A nematode-specific ribonucleoprotein complex mediates interactions between the major nematode spliced leader snRNP and its target pre-mRNAs

Spliced leader trans-splicing of pre-mRNAs is a critical step in the gene expression of many eukaryotes. How the spliced leader RNA and its target transcripts are brought together to form the trans-spliceosome remains an important unanswered question. Using immunoprecipitation followed by protein analysis via mass spectrometry and RIP-Seq, we show that the nematode-specific proteins, SNA-3 and SUT-1, form a complex with a set of enigmatic non-coding RNAs, the SmY RNAs. Our work redefines the SmY snRNP and shows for the first time that it is essential for nematode viability and is involved in spliced leader trans-splicing. SNA-3 and SUT-1 are associated with the 5' ends of most, if not all, nascent capped RNA polymerase II transcripts, and they also interact with components of the major nematode spliced leader (SL1) snRNP. We show that depletion of SNA-3 impairs the co-immunoprecipitation between one of the SL1 snRNP components, SNA-2, and several core spliceosomal proteins. We thus propose that the SmY snRNP recruits the SL1 snRNP to the 5' ends of nascent pre-mRNAs, an instrumental step in the assembly of the trans-spliceosome.

Nature of β-1,3-Glucan-Exposing Features on Candida albicans Cell Wall and Their Modulation

Candida albicans exists as a commensal of mucosal surfaces and the gastrointestinal tract without causing pathology. However, this fungus is also a common cause of mucosal and systemic infections when antifungal immune defenses become compromised. The activation of antifungal host defenses depends on the recognition of fungal pathogen-associated molecular patterns (PAMPs), such as β-1,3-glucan. In C. albicans, most β-1,3-glucan is present in the inner cell wall, concealed by the outer mannan layer, but some β-1,3-glucan becomes exposed at the cell surface. In response to host signals, such as lactate, C. albicans induces the Xog1 exoglucanase, which shaves exposed β-1,3-glucan from the cell surface, thereby reducing phagocytic recognition. We show here that β-1,3-glucan is exposed at bud scars and punctate foci on the lateral wall of yeast cells, that this exposed β-1,3-glucan is targeted during phagocytic attack, and that lactate-induced masking reduces β-1,3-glucan exposure at bud scars and at punctate foci. β-1,3-Glucan masking depends upon protein kinase A (PKA) signaling. We reveal that inactivating PKA, or its conserved downstream effectors, Sin3 and Mig1/Mig2, affects the amounts of the Xog1 and Eng1 glucanases in the C. albicans secretome and modulates β-1,3-glucan exposure. Furthermore, perturbing PKA, Sin3, or Mig1/Mig2 attenuates the virulence of lactate-exposed C. albicans cells in Galleria. Taken together, the data are consistent with the idea that β-1,3-glucan masking contributes to Candida pathogenicity. IMPORTANCE Microbes that coexist with humans have evolved ways of avoiding or evading our immunological defenses. These include the masking by these microbes of their "pathogen-associated molecular patterns" (PAMPs), which are recognized as "foreign" and used to activate protective immunity. The commensal fungus Candida albicans masks the proinflammatory PAMP β-1,3-glucan, which is an essential component of its cell wall. Most of this β-1,3-glucan is hidden beneath an outer layer of the cell wall on these microbes, but some can become exposed at the fungal cell surface. Using high-resolution confocal microscopy, we examine the nature of the exposed β-1,3-glucan at C. albicans bud scars and at punctate foci on the lateral cell wall, and we show that these features are targeted by innate immune cells. We also reveal that downstream effectors of protein kinase A (Mig1/Mig2, Sin3) regulate the secretion of major glucanases, modulate the levels of β-1,3-glucan exposure, and influence the virulence of C. albicans in an invertebrate model of systemic infection. Our data support the view that β-1,3-glucan masking contributes to immune evasion and the virulence of a major fungal pathogen of humans.

Biomarkers of caspofungin resistance in Candida albicans isolates: A proteomic approach

Candida albicans is a clinically important polymorphic fungal pathogen that causes life-threatening invasive infections in immunocompromised patients. Antifungal therapy failure is a substantial clinical problem, due to the emergence of an increasing number of drug-resistant isolates. Caspofungin is a common antifungal drug, often used as first-line therapy that inhibits cell wall β-(1,3)-glucan synthesis. In this work, the cell surface of different echinocandin-resistant C. albicans clinical isolates was compared with sensitive isolates and their responses to echinocandin treatment analyzed. Proteomic analysis detected changes in the repertoire of proteins involved in cell wall organization and maintenance, in drug-resistant strains compared to susceptible isolates and after incubation with caspofungin. Moreover, an interaction network was created from the differential expression results. Our findings suggest drug resistance may involve not only a different cell wall architecture, but also a different response to drugs.

The sting in the tail of severe falciparum malaria: Post-artesunate delayed haemolysis

Post-artesunate delayed haemolysis (PADH) is thought to occur because of delayed clearance of previously malarial infected erythrocytes spared by ‘pitting’ during treatment. We report a case of PADH following the treatment of Plasmodium (P.) falciparum malaria (32% parasitaemia), with a positive direct antiglobulin (DAT) test, suggesting an immune mechanism.

Changing HCW attitudes: a case study of normalizing HIV service delivery in emergency departments

Background

Delays in the implementation of evidence-based practices are significant and ubiquitous, compromising health outcomes. Resistance to change is a key factor in hindering adoption and integration of new evidence-based interventions. This study seeks to understand the impact of exposure to HIV testing within a research context on provider attitudes towards HIV counselling and testing (HCT) in emergency departments (ED).

Methods

This is a pre-and-post study design measuring the effect of a new ED-based HCT intervention, conducted by lay counsellors, on provider attitudes in Eastern Cape, South Africa. A validated, anonymized, 7-item survey was self-completed by routine care providers (physicians, nurses, and case managers). Questions were scored on a 5-point Likert scale with 5 consistently reflecting a positive attitude. Mean scores were calculated for each question and compared using a two-sample t-test to assess change in sample means for attitudes among providers surveyed before and after the intervention.

Results

A total of 132 surveys were completed across three EDs. Majority of respondents were female (70.5%), 20–29 years old (37.9%), of African race (81.1%), nurses (39.4%), and practicing medicine for 0–4 years (37.9%). Pre-intervention, providers displayed a positive attitude towards ‘the benefit of offering ED-based HCT to patients’ (4.33), ‘the ED offering HCT’ (3.53), ‘all ED patients receiving HCT’ (3.42), ‘concern about patient reaction to HCT’ (3.26), and ‘comfort with disclosing HCT results’ (3.21); and a mildly negative attitude towards ‘only high-risk ED patients receiving HCT’ (2.68), and ‘the burden of offering HCT in a clinical environment’ (2.80). Post-intervention, provider attitudes improved significantly towards ‘all ED patients receiving HCT’ (3.86, p < 0.05), ‘only high-risk ED patients receiving HCT’ (2.30, p < 0.05), ‘the burden of offering HCT in a clinical environment’ (3.21, p < 0.05), and ‘comfort with disclosing HCT results’ (3.81, p < 0.05).

Conclusions

Controlled exposure to new practices with a structured implementation period can shift attitudes beginning a process of practice normalization. In our study, we observed improvements in provider attitudes regarding the benefits of HCT and the burden of offering HCT to all patients in the ED. Research activities may have a role in mitigating resistance to change and supporting intervention adoption.

Cumulative incidence of SARS-CoV-2 and associated risk factors among healthcare workers: a cross-sectional study in the Eastern Cape, South Africa

OBJECTIVES

This study assesses the cumulative incidence of SARS-CoV-2 infection among healthcare workers (HCWs) during South Africa's first wave and examines the associated demographic, health-related and occupational risk factors for infection.

METHODS

Multistage cluster sampling was used in a cross-sectional study to recruit 1309 HCWs from two academic hospitals in the Eastern Cape, South Africa over 6 weeks in November and December 2020. Prior test results for SARS-CoV-2 PCR and participants' characteristics were recorded while a blood sample was drawn for detection of IgG antibodies against SARS-CoV-2 nucleocapsid protein. The primary outcome measure was the SARS-CoV-2 cumulative incidence rate, defined as the combined total of positive results for either PCR or IgG antibodies, divided by the total sample. The secondary outcome was significant risk factors associated with infection.

RESULTS

Of the total participants included in the analysis (n=1295), the majority were women (81.5%), of black race (78.7%) and nurses (44.8%). A total of 390 (30.1%) HCWs had a positive SARS-CoV-2 PCR result and SARS-CoV-2 antibodies were detected in 488 (37.7%), yielding a cumulative incidence of 47.2% (n=611). In the adjusted logistic regression model, being overweight (adjusted OR (aOR)=2.15, 95% CI 1.44 to 3.20), obese (aOR=1.37, 95% CI 1.02 to 1.85) and living with HIV (aOR=1.78, 95% CI 1.38 to 2.08) were independently associated with SARS-CoV-2 infection. There was no significant difference in infection rates between high, medium and low COVID-19 exposure working environments.

CONCLUSIONS

The high SARS-CoV-2 cumulative incidence in the cohort was surprising this early in the epidemic and probably related to exposure both in and outside the hospitals. To mitigate the impact of SARS-CoV-2 among HCWs, infection prevention and control strategies should target community transmission in addition to screening for HIV and metabolic conditions.

Anthemosoma garnhami in an HIV-Infected Man from Zimbabwe Living in South Africa

An HIV-positive man from Zimbabwe living in South Africa sought treatment for multiple clinical signs, including fever, weight loss, anemia, and splenomegaly. We identified in his blood an African rodent piroplasm, Anthemosoma garnhami, related to Babesia species. This finding extends the known geographic and host range of A. garnhami.

Acceptance of COVID-19 Vaccine among the Healthcare Workers in the Eastern Cape, South Africa: A Cross Sectional Study

BACKGROUND

This study assesses the perceptions and acceptance of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccination. It also examines its influencing factors among the healthcare workers (HCWs) in the Eastern Cape, South Africa.

METHODS

In this cross-sectional study performed in November and December 2020, a total of 1308 HCWs from two large academic hospitals participated in the Eastern Cape Healthcare Workers Acquisition of SARS-CoV-2 (ECHAS) study. Validated measures of vaccine hesitancy were explored using a questionnaire. Logistic regression was used to identify the determinants of vaccine hesitancy.

RESULTS

The majority were nurses (45.2%), and at risk for unfavourable Covid-19 outcome, due to obesity (62.9%) and having direct contact with individuals confirmed to have Covid-19 (77.1%). The overall acceptance of SARS-CoV-2 vaccine was 90.1%, which differed significantly by level of education. Individuals with lower educational attainment (primary and secondary education) and those with prior vaccine refusal were less likely to accept the SARS-CoV-2 vaccine. However, positive perceptions about the SARS-CoV-2 vaccine were independently associated with vaccine acceptance.

CONCLUSIONS

The high level of acceptance of SARS-CoV-2 vaccine is reassuring; however, HCWs with a lower level of education and those with prior vaccine refusal should be targeted for further engagements to address their concerns and fears.

Addition of Broad Bean Hull to Wheat Flour for the Development of High-Fiber Bread: Effects on Physical and Nutritional Properties

The seed coat (hull) of broad bean (Vicia faba) (BBH) is a significant secondary product of processing with a promising nutritional profile. Bean hull has a high fiber content (49%), yet it remains underexploited as an ingredient by the food industry. This study investigated the potential of this secondary product to partially replace wheat flour for the development of high-fiber breads. Bread formulations with a range of supplementation levels (0%, 11%, 21% and 31%) were developed and tested for their nutritional and physical properties. The proximate composition of breads revealed that at 31% replacement, the fiber content was 19.19 g/100 g bread, which was significantly higher (p < 0.05) than control breads (3.62 g/100 g bread). The physical (specific volume, density and color) and textural properties of breads were affected by the addition of bean hull. Specific volume and hardness of breads were significantly reduced at ≥21% replacement compared to the control, which may reduce acceptability of the product by some consumer groups. Enzyme-linked immunosorbent assay (ELISA) showed that the gluten content of breads was significantly reduced with bean hull addition (62% depletion for 31% replacement). At 11%, 21% and 31% replacement, one portion (80 g of bread) contains 6.8 g, 11.6 g and 15.3 g of dietary fiber, respectively, which contributes 23%, 38% and 51% of the recommended daily fiber intake (30 g/day). In conclusion, bean hull can be a valuable source of dietary fiber in bread formulations. The study showed BBH could be used to replace up to 21% of the wheat flour without significantly impacting on bread texture and volume.

Patient acceptance of HIV testing services in rural emergency departments in South Africa

Background

South Africa faces the highest burden of HIV infection globally. The National Strategic Plan on HIV recommends provider-initiated HIV counselling and testing (HCT) in all healthcare facilities. However, HIV continues to overwhelm the healthcare system. Emergency department (ED)-based HCT could address unmet testing needs.

Objectives

This study examines the reasons for accepting or declining HCT in South African EDs to inform the development of HCT implementation strategies.

Method

We conducted a prospective observational study in two rural EDs, from June to September 2017. Patients presenting to the ED were systematically approached and offered a point-of-care test in accordance with national guidelines. Patients demographics, presenting compaint, medical history and reasons for accepting/declining testing, were recorded. A pooled analysis is presented.

Results

Across sites, 2074 adult, non-critical patients in the ED were approached; 1880 were enrolled in the study. Of those enrolled, 19.7% had a previously known positive diagnosis, and 80.3% were unaware of their HIV status. Of those unaware, 90% patients accepted and 10% declined testing. The primary reasons for declining testing were ‘does not want to know status’ (37.6%), ‘in too much pain’ (34%) and ‘does not believe they are at risk’ (19.9%).

Conclusions

Despite national guidelines, a high proportion of individuals remain undiagnosed, of which a majority are young men. Our study demonstrated high patient acceptance of ED-based HCT. There is a need for investment and innovation regarding effective pain management and confidential service delivery to address patient barriers. Findings support a routine, non-targeted HCT strategy in EDs.

Calretinin is a novel candidate marker for adverse ovarian effects of early life exposure to mixtures of endocrine disruptors in the rat

Disruption of sensitive stages of ovary development during fetal and perinatal life can have severe and life-long consequences for a woman’s reproductive life. Exposure to endocrine disrupting chemicals may affect ovarian development, leading to subsequent reproductive disorders. Here, we investigated the effect of early life exposure to defined mixtures of human-relevant endocrine disrupting chemicals on the rat ovary. We aimed to identify molecular events involved in pathogenesis of ovarian dysgenesis syndrome that have potential for future adverse outcome pathway development. We therefore focused on the ovarian proteome. Rats were exposed to a mixture of phthalates, pesticides, UV-filters, bisphenol A, butyl-paraben, and paracetamol during gestation and lactation. The chemicals were tested together or in subgroups of chemicals with anti-androgenic or estrogenic potentials at doses 450-times human exposure. Paracetamol was tested separately, at a dose of 360 mg/kg. Using shotgun proteomics on ovaries from pup day 17 offspring, we observed exposure effects on the proteomes. Nine proteins were affected in more than one exposure group and of these, we conclude that calretinin is a potential key event biomarker of early endocrine disruption in the ovary.

β-Glucan is a major growth substrate for human gut bacteria related to Coprococcus eutactus

A clone encoding carboxymethyl cellulase activity was isolated during functional screening of a human gut metagenomic library using Lactococcus lactis MG1363 as heterologous host. The insert carried a glycoside hydrolase family 9 (GH9) catalytic domain with sequence similarity to a gene from Coprococcus eutactus ART55/1. Genome surveys indicated a limited distribution of GH9 domains among dominant human colonic anaerobes. Genomes of C. eutactus-related strains harboured two GH9-encoding and four GH5-encoding genes, but the strains did not appear to degrade cellulose. Instead, they grew well on β-glucans and one of the strains also grew on galactomannan, galactan, glucomannan and starch. Coprococcus comes and Coprococcus catus strains did not harbour GH9 genes and were not able to grow on β-glucans. Gene expression and proteomic analysis of C. eutactus ART55/1 grown on cellobiose, β-glucan and lichenan revealed similar changes in expression in comparison to glucose. On β-glucan and lichenan only, one of the four GH5 genes was strongly upregulated. Growth on glucomannan led to a transcriptional response of many genes, in particular a strong upregulation of glycoside hydrolases involved in mannan degradation. Thus, β-glucans are a major growth substrate for species related to C. eutactus, with glucomannan and galactans alternative substrates for some strains.

A Window Into the HIV Epidemic from a South African Emergency Department

The aim of the study was to describe the HIV care continuum in emergency department (ED) patients in the Eastern Cape region of South Africa. This is a cross-sectional, identity-unlinked serosurvey, whereby discarded/excess samples from all patients who had blood drawn during the study period for routine care and sufficient serum remaining were tested for HIV, hepatitis B virus, and hepatitis C virus infection; HIV viral load (VL); and presence of antiretroviral (ARV) drugs. We also estimated cross-sectional incidence using the Limiting-Antigen Avidity assay and HIV VL. The study was conducted between September and November 2016 at the Frere Hospital Emergency Department in East London, South Africa. The overall HIV prevalence in our study population was 26.9% [95% confidence interval (CI): 25.0-28.8; n = 2,100]. The highest prevalence was observed among females in the 30-39 years age group [60.3% (95% CI: 53.2-67.1)]. HIV prevalence was significantly higher among females compared with males in both the 20-29 years age group and 30-39 years age group (p < .05), but nearly identical to older age groups. ARV drugs were detected in 53.5% (95% CI: 48.1-58.9) of HIV-infected subjects. The frequency of HIV viral suppression (< 1,000 copies/mL) was 48.5% (95% CI: 44.3-52.7), and was not statistically different between males and females (age-adjusted prevalence ratio = 1.15, 95% CI: 0.95-1.39). The HIV incidence rate was estimated to be 2.6% (95% CI: 1.2-3.9). The Frere Hospital ED has an extremely high burden of HIV infection. The detection of ARV drugs and prevalence of viral suppression fall short of the World Health Organization 90-90-90 goals in this population. Furthermore, there were a large number of patients with recent infection in the ED. The ED is a critical venue for testing and linkage to care of high-yield population who are likely missed by current testing and linkage-to-care programs.

Incorporating salal berry (Gaultheria shallon) and blackcurrant (Ribes nigrum) pomace in yogurt for the development of a beverage with antidiabetic properties

In this study aqueous extracts from salal berry (SB) and blackcurrant pomace (BCP) were used to reformulate yogurt and the anti-diabetic properties of the beverage were investigated during 4 weeks of cold storage at 4 °C. Results indicated that α-amylase, α-glucosidase and DPP-IV inhibitory activities increased with storage time for all samples. At the end of storage period α-amylase, α-glucosidase and DPP-IV inhibition were >61%, 62% and 56% respectively for all yogurt types. This increase in bioactivity during cold storage is attributed to the viability of lactic acid bacteria (∼108 cfu/g), which is maintained for 4 weeks. Enzyme inhibition increased similarly for all yogurt types at 4 °C except for α-glucosidase. Yogurt with BCP showed the highest potency to inhibit α-glucosidase (>90%) with an IC50 value of 0.20 mg/ml (week 4). A peptidomic approach based on liquid chromatography coupled with mass spectrometry (LC-MS) was used for the separation and identification of peptides generated in three types of yogurt. A total of 486 peptides mainly from caseins were identified, of which 15 have documented bioactivity, predominantly as antimicrobial agents or ACE-inhibitors.

Implementing emergency department-based HIV testing in a low-resource setting: The value of a structured feasibility assessment tool

Introduction

HIV is a worldwide health problem with continuing high rates of new infections in many parts of the world. This lack of progress in decreasing overall incidence rates has sparked innovative HIV testing strategies, including expansion of testing into the emergency department (ED) setting. Emergency departments have been shown to be high-yield testing venues in the United States and other developed world settings. The feasibility of expanding public health HIV services in the ED in limited-resource countries is unclear.

Methods

We performed a cross-sectional feasibility assessment of a convenience sample of four hospitals in the Eastern Cape, South Africa. We administered three adapted interview tools from a previously field-tested survey instrument at each facility (total of 10 interviews) to gather an overview of the health facility, their HIV counselling and testing services, and their laboratory services.

Results

All of the health facilities had access to basic commodities such as water and electricity. Many had severe human resource limitations and provided care to wide population catchment areas. In addition, there was little integration of HIV testing into current daily ED operations. Hospital staff identified numerous barriers to future ED testing efforts.

Conclusions

Although control of the HIV epidemic requires innovative testing strategies and treatment, specific assessments are warranted on how to incorporate routine HIV testing into an acute care facility like the ED, which typically has many competing priorities. The use of a prospective structured tool incorporating both barriers and benefits can provide valuable field-tested guidance for increased programme planning for HIV testing.

HIV testing in a South African Emergency Department: A missed opportunity

BACKGROUND

South Africa has the largest HIV epidemic in the world, with 19% of the global number of people living with HIV, 15% of new infections and 11% of AIDS-related deaths. Even though HIV testing is mandated in all hospital-based facilities in South Africa (SA), it is rarely implemented in the Emergency Department (ED). The ED provides episodic care to large volumes of undifferentiated who present with unplanned injury or illness. Thus, the ED may provide an opportunity to capture patients with undiagnosed HIV infection missed by clinic-based screening programs.

METHODS AND FINDINGS

In this prospective exploratory study, we implemented the National South African HIV testing guidelines (counselor initiated non-targeted universal screening with rapid point of care testing) for 24-hours a day at Frere Hospital in the Eastern Cape from September 1st to November 30th, 2016. The purpose of our study was to quantify the burden of undiagnosed HIV infection in a South African ED setting. Furthermore, we sought to evaluate the effectiveness of the nationally recommended HIV testing strategy in the ED. All patients who presented for care in the ED during the study period, and who were clinically stable and fully conscious, were eligible to be approached by HIV counseling and testing (HCT) staff to receive a rapid point-of-care HIV test. A total of 2355 of the 9583 (24.6%) patients who presented to the ED for care during the study period were approached by the HCT staff, of whom 1714 (72.8%) accepted HIV testing. There was a high uptake of HIV testing (78.6%) among a predominantly male (58%) patient group who mostly presented with traumatic injuries (70.8%). Four hundred (21.6%) patients were HIV positive, including 115 (6.2%) with newly diagnosed HIV infection. The overall prevalence of HIV infection was twice as high in females (29.8%) compared to males (15.4%). Both sexes had a similar prevalence of newly diagnosed HIV infection (6.0% for all females and 6.4% for all males) in the ED.

CONCLUSIONS

Overall there was high HIV testing acceptance by ED patients. A non-targeted testing approached revealed a high HIV prevalence with a significant burden of undiagnosed HIV infection in the ED. Unfortunately, a counselor-driven HIV testing approach fell short of meeting the testing needs in this setting, with over 75% of ED patients not approached by HCT staff.

Patient and provider attitudes to emergency department-based HIV counselling and testing in South Africa

Background

The national South African HIV Counselling and Testing (HCT) guidelines mandate that voluntary counselling and testing (VCT) should be offered in all healthcare facilities. Emergency departments (EDs) are at the forefront of many healthcare facilities, yet VCT is not routinely implemented in this setting.

Methods

We conducted a cross-sectional study that surveyed patients and healthcare providers at a tertiary care ED in the spring and summer of 2016 to ascertain their attitudes to VCT in the ED. We also used two previously validated survey instruments to gather data on patients’ HIV knowledge and providers’ stigma against patients living with HIV, as we anticipated that these may have an impact on providers’ and patients’ attitudes to the provision of HIV testing within the ED, and may offer insights for future intervention development.

Results

A total of 104 patients and 26 providers were enrolled in the study. Overall, patients responded more favourably to ED-based HIV testing (92.3%) compared to providers (only 40% responded favourably). When asked about potential barriers to receiving or providing HIV testing, 16.4% of patients and 24% of providers felt that the subject of HIV was too sensitive and 58.7% of patients and 80% of providers indicated that privacy and confidentiality issues would pose major barriers to implementing ED-based HIV testing.

Conclusion

This study shows that while ED-based HIV testing is overall highly acceptable to patients, providers seem less willing to provide this service. The survey data also suggest that future development of ED-based testing strategies should take into consideration privacy and confidentiality concerns that may arise within a busy emergency care setting. Furthermore, every effort should be made to tackle HIV stigma among providers to improve overall attitudes towards HIV-positive individuals that present for care in the ED.

Postprandial hepatic protein expression in trout Oncorhynchus mykiss a proteomics examination

Following a meal, a series of physiological changes occurs in animals as they digest, absorb and assimilate ingested nutrients, the kinetics of these responses depends on metabolic rate and nutrient quality. Here we investigated the hepatic proteome in the ectothermic teleost, the rainbow trout, following a single meal to define the postprandial expression of hepatic proteins. The fish were fed a high marine fishmeal/fish oil single meal following a period of 24 h without feeding. Liver protein profiles were examined by 2D gel electrophoresis just before feeding (time 0 h) and at 6 and 12 h after feeding. Of a total of 588 protein spots analysed in a temporal fashion, 49 differed significantly in abundance between the three time groups (ANOVA, p<0.05), before and after feeding, 15 were increased and 34 were decreased in abundance after feeding. Amino acid metabolism-regulated proteins such as phenylalanine-4-hydroxylase and proliferating cell antigen were increased in abundance 12 and 6 h following the meal, suggesting by this time that the fish were increasing their protein turnover to utilize efficiently their dietary protein consumption. Overall, these results highlight some specificity of the trout metabolism and identify postprandial response of metabolism-related proteins 6–12 h after feeding a single meal.

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The effect of a single meal on the postprandial expression of hepatic proteins in fish is shown.

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Temporal changes occurred in the trout liver proteome following a single meal.

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There is a postprandial response of metabolism-related proteins 6–12 h after feeding a single meal.

The Rewiring of Ubiquitination Targets in a Pathogenic Yeast Promotes Metabolic Flexibility, Host Colonization and Virulence

Efficient carbon assimilation is critical for microbial growth and pathogenesis. The environmental yeast Saccharomyces cerevisiae is “Crabtree positive”, displaying a rapid metabolic switch from the assimilation of alternative carbon sources to sugars. Following exposure to sugars, this switch is mediated by the transcriptional repression of genes (carbon catabolite repression) and the turnover (catabolite inactivation) of enzymes involved in the assimilation of alternative carbon sources. The pathogenic yeast Candida albicans is Crabtree negative. It has retained carbon catabolite repression mechanisms, but has undergone posttranscriptional rewiring such that gluconeogenic and glyoxylate cycle enzymes are not subject to ubiquitin-mediated catabolite inactivation. Consequently, when glucose becomes available, C. albicans can continue to assimilate alternative carbon sources alongside the glucose. We show that this metabolic flexibility promotes host colonization and virulence. The glyoxylate cycle enzyme isocitrate lyase (CaIcl1) was rendered sensitive to ubiquitin-mediated catabolite inactivation in C. albicans by addition of a ubiquitination site. This mutation, which inhibits lactate assimilation in the presence of glucose, reduces the ability of C. albicans cells to withstand macrophage killing, colonize the gastrointestinal tract and cause systemic infections in mice. Interestingly, most S. cerevisiae clinical isolates we examined (67%) have acquired the ability to assimilate lactate in the presence of glucose (i.e. they have become Crabtree negative). These S. cerevisiae strains are more resistant to macrophage killing than Crabtree positive clinical isolates. Moreover, Crabtree negative S. cerevisiae mutants that lack Gid8, a key component of the Glucose-Induced Degradation complex, are more resistant to macrophage killing and display increased virulence in immunocompromised mice. Thus, while Crabtree positivity might impart a fitness advantage for yeasts in environmental niches, the more flexible carbon assimilation strategies offered by Crabtree negativity enhance the ability of yeasts to colonize and infect the mammalian host.

Most yeast species occupy environmental niches, but some infect humans. All species must assimilate carbon to grow and colonize their niche, but carbon source availability differs significantly between niches. The environmental yeast Saccharomyces cerevisiae is thought to have evolved under conditions of sugar feast and famine because it has evolved mechanisms to exploit energetically favourable sugars first, and then switch to using alternative carbon sources. These mechanisms depend on catabolite inactivation—the degradation of enzymes involved in the assimilation of alternative carbon sources when glucose is present. In the pathogenic yeast Candida albicans, which has evolved in sugar-poor host niches, these enzymes are not subject to catabolite inactivation. Consequently, C. albicans can simultaneously exploit sugars and alternative carbon sources. We demonstrate that this metabolic flexibility promotes resistance to macrophage killing, gut colonization, and the ability to cause systemic infection. We also show that many S. cerevisiae clinical isolates have lost catabolite inactivation, and hence can simultaneously assimilate sugars and alternative carbon sources. The disruption of catabolite inactivation in S. cerevisiae renders it more resistant to phagocytic killing, and more virulent. We conclude that virulence is enhanced by metabolic flexibility.

Biosimilars: A Multidisciplinary Perspective

A biosimilar is an officially regulated and approved copy of an originator biologic therapy. Improved affordability and consequent wider patient access compared with biologics are a significant appeal of biosimilars. Regulatory guidelines for biosimilar development and approval are rigorous and undergoing constant refinement. The process of licensing approval for all biosimilars requires demonstration of comparability in quality, efficacy, and safety between the biosimilar and reference (originator) product, which is undertaken in a stepwise procedure of nonclinical and clinical evaluation. The approval of >20 biosimilars in Europe in several drug classes, including the first monoclonal antibody biosimilar, bears testimony to the increasing regulatory acceptance of these agents. In contrast, the clinical application of biosimilars remains underrecognized by physicians across therapy areas. Therefore, this article aims to provide a comprehensive review of the biosimilar development process and to provide multidisciplinary guidance on the potential therapeutic utility of biosimilars in clinical practice. Specifically, experts discuss clinical developments in the introduction of biosimilars across the disciplines of gastroenterology, nephrology, oncology, and rheumatology, and from a payer perspective, and also highlight a common need for ongoing pharmacovigilance, robust head-to-head clinical studies, and real-world data to establish the long-term risk-benefit profile of biosimilars. In conclusion, significant potential exists for biosimilars to revolutionize biologic therapy by widening patient access across therapy areas.

AIDS-related mycoses: the way forward

The contribution of fungal infections to the morbidity and mortality of HIV-infected individuals is largely unrecognized. A recent meeting highlighted several priorities that need to be urgently addressed, including improved epidemiological surveillance, increased availability of existing diagnostics and drugs, more training in the field of medical mycology, and better funding for research and provision of treatment, particularly in developing countries.

Antibiotic stewardship ward rounds and a dedicated prescription chart reduce antibiotic consumption and pharmacy costs without affecting inpatient mortality or re-admission rates

Background

Antibiotic consumption is a major driver of bacterial resistance. To address the increasing burden of multi-drug resistant bacterial infections, antibiotic stewardship programmes are promoted worldwide to rationalize antibiotic prescribing and conserve remaining antibiotics. Few studies have been reported from developing countries and none from Africa that report on an intervention based approach with outcomes that include morbidity and mortality.

Methods

An antibiotic prescription chart and weekly antibiotic stewardship ward round was introduced into two medical wards of an academic teaching hospital in South Africa between January-December 2012. Electronic pharmacy records were used to collect the volume and cost of antibiotics used, the patient database was analysed to determine inpatient mortality and 30-day re-admission rates, and laboratory records to determine use of infection-related tests. Outcomes were compared to a control period, January-December 2011.

Results

During the intervention period, 475.8 defined daily doses were prescribed per 1000 inpatient days compared to 592.0 defined daily doses/1000 inpatient days during the control period. This represents a 19.6% decrease in volume with a cost reduction of 35% of the pharmacy’s antibiotic budget. There was a concomitant increase in laboratory tests driven by requests for procalcitonin. There was no difference in inpatient mortality or 30-day readmission rate during the control and intervention periods.

Conclusions

Introduction of antibiotic stewardship ward rounds and a dedicated prescription chart in a developing country setting can achieve reduction in antibiotic consumption without harm to patients. Increased laboratory costs should be anticipated when introducing an antibiotic stewardship program.

A proteomic analysis of the salt, cadmium and peroxide stress responses in Candida albicans and the role of the Hog1 stress-activated MAPK in regulating the stress-induced proteome

Stress responses are important for the virulence of the major fungal pathogen of humans, Candida albicans. In this study we employed a 2-DE approach to examine the impact of exposure to peroxide (5 mM H(2)O(2)), salt (300 mM NaCl) or cadmium stress (0.5 mM Cd(2+)) upon the C. albicans proteome. Highly reproducible changes in the C. albicans proteome were observed in response to each stress condition. Significantly more proteins were up-regulated in response to cadmium (77) than to the salt (35) or peroxide stresses (35). These proteomic changes displayed minimal overlap with those observed in the transcriptome under equivalent conditions and, importantly, revealed functional categories that respond to stress at the protein level but not the transcript level. Six proteins were up-regulated by all three conditions: Adh1, Atp2, Cip1, Eft2, Ssa1 and Ssb1, which is consistent with the concept that a core stress response exists in C. albicans. This is the first time that a fungal core stress response has been defined at the proteomic level. We have also shown that the Hog1 stress-activated mitogen-activated protein kinase, which is activated in response to the stresses examined in this study, makes a major contribution to the C. albicans stress proteome.

Risk factors for and clinical characteristics of severe hyperlactataemia in patients receiving antiretroviral therapy: a case-control study

BACKGROUND

Symptomatic hyperlactataemia and lactic acidosis (SHLA) are potentially life-threatening complications associated with stavudine (d4T), an antiretroviral therapy (ART) drug widely used in developing countries.

METHODS

Cases comprised all symptomatic patients with measured lactates >or= 5 mmol/L referred to a South African hospital between August 2003 and November 2005. Matched controls were selected according to facility and duration on ART.

RESULTS

Seventy-one cases and 142 controls were included in the study. The majority of cases presented between 6 and 18 months on ART. Female sex [adjusted odds ratio (AOR) 23.4; 95% confidence interval (CI) 4.0-136.6], a baseline weight between 60 and 75 kg (AOR 4.5; 95% CI 1.4-14.1) or, in particular, >or= 75 kg (AOR 19.4; 95% CI 4.1-82.5) at ART initiation and gaining >or= 6 kg in the first 3 months on therapy (AOR 3.5; 95% CI 1.3-9.5) were independent risk factors identifying patients who may subsequently develop SHLA. Weight loss of >or= 2 kg (AOR 6.1; 95% CI 2.0-18.3), a rise in alanine aminotransferase (ALT) >or= 10 U/L (AOR 3.1; 95% CI 1.1-8.9), the presence of at least one of three major symptoms (vomiting, nausea and abdominal pains) of SHLA (AOR 12.6; 95% CI 3.3-47.2) and peripheral neuropathy (AOR 3.4; 95% CI 1.1-9.8) were the clinical parameters that were most able to identify patients with early manifestations of SHLA.

CONCLUSIONS

This is the first case-control study for SHLA in Southern Africa. Given these findings, we advise that stavudine is avoided in overweight women. Weight loss, a rise in ALT, peripheral neuropathy and/or gastrointestinal symptoms should prompt healthcare workers to assess for SHLA, especially at between 6 and 18 months on ART.

Phylogenetic structure of Xanthomonas determined by comparison of gyrB sequences

Previously, we have produced a phylogeny of species type strains from the plant-pathogenic genus Xanthomonas based on gyrB sequences. To evaluate this locus further for species and infraspecies identification, we sequenced an additional 203 strains comprising all the pathovar reference strains (which have defined plant hosts), 67 poorly characterized pathovars, currently classified as Xanthomonas campestris, and 59 unidentified xanthomonads. The well-characterized pathovars grouped either in clades containing their respective species type strain or in clades containing species related to Xanthomonas axonopodis. The Xanthomonas euvesicatoria, Xanthomonas perforans and Xanthomonas alfalfae species complex, Xanthomonas fuscans and Xanthomonas citri were discriminated as X. axonopodis-related clades and comprised a large proportion of unidentified strains as well as 80 pathovars representing all the X. axonopodis pathovars and many poorly characterized pathovars, greatly increasing the plant host ranges of the constituent species. Most xanthomonads from these three large clades were isolated from a taxonomically diverse range of plant hosts, including many weed species, from field systems in India, suggesting that these lineages became established and diversified in agricultural areas in this region. The majority of these xanthomonads had minimal sequence diversity, consistent with rapid and highly extensive pathovar diversification that has occurred in relatively recent times. Low-intensity farming practices may have provided conditions conducive to pathovar development, and evidence for pathovar diversification within other regional angiosperm floras is discussed. The gyrB locus was sufficiently discriminating to identify diversity within many species. Seven branches or clades were sufficiently distinct to be considered as potential novel species. This study has provided a comprehensive xanthomonad classification framework and has firmly established gyrB sequencing as a rapid and efficient identification tool.

Severe Hyperlactataemia Complicating Stavudine First-Line Antiretroviral Therapy in South Africa

Background

In the public sector antiretroviral therapy (ART) programme in South Africa the standardized first-line regimen includes stavudine (d4T). Severe symptomatic hyperlactataemia (SHL) is a potentially life- threatening complication of d4T.

Methods

GF Jooste Hospital is a referral centre for six ART clinics. We retrospectively reviewed cases referred with lactate levels ≥5 mmol/l that were attributed to nucleoside reverse transcriptase inhibitors from August 2003 to November 2005. We calculated cumulative ART exposure in patients attending these clinics to derive a referral rate.

Results

In total, 75 patients were referred with severe SHL (71 female). All had been on d4T and on ART for a median of 10 months. The referral rate for severe SHL was 17.5 cases per 1,000 patient-years. In 53 patients (71%), lactic acidosis (standard bicarbonate [SHCO3]<20 mmol/l) was confirmed, resulting in a referral rate of 12.3 cases per 1,000 patient-years. Twelve patients (16%) died during acute admission (≤30 days). SHCO3<15 mmol/l and pH<7.2 were the only factors associated with acute mortality (odds ratio [OR] 22.5, 95% confidence interval [CI] 2.8–1,045.7 and OR 13.9, 95% CI 2.7–86.9, respectively). A total of 30 less severe cases were rechallenged with zidovudine without recurrence of SHL.

Conclusions

This study confirms a high incidence of severe SHL in Africa, which has been shown in previous studies. Rechallenge with zidovudine in less severe cases was found to be safe.

MNL1 regulates weak acid-induced stress responses of the fungal pathogen Candida albicans

MNL1, the Candida albicans homologue of an orphan Msn2-like gene (YER130c in Saccharomyces cerevisiae) has no known function. Here we report that MNL1 regulates weak acid stress responses. Deletion of MNL1 prevents the long-term adaptation of C. albicans cells to weak acid stresses and compromises their global transcriptional response under these conditions. The promoters of Mnl1-dependent genes contain a novel STRE-like element (SLE) that imposes Mnl1-dependent, weak acid stress-induced transcription upon a lacZ reporter in C. albicans. The SLE (HHYYCCCCTTYTY) is related to the Nrg1 response element (NRE) element recognized by the transcriptional repressor Nrg1. Deletion of NRG1 partially restores the ability of C. albicans mnl1 cells to adapt to weak acid stress, indicating that Mnl1 and Nrg1 act antagonistically to regulate this response. Molecular, microarray, and proteomic analyses revealed that Mnl1-dependent adaptation does not occur in cells exposed to proapoptotic or pronecrotic doses of weak acid, suggesting that Ras-pathway activation might suppress the Mnl1-dependent weak acid response in dying cells. Our work defines a role for this YER130c orthologue in stress adaptation and cell death.

Phylogenetic analysis of Xanthomonas species by comparison of partial gyrase B gene sequences

The genus Xanthomonas currently comprises 27 species with validly published names that are important crop and horticultural pathogens. We have constructed a phylogram from alignment of gyrase B (gyrB) sequences for all xanthomonad species, both to indicate inter-species relatedness and as an aid for rapid and accurate species-level identification. The phylogeny indicated a monophyletic group, with X. albilineans and X. sacchari as the most ancestral species. Three species, X. hyacinthi, X. translucens and X. theicola, formed an early-branching group. Three clades were supported by high bootstrap values: group 1 comprised X. cucurbitae, X. cassavae and X. codiaei; group 2 comprised X. arboricola, X. campestris, X. populi, X. hortorum, X. gardneri and X. cynarae; group 3 contained the remaining species, within which two further clades, supported by a 100 % bootstrap value, were identified. Group 3A comprised X. axonopodis, X. euvesicatoria, X. perforans and X. melonis, together with X. alfalfae, X. citri and X. fuscans, whose names were recently validly published. Group 3B contained the monocot pathogens X. vasicola and X. oryzae. Two recently identified species, X. cynarae and X. gardneri, were poorly discriminated and were related closely to X. hortorum. Three species, X. perforans, X. euvesicatoria and X. alfalfae, had identical gyrB sequences. Partial sequencing of a further five genes from these species found only minor sequence differences that confirmed their close relatedness. Although branch lengths between species varied, indicating different degrees of genetic distinctiveness, the majority (n=21) were well-differentiated, indicating the utility of the method as an identification tool, and we now use this method for routine diagnosis of xanthomonad species.

Severe hyperlactataemia complicating stavudine first-line antiretroviral therapy in South Africa

BACKGROUND

In the public sector antiretroviral therapy (ART) programme in South Africa the standardized first-line regimen includes stavudine (d4T). Severe symptomatic hyperlactataemia (SHL) is a potentially life-threatening complication of d4T.

METHODS

GF Jooste Hospital is a referral centre for six ART clinics. We retrospectively reviewed cases referred with lactate levels > or =5 mmol/l that were attributed to nucleoside reverse transcriptase inhibitors from August 2003 to November 2005. We calculated cumulative ART exposure in patients attending these clinics to derive a referral rate.

RESULTS

In total, 75 patients were referred with severe SHL (71 female). All had been on d4T and on ART for a median of 10 months. The referral rate for severe SHL was 17.5 cases per 1,000 patient-years. In 53 patients (71%), lactic acidosis (standard bicarbonate [SHCO3] <20 mmol/l) was confirmed, resulting in a referral rate of 12.3 cases per 1,000 patient-years. Twelve patients (16%) died during acute admission (< or =30 days). SHCO3 <15 mmol/l and pH < 7.2 were the only factors associated with acute mortality (odds ratio [OR] 22.5, 95% confidence interval [CI] 2.8-1,045.7 and OR 13.9, 95% CI 2.7-86.9, respectively). A total of 30 less severe cases were rechallenged with zidovudine without recurrence of SHL.

CONCLUSIONS

This study confirms a high incidence of severe SHL in Africa, which has been shown in previous studies. Rechallenge with zidovudine in less severe cases was found to be safe.

Proteomic changes associated with inactivation of the Candida glabrata ACE2 virulence-moderating gene

Inactivation of the gene encoding the transcriptional activator Ace2 in the fungal pathogen Candida glabrata results in an almost 200-fold increase in virulence characterised by acute mortality and a massive over-stimulation of the pro-inflammatory arm of the innate immune system. In this study we have adopted a proteomics approach to identify cellular functions regulated by C. glabrata Ace2 that might contribute to this increase in virulence. A two-dimensional polyacrylamide gel electrophoresis map of the C. glabrata proteome was constructed. We identified a total of 123 proteins, 61 of which displayed reproducible and statistically significant alterations in their levels following inactivation of ACE2. Of these, the levels of 32 proteins were elevated, and 29 were reduced in ace2 cells. These data show that Ace2 influences metabolism, protein synthesis, folding and targeting, and aspects of cell growth and polarisation. Some of these functions are likely to contribute to the effects of Ace2 upon the virulence of C. glabrata.

PEDRo: a database for storing, searching and disseminating experimental proteomics data

Background

Proteomics is rapidly evolving into a high-throughput technology, in which substantial and systematic studies are conducted on samples from a wide range of physiological, developmental, or pathological conditions. Reference maps from 2D gels are widely circulated. However, there is, as yet, no formally accepted standard representation to support the sharing of proteomics data, and little systematic dissemination of comprehensive proteomic data sets.

Results

This paper describes the design, implementation and use of a Proteome Experimental Data Repository (PEDRo), which makes comprehensive proteomics data sets available for browsing, searching and downloading. It is also serves to extend the debate on the level of detail at which proteomics data should be captured, the sorts of facilities that should be provided by proteome data management systems, and the techniques by which such facilities can be made available.

Conclusions

The PEDRo database provides access to a collection of comprehensive descriptions of experimental data sets in proteomics. Not only are these data sets interesting in and of themselves, they also provide a useful early validation of the PEDRo data model, which has served as a starting point for the ongoing standardisation activity through the Proteome Standards Initiative of the Human Proteome Organisation.

Proteomic response to amino acid starvation inCandida albicans andSaccharomyces cerevisiae

Saccharomyces cerevisiae activates general amino acid control (GCN) in response to amino acid starvation. Some aspects of this response are known to be conserved in other fungi including Candida albicans, the major systemic fungal pathogen of humans. Here, we describe a proteomic comparison of the GCN responses in S. cerevisiae and C. albicans. We have used high-resolution two-dimensional (2-D) gel electrophoresis and peptide mass fingerprinting to develop a 2-D protein map of C. albicans. A total of 391 protein spots, representing 316 open reading frames, were identified. Fifty-five C. albicans and 65 S. cerevisiae proteins were identified that responded reproducibly to 3-aminotriazole (3AT) in a Gcn4p-dependent fashion. The changes in the S. cerevisiae proteome correlated with the response in the S. cerevisiae transcript profile to 3AT treatment (rank correlation coefficient = 0.59; Natarajan et al., Molec. Cell. Biol. 2001, 21, 4347-4368). Significant aspects of the GCN response were conserved in C. albicans and S. cerevisiae. In both fungi, amino acid biosynthetic enzymes on multiple metabolic pathways were induced by 3AT in a Gcn4p-dependent fashion. Carbon metabolism functions were also induced. However, subtle differences were observed between these fungi. For example, purine biosynthetic enzymes were induced in S. cerevisiae, but were not significantly induced in C. albicans. These differences presumably reflect the contrasting niches of these relatively benign and pathogenic yeasts, respectively.

Roles of Fe superoxide dismutase and catalase in resistance of Campylobacter coli to freeze-thaw stress

We demonstrated that oxidative stress plays a role in freeze-thaw-induced killing of Campylobacter coli following analysis of mutants deficient in key antioxidant functions. Superoxide anions, but not H(2)O(2), were formed during the freeze-thaw process. However, a failure to detoxify superoxide anions may lead to spontaneous disproportionation of the radicals to H(2)O(2).

Sequential mechanical and pharmacological thromboprophylaxis in the surgery of hip fractures. A pilot study

Two hundred and thirty-eight patients with femoral neck fractures were entered into a randomised pilot study comparing the use of sequential treatment by 'Flowtron DVT' garments in the perioperative period followed by Enoxaparin (Clexane-Rhône-Poulenc Rorer), and Enoxaparin alone. One hundred and ninety-three patients were excluded indicating the difficulty of achieving pure comparisons in this population. The remaining 44 were randomised: 21 received Enoxaparin from the time of admission, and 23 had sequential treatment. There was no statistically significant difference in the incidence of thromboembolism. Patient preference did not indicate a favoured treatment subjectively. The operation field was drier in the sequential group, although this did not reach significance. Sequential treatment was not shown to be better or worse than treatment with Enoxaparin, but the trends favoured sequential treatment rather than drug treatment alone. The technique allows the operation to be carried out without the problems produced by low dose heparins and mobilisation is not hindered by compression garments.

A comparison of intermittent calf compression and enoxaparin for thromboprophylaxis in total hip replacement. A pilot study

A prospective randomised trial was carried comparing the use of Enoxaparin with intermittent pneumatic calf compression garments for thromboprophylaxis in total hip replacement. Fifty consecutive patients were studied and randomised to evaluate these two methods. There were 2 deep vein thromboses, one in each group, and no cases of pulmonary embolism. The operative field was judged to be drier in the compression group, but the mean fall in the postoperative haemoglobin level was the same in each. In the peroperative period, 6 patients in the Enoxaparin group needed 2 units of blood and one 3 units. In the compression group, 3 patients needed transfusions of 2 units. Intermittent calf compression has fewer problems than the use of Enoxaparin and has no contraindications.

The effect of hydroxycinnamic acids and potassium sorbate on the growth of 11 strains of spoilage yeasts

Hydroxycinnamic acids and their derivatives occur widely in plants, fruits and wine. The effect of the common hydroxycinnamic acids (caffeic, coumaric and ferulic acids), at concentrations of 100 and 500 mg l-1, on growth of 11 strains of spoilage yeasts was measured spectrophotometrically and compared with that of potassium sorbate. Ferulic acid was the most generally inhibitory hydroxycinnamic acid. At 500 mg l-1 it appreciably inhibited Pichia anomala, Debaryomyces hansenii and Saccharomyces cerevisiae and prevented detectable growth of one strain each of P. anomala and D. hansenii. Caffeic acid was the least inhibitory compound and coumaric acid had an intermediate effect. The more resistant strains of yeast were P. membranaefaciens, Saccharomycodes ludwigii and Zygosaccharomyces bailii. Sensitivity to hydroxycinnamic acid was, in general, associated with sensitivity to potassium sorbate; at a given concentration potassium sorbate was more inhibitory than were any of the hydroxycinnamic acids.

Production of extracellular lipases and proteinases during prolonged growth of strains of psychrotrophic bacteria in whole milk

Three strains of psychrotrophic Pseudomonas spp., each with different lipolytic and proteolytic phenotypes (including a proteinase-deficient mutant), were cultured separately in whole milk at 7 degrees C. Growth rates were the same during logarithmic growth phase, but during early stationary phase the cell densities were related to the activities of lipase and proteinase in the cultures. Only one strain underwent pronounced death phase. Proteinase activity was not detected in the culture of the proteinase-deficient mutant, but in those of the other strains it increased to a plateau, or continued to increase linearly. Lipase activity of the culture of each strain reached a peak in early stationary phase; in late stationary phase activity was highest for the proteinase-deficient mutant strain where degradation of lipase by bacterial proteinase would have been least. The ability of psychrotrophic bacteria both to survive for long periods and to produce high levels of proteinases and lipases on prolonged incubation in milk emphasizes the spoilage potential arising from psychrotrophic bacteria in inadequately cleaned dairy equipment.

Assay of proteinases of psychrotrophic bacteria in milk using hide powder azure and a simple procedure for clarification of milk

The clarification of milk by addition of solutions of Triton X-100 and EDTA after digestion of added Hide Powder Azure (HPA) was found to provide a simple method of determining the extracellular proteinase activity of Gram-negative psychrotrophic bacteria in pasteurized whole milk. The light absorbance of the clarified HPA digestion product was measured directly, after a brief incubation period, and was stable to storage of samples in diffuse daylight for at least 2 d. Proteinase produced by growth in refrigerated whole milk of as few as 2.5 X 10(6) cfu ml-1 of Pseudomonas fluorescens AR11 was detected.