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Diverse virulent pneumophages infect Streptococcus mitis.

ABSTRACT: Streptococcus mitis has emerged as one of the leading causes of bacterial endocarditis and is related to Streptococcus pneumoniae. Antibiotic resistance has also increased among strains of S. mitis and S. pneumoniae. Phages are being reinvestigated as alternatives to antibiotics for managing infections. In this study, the two virulent phages Cp-1 (Podoviridae) and Dp-1 (Siphoviridae), previously isolated from S. pneumoniae, were found to also infect S. mitis. Microbiological assays showed that both pneumophages could not only replicate in S. mitis but also produced more visible plaques on this host. However, the burst size and phage adsorption data were lower in S. mitis as compared to S. pneumoniae. A comparison of the genomes of each phage grown on both hosts produced identical nucleotide sequences, confirming that the same phages infect both bacterial species. We also discovered that the genomic sequence of podophage Cp-1 of the Félix d'Hérelle collection is different than the previously reported sequence and thus renamed SOCP.

SUBMITTER: Ouennane S

PROVIDER: S-EPMC4334900 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Diverse virulent pneumophages infect Streptococcus mitis.

Ouennane Siham S Leprohon Philippe P Moineau Sylvain S

PloS one 20150218 2

Streptococcus mitis has emerged as one of the leading causes of bacterial endocarditis and is related to Streptococcus pneumoniae. Antibiotic resistance has also increased among strains of S. mitis and S. pneumoniae. Phages are being reinvestigated as alternatives to antibiotics for managing infections. In this study, the two virulent phages Cp-1 (Podoviridae) and Dp-1 (Siphoviridae), previously isolated from S. pneumoniae, were found to also infect S. mitis. Microbiological assays showed that b ...[more]

PMID: 25692983

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Project description:The intracellular bacterial pathogen Coxiella burnetii is a category B select agent that causes human Q fever. In vivo, C.?burnetii targets alveolar macrophages wherein the pathogen replicates in a lysosome-like parasitophorous vacuole (PV). In vitro, C.?burnetii infects a variety of cultured cell lines that have collectively been used to model the pathogen's infectious cycle. However, differences in the cellular response to infection have been observed, and virulent C.?burnetii isolate infection of host cells has not been well defined. Because alveolar macrophages are routinely implicated in disease, we established primary human alveolar macrophages (hAMs) as an in vitro model of C.?burnetii-host cell interactions. C.?burnetii pathotypes, including acute disease and endocarditis isolates, replicated in hAMs, albeit with unique PV properties. Each isolate replicated in large, typical PV and small, non-fused vacuoles, and lipid droplets were present in avirulent C.?burnetii?PV. Interestingly, a subset of small vacuoles harboured single organisms undergoing degradation. Prototypical PV formation and bacterial growth in hAMs required a functional type IV secretion system, indicating C.?burnetii secretes effector proteins that control macrophage functions. Avirulent C.?burnetii promoted sustained activation of Akt and Erk1/2 pro-survival kinases and short-termphosphorylation of stress-related p38. Avirulent organisms also triggered a robust, early pro-inflammatory response characterized by increased secretion of TNF-? and IL-6, while virulent isolates elicited substantially reduced secretion of these cytokines. A corresponding increase in pro- and mature IL-1? occurred in hAMs infected with avirulent C.?burnetii, while little accumulation was observed following infection with virulent isolates. Finally, treatment of hAMs with IFN-? controlled intracellular replication, supporting a role for this antibacterial insult in the host response to C.?burnetii. Collectively, the current results demonstrate the hAM model is a human disease-relevant platform for defining novel innate immune responses to C.?burnetii.

Project description:The bacterium Streptococcus pneumoniae is one of the leading causes of fatal infections affecting humans. Intriguingly, phylogenetic analysis shows that the species constitutes one evolutionary lineage in a cluster of the otherwise commensal Streptococcus mitis strains, with which humans live in harmony. In a comparative analysis of 35 genomes, including phylogenetic analyses of all predicted genes, we have shown that the pathogenic pneumococcus has evolved into a master of genomic flexibility while lineages that evolved into the nonpathogenic S. mitis secured harmonious coexistence with their host by stabilizing an approximately 15%-reduced genome devoid of many virulence genes. Our data further provide evidence that interspecies gene transfer between S. pneumoniae and S. mitis occurs in a unidirectional manner, i.e., from S. mitis to S. pneumoniae. Import of genes from S. mitis and other mitis, anginosus, and salivarius group streptococci ensured allelic replacements and antigenic diversification and has been driving the evolution of the remarkable structural diversity of capsular polysaccharides of S. pneumoniae. Our study explains how the unique structural diversity of the pneumococcal capsule emerged and conceivably will continue to increase and reveals a striking example of the fragile border between the commensal and pathogenic lifestyles. While genomic plasticity enabling quick adaptation to environmental stress is a necessity for the pathogenic streptococci, the commensal lifestyle benefits from stability. Importance: One of the leading causes of fatal infections affecting humans, Streptococcus pneumoniae, and the commensal Streptococcus mitis are closely related obligate symbionts associated with hominids. Faced with a shortage of accessible hosts, the two opposing lifestyles evolved in parallel. We have shown that the nonpathogenic S. mitis secured harmonious coexistence with its host by stabilizing a reduced genome devoid of many virulence genes. Meanwhile, the pathogenic pneumococcus evolved into a master of genomic flexibility and imports genes from S. mitis and other related streptococci. This process ensured antigenic diversification and has been driving the evolution of the remarkable structural diversity of capsular polysaccharides of S. pneumoniae, which conceivably will continue to increase and present a challenge to disease prevention.

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Diverse virulent pneumophages infect Streptococcus mitis.

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Diverse virulent pneumophages infect Streptococcus mitis.

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