METHODS AND RESULTS: Cryptosporidium parvum and C. hominis oocysts were stored in buffered media at different pH values and with various acids. In addition, neutral solutions with high salt (4.5% w/v), glycerol (20% v/v), sucrose (50% w/v) or ethanol (9 and 40% v/v) were used to determine their effects on survival. After storage periods of between 1 h and 14 days, viability was assessed using sporozoite ratio or infection of MRC-5 cell monolayers (not previously reported for culture of this organism). With all treatments, and with both assay techniques, viable oocysts were found at the end of the storage periods. However, treatments with one of the following additions: high salt, glycerol, sucrose or ethanol showed a negative and statistically significant effect on survival. Decline was noted after 1 day or even 1 h of treatment. CONCLUSIONS: MRC-5 cells are suitable for infection by C. parvum and C. hominis. Both tissue culture and sporozoite ratio gave broadly similar survival results and the greatest effects were seen with addition of components which reduced water activity. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has provided useful additional information to the food industry when considering the risk posed by this organism.

Biocide use in the food industry and the disinfectant resistance of persistent strains of Listeria monocytogenes and Escherichia coli.

AIMS: The aims of the project were threefold: to survey the use of disinfectants in the UK food industry; to assess the product and environmental microflora of selected food factories for the persistence of Listeria monocytogenes and Escherichia coli; and to determine the disinfectant resistance of any persistent strains. METHODS AND RESULTS: A survey of the use of disinfectants in the UK food industry was undertaken in which a total of 40 sites were visited and a further 77 postal questionnaires were returned from farms, food manufacture, food transport and food retail sites. Quaternary ammonium compounds (QACs) were predominantly used, applied in small volumes as a mist. Approximately 30,000 samples from the product and environment of five chilled food factories were examined for L. monocytogenes and E. coli over a 3 year period. A total of 181 L. monocytogenes and 176 E. coli isolates were ribotyped to yield 19 and 34 ribogroups, respectively. Some strains were isolated only from the product, a number only from the environment and others from both niches. Some strains were seen to be persistent for the duration of the sampling exercise (2-3 years). The most common L. monocytogenes and E. coli strains, together with two environmental L. monocytogenes strains, were assessed for any resistance to commercial disinfectants as compared with a laboratory L. monocytogenes disinfectant testing strain. The resistance of the L. monocytogenes and E. coli strains isolated from the factory were not significantly different from the laboratory control strain. CONCLUSIONS: Persistent strains of L. monocytogenes and E. coli are found in the UK food industry, though this persistence is not related to their increased susceptibility to the most commonly used disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: The concept of a persistent microflora in food factories will have an impact on the future selection of suitable control options, including the use of biocides.

Biocide use in the food industry and the disinfectant resistance of persistent strains of Listeria monocytogenes and Escherichia coli.

AIMS: The aims of the project were threefold: to survey the use of disinfectants in the UK food industry; to assess the product and environmental microflora of selected food factories for the persistence of Listeria monocytogenes and Escherichia coli; and to determine the disinfectant resistance of any persistent strains. METHODS AND RESULTS: A survey of the use of disinfectants in the UK food industry was undertaken in which a total of 40 sites were visited and a further 77 postal questionnaires were returned from farms, food manufacture, food transport and food retail sites. Quaternary ammonium compounds (QACs) were predominantly used, applied in small volumes as a mist. Approximately 30,000 samples from the product and environment of five chilled food factories were examined for L. monocytogenes and E. coli over a 3 year period. A total of 181 L. monocytogenes and 176 E. coli isolates were ribotyped to yield 19 and 34 ribogroups, respectively. Some strains were isolated only from the product, a number only from the environment and others from both niches. Some strains were seen to be persistent for the duration of the sampling exercise (2-3 years). The most common L. monocytogenes and E. coli strains, together with two environmental L. monocytogenes strains, were assessed for any resistance to commercial disinfectants as compared with a laboratory L. monocytogenes disinfectant testing strain. The resistance of the L. monocytogenes and E. coli strains isolated from the factory were not significantly different from the laboratory control strain. CONCLUSIONS: Persistent strains of L. monocytogenes and E. coli are found in the UK food industry, though this persistence is not related to their increased susceptibility to the most commonly used disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: The concept of a persistent microflora in food factories will have an impact on the future selection of suitable control options, including the use of biocides.

Microbiological safety of water.

Significant advances in water treatment over the last century have resulted in massive improvements in the microbiological safety of public drinking water supplies in the UK and the developed countries. Incidences of illness due to poor treatment or post-treatment contamination are rare, but when they occur tend to attract considerable media attention. A well managed water treatment works and supply system can provide high quality drinking water wherever in the world it is located. As a rule, throughout the world, private supplies tend to be of a poorer quality than public supplies, but poorly managed public supplies have the potential to make a large number of people ill and continued effort is needed to maintain and improve drinking water quality world-wide.

Tuberculosis due to Mycobacterium bovis in the Australian population: cases recorded during 1970-1994.

OBJECTIVE: To determine the contribution of Mycobacterium bovis to active tuberculosis in the Australian population during 1970-1994, and to collate and analyse demographic data from bacteriologically proven cases. DESIGN: Summary data for tuberculosis cases notified by Australian public health agencies during 1970-1985 and 1991-1994 were obtained from the database of notifiable diseases maintained by the Department of Health and Family Services. More detailed demographic data for cases confirmed by bacteriology during 1970-1994 were supplied by the Australian Mycobacterium Reference Laboratory Network. RESULTS: At least 236 cases of bovine tuberculosis (TB) occurred in the Australian population during 1970-1994 (mean 9.4 cases; range 3-22 cases annually). The bovine strain has accounted for around 1% of Australian cases of TB during this period. Laboratory sources provided demographic data for 150 cases with positive bacteriology. For this group, the mean age was 54 years (range 22-86), and the male:female ratio was 2.4:1. The majority of cases (74%) involved pulmonary disease. Australian-born persons accounted for 68% of the total cases and typically had histories of employment in meat and/or livestock industries. CONCLUSION: M. bovis was responsible for less than 1.5% of cases of TB in the Australian population during 1970-1994. Most cases were apparently due to reactivation of infection acquired through occupational exposure. Thus, although virtual eradication of M. bovis from Australia's cattle herds has now reduced the risk of exposure, it can be expected that human cases of bovine TB will continue to be detected for years to come. The bovine strain should be considered as the possible agent of TB in foreign-born Australians.

Tuberculosis due to Mycobacterium bovis in the Australian population: DNA typing of isolates, 1970-1994.

SETTING: Bacteriologically confirmed cases of Mycobacterium bovis in the Australian population. OBJECTIVE: To evaluate the DNA fingerprinting techniques commonly used for M. bovis on isolates from humans and determine whether they were useful for determining the origin of human infection. DESIGN: M. bovis strains isolated between 1970 and 1994 were obtained from five Australian Reference Laboratories. Four DNA fingerprinting techniques, comprising Southern hybridisation with three different probes (the insertion sequence [IS]6110, the polymorphic guanine-cytosine-rich sequence [PGRS] and the direct repeat [DR]) and a PCR-based method (spoligotyping) were used. RESULTS: The PGRS, DR and IS6110 RFLP methods identified 32, 22 and 14 different types respectively from the 45 isolates available. Spoligotyping identified 18 different types. When all methods were combined 41 different strains were identified. Clear differences were found between many isolates from Australian-born patients and those from patients born overseas. CONCLUSIONS: The PGRS RFLP method was the most effective method for typing the human strains, but a combination of methods is recommended for maximum sensitivity. Most Australian-born patients that had worked in the meat and livestock industries were infected with strains similar to those that are commonly found in Australian cattle, confirming the occupational risk in these industries. Patients born overseas were typically infected with strains genetically different from those of patients born in Australia. This suggests that patients born overseas identified with M. bovis were presenting with reactivation of infection acquired outside Australia.

Subcutaneous granuloma caused by Mycobacterium avium complex infection in a cat.

A localised subcutaneous swelling developed on the nasal bridge of a cat receiving chemotherapy for alimentary tract lymphosarcoma. Cytological and histological examination of representative samples of the lesion demonstrated pyogranulomatous inflammation and abundant acid-fast bacilli. A Mycobacterium sp was cultured from tissue excised from the lesion. Extensive testing at three reference laboratories indicated the strain was a member of the Mycobacterium avium complex. The infection was treated successfully by cytoreductive surgery and a 6 weeks course of orally administered clofazimine.

A doorless entry system for high-energy radiation therapy rooms.

A doorless entry system has been designed for use in high-energy radiation therapy rooms. The doorless entry improves patient access, safety and throughput, increases the physical safety for the radiation therapists, and avoids the significant cost of heavy shielding doors. The design meets concerns relating to radiation safety, operational ease, and authorized entry. The new system is currently operating in one room housing a cobalt-60 unit and is to be employed in five additional rooms housing dual-energy accelerators (maximum energies of 10 and 18 MV). The doorless entry has received wide approval from the radiation therapists and no concerns have been expressed with respect to unauthorized entry or radiation safety.

Analysis of Mycobacterium avium complex serovars isolated from AIDS patients from southeast Brazil.

The purpose of this study was to assess the distribution of Mycobacterium avium serovars isolated from AIDS patients in São Paulo and Rio de Janeiro. Ninety single site or multiple site isolates from 75 patients were examined. The most frequent serovars found were 8 (39.2%), 4 (21.4%) and 1 (10.7%). The frequency of mixed infections with serovar 8 or 4 was 37.8%. Among the 90 strains examined, M. intracellulare serovars (7 strains) and M. scrofulaceum (4 strains) were found in 11 isolates (12%) indicating that M. avium (88%) was the major opportunistic species in the M. avium complex isolates in Brazilian AIDS patients.

PIP: Mycobacterium avium complex (MAC) organisms have been associated with severe opportunistic infections in patients with AIDS in the US. The present study analyzed the distribution of 90 MAC serovars isolated from 75 AIDS patients from Sao Paulo and Rio de Janeiro, Brazil, in 1990-94. 56 isolates (62.2%) showed a single serovar--predominantly serovars 8 (39.2%), 4 (21.4%), and 1 (10.7%). In the 34 isolates (37.8%) in which more than one serovar was identified, 19 (55.9%) were from a single site and 15 (44.1%) were isolated from different sites or from the same site but at different times. The most common serovars in mixed infections from both single and different sites were 8 (34.2% and 37%, respectively)) and 4 (21.1% and 25.9%, respectively). Only 11 isolates (12%) were M. intracellulare or M. scrofulaceum strains, indicating that M. avium was the opportunistic species in 88% of the MAC isolates in these Brazilian AIDS patients. Although the serovars detected in this series are similar to those found in US AIDS patients, the occurrence of mixed serovars was substantially higher in Brazilian AIDS patients. The clinical implications of polyclonal infections in Brazilian AIDS patients require further investigation, especially since serovars from distinct sites may have distinct drug resistance patterns.

Characterization of Mycobacterium avium complex related mycobacteria isolated from an African environment and patients with AIDS.

Thirteen isolates from African AIDS patients and from the environment in Zaire were identified as members of the Mycobacterium avium complex by phenotypic tests. RFLP analysis showed that the isolates belong to a genetically homogeneous cluster. The 16S rRNA sequence analysis suggests a close relationship with the P-49 strain (ATCC 35847), a reference strain for the serotype 7 of M. avium complex. This work shows the close relationship between certain M. avium complex strains responsible for disseminated infection in AIDS patients and M. avium complex strains isolated from the environment in Zaire. Further, our findings confirm that atypical mycobacteria may disseminate in AIDS patients in Africa and suggest that infection in these patients probably originates in their environment.

Mycobacterium asiaticum as the probable causative agent in a case of olecranon bursitis.

Mycobacterium asiaticum was isolated from fluid aspirated from an olecranon bursa that had become inflamed following a superficial injury. Other possible causes of the inflammation were excluded. No specific antimycobacterial therapy was given. The infection responded to drainage, regular dressing, and immobilization. Our experience suggests that M. asiaticum is a potential cause of infection of the joints and surrounding tissues.

Tuberculosis in Australia, 1989-1992. Bacteriologically confirmed cases and drug resistance.

OBJECTIVE: To collate statistics, including drug susceptibility, of patients with bacteriologically confirmed tuberculosis in Australia during 1989-1992. DESIGN: Collaborative project among the five Australian mycobacterial reference laboratories. STUDY POPULATION: 2509 Australian residents with bacteriologically confirmed tuberculosis. OUTCOME MEASURES: Patient and specimen data, and drug susceptibility results recorded for isolates of Mycobacterium tuberculosis and Mycobacterium bovis. RESULTS: The annual incidence during 1989-1992 was about 3.6 per 100,000. The male-to-female ratio was 1.4:1 and about half the patients were under 50. Older men had high rates of disease. Lymphatic disease was significantly more common in females; the converse was true for pulmonary and pleural disease. Resistance to at least one of the common antituberculosis drugs was detected in 14.4% of isolates, and usually involved streptomycin (7.6%) and isoniazid (8.4%). Fewer than 1% of isolates were resistant to isoniazid and rifampicin in combination. CONCLUSIONS: By international standards, Australia remains a "low-incidence" country for tuberculosis, with a static annual incidence. Multiple drug resistance is uncommon and most patients should respond to the standard four-drug regimen. Nevertheless, because clinical data confirm that the pool of infected persons is being supplemented through immigration, and that certain population subgroups have high rates of disease, it is essential that Australia maintain effective control programs.

Identification of Mycobacterium avium complex strains belonging to serovars 21-28 by three commercial DNA probe tests.

Various reference strains of Mycobacterium avium complex (MAC) belonging to serovars 21-28 were identified by three DNA probe tests, i.e., Gen-Probe, AccuProbe and SNAP tests. All of these DNA probe tests were in agreement for strains identified as M. avium or M. intracellulare. The tested serovar strains involved M. avium, M. intracellulare, MAC reactive only with Probe X of SNAP test ('Probe X-reactive MAC'), M. scrofulaceum reactive with Probe X of SNAP test ('Probe X-reactive M. scrofulaceum'), and typical M. scrofulaceum which did not react with any of the probes. Both reference strains belonging to serovar 21 were M. avium, and none of the other serovars included this species. On the contrary, M. intracellulare was found in serovars 22, 25, 26, and 28. 'Probe X-reactive MAC' were also widely found in serovars 23, 24, 26, 27, and 28, while 'Probe X-reactive M. scrofulaceum' was seen only in serovar 22. These results confirm the usefulness of SNAP test to identify the MAC showing no reactivity to Gen-Probe and AccuProbe.

Comparison of the virulence for mice of Mycobacterium avium and Mycobacterium intracellulare identified by DNA probe test.

The virulence of various serovars of Mycobacterium avium and M. intracellulare identified by DNA probe test was compared with each other. We found species- and serovar-dependencies of M. avium complex (MAC) virulence to mice in terms of mortality, incidence of lung lesions and bacterial load in the visceral organs, as follows. First, human- or environment-derived M. intracellulare was more virulent for mice, as compared to M. avium isolated from patients or environmental sources. Second, the virulence of MAC isolates belonging to serovars 1, 8, 9 (M. avium), 14 and 16 (M. intracellulare) is in the order of serovars 16 > 14 > 8 > 1 > 9. These aspects were different from those for MAC virulence to human and bird, swine and cattle.

Biochemical properties and fatty acid composition of Mycobacterium haemophilum: study of 16 isolates from Australian patients.

The biochemical properties and fatty acid compositions of 16 strains of Mycobacterium haemophilum from Australian patients were studied. The strains proved to be indistinguishable from each other but could readily be differentiated from other slowly growing mycobacteria with similar cultural features. Mycolic acid analyses revealed the presence of alpha-, methoxy-, and ketomycolates. The fatty acid composition supports the validity of the fact that M. haemophilum is a distinct species. The fatty acid composition was consistent among the 16 strains, but it was unusual in that there was some resemblance to the fatty acid composition of M. leprae. The wide range of pHs (5.4 to 7.4) that supported growth of M. haemophilum on artificial medium is in keeping with suggestions that M. haemophilum exists in an environmental habitat.