scholarly journals Coxiella burnetii Exhibits Morphological Change and Delays Phagolysosomal Fusion after Internalization by J774A.1 Cells

2000 ◽  
Vol 68 (7) ◽  
pp. 3815-3821 ◽  
Author(s):  
Dale Howe ◽  
Louis P. Mallavia
Keyword(s):  
Coxiella Burnetii ◽  
Q Fever ◽  
Large Cell ◽  
Infection Process ◽  
Thorium Dioxide ◽  
Small Cell Variant ◽  
Morphological Variants ◽  
Cell Variant ◽  
First Time

ABSTRACT Coxiella burnetii, the etiological agent of Q fever, is an obligate intracellular bacterium proliferating within the harsh environment of the phagolysosome. Mechanisms controlling trafficking to, and survival of pathogens within, the phagolysosome are unknown. Two distinct morphological variants have been implicated as playing a role in C. burnetii survival. The dormant small-cell variant (SCV) is resistant to extracellular stresses and the more metabolically active large-cell variant (LCV) is sensitive to environmental stresses. To document changes in the ratio of SCVs to LCVs in response to environment, a protein specific to SCV, ScvA, was quantitated. During the first 2 h after internalization ofC. burnetii by J774A.1 cells, the level of ScvA decreased, indicating a change from a population containing primarily SCVs to one containing primarily LCVs. In vitro experiments showed that 2 h of incubation at pH 5.5 caused a significant decrease in ScvA in contrast to incubation at pH 4.5. Measuring in vitro internalization of [35S]methionine-[35S]cysteine in response to pH, we found the uptake to be optimal at pH 5.5. To explore the possibility that after uptake C. burnetii was able to delay phagolysosomal fusion, we used thorium dioxide and acid phosphatase to label phagolysosomes during infection of J774A.1 cells. We determined that viable C. burnetii was able to delay phagolysosomal fusion. This is the first time that a delay in phagolysosomal fusion has been shown to be a part of the infection process of this pathogenic microorganism.

scholarly journals Sustained Axenic Metabolic Activity by the Obligate Intracellular Bacterium Coxiella burnetii

2008 ◽  
Vol 190 (9) ◽  
pp. 3203-3212 ◽  
Author(s):  
Anders Omsland ◽  
Diane C. Cockrell ◽  
Elizabeth R. Fischer ◽  
Robert A. Heinzen
Keyword(s):  
Host Cell ◽  
Coxiella Burnetii ◽  
Metabolic Activity ◽  
De Novo ◽  
Q Fever ◽  
Parasitophorous Vacuole ◽  
Chloride Concentration ◽  
Citrate Buffer ◽  
Cell Variant

ABSTRACT Growth of Coxiella burnetii, the agent of Q fever, is strictly limited to colonization of a viable eukaryotic host cell. Following infection, the pathogen replicates exclusively in an acidified (pH 4.5 to 5) phagolysosome-like parasitophorous vacuole. Axenic (host cell free) buffers have been described that activate C. burnetii metabolism in vitro, but metabolism is short-lived, with bacterial protein synthesis halting after a few hours. Here, we describe a complex axenic medium that supports sustained (>24 h) C. burnetii metabolic activity. As an initial step in medium development, several biological buffers (pH 4.5) were screened for C. burnetii metabolic permissiveness. Based on [35S]Cys-Met incorporation, C. burnetii displayed optimal metabolic activity in citrate buffer. To compensate for C. burnetii auxotrophies and other potential metabolic deficiencies, we developed a citrate buffer-based medium termed complex Coxiella medium (CCM) that contains a mixture of three complex nutrient sources (neopeptone, fetal bovine serum, and RPMI cell culture medium). Optimal C. burnetii metabolism occurred in CCM with a high chloride concentration (140 mM) while the concentrations of sodium and potassium had little effect on metabolism. CCM supported prolonged de novo protein and ATP synthesis by C. burnetii (>24 h). Moreover, C. burnetii morphological differentiation was induced in CCM as determined by the transition from small-cell variant to large-cell variant. The sustained in vitro metabolic activity of C. burnetii in CCM provides an important tool to investigate the physiology of this organism including developmental transitions and responses to antimicrobial factors associated with the host cell.

The Small Cell Variant of Anaplastic Large Cell Lymphoma

2010 ◽  
Vol 134 (11) ◽  
pp. 1706-1710 ◽  
Author(s):  
Thomas A. Summers ◽  
Joel T. Moncur
Keyword(s):  
Anaplastic Large Cell Lymphoma ◽  
Anaplastic Lymphoma Kinase ◽  
Cell Lymphoma ◽  
Large Cell ◽  
Short Review ◽  
Small Cell ◽  
Anaplastic Lymphoma ◽  
Small Cell Variant ◽  
Large Cell Lymphoma ◽  
Cell Variant

Abstract Anaplastic large cell lymphomas constitute a heterogeneous group of hematopoietic neoplasms that are characterized by immunopositivity for CD30 and the presence, in varying degrees, of large, pleomorphic “hallmark” cells. Primary systemic anaplastic lymphoma kinase-positive anaplastic large cell lymphomas are a subset of this group. Numerous heterogeneous histomorphologic patterns have been described in anaplastic lymphoma kinase-positive anaplastic large cell lymphomas, and all patterns tend to have a better prognosis than that found in anaplastic lymphoma kinase-negative cases. We provide a short review of the small cell variant of anaplastic large cell lymphoma to facilitate the diagnosis of this difficult-to-recognize entity, which may be confused with reactive processes, commonly presents with disseminated disease, and pursues an aggressive clinical course.

scholarly journals The Effect of pH on Antibiotic Efficacy against Coxiella burnetii in Axenic Media

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Cody B. Smith ◽  
Charles Evavold ◽  
Gilbert J. Kersh
Keyword(s):  
Coxiella Burnetii ◽  
Antimicrobial Agents ◽  
Q Fever ◽  
Antimicrobial Treatment ◽  
Etiologic Agent ◽  
Growth And Survival ◽  
Intracellular Compartments ◽  
The Impact

AbstractCoxiella burnetii, the etiologic agent of Q fever, replicates in an intracellular phagolysosome with pH between 4 and 5. The impact of this low pH environment on antimicrobial treatment is not well understood. An in vitro system for testing antibiotic susceptibility of C. burnetii in axenic media was set up to evaluate the impact of pH on C. burnetii growth and survival in the presence and absence of antimicrobial agents. The data show that C. burnetii does not grow in axenic media at pH 6.0 or higher, but the organisms remain viable. At pH of 4.75, 5.25, and 5.75 moxifloxacin, doxycycline, and rifampin are effective at preventing growth of C. burnetii in axenic media, with moxifloxacin and doxycycline being bacteriostatic and rifampin having bactericidal activity. The efficacy of doxycycline and moxifloxacin improved at higher pH, whereas rifampin activity was pH independent. Hydroxychloroquine is thought to inhibit growth of C. burnetii in vivo by raising the pH of typically acidic intracellular compartments. It had no direct bactericidal or bacteriostatic activity on C. burnetii in axenic media, suggesting that raising pH of acidic intracellular compartments is its primary mechanism of action in vivo. The data suggest that doxycycline and hydroxychloroquine are primarily independent bacteriostatic agents.

scholarly journals Bacteriostatic and Bactericidal Activities of Tigecycline against Coxiella burnetii and Comparison with Those of Six Other Antibiotics

2009 ◽  
Vol 53 (6) ◽  
pp. 2690-2692 ◽  
Author(s):  
Ioanna Spyridaki ◽  
Anna Psaroulaki ◽  
Iosif Vranakis ◽  
Yannis Tselentis ◽  
Achilleas Gikas
Keyword(s):  
Coxiella Burnetii ◽  
Q Fever ◽  
Vero Cells ◽  
In Vitro Susceptibility ◽  
Shell Vial ◽  
Bactericidal Activities ◽  
Acute Q Fever ◽  
Reference Strains ◽  
Shell Vial Assay

ABSTRACT The present article is a study of the in vitro susceptibility of eight Greek Coxiella burnetii isolates, derived from patients with acute Q fever, and two reference strains of Coxiella burnetii to tigecycline. The bacteriostatic activity of tigecycline was compared with those of six other antibiotics using a shell vial assay. The MICs of the examined antibiotics were as follows: tigecycline ranged from 0.25 to 0.5 μg/ml; doxycycline, trovafloxacin, and ofloxacin ranged from 1 to 2 μg/ml; linezolid and clarithromycin ranged from 2 to 4 μg/ml; and ciprofloxacin ranged from 4 to 8 μg/ml. Tigecycline was effective in inhibiting the infection of Vero cells by C. burnetii. No bactericidal activity was observed against C. burnetii at 4 μg/ml.

scholarly journals Coxiella burnetii Interaction with Neutrophils and MacrophagesIn Vitroand in SCID Mice following Aerosol Infection

2013 ◽  
Vol 81 (12) ◽  
pp. 4604-4614 ◽  
Author(s):  
Alexandra Elliott ◽  
Ying Peng ◽  
Guoquan Zhang
Keyword(s):  
Immune Response ◽  
Coxiella Burnetii ◽  
Q Fever ◽  
Natural Infection ◽  
Scid Mice ◽  
Innate Immune ◽  
Content Type ◽  
Aerosol Infection

ABSTRACTCoxiella burnetiiis an obligate intracellular bacterium that causes acute and chronic Q fever in humans. Human Q fever is mainly transmitted by aerosol infection. However, there is a fundamental gap in the knowledge regarding the mechanisms of pulmonary immunity againstC. burnetiiinfection. This study focused on understanding the interaction betweenC. burnetiiand innate immune cellsin vitroandin vivo. Both virulentC. burnetiiNine Mile phase I (NMI) and avirulent Nine Mile phase II (NMII) were able to infect neutrophils, while the infection rates were lower than 29%, suggesting thatC. burnetiican infect neutrophils, but infection is limited. Interestingly,C. burnetiiinside neutrophils can infect and replicate within macrophages, suggesting that neutrophils cannot killC. burnetiiandC. burnetiimay be using infection of neutrophils as an evasive strategy to infect macrophages. To elucidate the mechanisms of the innate immune response toC. burnetiinatural infection, SCID mice were exposed to aerosolizedC. burnetii. Surprisingly, neutrophil influx into the lungs was delayed until day 7 postinfection in both NMI- and NMII-infected mice. This result suggests that neutrophils may play a unique role in the early immune response against aerosolizedC. burnetii. Studying the interaction betweenC. burnetiiand the innate immune system can provide a model system for understanding how the bacteria evade early immune responses to cause infection.

Sign in / Sign up

Export Citation Format

Share Document