Response of the Extract-Release Volume and Water-Holding Capacity Phenomena to Microbiologically Spoiled Beef and Aged Beef

The aging of ground beef was effected by storing in gas-impermeable, sterile plastic bags with incubation at 7 and 15 C. Control meat from the same preparations was wrapped in aluminum foil and stored at the same temperature. In three experiments where control meat was tested, aged meat did not attain a log bacterial number of ca. 8.4 per gram until an average of 6 days after this level was reached in control meats. This degree of difference was shown in values for both extract-release volume (ERV) and water-holding capacity. The previously reported ERV value of around 25, which was found to correspond to an average log bacterial number of ca. 8.5 per gram for ground beef allowed to spoil in aluminum foil and freezer paper, was approximated for aged meats, which required an average of 9.7 days to attain this number compared with 4.1 days for unaged meats. Plate count methods indicated the predominant flora of aged beef to be gram-negative, facultatively psychrophilic rods.     

Use of a Titrimetric Method to Assess the Bacterial Spoilage of Fresh Beef

A new method of determining bacterial spoilage in fresh beef is presented. The technique is based upon the fact that as beef undergoes refrigerator spoilage, there is a gradual increase in the production of alkaline substances by the spoilage flora. The level of these substances was measured by titrating meat homogenates to a pH 5.00 end point, employing 0.02 n HCl and an autotitrator. When 23 samples of ground beef from retail stores were tested, an average of 1.32 ml of acid was required for titration of 1 g of fresh beef to pH 5.00, whereas 2.58 ml was required for the same meat at the onset of spoilage. Preliminary data indicate that beef which requires more than 2 ml of 0.02 n HCl/g to lower its pH to 5.00 under the conditions of the test is in some state of incipient spoilage. The statistical correlation between titration values, log bacterial numbers, and extract-release volume was high (P < 0.001). The technique is simple to execute and is highly reproducible, and duplicate samples can be run within 15 min.     

Further Evaluation of a Rapid Immunofluorescence Technique for Detecting Salmonellae in Meat and Poultry

A rapid 18–24 h immunofluorescence technique detected 14 of 15 positive samples in tests on 706 routine samples, which included 656 home produced raw beef samples. The rapid technique also recorded 49 false positive results, i.e. samples which proved negative in subsequent cultural tests. The immunofluorescence technique could be used as a presumptive screening test aimed at the rapid detection of negative samples. In this way salmonella free raw materials should usually be cleared for production within 1 day of sampling.     

Evaluation of a Rapid Diagnostic Test for Yaws Infection in a Community Surveillance Setting

Yaws is a non-venereal treponemal infection caused by Treponema pallidum ssp. pertenue. The WHO has launched a worldwide control programme, which aims to eradicate yaws by 2020. The development of a rapid diagnostic test (RDT) for serological diagnosis in the isolated communities affected by yaws is a key requirement for the successful implementation of the WHO strategy. We conducted a study to evaluate the utility of the DPP test in screening for yaws, utilizing samples collected as part of a community prevalence survey conducted in the Solomon Islands. 415 serum samples were tested using both traditional syphilis serology (TPPA and quantitative RPR) and the Chembio DPP Syphilis Screen and Confirm RDT. We calculated the sensitivity and specificity of the RDT as compared to gold standard serology. The sensitivity of the RDT against TPPA was 58.5% and the specificity was 97.6%. The sensitivity of the RDT against RPR was 41.7% and the specificity was 95.2%. The sensitivity of the DPP was strongly related to the RPR titre with a sensitivity of 92.0% for an RPR titre of >1/16. Wider access to DPP testing would improve our understanding of worldwide yaws case reporting and the test may play a key role in assessing patients presenting with yaws like lesions in a post-mass drug administration (MDA) setting.     

新型冠状病毒胶体金抗原快速检测试剂的研制及性能评价*

目的:建立新型冠状病毒(severe acute respiratory syndrome coronavirus 2,SARS-CoV-2)胶体金抗原快速检测试剂的制备方法,并对检测试剂的性能指标进行评价。方法:采用柠檬酸三钠还原法制备胶体金溶液,用鼠抗核衣壳蛋白(nucleocapsid protein, NP)单克隆抗体及二硝基苯酚-牛血清白蛋白(DNP-BSA)作为标记抗体,硝酸纤维素膜上分别包被鼠抗核衣壳蛋白单克隆抗体和兔抗DNP多抗作为检测线和质控线制备免疫胶体金试纸条;对试剂最低检出限、交叉反应性、加速稳定性及临床诊断特异性和灵敏度进行性能评价。结果:检测热灭活培养物的最低检出限为2.0×10² TCID₅₀/mL;测试16种常见呼吸道病原体高浓度样本均无交叉反应;试剂盒50℃加速破坏8周稳定。临床及健康人群鼻咽拭子样本测试,诊断灵敏度为96.67%(29/30),特异性为99.23%(129/130),总符合率为98.75%(158/160);一致性检验Kappa值为0.959 0,P<0.05。结论:SARS-CoV-2胶体金抗原快速检测试剂检测灵敏度和特异性高,检测速度快,操作便携,无需设备,肉眼观察,可作为现有核酸检测法的补充手段,用于新型冠状病毒的早期筛查。     

Direct Bacterial Count as a Rapid Freshness Test for Fish Fillets

Comparison of various indices of deterioration of refrigerated fish fillets showed that the direct bacterial count can be used to predict the storage life of the foodstuff. For direct counts, a thin film made from fillet surface material was spread on a microscope slide, stained, and read. Initial counts were found to correlate well with keeping quality; a period of freshness of 24 or 48 hr at 5 C could be reliably predicted. Preliminary data indicated that hypoxanthine estimation could probably also be used for the prediction of shelf life but that the relative complexity of the procedure detracted from its usefulness.     

Evaluation of Rapid IgG4 Test for Diagnosis of Gnathostomiasis

Human gnathostomiasis is a parasitic disease caused by Gnathostoma nematode infection. A rapid, reliable, and practical immunoassay, named dot immuno-gold filtration assay (DIGFA), was developed to supporting clinical diagnosis of gnathostomiasis. The practical tool detected anti-Gnathostoma-specific IgG4 in human serum using crude extract of third-stage larvae as antigen. The result of the test was shown by anti-human IgG4 monoclonal antibody conjugated colloidal gold. The sensitivity and specificity of the test were both 100% for detection in human sera from patients with gnathostomiasis (13/13) and from healthy negative controls (50/50), respectively. Cross-reactivity with heterogonous serum samples from patients with other helminthiases ranged from 0 (trichinosis, paragonimiasis, clonorchiasis, schistosomiasis, and cysticercosis) to 25.0% (sparganosis), with an average of 6.3% (7/112). Moreover, specific IgG4 antibodies diminished at 6 months after treatment. This study showed that DIGFA for the detection of specific IgG4 in human sera could be a promising tool for the diagnosis of gnathostomiasis and useful for evaluating therapeutic effects.     

Evaluation of a Density-Based Rapid Diagnostic Test for Sickle Cell Disease in a Clinical Setting in Zambia

Although simple and low-cost interventions for sickle cell disease (SCD) exist in many developing countries, child mortality associated with SCD remains high, in part, because of the lack of access to diagnostic tests for SCD. A density-based test using aqueous multiphase systems (SCD-AMPS) is a candidate for a low-cost, point-of-care diagnostic for SCD. In this paper, the field evaluation of SCD-AMPS in a large (n = 505) case-control study in Zambia is described. Of the two variations of the SCD-AMPS used, the best system (SCD-AMPS-2) demonstrated a sensitivity of 86% (82–90%) and a specificity of 60% (53–67%). Subsequent analysis identified potential sources of false positives that include clotting, variation between batches of SCD-AMPS, and shipping conditions. Importantly, SCD-AMPS-2 was 84% (62–94%) sensitive in detecting SCD in children between 6 months and 1 year old. In addition to an evaluation of performance, an assessment of end-user operability was done with health workers in rural clinics in Zambia. These health workers rated the SCD-AMPS tests to be as simple to use as lateral flow tests for malaria and HIV.     

Evaluation of the Corneal Test as a Laboratory Method for Rabies Diagnosis

The corneal test (CT) for rabies diagnosis was evaluated in samples from 313 subjects of different species. Some of the subjects were inoculated experimentally and others were naturally infected. When the CT was compared with immunofluorescence staining and mouse inoculation tests on brains of the same subjects, a sensitivity of 41.7% and a specificity of 100% were found. The authors conclude that a positive CT result would confirm the diagnosis of rabies, but a negative one would not exclude the possibility of disease.     

The Limulus Lysate Endotoxin Assay as a Test of Microbial Quality of Ground Beef

The Limulus lysate test (LLT) for endotoxin assay has been found to be an excellent, simple and rapid test of microbial quality of refrigerated ground beef. In fresh ground beef held at 5°C for 7–12 d, LLT titres increased from 10²–10⁵ and correlated very highly with extract-release volume (ERV) data and total viable Gram negative counts at both 5° and 30°C. The LLT was negative for fresh beef containing low numbers of bacteria and on aged beef in the absence of increasing numbers of Gram negative bacteria. Of 14 Gram negative meat isolates, all gave a positive LLT while none of eight miscellaneous Gram positive bacteria did. The use of this test provides objective information on the microbial quality of fresh refrigerated ground meats in 1 h. Based upon this study, it is suggested that a 0·1 ml inoculum from a 10³ dilution of good quality ground beef should produce a negative lysate test and thus serve as an additional rapid screening test of meat microbial quality.     

Evaluation of a Rapid Point of Care Test for Detecting Acute and Established HIV Infection,and Examining the Role of Study Quality on Diagnostic Accuracy: A Bayesian Meta-Analysis

Introduction

Fourth generation (Ag/Ab combination) point of care HIV tests like the FDA-approved Determine HIV1/2 Ag/Ab Combo test offer the promise of timely detection of acute HIV infection, relevant in the context of HIV control. However, a synthesis of their performance has not yet been done. In this meta-analysis we not only assessed device performance but also evaluated the role of study quality on diagnostic accuracy.

Methods

Two independent reviewers searched seven databases, including conferences and bibliographies, and independently extracted data from 17 studies. Study quality was assessed with QUADAS-2. Data on sensitivity and specificity (overall, antigen, and antibody) were pooled using a Bayesian hierarchical random effects meta-analysis model. Subgroups were analyzed by blood samples (serum/plasma vs. whole blood) and study designs (case-control vs. cross-sectional).

Results

The overall specificity of the Determine Combo test was 99.1%, 95% credible interval (CrI) [97.3–99.8]. The overall pooled sensitivity for the device was at 88.5%, 95% [80.1–93.4]. When the components of the test were analyzed separately, the pooled specificities were 99.7%, 95% CrI [96.8–100] and 99.6%, 95% CrI [99.0–99.8], for the antigen and antibody components, respectively. Pooled sensitivity of the antibody component was 97.3%, 95% CrI [60.7–99.9], and pooled sensitivity for the antigen component was found to be 12.3%, 95% (CrI) [1.1–44.2]. No significant differences were found between subgroups by blood sample or study design. However, it was noted that many studies restricted their study sample to p24 antigen or RNA positive specimens, which may have led to underestimation of overall test performance. Detection bias, selection (spectrum) bias, incorporation bias, and verification bias impaired study quality.

Conclusions

Although the specificity of all test components was high, antigenic sensitivity will merit from an improvement. Besides the accuracy of the device itself, study quality, also impacts the performance of the test. These factors must be kept in mind in future evaluations of an improved device, relevant for global scale up and implementation.     

Assessment of Limulus Test for Detecting Endotoxaemia

The occurrence of endotoxaemia in 46 surgical patients has been investigated using a sensitive preparation of limulus lysate. Altogether 23 patients with local and systemic Gram-negative infections were shown to have endotoxaemia. An overt infection is not a prerequisite for a positive limulus test result, since endotoxin can be absorbed via the peritoneal cavity in patients with “chemical” peritonitis. Over 70% of the tests performed during episodes of Gram-negative infection or peritonitis gave positive results. In 23 patients without clinical evidence of infection or peritonitis only 15% of the limulus test results were positive. The implications of these findings and the use of the test in clinical practice are discussed.     

Low-Temperature Irradiation of Beef and Methods for Evaluation of a Radappertization Process

An inoculated, irradiated beef pack (1,240 cans) study was conducted for the determination of microbiological safety for unrestricted human consumption. Each can contained a mixture of 10⁶ spores of each of 10 strains of Clostridium botulinum (5 type A and 5 type B), or a total of 10⁷ spores/can. The cans were irradiated to various doses (100 cans/dose) with ⁶⁰Co gamma rays at -30 ± 10 C, incubated at 30 ± 2 C for 6 months, and examined for swelling, toxicity, and recoverable botulinal cells. The minimal experimental sterilizing dose based on nonswollen, nontoxic sterile cans was 2.2 < experimental sterilizing dose ≤ 2.6 Mrad. Using recoverable cells as the most stringent criterion of spoilage, and assuming the conventional simple exponential (without an initial shoulder) rate of spore kill, the “12D” dose was 3.7 Mrad when estimated on the basis of a mixture of 10 strains totaling 10⁷ spores/can, and 4.3 Mrad if it is assumed that each can of beef contained 10⁶ spores of a single most resistant strain and all of these spores were of identical resistances. However, an analysis of the data by extreme value statistics indicated with 90% confidence that the spore death rate was not a simple exponential but might be a shifted exponential (with an initial shoulder), Weibull, lognormal, or normal, with a “12D” equivalent of about 3.0 Mrad regardless of the initial spore density per can. There was an apparent antagonism between the irradiated type A and B strains in the cans. Some of the cans contained type B toxin but did not include type B viable cells. Other cans had a mixture of type A and B toxins, but a large number of these cans did not yield recoverable type B cells. However, type A viable cells could always be demonstrated in those cans containing type A toxin.     

A Locally Most Powerful Test for Detecting a Treatment Effect in the Presence of Nonresponders

A problem that frequently occurs in many biological experiments is when some subjects in the treatment group may be unaffected by the treatment. For this reason, the distribution of responses in the treatment group is expressed as a two-component mixture, where Lehmann alternatives are used to relate the distributions of affected and unaffected patients. A distribution-free approach is proposed for testing the hypothesis of no treatment effect against the alternative that a subset of the treated subjects respond to the treatment. The test is locally optimal and structured on the basis of the empirical distribution of the untreated subjects. The properties of the test are discussed and the power function is derived. It is shown that the power increases with the proportion of responders in the experiment.     

Gold Immunochromatography Assay for the Rapid Detection of Spiramycin in Milk and Beef Samples Based on a Monoclonal Antibody

Spiramycin (SP) residues in food do harm to human health. It is necessary to establish rapid detection method for SP. In this work, a monoclonal antibody (mAb)‐based gold immunochromatography assay (GICA) is developed for the rapid detection of SP. Under optimum conditions, the half‐maximal inhibitory concentration of SP‐mAb is 0.43 ng mL^–1. The subtype of SP‐mAb is IgG2b. This antibody has no cross‐reactivity with other analogues and has high affinity (4.52 × 10¹⁰ L mol^–1). Qualitative results can be visualized with the naked eye, with a visual detection limit of 1.0 ng mL^–1 and cut‐off value of 10 ng mL^–1. A hand‐held strip scanner is used for the quantitative analysis, with LOD 0.43 ng mL^–1 in assay buffer. The recoveries of SP ranged from 72.3% to 112% in milk and 98.5% to 115% in beef, with variable coefficient ranging from 9.4% to 11.7% in milk and 8.14% to 15.4% in beef. Besides, the proposed GICA method for SP is confirmed by LC–MS/MS in SP‐spiked milk and beef samples. Overall, the developed GICA can be a useful tool for SP residues on‐site screening in milk and beef samples.