Verification, Analytical Sensitivity, Cost-effectiveness, and Comparison of 4 Candida auris Screening Methods.

In this verification study, we compare and contrast the performance characteristics of chromogenic agar culture, direct polymerase chain reaction (PCR), and broth enrichment followed by culture or PCR for the detection of Candida auris colonization. We find that culture and PCR both offer excellent performance, with broth enrichment offering little performance advantage given its cost.

Nervous Necrosis Virus Modulation of European Sea Bass (Dicentrarchus labrax, L.) Immune Genes and Transcriptome towards Establishment of Virus Carrier State.

Viral infections of teleost fish have great environmental and economic implications in aquaculture. Nervous necrosis virus (NNV) is a pathogen affecting more than 120 different species, causing high mortality and morbidity. Herein, we studied the course of NNV experimental infection of D. labrax, focusing on survivors which indicated viral carrier state. To determine the carrier state of D. labrax head kidney, we performed a gene expression analysis of selected immune-related genes and we profiled its transcriptome 14 days post infection (dpi). All tested genes showed clear differentiations in expression levels while most of them were up-regulated 14 dpi suggesting that their role is not limited in early antiviral responses, but they are also implicated in disease persistence. To gain a better understanding of the fish that survived the acute infection but still maintained a high viral load, we studied the differential expression of 124 up-regulated and 48 down-regulated genes in D. labrax head kidney, at 14 dpi. Concluding, the NNV virus persistent profile was assessed in D. labrax, where immune-related gene modification was intense (14 dpi) and the head kidney transcriptome profile at this time point offered a glimpse into host attempts to control the infection in asymptomatic carriers.

Who should be screened for carbapenemase-producing Enterobacterales and when? A systematic review.

Carbapenemase-producing Enterobacterales (CPE) cases increases every year in Denmark and the proportion of CPE-positive cases with a travel history decreases. Several epidemiological links show transmission in Danish healthcare setting indicating infection prevention and control challenges and raising questions about the Danish CPE screening protocol. The aim of this review was to identify additional risk factors to those described in the Danish CPE-screening protocol in order to detect the Danish CPE-positive patients and thereby reduce the risk of transmission and outbreaks. A systematic literature search was conducted in PubMed, Embase and Cochrane Library during March 2022. A total of 1487 articles were screened, and 19 studies were included. Retrieved studies dealt with patients with laboratory-confirmed CPE (colonization and/or infection) and associated risk factors. Antimicrobial therapy, especially broad-spectrum antimicrobial agents, prior or current hospitalization of approximately one week in ICU and 20-28 days in other wards and travel history with or without hospitalization abroad were significant risk factors associated with CPE acquisition. Comorbidities and invasive procedures were identified as risk factors, but without identifying specific comorbidities or invasive procedures associated with risk for CPE-acquisition. This study suggests the need to develop an additional algorithm for CPE-screening in Denmark. In addition to risk-based screening on admission, screening of inpatients should be considered. The screening protocol might include screening of inpatients with comorbidities who are hospitalized >1 week in ICU or >3 weeks in other wards and who have previously received or currently are receiving antibiotic treatment. Further research is needed to develop a new CPE-screening algorithm.

The Resistance to Lethal Challenge with Ostreid herpesvirus-1 of Pacific Oysters (Crassostrea gigas) Previously Exposed to This Virus.

Pacific oyster (Crassostrea gigas) aquaculture has been economically impacted in many countries by Pacific oyster mortality syndrome (POMS), a disease initiated by Ostreid herpesvirus 1. The objectives of this study were to determine whether naturally exposed, adult C. gigas could act as reservoirs for OsHV-1 and explain the recurrent seasonal outbreaks of POMS and to test whether or not they were resistant to OsHV-1. In a laboratory infection experiment using thermal shock, OsHV-1 replication was not reactivated within the tissues of such oysters and the virus was not transmitted to naïve cohabitating spat. The adult oysters were resistant to intramuscular injection with a lethal dose of OsHV-1 and had 118 times lower risk of mortality than naïve oysters. Considered together with the results of other studies in C. gigas, natural exposure or laboratory exposure to OsHV-1 may result in immunity during subsequent exposure events, either in the natural environment or the laboratory. While adult C. gigas can carry OsHV-1 infection for lengthy periods, reactivation of viral replication leading to mortality and transmission of the virus to naïve oysters may require specific conditions that were not present in the current experiment. Further investigation is required to evaluate the mechanisms responsible for resistance to disease in oysters previously exposed to OsHV-1, whether immunity can be exploited commercially to prevent POMS outbreaks and to determine the source of the virus for recurrent seasonal outbreaks.

Therapeutic efficacy of enrofloxacin in treatment of Francisella orientalis infections in juvenile Nile tilapia (Oreochromis niloticus L.).

Outbreaks of infections by Francisella orientalis represent one of the main obstacles to Nile tilapia (Oreochromis niloticus L.) farming. It is responsible for acute mortality in fingerlings and juveniles. The main control measure available is oral antibiotic therapy. This study compared the therapeutic efficacy of the antibiotics enrofloxacin and oxytetracycline, the most commonly used antimicrobial, against francisellosis in juvenile Nile tilapia (O. niloticus). Fish were challenged with a virulent isolate of F. orientalis and treated with medicated feed containing one of two doses of oxytetracycline (100 or 300 mg/kg of live weight (LW)) or 10 mg/kg of LW of enrofloxacin. The positive and negative control groups received feed without antibiotics; the negative control group was unchallenged. The results showed that enrofloxacin at a dose of 10 mg/kg of LW is effective against francisellosis in juvenile Nile tilapia (O. niloticus). Treatment with oxytetracycline did not eliminate the pathogen from the infected host, and the surviving fish became carriers. Enrofloxacin was able to cure the fish of infection with F. orientalis. This study suggests that enrofloxacin is a better option for treating francisellosis in Nile tilapia (O. niloticus L.). It controls mortality and avoids the carrier state in the fish, thus reducing the possibility of recurrence in the affected batches.

A multicenter randomized-controlled trial of nucleos(t)ide analogue cessation in HBeAg-negative chronic hepatitis B.

BACKGROUND & AIMS: Nucleos(t)ide analogues (NUCs) are the standard and mostly lifelong treatment for chronic HBeAg-negative hepatitis B, as functional cure (loss of HBsAg) is rarely achieved. Discontinuation of NUC treatment may lead to functional cure; however, to date, the evidence for this has been based on small or non-randomized clinical trials. The STOP-NUC trial was designed with the aim of increasing the HBsAg loss rate using a NUC treatment interruption approach. METHODS: In this multicenter, randomized-controlled trial, 166 HBeAg-negative patients with chronic hepatitis B on continuous long-term NUC treatment, with HBV DNA <172 IU/ml (1,000 copies/ml) for ≥4 years, were randomized to either stop (Arm A) or continue NUC treatment (Arm B) for a 96-week observation period. In total, 158 patients were available for final analysis, 79 per arm. The primary endpoint was sustained HBsAg loss up to week 96. RESULTS: Our study met its primary objective by demonstrating HBsAg loss in eight patients (10.1%, 95% CI 4.8%-19.5%) in Arm A and in no patient in Arm B (p = 0.006). Among patients with baseline HBsAg levels <1,000 IU/ml, seven (28%) achieved HBsAg loss. In Arm A, re-therapy was initiated in 11 (13.9%) patients, whereas 32 (40.5%) patients achieved sustained remission. A decrease of HBsAg >1 log IU/ml was observed in 16 patients (20.3%) in Arm A and in one patient (1.3%) in Arm B. No serious adverse events related to treatment cessation occurred. CONCLUSIONS: Cessation of NUC treatment was associated with a significantly higher rate of HBsAg loss than continued NUC treatment, which was largely restricted to patients with end of treatment HBsAg levels <1,000 IU/ml. IMPACT AND IMPLICATIONS: As HBeAg-negative patients with chronic hepatitis B on nucleos(t)ide analogues (NUCs) rarely achieve functional cure, treatment is almost always lifelong. The STOP-NUC trial was conducted to investigate whether discontinuing long-term NUC treatment can increase the cure rate. We found that some patients achieved functional cure after stopping NUCs, which was especially pronounced in patients with HBsAg levels <1,000 at the end of NUC treatment, and that many did not need to resume therapy. The results of the Stop-NUC trial provide evidence for the concept of stopping NUC treatment as a therapeutic option that can induce functional cure.

Changing incidence of hepatitis B and persistent infection risk in adults: a population-based follow-up study from 2011 in China.

BACKGROUND: This study aimed to estimate hepatitis B incidence and chronicity risk in rural adults in China under the background of eliminating viral hepatitis. METHODS: Hepatitis B surface antigen (HBsAg) screening was conducted every 2 years in demonstration areas since 2011. Individuals with baseline HBsAg-negative were included. Incidence was calculated as the number of HBsAg-positive cases divided by the total person-times. HBsAg-positive individuals were followed up to study the persistent infection (> 6 months), chronic infection (> 12 months), and recovery with hepatitis B surface antibody (anti-HBs). The chi-square test and cox proportional regression analysis were performed. RESULTS: There were 8,942 incident cases over 2,138,532 person-years, yielding an average incidence of 0.42 per 100 person-years. HBV incidence decreased rapidly in both genders and all age groups and then kept stable. Male gender, low population density, low gross domestic product per capita, and islanders were associated with higher incidence. Of the positive cases, 4,989 (55.8%) patients were followed up. The persistent infection, chronic infection, and recovery with anti-HBs rates were 32.3%, 31.0%, and 31.4%, respectively. Persistent or chronic infection was more common in younger adults and males, while seroconversion had no concern with gender or age. CONCLUSIONS: HBV incidence in adult rural residents was decreasing and stayed low. The chronicity rate was relatively high and protective antibodies were induced in only one third. The importance of population-based screening and vaccination for susceptible individuals should be addressed.

New Microviridae isolated from Sulfitobacter reveals two cosmopolitan subfamilies of single-stranded DNA phages infecting marine and terrestrial Alphaproteobacteria.

The Microviridae family represents one of the major clades of single-stranded DNA (ssDNA) phages. Their cultivated members are lytic and infect Proteobacteria, Bacteroidetes, and Chlamydiae. Prophages have been predicted in the genomes from Bacteroidales, Hyphomicrobiales, and Enterobacteriaceae and cluster within the 'Alpavirinae', 'Amoyvirinae', and Gokushovirinae. We have isolated 'Ascunsovirus oldenburgi' ICBM5, a novel phage distantly related to known Microviridae. It infects Sulfitobacter dubius SH24-1b and uses both a lytic and a carrier-state life strategy. Using ICBM5 proteins as a query, we uncovered in publicly available resources sixty-five new Microviridae prophages and episomes in bacterial genomes and retrieved forty-seven environmental viral genomes (EVGs) from various viromes. Genome clustering based on protein content and phylogenetic analysis showed that ICBM5, together with Rhizobium phages, new prophages, episomes, and EVGs cluster within two new phylogenetic clades, here tentatively assigned the rank of subfamily and named 'Tainavirinae' and 'Occultatumvirinae'. They both infect Rhodobacterales. Occultatumviruses also infect Hyphomicrobiales, including nitrogen-fixing endosymbionts from cosmopolitan legumes. A biogeographical assessment showed that tainaviruses and occultatumviruses are spread worldwide, in terrestrial and marine environments. The new phage isolated here sheds light onto new and diverse branches of the Microviridae tree, suggesting that much of the ssDNA phage diversity remains in the dark.

Pre-operative Colonization by Staphylococcus aureus and Cephalosporin Non-susceptible Bacteria in Patients with Proximal Femoral Fractures.

Objective To estimate the frequency of Staphylococcus aureus and cephalosporin nonsusceptible bacteria colonization in patients with proximal femoral fracture during preoperative hospitalization. Methods Prevalence and incidence assessment in 63 hospitalized patients over 1 year. The median time of pretreatment hospitalization was 12 days. Samples were collected from the nostrils, groin skin and anal mucosa during the pretreatment hospitalization and were tested by the disc-diffusion technique. Results The hospital colonization incidence and the prevalence of positive results were 14.3 and 44.4% for S. aureus ; 3.2 and 6.4% for meticillin-resistant S. aureus ; 28.6 and 85.7% for meticillin-resistant coagulase-negative Staphylococcus ; 28.6 and 61.9% for cefazolin nonsusceptible Enterobacteriaceae (KFNSE); and 20.6 and 28.6% for cefuroxime nonsusceptible Enterobacteriaceae (CXNSE). In addition, factors such as to the duration of the pretreatment hospitalization period, being non-walker before fracture, antimicrobial use, American Society of Anesthesiologists (ASA) 4 surgical risk, and previous hospitalization, were related to an increase in the incidence of hospital acquisition and prevalence of colonization by the evaluated strains. The prevalence of colonization by KFNSE was three times higher than by CXNSE on admission, and twice as high at the time of fracture treatment. Conclusion There was a high incidence of hospital colonization and prevalence of colonization by all strains studied, which may guide the indication of prophylactic measures for infection.

Pre-operative Colonization by Staphylococcus aureus and Cephalosporin Non-susceptible Bacteria in Patients with Proximal Femoral Fractures / Colonização pré-operatória por Staphylococcus aureus e as bactérias não suscetíveis à cefalosporina, em pacientes com fratura proximal do fêmur

Abstract Objective To estimate the frequency of Staphylococcus aureus and cephalosporin nonsusceptible bacteria colonization in patients with proximal femoral fracture during preoperative hospitalization. Methods Prevalence and incidence assessment in 63 hospitalized patients over 1 year. The median time of pretreatment hospitalization was 12 days. Samples were collected from the nostrils, groin skin and anal mucosa during the pretreatment hospitalization and were tested by the disc-diffusion technique. Results The hospital colonization incidence and the prevalence of positive results were 14.3 and 44.4% for S. aureus; 3.2 and 6.4% for meticillin-resistant S. aureus; 28.6 and 85.7% for meticillin-resistant coagulase-negative Staphylococcus; 28.6 and 61.9% for cefazolin nonsusceptible Enterobacteriaceae (KFNSE); and 20.6 and 28.6% for cefuroxime nonsusceptible Enterobacteriaceae (CXNSE). In addition, factors such as to the duration of the pretreatment hospitalization period, being non-walker before fracture, antimicrobial use, American Society of Anesthesiologists (ASA) 4 surgical risk, and previous hospitalization, were related to an increase in the incidence of hospital acquisition and prevalence of colonization by the evaluated strains. The prevalence of colonization by KFNSE was three times higher than by CXNSE on admission, and twice as high at the time of fracture treatment. Conclusion There was a high incidence of hospital colonization and prevalence of colonization by all strains studied, which may guide the indication of prophylactic measures for infection.

Resumo Objetivo Estimar a frequência da colonização por Staphylococcus aureus e as bactérias não suscetíveis à cefalosporina, em pacientes com fratura proximal do fêmur durante a internação pré-operatória. Métodos Avaliação da prevalência e incidência em 63 pacientes hospitalizados ao longo de um ano. O tempo médio de internação pré-tratamento foi de 12 dias. As amostras foram coletadas das narinas, pele da virilha e mucosa anal, durante a internação prévia ao tratamento e testadas pela técnica de disco-difusão. Resultados A incidência da colonização hospitalar e a prevalência de resultados positivos foram de 14,3% e 44,4% para Staphylococcus aureus; 3,2% e 6,4% para S. aureus resistente à meticilina; 28,6% e 85,7% para Staphylococcus coagulase-negativo resistente à meticilina; 28,6% e 61,9% para Enterobacteriaceae não suscetível à cefazolina (KFNSE); e 20,6% e 28,6% para Enterobacteriaceae não suscetível à cefuroxima (CXNSE). Além da duração do período de internação pré-tratamento, os pacientes não deambularam previamente à ocorrência da fratura e nem fizeram uso de antimicrobiano. Além disso, a duração do período de internação pré-tratamento cirúrgico, ser não-deambulador antes da fratura, uso de antimicrobianos, risco cirúrgico IV pela American Society of Anesthesiologists (ASA) e internação anterior, estiveram relacionados a um aumento na incidência de aquisição hospitalar e prevalência de colonização pelas cepas avaliadas. A prevalência de colonização pela KFNSE foi três vezes maior do que pela CXNSE na admissão e duas vezes maior no momento do tratamento da fratura. Conclusão Observou-se uma alta incidência da colonização hospitalar e prevalência da colonização por todas as cepas estudadas, o que pode orientar a indicação de medidas profiláticas contra a infecção.

Low rate of asymptomatic carriage and salivary immunoglobulin A response to Group A Streptococci in the healthy adult population in Finland.

Streptococcus pyogenes, also called group A streptococcus (GAS), is a human pathogen causing a wide range of infections ranging from mild tonsillitis to severe, life threatening conditions such as bacteraemia, necrotizing fasciitis, and streptococcal toxic shock syndrome. GAS may also colonise the oropharynx without causing any signs of disease which is known as asymptomatic carriage. This study aims to investigate IgA responses against GAS and oral streptococci from saliva samples collected from healthy Finnish adults. In addition, asymptomatic throat GAS carriage was studied. The study participants consisted of healthy adult volunteers who provided one saliva sample, a throat swab, and a background questionnaire. Total salivary IgA, and GAS specific IgA were analysed from the saliva samples using enzyme-linked immunosorbent assays (ELISA) and the results were compared to oral streptococci specific IgA levels. Asymptomatic GAS throat carriers were identified by bacterial culture, and the isolates were emm typed. Samples from a total of 182 individuals were analysed. The median salivary IgA concentration was 62.9 µg/ml (range 17.3-649.9 µg/ml), and median GAS and oral streptococcal specific IgA concentrations 2.7 and 3.3 arbitrary units (AU, range 1.4-7.4 AU and 1.6-12.0 AU), respectively. Three individuals with asymptomatic GAS throat carriage were identified.

Kinetics of the invasion of a non-phagocytic fish cell line, RTG-2 by Yersinia ruckeri serotype O1 biotype 1.

Yersiniosis, caused by the fish pathogen Yersinia ruckeri, is a serious bacterial septicaemia affecting mainly salmonids worldwide. The acute infection may result in high mortality without apparent external disease signs, while the chronic one causes moderate to considerable mortality. Survivors of yersiniosis outbreaks become carriers. Y. ruckeri is able to adhere to, and to invade, phagocytic and non-phagocytic fish cells by using unknown molecular mechanisms. The aim of this study was to describe the kinetics of cell invasion by Y. ruckeri serotype O1 biotype 1 in a fish cell line (RTG-2) originating from rainbow trout gonads. The efficiency of invasion by Y. ruckeri was found to be temperature dependent, having a maximum at 20 °C. The bacterium was able to survive up to 96 h postinfection. The incubation of the cells at 4 °C and the pre-incubation of the bacteria with sugars or heat-inactivated antiserum significantly decreased the efficiency of invasion or even completely prevented the invasion of RTG-2 cells. These findings indicate that Y. ruckeri is capable of adhering to, entering and surviving within non-phagocytic cells, and that the intracellular environment may constitute a suitable niche for this pathogen that can favour the spread of infection and/or the maintenance of a carrier state of fish.

Two In Vivo Models to Study Salmonella Asymptomatic Carrier State in Chicks.

In chicken, Salmonella Enteritidis and Salmonella Typhimurium, the two main serotypes isolated in human infections, can persist in the host organism for many weeks and up to many years without causing any symptoms. This persistence generally occurs after a short systemic infection that may either lead to death of very young birds or develop into cecal asymptomatic persistence, which is often accompanied by a high level of bacterial excretion, facilitating Salmonella transmission to counterparts. Here we describe two models of chick infection. The first model reproduces well the poultry infection in farm flocks. Numerous reinfections and animal-animal recontaminations occur leading to a high level of cecal colonization and fecal excretion in all chicks in the flock, over several weeks. In the second model, these animal reinfections and recontaminations are hampered leading to heterogeneity of infection characterized by the presence of low and super-shedders. This model allows for more mechanistic studies of Salmonella/chicks interactions as animal recontaminations are lowered.

Superinfection exclusion factors drive a history-dependent switch from vertical to horizontal phage transmission.

Temperate bacterial viruses are commonly thought to favor vertical (lysogenic) transmission over horizontal (lytic) transmission when the virion-to-host-cell ratio is high and available host cells become scarce. In P22-infected Salmonella Typhimurium populations, however, we find that host subpopulations become lytically consumed despite high phage-to-host ratios that would normally favor lysogeny. These subpopulations originate from the proliferation of P22-free siblings that spawn off from P22-carrier cells from which they cytoplasmically inherit P22-borne superinfection exclusion factors (SEFs). In fact, we demonstrate that the gradual dilution of these SEFs in the growing subpopulation of P22-free siblings restricts the number of incoming phages, thereby imposing the perception of a low phage-to-host ratio that favors lytic development. Although their role has so far been neglected, our data indicate that phage-borne SEFs can spur complex infection dynamics and a history-dependent switch from vertical to horizontal transmission in the face of host-cell scarcity.

Hand eczema and temporal variation of Staphylococcus aureus clonal complexes: A prospective observational study.

BACKGROUND: Hand eczema (HE) is frequently associated with Staphylococcus aureus; however, its role in the pathogenesis of HE is poorly understood. OBJECTIVE: To investigate the temporal variation in S aureus subtypes, ie, clonal complex (CC) types, on the hands and relate it to S aureus colonization in the nose and severity in a cohort of HE patients. METHODS: S aureus from the hands and nose of 50 adult HE patients and 50 controls was prospectively identified at 5 visits over 3 weeks. RESULTS: S aureus was identified on the hands of 23 (46%) patients at 2 or more visits and on the hands of 1 control once. Of the HE patients with S aureus colonization, 78% had the same S aureus CC type over time. Twenty-one patients had the same S aureus CC type on the hands and in the nose. Persistent colonization was strongly related to an increased disease severity. LIMITATIONS: A relatively small S aureus culture-positive population. CONCLUSION: The temporal stability of S aureus CC type and high occurrence of the identical subtypes on the hands and in the nose imply that S aureus colonization in patients with HE is of a more permanent nature. Taken together with the finding that persistent colonization and HE severity are clearly related, our results indicate that S aureus may contribute to the perpetuating course of HE.

COVID-19 containment management strategies in a nursing home

ABSTRACT Objective: To describe the first COVID-19 pandemic at Casa Ondina Lobo, a philanthropic nursing home in São Paulo city, and the containment measures against the pandemic that proved to be effective. Methods: Several preventive measures were taken before and during the pandemic, with emphasis on universal testing by reverse transcription polymerase chain reaction for COVID-19. All residents and employees were tested twice in a D9 period. Results: Among the 62 residents and 55 employees, in both testing, eight residents and nine employees tested positive for COVID-19. Of 22% of employees and 75% of residents evolved asymptomatic, emphasizing the importance of universal testing for the detection and isolation of these cases. A quarter of residents evolved without any symptoms, however, with COVID-19 signs, reinforcing the importance of monitoring vital signs. The second testing did not detect any new cases among residents, demonstrating the effectiveness of the containment measures, however, it found four new cases among employees. This emphasized their role in COVID-19 outbreaks in nursing homes. Only one patient died, a 12.5% lethality among those known to be infected and a 1.6% mortality in the total population of residents were seen. Conclusion: The adoption of appropriate containment measures enabled to contain an COVID-19 pandemic in studied nursing home. Universal reverse transcription polymerase chain reaction testing for COVID-19 has proved to be particularly important and effective.

Revisiting Persistent Salmonella Infection and the Carrier State: What Do We Know?

One characteristic of the few Salmonella enterica serovars that produce typhoid-like infections is that disease-free persistent infection can occur for months or years in a small number of individuals post-convalescence. The bacteria continue to be shed intermittently which is a key component of the epidemiology of these infections. Persistent chronic infection occurs despite high levels of circulating specific IgG. We have reviewed the information on the basis for persistence in S. Typhi, S. Dublin, S. Gallinarum, S. Pullorum, S. Abortusovis and also S. Typhimurium in mice as a model of persistence. Persistence appears to occur in macrophages in the spleen and liver with shedding either from the gall bladder and gut or the reproductive tract. The involvement of host genetic background in defining persistence is clear from studies with the mouse but less so with human and poultry infections. There is increasing evidence that the organisms (i) modulate the host response away from the typical Th1-type response normally associated with immune clearance of an acute infection to Th2-type or an anti-inflammatory response, and that (ii) the bacteria modulate transformation of macrophage from M1 to M2 type. The bacterial factors involved in this are not yet fully understood. There are early indications that it might be possible to remodulate the response back towards a Th1 response by using cytokine therapy.

Black box of phage-bacterium interactions: exploring alternative phage infection strategies.

The canonical lytic-lysogenic binary has been challenged in recent years, as more evidence has emerged on alternative bacteriophage infection strategies. These infection modes are little studied, and yet they appear to be more abundant and ubiquitous in nature than previously recognized, and can play a significant role in the ecology and evolution of their bacterial hosts. In this review, we discuss the extent, causes and consequences of alternative phage lifestyles, and clarify conceptual and terminological confusion to facilitate research progress. We propose distinct definitions for the terms 'pseudolysogeny' and 'productive or non-productive chronic infection', and distinguish them from the carrier state life cycle, which describes a population-level phenomenon. Our review also finds that phages may change their infection modes in response to environmental conditions or the physiological state of the host cell. We outline known molecular mechanisms underlying the alternative phage-host interactions, including specific genetic pathways and their considerable biotechnological potential. Moreover, we discuss potential implications of the alternative phage lifestyles for microbial biology and ecosystem functioning, as well as applied topics such as phage therapy.

Long-term persistence of crAss-like phage crAss001 is associated with phase variation in Bacteroides intestinalis.

BACKGROUND: The crAss-like phages are ubiquitous and highly abundant members of the human gut virome that infect commensal bacteria of the order Bacteroidales. Although incapable of lysogeny, these viruses demonstrate long-term persistence in the human gut microbiome, dominating the virome in some individuals. RESULTS: Here we show that rapid phase variation of alternate capsular polysaccharides in Bacteroides intestinalis cultures plays an important role in a dynamic equilibrium between phage sensitivity and resistance, allowing phage and bacteria to multiply in parallel. The data also suggests the role of a concomitant phage persistence mechanism associated with delayed lysis of infected cells, similar to carrier state infection. From an ecological and evolutionary standpoint, this type of phage-host interaction is consistent with the Piggyback-the-Winner model, which suggests a preference towards lysogenic or other "benign" forms of phage infection when the host is stably present at high abundance. CONCLUSION: Long-term persistence of bacteriophage and host could result from mutually beneficial mechanisms driving bacterial strain-level diversity and phage survival in complex environments.

Merozoites of Theileria orientalis buffeli reduce the parasitaemia of T. orientalis ikeda following tick challenge.

Theileria orientalis is a tick-borne protozoal parasite causing anaemia and death in susceptible cattle. This investigation aimed to confirm whether immunisation with the "benign" buffeli genotype of T. orientalis could reduce the parasitaemia of the virulent ikeda genotype. Calves were inoculated intravenously or subcutaneously with bovine blood containing merozoites of T. orientalis buffeli and when recipients became positive by PCR, they and control calves were challenged with unfed nymphs of Haemaphysalis longicornis ticks infected as larvae with T. orientalis ikeda. All calves became positive for the challenge within 12 days after tick application. In the immunised calves, the first wave of parasitaemia with T. orientalis ikeda from 4 to 6 weeks was reduced significantly by >80 % before the parasite burden declined into the carrier state by 9 weeks. The parasitaemias in two calves which exhibited low infections with T. orientalis ikeda shortly after arrival, were also significantly reduced after tick challenge. The results confirm the previous studies on immunity to T. sergenti in Japan, and field experience with theileriosis in endemic zones where the carrier state appears to prevent clinical disease despite repeated, seasonal tick infestations with virulent genotypes of the parasite. This method offers a means to reduce the severity of the first wave of theilerial parasitaemia after tick challenge and possibly recover associated production losses.