Prevalence and Predictors of Bacterial Contamination in Excisional Lymph Node Biopsies: Implications for Diagnosis and Management.

Routine tissue handling exposes lymph node specimens to microbial contamination that can confound microbiological culture results and interfere with diagnosis. The scope and impact of this problem remain poorly understood. We combined over 13 years of lymph node pathology, culture data, and patient records to define the prevalence, predisposing factors, microbiology, and clinical management of false-positive lymph node cultures at a large academic medical center. Nearly one third (31.9%) of 216 cultured lymph nodes yielded bacterial growth. Approximately 90% of positive bacterial cultures grew 1 of 2 common skin-resident taxa-coagulase-negative Staphylococcus and Cutibacterium acnes-with well-documented predispositions for contamination in other clinical settings. Lymph nodes excised from axillary, cervical, and inguinal regions yielded higher positive culture rates than nodes excised from the mediastinum, suggesting proximity to the skin surface may increase contamination risk. Accordingly, cultures from thoracoscopic pulmonary resections displayed contamination rates over 5-fold lower than those from percutaneously accessed lymph nodes. Lymph nodal tissue allocated for culture in the operating room yielded unexpectedly high contamination rates, significantly higher than cultures sent from the frozen section processing area. A significant minority of contamination events were noted in the clinical record and prompted antibiotic therapy on multiple occasions. Collectively, our results illuminate the risk factors contributing to bacterial contamination and argue that routine lymph node bacterial cultures provide minimal clinical benefit for adult patients. This widespread bacterial contamination also warrants cautious implementation of increasingly sensitive molecular microbiology tools for excised tissues.

Microbiological assessment of sheep lymph nodes with lymphadenitis found during post-mortem examination of slaughtered sheep: implications for veterinary-sanitary meat control.

BACKGROUND: Microbiological examination of lesions found in slaughtered animals during meat inspection is an important part of public health protection as such lesions may be due to zoonotic agents that can be transmitted by meat. Examination of inflamed lymph nodes also plays a particular important role, as lymphadenitis may reflect a more widespread infection. Such lesions in sheep are mainly caused by pyogenic bacteria but also mycobacteria are occasionally found. Meat inspection data from 2017 to 2018 from southern Poland, especially from the Malopolska region, indicate that purulent or caseous lymphadenitis involving the mediastinal and tracheobronchial lymph nodes (MTLNs) is a common finding. The primary aim of the current study was to determine the aetiology of these lesions. Furthermore, it was investigated how presence of lesions was correlated with age and grazing strategy of affected sheep. RESULTS: Post-mortem examination revealed purulent or caseous lymphadenitis in the MTLNs of 49 out of 284 animals (17.3%). Subsequent microbiological examination revealed the presence of Corynebacterium pseudotuberculosis (34.7%), Streptococcus dysgalactiae subsp. equisimilis (34.7%), Staphylococcus aureus (8.2%), Enterococcus spp. (2.0%), Trueperella pyogenes (2.0%), and ß-haemolytic strains of Escherichia coli (2.0%). Mycobacterium spp. and Rhodococcus equi were not detected. In older sheep, the probability of the presence of purulent or caseous lymphadenitis was higher than in younger, and the risk was increasing by 1.5% with each month of life. Sheep grazing locally had 4.5-times greater risk of having purulent or caseous lymphadenitis than individuals summer grazing in the mountains. CONCLUSION: The most common aetiological agents of purulent or caseous lymphadenitis in the MTLNs of sheep in the Malopolska region were C. pseudotuberculosis and S. dysgalactiae subsp. equisimilis. Particular attention during post-mortem examination should be paid to the carcasses of older sheep and sheep grazing on permanent pastures, as they seem more prone to develop purulent or caseous lymphadenitis.

Pancreatic tuberculosis: A systematic review of symptoms, diagnosis and treatment.

INTRODUCTION: Although pancreatic tuberculosis (TB) is traditionally considered to be a rare clinical entity, in recent times, an increase in the number of reports of pancreatic TB has been noted. We conducted a systematic review in order to summarise currently available data on pancreatic TB. METHODS: A comprehensive literature search of Medline, Scopus and ISI Web of Science databases was conducted in order to identify papers reporting cases of pancreatic TB. The eligibility criteria for inclusion in the review required that the studies reported patient(s) affected by pancreatic TB and that individual data on age, sex, clinical presentation and outcome were available. RESULTS: In total, 116 studies reporting data on 166 patients were included in the analysis. The majority of patients were males (62.1%) diagnosed at a mean age of 41.61 ± 13.95 years. Most cases were diagnosed in Asia (50.0%), followed by North America (22.9%), Europe (20.5%), Africa (4.2%) and South America (2.4%). Human immunodeficiency virus (HIV) infection was diagnosed in 25.3% of those affected. Pancreatic TB most frequently presented itself in the form of a pancreatic mass (79.5%) localised mainly in the head (59.0%) and less frequently in the body (18.2%) and tail (13.4%). Extrapancreatic TB involvement most frequently affected the peripancreatic lymph nodes (47.3%). More than half of patients (55.2%) were subjected to laparotomy, while 21.08% underwent endoscopic ultrasound fine-needle aspiration biopsy. The presence of TB was identified most frequently through histological analysis (59.6%), followed by culture (28.9%), staining (27.7%) and, in a smaller number, by polymerase chain reaction (9.6%) and cytology (6.6%). Almost all patients received anti-tubercular pharmacological therapy (98.2%), while 24.1% underwent surgery. Despite treatment, 8.7% of patients died. CONCLUSION: Increased awareness of pancreatic TB is needed, not only in endemic areas but especially in relation to HIV infection and other clinical conditions associated with immunoincompetence.

Interventions Targeting Deep Tissue Lymph Nodes May Not Effectively Reduce the Risk of Salmonellosis from Ground Pork Consumption: A Quantitative Microbial Risk Assessment.

The inclusion of deep tissue lymph nodes (DTLNs) or nonvisceral lymph nodes contaminated with Salmonella in wholesale fresh ground pork (WFGP) production may pose risks to public health. To assess the relative contribution of DTLNs to human salmonellosis occurrence associated with ground pork consumption and to investigate potential critical control points in the slaughter-to-table continuum for the control of human salmonellosis in the United States, a quantitative microbial risk assessment (QMRA) model was established. The model predicted an average of 45 cases of salmonellosis (95% CI = [19, 71]) per 100,000 Americans annually due to WFGP consumption. Sensitivity analysis of all stochastic input variables showed that cooking temperature was the most influential parameter for reducing salmonellosis cases associated with WFGP meals, followed by storage temperature and Salmonella concentration on contaminated carcass surface before fabrication. The input variables were grouped to represent three main factors along the slaughter-to-table chain influencing Salmonella doses ingested via WFGP meals: DTLN-related factors, factors at processing other than DTLNs, and consumer-related factors. The evaluation of the impact of each group of factors by second-order Monte Carlo simulation showed that DTLN-related factors had the lowest impact on the risk estimate among the three groups of factors. These findings indicate that interventions to reduce Salmonella contamination in DTLNs or to remove DTLNs from WFGP products may be less critical for reducing human infections attributable to ground pork than improving consumers' cooking habits or interventions of carcass decontamination at processing.

Assessment of Salmonella Prevalence in Lymph Nodes of U.S. and Mexican Cattle Presented for Slaughter in Texas.

Foodborne salmonellosis has been traced to undercooked ground beef and other beef products in the past, and peripheral lymph node (LN) presence in the fatty tissues of beef carcasses is one possible source of Salmonella contamination. Researchers have previously reported higher rates of Salmonella prevalence in LNs from cattle raised and harvested in Mexico compared with rates typically observed from cattle harvested in the United States. With cattle of Mexican origin comprising the majority of U.S. live cattle imports, the objectives of this study were designed to determine whether Salmonella prevalence in LNs differed (i) between cattle of Mexican and U.S. origins when exposed to the same South Texas feeding operation and (ii) between warm and cool seasons. To meet these objectives, paired (left and right sides) subiliac LNs ( n = 800 LNs; n = 400 pooled samples) were collected from 100 carcasses per origin (Mexico and United States) per season (cool, December to January; warm, July to September). Overall, Salmonella prevalence in LN samples was 52.0% (208 of 400). No difference ( P = 0.4836) was seen in Salmonella prevalence as a function of origin, with 54.0% (108 of 200) and 50.0% (100 of 200) of LN samples returning Salmonella-positive results from cattle of Mexican and U.S. origin, respectively. Salmonella prevalence differed ( P = 0.0354) between seasons, with 46.5% (93 of 200) of cool and 57.5% (115 of 200) of warm season samples returning Salmonella-positive results. Serotyping of PCR-confirmed positive samples resulted in 14 different serovars being identified, with Cerro (21.6%), Anatum (19.7%), Muenchen (17.8%), Montevideo (14.4%), and Kentucky (12.0%) comprising the majority of serovars. These results suggest that factors other than cattle origin may be impacting Salmonella prevalence rates in bovine LNs and that additional research is needed to better understand the role of environment and management-related factors on Salmonella prevalence in bovine LNs.

Low-dose BCG vaccination protects free-ranging cattle against naturally-acquired bovine tuberculosis.

Vaccination of cattle with Mycobacterium bovis BCG has been shown to protect against infection with virulent strains of M. bovis, and against resultant bovine tuberculosis (TB). Here we report on a large-scale trial in New Zealand where free-ranging cattle were vaccinated with 3 x 105 BCG via injection, a lower dose than any previously trialed in cattle against exposure to a natural force of M. bovis infection. In a multi-year enrolment study involving >800 animals, three cohorts of 1-2 year old cattle were randomised to receive vaccine or to serve as non-vaccinated controls. Cattle were slaughtered and subject to standard abattoir post mortem examination for M. bovis culture-positive TB lesions after up to 3.7 years of in-field exposure; additionally, lymph node samples from approximately half of the cattle were examined further to identify infection in the absence of lesions. Overall TB prevalence, as identified by gross lesions detected at slaughter, was low among farmed cattle at the study site (<4% annually). There were two lesioned cases among 520 vaccinated trial cattle (0.38%) compared to eight among 297 non-vaccinated trial cattle (2.69%). Trial vaccine efficacy was 85.7% against abattoir-detectable TB (statistically significant protection), and 86.7% when adjusted for duration of exposure. BCG vaccination did not significantly affect the response rates of cattle to ante mortem skin- or blood-tests in diagnostic tests conducted >7 months post-vaccination. Use of a reduced, yet effective, dose of BCG would increase the cost effectiveness of using this vaccine in a bovine TB control programme.

Assessment of Clinically Suspected Tubercular Lymphadenopathy by Real-Time PCR Compared to Non-Molecular Methods on Lymph Node Aspirates.

BACKGROUND: The diagnosis of tubercular lymphadenitis (TBLN) is challenging. This study assesses the role of diagnostic intervention with real-time PCR in clinically suspected tubercular lymphadenopathy in relation to cytology and microbiological methods. METHODS: The cross-sectional study involved 214 patients, and PCR, cytology, and Ziehl-Neelsen (ZN) staining was performed on aspirates. The findings were compared with culture on Lowenstein-Jensen medium. The overall concordance of cytology and PCR, both individually and combined, was calculated. χ2 and Phi values were assessed between cytology, PCR, and culture. RESULTS: A cytological diagnosis of tuberculosis (TB), reactive lymphoid hyperplasia, and suppurative lymphadenitis was made in 71, 112, and 6 patients, respectively. PCR and culture were positive in 40% of the cases. Among the TBLN patients, PCR showed higher positivity in necrosis and culture showed higher positivity in necrotizing granuloma. Positive ZN staining was observed in 29.6% of the TBLN cases, with an overall positivity of 11%. PCR could additionally detect 82 cases missed by ZN staining. The overall concordance rate for either diagnostic modality, i.e., PCR or cytology, was highest (75%), and for PCR alone was 74%. Phi values were observed to be 0.47 between PCR and culture. CONCLUSION: Real-time PCR for Mycobacterium tuberculosis complex on aspirates offers a definitive and comparable diagnosis of TBLN. Including this approach as the primary investigation in the work-up of TBLN could reduce the burden of TB.

Assessment of lymph node tuberculosis in two provinces in Turkey.

The aim of this study was to evaluate lymph node tuberculosis (LNT) cases in two provinces in Turkey with different demographic and socioeconomic characteristics. A total of 109 LNT cases were reviewed retrospectively. The cases were analyzed and compared for symptoms, findings, age, vaccination status, and diagnostic procedures. Socioeconomic conditions were also assessed for the two provinces. A palpable cervical node was considered a significant predictor for all LNT. Mediastinal lymph node involvement was found to be common in cases of pulmonary manifestation of LNT. Female patients were predominantly from the Van Province, while older patients were found to be from Izmir Province. LNT should be suspected in lymphadenitis patients of all age-groups especially in young adolescents with cervical lymph node enlargements. In the presence of mediastinal lymphadenopathy, pulmonary tuberculosis should be investigated.

The use of light-emitting diode fluorescence to diagnose mycobacterial lymphadenitis in fine-needle aspirates from children.

BACKGROUND: Fine-needle aspiration biopsy (FNAB) is a simple, safe and effective method for investigating suspected mycobacterial lymphadenitis in children. Fluorescence microscopy can provide rapid mycobacterial confirmation. Light-emitting diodes (LEDs) provide a cheap and robust excitation light source, making fluorescence microscopy feasible in resource-limited settings. OBJECTIVE: To compare the diagnostic performance of LED fluorescence microscopy on Papanicolaou (PAP) stained smears with the conventional mercury vapour lamp (MVL). METHODS: FNAB smears routinely collected from palpable lymph nodes in children with suspected mycobacterial disease were PAP-stained and evaluated by two independent microscopists using different excitatory light sources (MVL and LED). Mycobacterial culture results provided the reference standard. A manually rechargeable battery-powered LED power source was evaluated in a random subset. RESULTS: We evaluated 182 FNAB smears from 121 children (median age 31 months, interquartile range 10-67). Mycobacterial cultures were positive in 84 of 121 (69%) children. The mean sensitivity with LED (mains-powered), LED (rechargeable battery-powered) and MVL was respectively 48.2%, 50.0% and 51.8% (specificity 78.4%, 86.7% and 78.4%). Inter-observer variation was similar for LED and MVL (κ = 0.5). CONCLUSION: LED fluorescence microscopy provides a reliable alternative to conventional methods and has many favourable attributes that would facilitate improved, decentralised diagnostic services.

Management practices and their association with Mycobacterium tuberculosis complex prevalence in red deer populations in Southwestern Spain.

Intensification of game management may increase the prevalence of tuberculosis (TB) in wildlife despite eradication programs implemented in cattle herds in the same areas. In this cross-sectional study, we investigated the association between wild game management practices and the presence of tuberculosis in red deer populations in Southwestern Spain. Five hundred and fifty-one animals were examined by necropsy to detect tuberculosis-like lesions in the main lymph nodes. Prevalence, as determined by TB-like lesions, was estimated to be 5.1% of animals, with 77% of TB-like lesions confirmed by PCR. Our results suggest that population density, in addition to factors which promote the local aggregation of animals, is factors associated with increased prevalence of TB in red deer populations. We suggest that management practices including supplementary feeding, fencing, water ponds and interaction with domestic livestock should be revised in order to prevent TB in wild deer both.

Assessment of different formulations of oral Mycobacterium bovis Bacille Calmette-Guérin (BCG) vaccine in rodent models for immunogenicity and protection against aerosol challenge with M. bovis.

Bovine tuberculosis (bTB) caused by infection with Mycobacterium bovis is causing considerable economic loss to farmers and Government in the United Kingdom as its incidence is increasing. Efforts to control bTB in the UK are hampered by the infection in Eurasian badgers (Meles meles) that represent a wildlife reservoir and source of recurrent M. bovis exposure to cattle. Vaccination of badgers with the human TB vaccine, M. bovis Bacille Calmette-Guérin (BCG), in oral bait represents a possible disease control tool and holds the best prospect for reaching badger populations over a wide geographical area. Using mouse and guinea pig models, we evaluated the immunogenicity and protective efficacy, respectively, of candidate badger oral vaccines based on formulation of BCG in lipid matrix, alginate beads, or a novel microcapsular hybrid of both lipid and alginate. Two different oral doses of BCG were evaluated in each formulation for their protective efficacy in guinea pigs, while a single dose was evaluated in mice. In mice, significant immune responses (based on lymphocyte proliferation and expression of IFN-gamma) were only seen with the lipid matrix and the lipid in alginate microcapsular formulation, corresponding to the isolation of viable BCG from alimentary tract lymph nodes. In guinea pigs, only BCG formulated in lipid matrix conferred protection to the spleen and lungs following aerosol route challenge with M. bovis. Protection was seen with delivery doses in the range 10(6)-10(7) CFU, although this was more consistent in the spleen at the higher dose. No protection in terms of organ CFU was seen with BCG administered in alginate beads or in lipid in alginate microcapsules, although 10(7) in the latter formulation conferred protection in terms of increasing body weight after challenge and a smaller lung to body weight ratio at necropsy. These results highlight the potential for lipid, rather than alginate, -based vaccine formulations as suitable delivery vehicles for an oral BCG vaccine in badgers.

Comparison of the recovery of Mycobacterium bovis isolates using the BACTEC MGIT 960 system, BACTEC 460 system, and Middlebrook 7H10 and 7H11 solid media.

The BACTEC Microbacteria Growth Indicator Tube (MGIT) 960 system was evaluated to determine how it compares with the BACTEC 460 radiometric system and solid media for recovery of Mycobacterium bovis from tissue samples. A total of 506 bovine lymph node samples were collected from abattoirs in the United States and Mexico between November 2003 and September 2004. Processed samples were inoculated into an MGIT 960 tube, BACTEC 460 vial, and Middlebrook 7H10 and Middlebrook 7H11 solid media. Ziehl-Neelsen slides were prepared to check for contaminants and confirm the presence of acid-fast positive bacilli. Samples containing acid-fast bacilli were confirmed as members of the Mycobacterium tuberculosis complex by a nucleic acid assay. Niacin and nitrate biochemical tests were used to distinguish M. bovis from M. tuberculosis isolates. Statistical analyses were performed to compare recovery rate, mean time to detection, contamination rates, as well as pair-wise comparisons in each category. The results showed that the MGIT 960 system had a higher recovery rate of M. bovis (122/129) than did the BACTEC 460 (102/129) and solid media system (96/129). The average time to detection was 15.8 days for the MGIT 960 system, 28.2 days for the BACTEC 460 system, and 43.4 days for solid media. Contamination rates were 6.9% for the MGIT 960 system, 3.4% for the BACTEC 460 system, and 21.7% for solid media. These results indicate the MGIT 960 system can be used as an alternative to the BACTEC 460 system for recovering M. bovis from tissue samples.

Resting pigs on transport trailers as an intervention strategy to reduce Salmonella enterica prevalence at slaughter.

Recent research has shown that much preharvest Salmonella enterica infection in pigs occurs immediately before slaughter during this rest period in the contaminated abattoir holding pens. The objective of this study was to evaluate a potential intervention strategy to reduce the prevalence of S. enterica-positive pigs at slaughter, which consisted of resting pigs prior to slaughter on their transport vehicle, instead of in the abattoir holding pen. Additionally, the effect of transportation of pigs from farm to the abattoir on S. enterica prevalence was investigated. A total of 120 animals were included in the experiment, divided in four replicates (n = 30 pigs per replicate). Fecal samples were collected from each animal at the farm and at the abattoir, where 15 randomly chosen pigs were unloaded and moved to a holding pen, while the remaining 15 pigs stayed in the transport trailer. After approximately 1.5 h of resting, both groups were slaughtered. Samples collected included distal ileum portion, cecal contents, and ileocecal lymph node. The overall S. enterica prevalence (pigs positive in at least one of the samples collected at slaughter) was higher for pigs held in the abattoir pens (40.7% versus 13.3%, P < 0.05). There was no difference (P > 0.05) for the S. enterica prevalence before and after transportation from farm to abattoir (5.8% versus 0.8%, respectively). This study demonstrates that resting pigs on the transport vehicle has the potential to decrease S. enterica levels entering the abattoir.

Critical assessment of the methods used for detection of bacterial translocation.

AIM: Bacterial translocation (BT) can be demonstrated by blood and lymph node cultures and also by polymerase chain reaction (PCR) detection of DNA of enteric bacteria. Aiming at investigating BT after gastrointestinal operations we assessed it on two endpoints after ischemia-reperfusion (IR) or sham operation (SO). METHODS: 2 groups of 200-g Brown Norway male rats were treated as follows: SO animals ( n=12) had laparotomy alone and IR animals ( n=12) had successively 15 min clamping of the portal vein and the mesenteric artery. Half the animals in each group were killed on postoperative (p.o.) day 2 the other half on p.o. day 7. Under sterile conditions regional lymph nodes and vena cava and portal vein blood samples were recovered and cultured for aerobes and anaerobes. Escherichia coli beta-galactosidase DNA was assessed in blood samples by PCR. The findings in the two groups were compared by means of chi(2) tests. RESULTS: Post-hepatic (peripheral blood) BT was detected by cultures of gram-negative bacteria in 16% and 0% of SO and IR animals, respectively, on p.o. day 2 and in 16% and 50% on p.o. day 7. These differences were not significant (ns). E. coli DNA was found in one SO rat. Pre-hepatic BT (portal blood and/or lymph nodes) of gram-negative bacteria was found in 16% and 33%, respectively, on day 2 and in 16% and 16% on day 7 (ns). However, if gram-positive cultures were taken into account, the figures were 66% and 66% on day 2 and 66% and 83% on day 7 (ns). No anaerobes could be cultured. CONCLUSIONS: (1) BT is frequent in surgically manipulated animals. (2) To limit the assessment of BT to Enterobacteriaceae is probably misleading, since consistent amounts of gram-positive bacteria are found in the pre-hepatic territory. (3) PCR tests limited to E. coli DNA alone are likely incomplete. (4) Short periods of vascular clamping do not increase BT on the two endpoints selected in comparison with SO animals.

The use of fine needle aspiration biopsy in the evaluation of lymphadenopathy.

Fine needle aspiration biopsy is an important diagnostic tool in the evaluation and triage of patients with lymphadenopathy. It offers a simple and inexpensive test for diagnosis of reactive hyperplasia, infections, granulomatous lymphadenopathies, and metastatic diseases. Although previously regarded as limited in its use for diagnosing primary lymphoid malignancies, fine needle aspiration in combination with immunophenotypic and genotype studies is gaining respect in providing accurate diagnosis of lymphoma for primary treatment in selected patients.

[Clinical evaluation of the Amplified Mycobacterium Tuberculosis Direct 2 test]. / Valoración clínica de la prueba Amplified Mycobacterium tuberculosis Direct 2 (AMTD-2, GenProbe) en el diagnóstico rápido de la tuberculosis.

OBJECTIVE: To evaluate the performance of the Amplified Mycobacterium tuberculosis Direct Test 2- Gen Probe (AMTD- 2) for direct detection of Mycobacterium tuberculosis in smear-negative samples. PATIENTS AND METHODS: From January to December 1999, 683 specimens, 333 respiratory and 350 non-respiratory ones collected from 457 patients, were included in the study. All the samples of HIV-positive patients, the respiratory samples from patients suspected of having pulmonary tuberculosis (at least two by patient) and all non-respiratory samples were included. As diagnosis method of reference, the culture isolation was considered. Clinical data were analyzed in case of discrepant results and clinical diagnosis was considered the reference criteria. The technique was performed once a week. RESULTS: The sensitivity, specificity, and positive and negative predictive values of this assay were 58.9%, 93.9%, 37.1% and 97.4% respectively related to the standard culture. When referred to clinical diagnosis of active tuberculosis, these values improved to 70.4%, 97.7%, 73.1% and 96.8% respectively (in respiratory samples were 67.6%, 98.6%, 86.2% and 95.9% and in nonrespiratory ones 76.5%, 96.9%, 56.5% and 98.7% respectively). The mean time of diagnosis by culture and by AMTD-2 were 20.3 days (range 10-63) and 5.7 days (range 2-20) respectively. DISCUSSION: It is concluded that AMTD-2 is a rapid diagnosis method when clinical data are sugestive with active tuberculosis. However, due to the low positive predictive value, it would be convenient to obtain successive samples to confirm the result in patients without clinical evidence of tuberculosis.

Assessment of the long-term shedding pattern of Salmonella serovar choleraesuis following experimental infection of neonatal piglets.

In the United States, swine salmonellosis is most often attributed to infections by Salmonella serovar choleraesuis. As a host-adapted pathogen rarely found in nonswine sources, S. choleraesuis is thought to be spread primarily via horizontal transmission, with carrier animals playing an important role. Little has been reported regarding infection of neonatal piglets, particularly regarding their potential to become carriers. Evidence reported herein demonstrates that piglets experimentally infected by S. choleraesuis at 2 days of age were capable of shedding the pathogen for up to 85 days postinfection, at which time the study was concluded. This study also presents findings supporting the use of GN-Hajna as a preenrichment medium for the isolation of S. choleraesuis.

Risk assessment of organoleptic postmortem inspection procedures for pigs.

A systematic quantification of foodborne hazards in abnormal and normal tissues of pig carcases was undertaken to provide a risk-based assessment of the effectiveness of traditional organoleptic meat inspection. A total of 36,059 pigs, representing all major pig-producing areas and systems in Australia, were inspected on a seasonal basis at three abattoirs over 12 months. The prevalence of grossly detectable abnormalities of possible food-borne disease significance was recorded. A subset of the grossly detectable abnormalities, together with tissues classified by inspection as normal (controls) were submitted for the detection of a broad range of food-borne hazards. The potential exposure of consumers to hazards in fresh pork was characterised as the number of carcases per 10,000 containing hazards in selected tissues. The results indicated that the level of exposure of consumers to microbiological hazards in fresh pork is unlikely to be reduced significantly by the detection and removal of gross abnormalities in the tissues examined. On the basis of carcase throughput, the rate of contamination of normal lymph nodes was commonly 100 times higher, and no hazards were isolated from two types of grossly abnormal nodes. While further processing, cooking and handling may alter the exposure characterisation, the study nevertheless identifies the proportional contribution of abnormal and normal tissues to risks to consumers and clearly identifies the need for consideration of 'visual only' inspection in the re-evaluation of traditional inspection procedures.

Development, testing and commercialization of a new brucellosis vaccine for cattle.

Vaccines used against brucellosis do not generally protect completely against infection or abortion. Genetic analysis has revealed differences in arrangements of DNA sequences between these vaccine strains and the virulent parent strain and permits the specific identification of field isolates of B. abortus as wild-type or vaccine strain. B. abortus strain 19 is a low-virulence, live vaccine developed for use in cattle. Although it is effective, strain 19 vaccine had a tropism for the placenta and caused abortion when given to pregnant cows, was infectious for humans, and caused serologic responses in calves that could not be differentiated from those in cattle infected with natural field strains. In the mid-1980s the need for a new vaccine emerged when the USDA increased its efforts in brucellosis eradication. In the 1990s, research on biosafety, vaccine efficacy and field application rapidly established the fact that strain RB51 is protective in cattle at doses comparable to those of strain 19. Thus, Brucella abortus strain RB51 is the vaccine of choice against brucellosis of cattle in the United States. Studies have established the relative efficacy of strain RB51 vaccine on bison, and the vaccine has also been accepted for use in commercial bison herds in the U.S.

Polymerase chain reaction for the detection of Mycobacterium tuberculosis DNA in tissue and assessment of its utility in the diagnosis of hepatic granulomas.

A polymerase chain reaction (PCR) assay for the rapid identification of Mycobacterium tuberculosis, based on amplification of the IS6110 insertion sequences, was tested in paraffin-embedded tissue from 64 biopsy samples with either positive or negative cultures for Mycobacterium tuberculosis. The utility of this PCR assay in the diagnosis of tuberculosis among patients with hepatic granulomas (HGs) was then tested by examining 43 liver biopsy samples. They were classified as either having definitive or probable tuberculosis or as being of nontuberculous origin, on the basis of clinical and microbiologic data and on their response to antituberculous treatment. PCR was 100% sensitive in the diagnosis of culture-positive M. tuberculosis infection in the lymph node, lung, and liver. The sensitivity of the PCR in the diagnosis of HG of definitive tuberculous origin was 58%, and the specificity was 96%. PCR is a valuable test for the demonstration of mycobacterial DNA in tissues. Although it is not highly sensitive, the DNA amplification method may also be more sensitive than culture in the diagnosis of M. tuberculosis-associated HG.