Alternative bacteriophage life cycles: the carrier state of Campylobacter jejuni

Members of the genus Campylobacter are frequently responsible for human enteric disease, often through consumption of contaminated poultry products. Bacteriophages are viruses that have the potential to control pathogenic bacteria, but understanding their complex life cycles is key to their successful exploitation. Treatment of Campylobacter jejuni biofilms with bacteriophages led to the discovery that phages had established a relationship with their hosts typical of the carrier state life cycle (CSLC), where bacteria and bacteriophages remain associated in equilibrium. Significant phenotypic changes include improved aerotolerance under nutrient-limited conditions that would confer an advantage to survive in extra-intestinal environments, but a lack in motility eliminated their ability to colonize chickens. Under these circumstances, phages can remain associated with a compatible host and continue to produce free virions to prospect for new hosts. Moreover, we demonstrate that CSLC host bacteria can act as expendable vehicles for the delivery of bacteriophages to new host bacteria within pre-colonized chickens. The CSLC represents an important phase in the ecology of Campylobacter bacteriophage

Healthcare-associated pneumonia: a prospective study in Spain

Objective: The aim of the study was to describe the epidemiological characteristics and factors related to outcome in Streptococcus pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA) healthcare-associated pneumonia (HCAP). Methods: A 3-year prospective observational epidemiological case study of HCAP was conducted in seven Spanish hospitals. Microbiological and patient characteristics and outcomes were collected and classified by causative pathogen into 4 categories: "S. pneumoniae", "MRSA", "Others" and "Unknown". Patients were followed up 30 days after discharge. Results: A total of 258 (84.6%) patients were enrolled (170 were men [65.9%]). Mean age was 72.4 years ± 15 years (95% CI [70.54-74.25]). The etiology of pneumonia was identified in 73 cases (28.3%): S. pneumoniae in 35 patients (13.6%), MRSA in 8 (3.1%), and other microorganisms in 30 patients (11.6%). Significant differences in rates of chronic obstructive pulmonary disease (p < 0.05), previous antibiotic treatment (p<0.05), other chronic respiratory diseases, inhaled corticosteroids (p <0.01), and lymphoma (p < 0.05) were observed among the four groups. Patients with MRSA pneumonia had received more previous antibiotic treatment (87.5%). Thirty-three (12.8%) patients died during hospitalisation; death in 27 (81.2%) was related to pneumonia. Conclusions: The etiology of HCAP was identified in only one quarter of patients, with S. pneumoniae being the most prevalent microorganism. Patients with chronic respiratory diseases more frequently presented HCAP due to MRSA than to S. pneumoniae. Death at hospital discharge was related in most cases to pneumonia.Objetivo: Describir las características epidemiológicas y factores relacionados con la neumonía asociada a cuidados sanitarios (NACS) causada por Streptococcus pneumoniae y Staphylococcus aureus resistente a meticilina (SARM). Pacientes y métodos: Estudio epidemiológico observacional prospectivo de casos a 3 años en siete hospitales españoles. Se recogieron las características microbiológicas y de los pacientes y sus resultados y se clasificaron en función del patógeno causante en 4 categorías: ?S. pneumoniae?, ?SARM?, ?Otros? y ?Desconocido?. Al alta, se realizó un seguimiento de 30 días. Resultados: Se incluyeron 258 (84,6%) pacientes (170 hombres [65.9%]; edad media 72,4 años ± 15 años (95% IC [70,54-74,25]). La etiología de la neumonía se identificó en 73 casos (28,3%):S. pneumoniae en 35 pacientes (13,6%), SARM en 8 (3,1%) y otros microorganismos en 30 pacientes (11,6%). Hubo diferencias significativas en tasas de enfermedad pulmonar obstructiva crónica (p < 0,05), tratamiento antibiótico previo (p < 0,05), otras enfermedades respiratorias crónicas, corticoides inhalados (p < 0,01) y linfoma (p < 0,05) entre los cuatro grupos. Los pacientes con NACS causada por SARM recibieron tratamiento antibiótico previo en mayor medida (87,5%). Treinta y tres (12,8%) pacientes murieron durante la hospitalización; en 27 (81,2%) debido a la neumonía. Conclusiones: Se identificó la etiología de la NACS en solo un cuarto de los pacientes, siendo S. pneumoniae el patógeno más frecuente. En los pacientes con enfermedades respiratorias crónicas fue más frecuente la NACS causada por SARM. La muerte tras el alta hospitalaria se relacionó con la neumonía en la mayoría de los casos

Defining Life: The Virus Viewpoint

Are viruses alive? Until very recently, answering this question was often negative and viruses were not considered in discussions on the origin and definition of life. This situation is rapidly changing, following several discoveries that have modified our vision of viruses. It has been recognized that viruses have played (and still play) a major innovative role in the evolution of cellular organisms. New definitions of viruses have been proposed and their position in the universal tree of life is actively discussed. Viruses are no more confused with their virions, but can be viewed as complex living entities that transform the infected cell into a novel organism—the virus—producing virions. I suggest here to define life (an historical process) as the mode of existence of ribosome encoding organisms (cells) and capsid encoding organisms (viruses) and their ancestors. I propose to define an organism as an ensemble of integrated organs (molecular or cellular) producing individuals evolving through natural selection. The origin of life on our planet would correspond to the establishment of the first organism corresponding to this definition

Prophage Spontaneous Activation Promotes DNA Release Enhancing Biofilm Formation in Streptococcus pneumoniae

Streptococcus pneumoniae (pneumococcus) is able to form biofilms in vivo and previous studies propose that pneumococcal biofilms play a relevant role both in colonization and infection. Additionally, pneumococci recovered from human infections are characterized by a high prevalence of lysogenic bacteriophages (phages) residing quiescently in their host chromosome. We investigated a possible link between lysogeny and biofilm formation. Considering that extracellular DNA (eDNA) is a key factor in the biofilm matrix, we reasoned that prophage spontaneous activation with the consequent bacterial host lysis could provide a source of eDNA, enhancing pneumococcal biofilm development. Monitoring biofilm growth of lysogenic and non-lysogenic pneumococcal strains indicated that phage-infected bacteria are more proficient at forming biofilms, that is their biofilms are characterized by a higher biomass and cell viability. The presence of phage particles throughout the lysogenic strains biofilm development implicated prophage spontaneous induction in this effect. Analysis of lysogens deficient for phage lysin and the bacterial major autolysin revealed that the absence of either lytic activity impaired biofilm development and the addition of DNA restored the ability of mutant strains to form robust biofilms. These findings establish that limited phage-mediated host lysis of a fraction of the bacterial population, due to spontaneous phage induction, constitutes an important source of eDNA for the S. pneumoniae biofilm matrix and that this localized release of eDNA favors biofilm formation by the remaining bacterial population

Cryptic prophages help bacteria cope with adverse environments

Phages are the most abundant entity in the biosphere and outnumber bacteria by a factor of 10. Phage DNA may also constitute 20% of bacterial genomes; however, its role is ill defined. Here, we explore the impact of cryptic prophages on cell physiology by precisely deleting all nine prophage elements (166 kbp) using Escherichia coli. We find that cryptic prophages contribute significantly to resistance to sub-lethal concentrations of quinolone and β-lactam antibiotics primarily through proteins that inhibit cell division (for example, KilR of rac and DicB of Qin). Moreover, the prophages are beneficial for withstanding osmotic, oxidative and acid stresses, for increasing growth, and for influencing biofilm formation. Prophage CPS-53 proteins YfdK, YfdO and YfdS enhanced resistance to oxidative stress, prophages e14, CPS-53 and CP4-57 increased resistance to acid, and e14 and rac proteins increased early biofilm formation. Therefore, cryptic prophages provide multiple benefits to the host for surviving adverse environmental conditions

Irradiation-Induced Deinococcus radiodurans Genome Fragmentation Triggers Transposition of a Single Resident Insertion Sequence

Stress-induced transposition is an attractive notion since it is potentially important in creating diversity to facilitate adaptation of the host to severe environmental conditions. One common major stress is radiation-induced DNA damage. Deinococcus radiodurans has an exceptional ability to withstand the lethal effects of DNA–damaging agents (ionizing radiation, UV light, and desiccation). High radiation levels result in genome fragmentation and reassembly in a process which generates significant amounts of single-stranded DNA. This capacity of D. radiodurans to withstand irradiation raises important questions concerning its response to radiation-induced mutagenic lesions. A recent study analyzed the mutational profile in the thyA gene following irradiation. The majority of thyA mutants resulted from transposition of one particular Insertion Sequence (IS), ISDra2, of the many different ISs in the D. radiodurans genome. ISDra2 is a member of a newly recognised class of ISs, the IS200/IS605 family of insertion sequences

The discovery of endogenous retroviruses

When endogenous retroviruses (ERV) were discovered in the late 1960s, the Mendelian inheritance of retroviral genomes by their hosts was an entirely new concept. Indeed Howard M Temin's DNA provirus hypothesis enunciated in 1964 was not generally accepted, and reverse transcriptase was yet to be discovered. Nonetheless, the evidence that we accrued in the pre-molecular era has stood the test of time, and our hypothesis on ERV, which one reviewer described as 'impossible', proved to be correct. Here I recount some of the key observations in birds and mammals that led to the discovery of ERV, and comment on their evolution, cross-species dispersion, and what remains to be elucidated

Carrier cultures of human fetal diploid cells infected with coxsackievirus type B2

Carrier cultures of coxsackievirus type B2, strain V1-013 were established without the use of “normal” human serum or serum containing viral antibodies, and without frequent changes of medium. Blind passage of virus strain V1-013 in human fetal diploid (HFD) cell cultures on maintenance medium resulted in viral multiplication without apparent CPE. In addition, human fetal diploid cultures infected with the V1-013 virus strain could be subcultivated for over 20 transfers, and infectious virus and antigen demonstrable by immunofluorescent staining were present at each passage level; again, viral multiplication occurred without apparent CPE. Sustained infections were not observed when HFD cells were inoculated with two other (Ohio and Lincoln) B2 coxsackievirus strains; however, the life-span of inoculated cultures was reduced in comparison to that of control cultures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41684/1/705_2005_Article_BF01556144.pd