Fatal hemophagocytic lymphohistiocytosis-induced multiorgan dysfunction secondary to Burkholderia pseudomallei sepsis: A case report

BACKGROUND

Burkholderia pseudomallei (B. pseudomallei) is a short, straight, medium-sized Gram-negative bacterium that mostly exists alone, without a capsule or spores, has more than three flagella at one end, and actively moves. B. pseudomallei confers high morbidity and mortality, with frequent granulocytopenia in B. pseudomallei sepsis-related deaths. However, mortality may be related to hemophagocytic lymphohistiocytosis (HLH) secondary to B. pseudomallei infection.

CASE SUMMARY

A 12-year-old female was referred from a local hospital to the pediatric intensive care unit with suspected septic shock and fever, cough, dyspnea, and malaise. After admission, supportive symptomatic treatments including fluid resuscitation, anti-infective therapy, mechanical ventilation, and a vasoactive drug maintenance cycle were carefully initiated. The patient became unconscious, her blood pressure could not be maintained even under the exposure of vasoactive drugs, and she experienced cardiorespiratory arrest. The patient died due to ineffective high-quality in-hospital cardiopulmonary resuscitation. A subsequent bone marrow smear examination revealed extensive phagocytosis, and the blood culture was positive for B. pseudomallei. Family history revealed a sibling death from B. pseudomallei sepsis 5 years earlier.

CONCLUSION

The higher mortality rate in patients with B. pseudomallei sepsis may be related to secondary HLH after infection, wherein multiorgan dysfunction syndrome may be directly related to infection or immune damage caused by secondary HLH. Patients with B. pseudomallei can be asymptomatic and can become an infective source.

Clinical course and challenging management of early COVID-19 infection after heart transplantation: case report of two patients

BACKGROUND

There are limited data on Coronavirus disease 2019 (COVID-19) in solid organ transplant patients, especially in heart transplant recipients, with only a few case reports and case series described so far. Heart transplant recipients may be at particular high risk due to their comorbidities and immunosuppressed state.

CASE PRESENTATION

This report describes the clinical course and the challenging management of early COVID-19 infection in two heart transplant recipients who tested positive for the SARS-CoV-2 virus in the perioperative period of the transplant procedure. The two patients developed a severe form of the disease and ultimately died despite the initiation of an antiviral monotherapy with hydroxychloroquine coupled with the interruption of mycophenolate mofetil.

CONCLUSIONS

These two cases illustrate the severity and poor prognosis of COVID-19 in the perioperative period of a heart transplant. Thorough screening of donors and recipients is mandatory, and the issue of asymptomatic carriers needs to be addressed.

Plasmodium-a brief introduction to the parasites causing human malaria and their basic biology

Malaria is one of the most devastating infectious diseases of humans. It is problematic clinically and economically as it prevails in poorer countries and regions, strongly hindering socioeconomic development. The causative agents of malaria are unicellular protozoan parasites belonging to the genus Plasmodium. These parasites infect not only humans but also other vertebrates, from reptiles and birds to mammals. To date, over 200 species of Plasmodium have been formally described, and each species infects a certain range of hosts. Plasmodium species that naturally infect humans and cause malaria in large areas of the world are limited to five—P. falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi. The first four are specific for humans, while P. knowlesi is naturally maintained in macaque monkeys and causes zoonotic malaria widely in South East Asia. Transmission of Plasmodium species between vertebrate hosts depends on an insect vector, which is usually the mosquito. The vector is not just a carrier but the definitive host, where sexual reproduction of Plasmodium species occurs, and the parasite’s development in the insect is essential for transmission to the next vertebrate host. The range of insect species that can support the critical development of Plasmodium depends on the individual parasite species, but all five Plasmodium species causing malaria in humans are transmitted exclusively by anopheline mosquitoes. Plasmodium species have remarkable genetic flexibility which lets them adapt to alterations in the environment, giving them the potential to quickly develop resistance to therapeutics such as antimalarials and to change host specificity. In this article, selected topics involving the Plasmodium species that cause malaria in humans are reviewed.

Digital PCR is a sensitive new technique for SARS-CoV-2 detection in clinical applications

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Digital PCR is a sensitive new technique for SARS-CoV-2 detection in clinical applications.

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Digital PCR would substantially reduce the rates of false-negative COVID-19 test results, in particular those pertaining to asymptomatic carriers.

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Real-time reverse-transcriptase (RT)-PCR is a fast and convenient method for viral nucleic acid detection, but it’s results can be compromised by numerous factors and can yield false-negative results.

The global coronavirus disease 2019 (COVID-19) pandemic has posed great challenges in people’s daily lives. Highly sensitive laboratory techniques played a critical role in clinical COVID-19 diagnosis and management. In this study the feasibility of using a new digital PCR-based detection assay for clinical COVID-19 diagnosis was investigated by comparing its performance with that of RT-PCR. Clinical patient samples and samples obtained from potentially contaminated environments were analyzed. The study included 10 patients with confirmed COVID-19 diagnoses, 32 validated samples of various types derived from different clinical timepoints and sites, and 148 environmentally derived samples. SARS-CoV-2 nucleic acids were more readily detected in respiratory tract samples (35.0%). In analyses of environmentally derived samples, the positivity rate of air samples was higher than that of surface samples, probably due to differences in virus concentrations. Digital PCR detected SARS–CoV–2 in several samples that had previously been deemed negative, including 3 patient-derived samples and 5 environmentally derived samples. In this study digital PCR exhibited higher sensitivity than conventional RT-PCR, suggesting that it may be a useful new method for clinical SARS-CoV-2 detection. Improvement of SARS-CoV-2 detection would substantially reduce the rates of false-negative COVID-19 test results, in particular those pertaining to asymptomatic carriers.

[Analysis on transmission chain of a cluster epidemic of COVID-19, Nanchang]

Objective: Based on an investigation of an outbreak of COVID-19 in Nanchang, to understand the transmission process, analyze the infectivity of the cases in incubation period and asymptomatic carrier, and evaluate the transmission risks in different exposures. Methods: Case investigation was based on the traditional epidemiological survey, combined with analysis based on big data about population movement trajectories. Transmission chain was identified to indicate transmission relationship. Results: A total of 27 cases were found in this cluster epidemic, including 25 confirmed cases, 1 suspected case (index case) and 1 asymptomatic carrier. A total of 347 close contacts were found. The secondary attack rate was 7.2% (25/347). The infection rates in close contacts of the first, second, third and fourth generation cases were 52.6% (10/19), 6.1% (13/213), 2.3% (2/88) and 0.0% (0/27), respectively. Asymptomatic carrier caused household transmission. The infection rates in close contacts after having meals, sharing rooms/beds, having work contacts, having neighbor contacts, having same time medical services or sharing wards and sharing vehicles with the patients were 10.6%(17/160), 10.0%(20/201), 5.3%(5/94), 0.0%(0/30), 0.0%(0/18) and 0.0%(0/17), respectively. Conclusions: The infection source of this cluster epidemic was a suspected case from Wuhan. Analysis based on big data about population movement trajectories can help to search the cases and close contacts accurately. The proposed epidemic prevention and control measures based on this investigation were effective.

Forecasting COVID-19 pandemic: A data-driven analysis

In this paper, a new Susceptible-Exposed-Symptomatic Infectious-Asymptomatic Infectious-Quarantined-Hospitalized-Recovered-Dead (SEI_DI_UQHRD) deterministic compartmental model has been proposed and calibrated for interpreting the transmission dynamics of the novel coronavirus disease (COVID-19). The purpose of this study is to give tentative predictions of the epidemic peak for Russia, Brazil, India and Bangladesh which could become the next COVID-19 hotspots in no time by using a newly developed algorithm based on well-known Trust-region-reflective (TRR) algorithm, which is one of the robust real-time optimization techniques. Based on the publicly available epidemiological data from late January until 10 May, it has been estimated that the number of daily new symptomatic infectious cases for the above mentioned countries could reach the peak around the middle of June with the peak size of  ∼ 15, 774 (95% CI, 12,814-16,734) symptomatic infectious cases in Russia,  ∼ 26, 449 (95% CI, 25,489-31,409) cases in Brazil,  ∼ 9, 504 (95% CI, 8,378-13,630) cases in India and  ∼ 2, 209 (95% CI, 2,078-2,840) cases in Bangladesh if current epidemic trends hold. As of May 11, 2020, incorporating the infectiousness capability of asymptomatic carriers, our analysis estimates the value of the basic reproductive number (R ₀) was found to be  ∼ 4.234 (95% CI, 3.764-4.7) in Russia,  ∼ 5.347 (95% CI, 4.737-5.95) in Brazil,  ∼ 5.218 (95% CI, 4.56-5.81) in India,  ∼ 4.649 (95% CI, 4.17-5.12) in the United Kingdom and  ∼ 3.53 (95% CI, 3.12-3.94) in Bangladesh. Moreover, Latin hypercube sampling-partial rank correlation coefficient (LHS-PRCC) which is a global sensitivity analysis (GSA) method has been applied to quantify the uncertainty of our model mechanisms, which elucidates that for Russia, the recovery rate of undetected asymptomatic carriers, the rate of getting home-quarantined or self-quarantined and the transition rate from quarantined class to susceptible class are the most influential parameters, whereas the rate of getting home-quarantined or self-quarantined and the inverse of the COVID-19 incubation period are highly sensitive parameters in Brazil, India, Bangladesh and the United Kingdom which could significantly affect the transmission dynamics of the novel coronavirus disease (COVID-19). Our analysis also suggests that relaxing social distancing restrictions too quickly could exacerbate the epidemic outbreak in the above-mentioned countries.

Low prevalence of Clostridium difficile colonization in patients in long-term care facilities in Graz, Austria: A point-prevalence study

BACKGROUND

We aimed to determine the prevalence of asymptomatic colonization by C. difficile in stool of residents in four long-term care facilities (LTCFs) in Graz, Austria and to identify factors associated with colonization.

METHODS

We conducted a point-prevalence study in March 2018. Stool samples were examined by GDH enzyme immunoassay and when positive a toxin A/B-enzyme immunoassay was carried out. Additionally, all samples were tested by toxin A and B PCR and were plated manually as well as in automated fashion onto selective C. difficile agar.

RESULTS

In 4/144 (2.8%) residents the GDH assay was positive. Each resident was colonized by a different C. difficile ribotype. C. difficile was not detected in any of the environmental samples. Significantly more colonized residents (60%) had stayed at a hospital in the 3 months previous to the study compared to 10% of non-colonized patients (p=0.01).

CONCLUSIONS

The prevalence of colonization by toxigenic C. difficile was 2.8% in patients in LTCFs in Graz, Austria.

The incidence of the novel coronavirus SARS-CoV-2 among asymptomatic patients: A systematic review

BACKGROUND

The recent outbreak of the coronavirus disease 2019 (COVID-19) has quickly spread globally since its discovery in Wuhan, China, in December 2019. A comprehensive strategy - including surveillance, diagnostics, research, and clinical treatment - is urgently needed to win the battle against COVID-19. Recently, numerous studies have reported the incidence of SARS-CoV-2 in asymptomatic patients. Yet, the incidence and viral transmission from the asymptomatic cases are not yet apparent.

AIM

To estimate the incidence of COVID-19 among asymptomatic cases and describe its epidemiological and clinical significance this review systematically examined the published literature on SARS-CoV-2 in asymptomatic patients.

METHODS

The literature was searched through four scientific databases: PubMed, Web of Science, Scopus, and Science Direct.

RESULTS

Sixty-three studies satisfied the inclusion criteria. The majority of the reported studies were from China. However, there was a lack of SARS-CoV-2 epidemiological studies, from several countries worldwide, tracing the actual incidence of COVID-19, especially in asymptomatic patients. Studies with a large sample size (>1000) estimated that the percentage of people contracting SARS-CoV-2 and likely to be asymptomatic ranged from 1.2-12.9%. However, other studies with a smaller sample size reported a much higher incidence and indicated that up to 87.9% of COVID-19 infected individuals could be asymptomatic. Most of these studies indicated that asymptopatics are a potential source of infection to the community.

CONCLUSION

This review highlighted the need for more robust and well-designed studies to better estimate COVID-19 incidence among asymptomatic patients worldwide. Early identification of asymptomatic cases, as well as monitoring and tracing close contacts, could help in mitigating the spread of COVID-19.

The descriptive epidemiology of coronavirus disease 2019 during the epidemic period in Lu'an, China: achieving limited community transmission using proactive response strategies

Hubei province in China has had the most confirmed coronavirus disease 2019 (COVID-19) cases and has reported sustained transmission of the disease. Although Lu'an city is adjacent to Hubei province, its community transmission was blocked at the early stage, and the impact of the epidemic was limited. Therefore, we summarised the overall characteristics of the entire epidemic course in Lu'an to help cities with a few imported cases better contain the epidemic. A total of 69 confirmed COVID-19 cases and 11 asymptomatic carriers were identified in Lu'an during the epidemic from 12 January to 21 February 2020. Fifty-two (65.0%) cases were male, and the median age was 40 years. On admission, 56.5% of cases had a fever as the initial symptom, and pneumonia was present in 89.9% of cases. The mean serial interval and the mean duration of hospitalisation were 6.5 days (95% CI: 4.8-8.2) and 18.2 days (95% CI: 16.8-19.5), respectively. A total of 16 clusters involving 60 cases (17 first-generation cases and 43 secondary cases) were reported during the epidemic. We observed that only 18.9% (7/37) index cases resulted in community transmission during the epidemic in Lu'an, indicating that the scale of the epidemic was limited to a low level in Lu'an city. An asymptomatic carrier caused the largest cluster, involving 13 cases. Spread of COVID-19 by asymptomatic carriers represents an enormous challenge for countries responding to the pandemic.

COVID-19: asymptomatic carrier transmission is an underestimated problem

At the present time, COVID-19 is spreading rapidly [1]. The global prevention and control of COVID-19 is focused on the estimation of the relevant incubation period, basic reproduction number (R0), effective reproduction number (Rt) and death risk. Although the prevention and control of COVID-19 requires a reliable estimation of the relevant incubation period, R0, Rt and death risk. Another key epidemiological parameter-asymptomatic ratio that provides strength and range for social alienation strategies of COVID-19, which is widely defined as the proportion of asymptomatic infections among all disease infections. In fact, the ratio of asymptomatic infection is a useful indicator of the burden of disease and a better measurement of the transmissibility of the virus. So far, people have not paid enough attention to asymptomatic carriers. The asymptomatic carriers discussed in this study are recessive infections, that is, those who have never shown symptoms after onset of infection. We will discuss three aspects: detection, infectivity and proportion of healthy carriers.

Asymptomatic carrier state, acute respiratory disease, and pneumonia due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): Facts and myths

Since the emergence of coronavirus disease 2019 (COVID-19) (formerly known as the 2019 novel coronavirus [2019-nCoV]) in Wuhan, China in December 2019, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more than 75,000 cases have been reported in 32 countries/regions, resulting in more than 2000 deaths worldwide. Despite the fact that most COVID-19 cases and mortalities were reported in China, the WHO has declared this outbreak as the sixth public health emergency of international concern. The COVID-19 can present as an asymptomatic carrier state, acute respiratory disease, and pneumonia. Adults represent the population with the highest infection rate; however, neonates, children, and elderly patients can also be infected by SARS-CoV-2. In addition, nosocomial infection of hospitalized patients and healthcare workers, and viral transmission from asymptomatic carriers are possible. The most common finding on chest imaging among patients with pneumonia was ground-glass opacity with bilateral involvement. Severe cases are more likely to be older patients with underlying comorbidities compared to mild cases. Indeed, age and disease severity may be correlated with the outcomes of COVID-19. To date, effective treatment is lacking; however, clinical trials investigating the efficacy of several agents, including remdesivir and chloroquine, are underway in China. Currently, effective infection control intervention is the only way to prevent the spread of SARS-CoV-2.

A study on infectivity of asymptomatic SARS-CoV-2 carriers

BACKGROUND

An ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread around the world. It is debatable whether asymptomatic COVID-19 virus carriers are contagious. We report here a case of the asymptomatic patient and present clinical characteristics of 455 contacts, which aims to study the infectivity of asymptomatic carriers.

MATERIAL AND METHODS

455 contacts who were exposed to the asymptomatic COVID-19 virus carrier became the subjects of our research. They were divided into three groups: 35 patients, 196 family members and 224 hospital staffs. We extracted their epidemiological information, clinical records, auxiliary examination results and therapeutic schedules.

RESULTS

The median contact time for patients was four days and that for family members was five days. Cardiovascular disease accounted for 25% among original diseases of patients. Apart from hospital staffs, both patients and family members were isolated medically. During the quarantine, seven patients plus one family member appeared new respiratory symptoms, where fever was the most common one. The blood counts in most contacts were within a normal range. All CT images showed no sign of COVID-19 infection. No severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections was detected in 455 contacts by nucleic acid test.

CONCLUSION

In summary, all the 455 contacts were excluded from SARS-CoV-2 infection and we conclude that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak.

Viral kinetics of SARS-CoV-2 in asymptomatic carriers and presymptomatic patients

From a total of 71 laboratory-confirmed cases, three presymptomatic patients and 10 patients with entirely asymptomatic infections were identified. In two of the three incubation period patients, the viral titer in the presymptomatic period was very high (Ct value<20). The median number of days to first negative RT-PCR in the asymptomatic carriers was 4.5 (range 2.5-9), and all asymptomatic carriers reached a first RT-PCR Ct>35 within 14 days after diagnosis. Patients who have COVID-19 may already be infectious before there are symptoms, and 14 days of isolation after diagnosis may be sufficient in entirely asymptomatic cases.

Delivery of infection from asymptomatic carriers of COVID-19 in a familial cluster

OBJECTIVES

With the ongoing outbreak of COVID-19 around the world, it has become a worldwide health concern. One previous study reported a family cluster with an asymptomatic transmission of COVID-19. Here, we report another series of cases and further demonstrate the repeatability of the transmission of COVID-19 by pre-symptomatic carriers.

METHODS

A familial cluster of five patients associated with COVID-19 was enrolled in the hospital. We collected epidemiological and clinical characteristics, laboratory outcomes from electronic medical records, and also verified them with the patients and their families.

RESULTS

Among them, three family members (Case 3/4/5) had returned from Wuhan. Additionally, two family members, those who had not traveled to Wuhan, also contracted COVID-19 after contacting with the other three family members. Case 1 developed severe pneumonia and was admitted to the ICU. Case 3 and Case 5 presented fever and cough on days two through three of hospitalization and had ground-glass opacity changes in their lungs. Case 4 presented with diarrhea and pharyngalgia after admission without radiographic abnormalities. Case 2 presented no clinical nor radiographic abnormalities. All five cases had an increasing level of C-reactive protein.

CONCLUSIONS

Our findings indicate that COVID-19 can be transmitted by asymptomatic carriers during the incubation period.

Pneumocystis pneumonia in a treatment-naive rheumatoid arthritis patient

A HIV-negative, newly diagnosed patient with rheumatoid arthritis (RA) was found to have pneumocystis jiroveci pneumonia. The infection was treated with three weeks of atovaquone and corticosteroids. Clinicians should be aware of pneumocystis pneumonia as an infection in RA patients not receiving treatment.

Genes Encoding Proteolytic Enzymes Fungalysin and Subtilisin in Dermatophytes of Human and Animal Origin: A Comparative Study

Dermatophytes are among the most successful fungal pathogens in humans, but their virulence mechanisms have not yet been fully characterized. Dermatophytic fungi secrete proteases in vivo, which are responsible for fungal colonization and degradation of the keratinized tissue during infection. In the present study, we used PCR to investigate the presence of genes encoding fungalysins (MEP) and subtilisins (SUB) in three dermatophyte species whose incidence is increasing in Europe: the anthropophilic Trichophyton rubrum (n = 58), zoophilic Microsporum canis (n = 33), and Trichophyton benhamiae (n = 6). MEP2 and SUB4 genes were significantly correlated with T. rubrum; MEP3 and SUB1 were mostly frequently harbored by M. canis; and MEP1, 2, and 4 and SUB3-7 were most frequently harbored by T. benhamiae isolates (p < 0.05). Furthermore, MEP1-5 and SUB1-3 genes were significantly more prevalent among human clinical isolates of M. canis (n = 17) than among asymptomatic cat isolates of M. canis (n = 16; p < 0.05). Unidentified MEP and/or SUB genes in some isolates in the current study may suggest that other gene repertoires may be involved in the degradation of keratin. The presented analysis of the incidence of MEP and SUB virulence genes in three dermatophyte species of diverse origins provides an insight into the host-fungus interaction and dermatophyte pathogenesis.

Modeling the role of carrier and mobile herds on foot-and-mouth disease virus endemicity in the Far North Region of Cameroon

Foot and mouth disease virus (FMDV) is an RNA virus that infects cloven-hoofed animals, often produces either epidemic or endemic conditions, and negatively affects agricultural economies worldwide. FMDV epidemic dynamics have been extensively studied, but understanding of drivers of disease persistence in areas in which FMDV is endemic, such as most of sub-Saharan Africa, is lacking. We present a spatial stochastic model of disease dynamics that incorporates a spatial transmission kernel in a modified Gillespie algorithm, and use it to evaluate two hypothesized drivers of endemicity: asymptomatic carriers and the movement of mobile herds. The model is parameterized using data from the pastoral systems in the Far North Region of Cameroon. Our computational study provides evidence in support of the hypothesis that asymptomatic carriers, but not mobile herds, are a driver of endemicity.

Double trouble: visceral leishmaniasis in twins after traveling to Tuscany - a case report

Background

Leishmaniasis is endemic in many countries worldwide, with a prevalence of 12 million people infected, and an estimated annual incidence of 500 000 visceral leishmaniasis cases. In Europe visceral leishmaniasis is considered endemic mainly in the Mediterranean countries and cases in non-endemic European countries north of the Alps have primarily been reported in returning travellers. The incubation period is typically described between 6 weeks to 6 months. The cases presented highlight the occurrence of longer incubation periods and illustrate the individual variability for progression from infection to disease.

Case presentation

We report the cases of 18-months-old twin girls living at the German-Swiss border, who developed visceral leishmaniasis 7 and 15 months after travelling to Tuscany. They presented with fever of unknown origin and pancytopenia. Both had splenomegaly and in the first case haemophagocytic lymphohistiocytosis or leukaemia was initially included in the differential diagnosis. Diagnosis of visceral leishmaniasis was confirmed by presence of intracytoplasmic localised leishmania parasites on bone marrow aspirate and/or positive leishmania serology. Both girls responded well to treatment with liposomal amphotericin B. The mother and two older siblings remained uninfected, while the father was diagnosed to be an asymptomatic carrier.

Conclusion

Visceral leishmaniasis is an important differential diagnosis for fever of unknown origin and pancytopenia in young children living in countries with endemic disease and highlights the importance of obtaining a detailed travel history. Hemophagocytic lymphohistiocytosis and acute leukaemia present with similar symptoms and consequently are important differential diagnoses. Factors determining progression from infection to disease are not fully understood but younger age seems to be an important risk factor. Screening of siblings from affected individuals therefore may be warranted.

Molecular characterization of Clostridium difficile isolated from carriage and association of its pathogenicity to prevalent toxic genes

BACKGROUND

There are reports of non-toxigenic C. difficile strains from asymptomatic carriers are increasing source of transmission. Asymptomatic carriage transmission in the hospital or community settings might have changed over the years. Therefore, we initiated a prospective epidemiological study to define the risk factors and pathogenicity of asymptomatic C. difficile carriage.

METHODS

Stools sample from 188 subjects with diarrhoea due to C. difficile toxin and colonization without diarrhoea was subjected to routine microbial culture, molecular characterization for identification of toxin genes and mechanisms of resistance in C.difficile. Demographic data were recorded. Fifty five were positive for C. difficile includes thirty nine toxigenic C. difficile (TCD) and sixteen non toxigenic C. difficile (NTCD) isolates. Pathogenecity of toxic and nontoxic strains were analysed using AO/EB staining, Annexin V staining using flow cytometer and Galleria mellonella survival analyses.

RESULTS

Among 188, fifty five were positive for C.difficile. Infected or colonized individual with TCD or NTCD were more frequently exposed to hemodialysis compared with uncolonized patients. Isolates showed more resistant to clindamycin and levofloxacin. All TCD and eight of NTCD were tcdA-positive. Only four of TCD were positive for cdtA, tcdA, and tcdB (7%, n = 55). In thirty isolates erm (B) gene was found to be prevelant gene. High virulence was found with TCD strain and it was validated using in Galleria mellonella infection model which supported in vitro experiments. The strain with cdtA, tcdA, and tcdB, seen to have elevated virulence to increased resistance and virulence subsequently led to raised virulence in this pathogen.

CONCLUSION

Asymptomatic TCD colonization was relatively high, however, with a small number of enrolled subjects the significant of results might have limitations and the occurrence of CDI among different age group still remains unclear.

Assessment of asymptomatic Plasmodium spp. infection by detection of parasite DNA in residents of an extra-Amazonian region of Brazil

Background

The hypotheses put forward to explain the malaria transmission cycle in extra-Amazonian Brazil, an area of very low malaria incidence, are based on either a zoonotic scenario involving simian malaria, or a scenario in which asymptomatic carriers play an important role.

Objectives

To determine the incidence of asymptomatic infection by detecting Plasmodium spp. DNA and its role in residual malaria transmission in a non-Amazonian region of Brazil.

Methods

Upon the report of the first malaria case in 2010 in the Atlantic Forest region of the state of Espírito Santo, inhabitants within a 2 km radius were invited to participate in a follow-up study. After providing signed informed consent forms, inhabitants filled out a questionnaire and gave blood samples for PCR, and thick and thin smears. Follow-up visits were performed every 3 months over a 21 month period, when new samples were collected and information was updated.

Results

Ninety-two individuals were initially included for follow-up. At the first collection, all of them were clearly asymptomatic. One individual was positive for Plasmodium vivax, one for Plasmodium malariae and one for both P. vivax and P. malariae, corresponding to a prevalence of 3.4% (2.3% for each species). During follow-up, four new PCR-positive cases (two for each species) were recorded, corresponding to an incidence of 2.5 infections per 100 person-years or 1.25 infections per 100 person-years for each species. A mathematical transmission model was applied, using a low frequency of human carriers and the vector density in the region, and calculated based on previous studies in the same locality whose results were subjected to a linear regression. This analysis suggests that the transmission chain is unlikely to be based solely on human carriers, regardless of whether they are symptomatic or not.

Conclusion

The low incidence of cases and the low frequency of asymptomatic malaria carriers investigated make it unlikely that the transmission chain in the region is based solely on human hosts, as cases are isolated one from another by hundreds of kilometers and frequently by long periods of time, reinforcing instead the hypothesis of zoonotic transmission.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2263-z) contains supplementary material, which is available to authorized users.

A periodic disease transmission model with asymptomatic carriage and latency periods

In this paper, the global dynamics of a periodic disease transmission model with two delays in incubation and asymptomatic carriage periods is investigated. We first derive the model system with a general nonlinear incidence rate function by stage-structure. Then, we identify the basic reproduction ratio [Formula: see text] for the model and present numerical algorithm to calculate it. We obtain the global attractivity of the disease-free state when [Formula: see text] and discuss the disease persistence when [Formula: see text]. We also explore the coexistence of endemic state in the nonautonomous system and prove the uniqueness with constants coefficients. Numerical simulations are provided to present a case study regarding the meningococcal meningitis disease transmission and discuss the influence of carriers on [Formula: see text].

Detecting asymptomatic rams infected with Mycoplasma agalactiae in ovine artificial insemination centers

Mycoplasma agalactiae (Ma) is the main causative agent of ovine contagious agalactia, which is a serious disease of small ruminants. In endemic areas, its most common clinical situation consists of chronically infected herds, and asymptomatic infected individuals represent an epidemiological risk regarding the transmission of this disease. The aim of this work was to detect the presence of asymptomatic rams infected with Ma in different artificial insemination centers, and to determine the most effective way to identify these individuals so as to implement adequate surveillance protocols. For this purpose, 215 rams and 14 teaser sheep were sampled taking auricular, nasal, and vaginal swabs and serum samples. In addition, ejaculates from 147 rams were analyzed. These samples were subjected to specific culture and molecular techniques to isolate and identify mycoplasmas, and to a serological test to detect antibodies against Ma. Mycoplasma agalactiae was detected in 47 (4.4%) of the 1077 samples analyzed, and also one individual resulted seropositive. Thus, 37 (17.2%) of the 215 studied rams were infected with Ma. The specimens which proportionally yielded the greatest number of positive results for this pathogen were semen samples (13.6%), followed by nasal swabs (5.8%). In contrast, the sampling of the external auricular canal and the serological analyses resulted insufficient to effectively detect infected individuals. Asymptomatic rams infected with Ma were detected in all the analyzed artificial insemination centers, highlighting the need to implement adequate surveillance protocols to prevent the presence of these individuals in these centers, reducing the risk of transmitting contagious agalactia.

Asymptomatic and yet C. difficile-toxin positive? Prevalence and risk factors of carriers of toxigenic Clostridium difficile among geriatric in-patients

Background

Clostridium difficile infections (CDI) are the most frequent cause of diarrhoea in hospitals. Geriatric patients are more often affected by the condition, by a relapse and complications. Therefore, a crucial question is how often colonization with toxigenic Clostridium difficile strains occurs in elderly patients without diarrhoea and whether there is a “risk pattern” of colonized patients that can be defined by geriatric assessment. Furthermore, the probability for those asymptomatic carriers to develop a symptomatic infection over time has not been sufficiently explored.

Methods

We performed a cohort study design to assess the association of clinical variables with Clostridium difficile colonization. The first stool sample of 262 consecutive asymptomatic patients admitted to a geriatric unit was tested for toxigenic Clostridium difficile using PCR (GeneXpert, Cepheid). A comprehensive geriatric assessment (CGA) including Barthel Index, Mini Mental State Examination (MMSE) and hand grip-strength was performed. In addition, Charlson Comorbidity Index, body mass index, number and length of previous hospital stays, previous treatment with antibiotics, institutionalization, primary diagnoses and medication were recorded and evaluated as possible risk factors of colonization by means of binary logistic regression. Secondly, we explored the association of C. difficile colonization with subsequent development of CDI during hospital stay.

Results

At admission, 43 (16.4%) patients tested positive for toxin B by PCR. Seven (16.3%) of these colonized patients developed clinical CDI during hospital stay, compared to one out of 219 patients with negative or invalid PCR testing (Odds ratio 12,3; Fisher’s exact test: p = 0.000). Overall, 7 out of 8 (87.5%) CDI patients had been colonized at admission. Risk factors of colonization with C. difficile were a history of CDI, previous antibiotic treatment and hospital stays. The parameters of the CGA were not significantly associated with colonization.

Conclusion

Colonization with toxigenic Clostridium difficile strains occurs frequently in asymptomatic patients admitted to a geriatric unit. Previous CDI, antibiotic exposure and hospital stay, but not clinical variables such as CGA, are the main factors associated with asymptomatic Clostridium difficile carriage. Colonization is a crucial risk factor for subsequent development of symptomatic CDI.

Presence of Mycoplasma agalactiae in semen of naturally infected asymptomatic rams

The purpose of the present study was to assess the presence of Mycoplasma agalactiae (Ma), the main causative agent of ovine contagious agalactia (CA), in semen of naturally infected rams. Therefore, semen samples from 167 rams residing in three different artificial insemination (AI) centers of a CA-endemic area were studied by microbiological and molecular techniques. In addition, serial ejaculates from the same rams were evaluated to determine the excretion dynamics of Ma. Of the 384 samples studied, Ma was detected in 56 (14.58%) which belonged to 44 different rams (26.35%). These findings confirm the ability of Ma to be excreted in semen of asymptomatic rams. Furthermore, these results also evidence the presence of these asymptomatic carriers of Ma in ovine AI centers, representing a serious health risk regarding the spread and maintenance of CA, especially in endemic areas. Moreover, the excretion of Ma in semen also points to the risk of venereal transmission of this disease. The current results highlight the need to implement control measures to prevent the admission of infected rams in AI centers and the necessity to continuously monitor semen samples to effectively detect infected individuals.

[Outbreak of Trichophyton tonsurans ringworm in a health area of the Community of Madrid (Spain)]

BACKGROUND

Trichophyton tonsurans is a dermatophyte fungus that can cause ringworm outbreaks. In our health area in September 2013, two cases of T. tonsurans ringworm were diagnosed in children who lived in a Children's Centre.

AIMS

To determine the origin and extent of the outbreak.

METHODS

Mycological cultures of scalp and skin samples from the contacts of the diagnosed cases were performed, as well as environmental samples from the Children's Centre. The patients started with a treatment for their ringworm, and an environmental disinfection of the centre was performed.

RESULTS

Twelve cases of ringworm were detected, along with three asymptomatic scalp carriers of T. tonsurans among 20 children in the Centre. The index case was a resident in whose family, that had just returned from their country of origin, Nigeria, three cases of ringworm were diagnosed. From November 2013 to February 2014 another five cases of ringworm were diagnosed among schoolmates of three cases from the Children's Centre.

CONCLUSIONS

The antifungal treatment of the children resulted in the mycological and clinical resolution, and from February to November 2014 no other cases of ringworm by T. tonsurans in the same health area were diagnosed.

Insight into alteration of gut microbiota in Clostridium difficile infection and asymptomatic C. difficile colonization

Clostridium difficile is well recognized as the common pathogen of nosocomial diarrhea, meanwhile, asymptomatic colonization with C. difficile in part of the population has also drawn public attention. Although gut microbiota is known to play an important role in the pathogenesis of C. difficile infection (CDI), whether there is any alteration of gut microbial composition in asymptomatic C. difficile carriers hasn't been clearly described. The purpose of this study was to explore the differences in gut microbiome among CDI patients, asymptomatic C. difficile carriers and healthy individuals. We performed fecal microbiota analysis on the samples of eight CDI patients, eight asymptomatic C. difficile carriers and nine healthy subjects using 16S rRNA gene pyrosequencing. CDI patients and asymptomatic carriers showed reduced microbial richness and diversity compared with healthy subjects, accompanied with a paucity of phylum Bacteroidetes and Firmicutes as well as an overabundance of Proteobacteria. Some normally commensal bacteria, especially butyrate producers, were significantly depleted in CDI patients and asymptomatic carriers. Furthermore, the differences observed in microbial community structure between CDI patients and asymptomatic carriers suggested that the gut microbiota may be a potential factor of disease state for CDI. Our study demonstrates the characterization and diversity of gut microbiota in CDI and asymptomatic C. difficile colonization, which will provide new ideas for surveillance of the disease state and development of microbiota-targeted agents for CDI prevention and treatment.

The differential diagnostic model for serous peptidomics in HBV carriers established by MALDI-TOF-MS analysis

OBJECTIVES

Hepatitis B virus (HBV) can result in asymptomatic carrier (AsC) state or chronic inflammation of liver, which depends on the host immunity. We therefore investigated the peptidomic profiling in the process of HBV infection.

DESIGN AND METHODS

In this study, serum from 116 HBV infected (AsC and chronic hepatitis), 60 HBV-immunized and 70 normal subjects was treated with MB-WCX (weak cation exchange based magnetic beads) kits and analyzed by the Clinprot/Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) techniques. Purified serous proteins were subjected to FT-ICR-MS analysis, and Western blot further confirmed the results.

RESULTS

The specific model comprised of two peptides m/z 2882.89 and 4476.12 could distinguish HBV infected from healthy (HBV-immunized and normal) group and showed 95.5% of the sensitivity and 95.4% of the specificity by cross-validation analysis. 40/56 HBV infected and 43/50 healthy subjects could be correctly classified by the model. The area under the receiving operating curves (AUROC) of m/z 2882.89 and 4476.12, identified as subunits of fibrinogen beta chain (FBG) Bβ10-42 and nucleophosmin (NPM) respectively, were both up to 0.88 when discriminating AsC from the healthy group. The expression of Bβ10-42 and NPM decreased significantly in the plasma of HBV infected individuals by Western blot analysis.

CONCLUSIONS

There were specific serum peptide profilings for host responses to HBV infection, and m/z 2882.89 and 4476.12 could be valuable follow-up and prognostic tools for HBV infection.