recA mediated spontaneous deletions of the icaADBC operon of clinical Staphylococcus epidermidis isolates: a new mechanism of phenotypic variations

Phenotypic variation of Staphylococcus epidermidis involving the slime related ica operon results in heterogeneity in surface characteristics of individual bacteria in axenic cultures. Five clinical S. epidermidis isolates demonstrated phenotypic variation, i.e. both black and red colonies on Congo Red agar. Black colonies displayed bi-modal electrophoretic mobility distributions at pH 2, but such phenotypic variation was absent in red colonies of the same strain as well as in control strains without phenotypic variation. All red colonies had lost ica and the ability to form biofilms, in contrast to black colonies of the same strain. Real time PCR targeting icaA indicated a reduction in gene copy number within cultures exhibiting phenotypic variation, which correlated with phenotypic variations in biofilm formation and electrophoretic mobility distribution of cells within a culture. Loss of ica was irreversible and independent of the mobile element IS256. Instead, in high frequency switching strains, spontaneous mutations in lexA were found which resulted in deregulation of recA expression, as shown by real time PCR. RecA is involved in genetic deletions and rearrangements and we postulate a model representing a new mechanism of phenotypic variation in clinical isolates of S. epidermidis. This is the first report of S. epidermidis strains irreversibly switching from biofilm-positive to biofilm-negative phenotype by spontaneous deletion of icaADBC

Phenotypic Variation and Bistable Switching in Bacteria

Microbial research generally focuses on clonal populations. However, bacterial cells with identical genotypes frequently display different phenotypes under identical conditions. This microbial cell individuality is receiving increasing attention in the literature because of its impact on cellular differentiation, survival under selective conditions, and the interaction of pathogens with their hosts. It is becoming clear that stochasticity in gene expression in conjunction with the architecture of the gene network that underlies the cellular processes can generate phenotypic variation. An important regulatory mechanism is the so-called positive feedback, in which a system reinforces its own response, for instance by stimulating the production of an activator. Bistability is an interesting and relevant phenomenon, in which two distinct subpopulations of cells showing discrete levels of gene expression coexist in a single culture. In this chapter, we address techniques and approaches used to establish phenotypic variation, and relate three well-characterized examples of bistability to the molecular mechanisms that govern these processes, with a focus on positive feedback.

A Biodiverse Rich Environment Does Not Contribute to a Better Diet: A Case Study from DR Congo

The potential of biodiversity to increase and sustain nutrition security is increasingly recognized by the international research community. To date however, dietary assessment studies that have assessed how biodiversity actually contributes to human diets are virtually absent. This study measured the contribution of wild edible plants (WEP) to the dietary quality in the high biodiverse context of DR Congo. The habitual dietary intake was estimated from 2 multiple-pass 24 h dietary recalls for 363 urban and 129 rural women. All WEP were collected during previous ethnobotanical investigations and identified and deposited in the National Botanical Garden of Belgium (BR). Results showed that in a high biodiverse region with precarious food security, WEP are insufficiently consumed to increase nutrition security or dietary adequacy. The highest contribution came from Dacryodes edulis in the village sample contributing 4.8% of total energy intake. Considering the nutrient composition of the many WEP available in the region and known by the indigenous populations, the potential to increase nutrition security is vast. Additional research regarding the dietary contribution of agricultural biodiversity and the nutrient composition of WEP would allow to integrate them into appropriate dietary guidelines for the region and pave the way to domesticate the most interesting WEP

COVID-19, systemic crisis, and possible implications for the wild meat trade in sub-Saharan Africa

Wild animals play an integral and complex role in the economies and ecologies of many countries across the globe, including those of West and Central Africa, the focus of this policy perspective. The trade in wild meat, and its role in diets, have been brought into focus as a consequence of discussions over the origins of COVID-19. As a result, there have been calls for the closure of China’s “wet markets”; greater scrutiny of the wildlife trade in general; and a spotlight has been placed on the potential risks posed by growing human populations and shrinking natural habitats for animal to human transmission of zoonotic diseases. However, to date there has been little attention given to what the consequences of the COVID-19 economic shock may be for the wildlife trade; the people who rely on it for their livelihoods; and the wildlife that is exploited. In this policy perspective, we argue that the links between the COVID-19 pandemic, rural livelihoods and wildlife are likely to be more complex, more nuanced, and more far-reaching, than is represented in the literature to date. We develop a causal model that tracks the likely implications for the wild meat trade of the systemic crisis triggered by COVID-19. We focus on the resulting economic shockwave, as manifested in the collapse in global demand for commodities such as oil, and international tourism services, and what this may mean for local African economies and livelihoods. We trace the shockwave through to the consequences for the use of, and demand for, wild meats as households respond to these changes. We suggest that understanding and predicting the complex dynamics of wild meat use requires increased collaboration between environmental and resource economics and the ecological and conservation sciences

Global extent and drivers of mammal population declines in protected areas under illegal hunting pressure

Illegal hunting is a persistent problem in many protected areas, but an overview of the extent of this problem and its impact on wildlife is lacking. We reviewed 40 years (1980–2020) of global research to examine the spatial distribution of research and socio-ecological factors influencing population decline within protected areas under illegal hunting pressure. From 81 papers reporting 988 species/site combinations, 294 mammal species were reported to have been illegally hunted from 155 protected areas across 48 countries. Research in illegal hunting has increased substantially during the review period and showed biases towards strictly protected areas and the African continent. Population declines were most frequent in countries with a low human development index, particularly in strict protected areas and for species with a body mass over 100 kg. Our results provide evidence that illegal hunting is most likely to cause declines of large-bodied species in protected areas of resource-poor countries regardless of protected area conservation status. Given the growing pressures of illegal hunting, increased investments in people’s development and additional conservation efforts such as improving anti-poaching strategies and conservation resources in terms of improving funding and personnel directed at this problem are a growing priority

Antibiotic treatment and resistance of unselected uropathogens in the elderly.

A population-based study was conducted among women over the age of 70 years with complaints of uncomplicated urinary tract infections (UTIs). The positive predictive value of the nitrite test alone or in combination with the leukocyte esterase test ranged between 83% and 99%. The nitrofurantoin prescription rate decreased whereas fluoroquinolone and amoxicillin/clavulanic acid prescriptions increased with increasing age. The aetiology of infection was age-dependent. Escherichia coli was the most commonly isolated uropathogen, followed by Proteus mirabilis and Klebsiella pneumoniae. For these uropathogens, the lowest susceptibility percentages were found for amoxicillin, trimethoprim and co-trimoxazole. As trimethoprim susceptibility reached approximately 75%, it may be advisable not to use this as a first-choice agent in the treatment of uncomplicated UTIs in the elderly. (aut. ref.

Urinary tract infections in general practice patients: diagnostic tests versus bacteriological culture.

Objectives: Urinary tract infections (UTIs) are common bacterial infections encountered in general practice. For the optimal treatment the general practitioner (GP) should rely on the results of diagnostic tests and recent antimicrobial susceptibility of uropathogens. Patients and methods: In total 1993 female patients (11–70 years) with complaints of an acute uncomplicated UTI were included. The performance characteristics of the diagnostic tests used were determined and compared with the antibiotic prescription rate. The antibiotic therapy (agent and duration), the uropathogens and the antibiotic susceptibility of Escherichia coli were determined for each age group. Results: The positive predictive value (PPV) (96%) and the specificity (94%) of the nitrite test were high for all samples. A negative nitrite with a positive leucocyte-esterase (LE) test showed a high PPV (79%) and sensitivity (82%). When both nitrite and LE tests were negative 50% of the samples were culture positive. Of the patients, 94% of those with a positive nitrite test and 71% of those with a negative nitrite and positive LE test were prescribed antibiotics, mostly nitrofurantoin and trimethoprim. Nitrofurantoin prescriptions decreased and those of fluoroquinolones increased with increasing age. Nitrofurantoin was equally prescribed for 3–7 days in all patients. Trimethoprim was mostly prescribed for 3 days in patients aged 21–50 years and for 5 days in the other patients. E. coli, the uropathogen mostly isolated, decreased in frequency with increasing age. Proteus mirabilis was found more in the oldest patients and Staphylococcus saprophyticus in the younger patients. The antimicrobial susceptibility of E. coli was not age related. The lowest percentages were found for amoxicillin (67%) and trimethoprim (77%). Fluoroquinolone resistance was emerging in the older patients. Conclusions: For female patients with symptoms of an acute uncomplicated UTI a positive nitrite test or a negative nitrite test with a positive LE test confirmed UTI whereas a negative nitrite together with a negative LE test did not rule out infection. For empirical treatment GPs should take into account the changing aetiology with increasing age. Prudent use of antibiotics in general and more specificly fluoroquinolones remains recommended. As trimethoprim resistance reached 20% it might be advisable to no longer use it as therapy of first choice for acute uncomplicated UTIs in The Netherlands. (aut. ref.