Faculty Opinions recommendation of Antagonistic activities of some Bifidobacterium sp. strains isolated from resident infant gastrointestinal microbiota on Gram-negative enteric pathogens.

The effect of wide variations in incubation temperatures and long periods of incubation on transport and enrichment broths and plating media was determined by exhaustive analysis of 132 diarrheal stools for salmonellae and shigellae. Homogenized stools were streaked onto eosin methylene blue (EMB), Salmonella-Shigella (SS), and xylose lysine deoxycholate (XLD) agar plates, and into saline, Cary-Blair (CB) transport medium, and Selenite F and gram-negative (GN) enrichment broths. Incubation temperatures were compared at 20 C, 35 C, 40 C and ambient, and over a range of 4 to 52 C for media incubated in an insulated picnic cooler in an auto trunk. At 1, 2, 4, and 7 days the plates were observed, and the broths were subcultured. Each stool was streaked to 12 plates for 48 observations and pickings, and to 48 tubes, subcultured to 192 plates, for a total of 240 observations for pathogens. Analysis of data from 6,246 Salmonella-positive plates showed direct streaking to be most effective after 2 days of incubation, but broths were equally effective at 1 or 2 days. By day 4 many plates were overgrown, and both plates and broths showed diminution of positives by about 10% and at day 7, 19%. The 2,434 Shigella-positive plates were more demanding in all times and temperatures of incubation than salmonellae. Although at day 2 best results were obtained on direct streaking, shigellae die-offs in broths were excessive, with positive declining 23.7% by day 2, 49% by day 4, and 60% by day 7. Direct plating of both pathogens was poor at 20 C with about 48% success, but salmonellae preferred higher temperatures (35 and 40 C), whereas shigellae chose 35 C and ambient, which averaged 28 C for the 10-month study. Temperature was immaterial to salmonellae in broths with ambient slightly better than 35 C, but shigellae preferred 20 C and showed a 50% failure rate at 40 C, ambient being equal to 35 C. The preferential rank of broths in efficacy was GN greater than selenite greater than saline greater than CB greater than direct for salmonellae; for shigellae, GN greater than saline greater than direct greater than CB greater than selenite, with selenite proving to be unsuitable for shigellae. Plating media preferences were XLD greater than EMB greater than SS. Ten of 39 shigellae strains could not be recovered from the selenite and SS media combination, the many replications notwithstanding. The effectiveness of salmonellae and shigellae detection at ambient temperatures in Louisiana during the 10-month study period, as compared to controlled incubation temperatures, indicates that satisfactory enteric bacteriology can be done in warm climates without constant temperature incubators.

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Evaluation of Statens Serum Institut Enteric Medium for Detection of Enteric Pathogens

Journal of Clinical Microbiology ◽

10.1128/jcm.37.7.2312-2316.1999 ◽

1999 ◽

Vol 37 (7) ◽

pp. 2312-2316 ◽

Cited By ~ 42

Author(s):

Marianne Blom ◽

Aase Meyer ◽

Peter Gerner-Smidt ◽

Knud Gaarslev ◽

Frank Espersen

Keyword(s):

Detection Limit ◽

Growth Rates ◽

Bacterial Species ◽

Rapid Diagnosis ◽

Enteric Pathogens ◽

Biochemical Reactions ◽

Direct Identification ◽

Detection Rates ◽

Gram Negative ◽

Gram Positive Bacteria

The efficacy of the Statens Serum Institut (SSI) enteric medium for isolation and direct identification of enteric pathogens was evaluated. Six different biochemical reactions can be read by using the SSI enteric medium, allowing direct identification of a range of enteric pathogens. All 248 gram-negative bacterial species that were tested grew on the SSI enteric medium. Only 10 of 248 bacteria (4%) showed discrepant results in the biochemical reactions, and none of these were enteric pathogens. Forty-three of 47 enteric pathogens (92%) produced identical rates of semiquantitative growth on the SSI enteric medium and 5% blood agar, whereas three Vibrio spp. and oneAeromonas spp. showed reduced growth. Gram-positive bacteria did not grow on the SSI enteric medium. Most enteric pathogens had a detection limit of 50 bacteria per ml of feces, but higher numbers of Vibrio spp. and some Shigella spp. were required for detection. The growth rates of 125 enteric pathogens and 12 Yersinia spp. on the SSI enteric medium, xylose lysine deoxycholate (XLD), Hektoen enteric (HE),Salmonella-Shigella (SS), and cefsulodin-irgasan-novobiocin (CIN) agar were compared. Detection rates after application of 200 CFU were 99% for SSI enteric medium, 92% for XLD, 88% for HE, and 82% for SS agar. The 12 Yersinia spp. grew excellently on both the SSI enteric medium and CIN agar. We conclude that the performance of the SSI enteric medium compares favorably to those of other media tested. Its ability to detect Yersinia spp. may limit the number of media needed in the typical laboratory. The direct identification of enteric pathogens on the medium may also provide a more rapid diagnosis.

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Microbiota and Pathogen Proteases Modulate Type III Secretion Activity in EnterohemorrhagicEscherichia coli

mBio ◽

10.1128/mbio.02204-18 ◽

2018 ◽

Vol 9 (6) ◽

Cited By ~ 7

Author(s):

Elizabeth A. Cameron ◽

Meredith M. Curtis ◽

Aman Kumar ◽

Gary M. Dunny ◽

Vanessa Sperandio

Keyword(s):

Gut Microbiota ◽

Host Cell ◽

Type Iii Secretion ◽

Cell Function ◽

Enteric Pathogens ◽

Host Cells ◽

Secretion Systems ◽

Gram Negative ◽

Content Type ◽

Type Iii

ABSTRACTEnteric pathogens have complex interactions with the gut microbiota. Most of what is known about them has focused on microbiota-derived metabolites or small molecules that serve as nutrients and/or signals to aid in growth or transcriptionally regulate virulence gene expression. A common virulence strategy is to express a type III secretion system (T3SS), which is a molecular syringe deployed by many Gram-negative pathogens to hijack host cell function. EnterohemorrhagicEscherichiacoli(EHEC) requires its T3SS to colonize the intestinal tract and cause disease. Here we report that a prominent member of the intestinal microbiota,Bacteroides thetaiotamicron(Bt), secretes proteases that cleave the translocon of the T3SS of EHEC to enhance effector translocation into host cells. This is in contrast from an endogenous protease from EHEC itself (namely, EspP) that cleaves the translocon protein EspB in a different site to limit effector translocation. The EspB protein forms the T3SS pore in mammalian cells, and pore proteins are conserved in the T3SSs from several pathogens. This is the first demonstration of a commensal species directly processing a pathogen’s T3SS, posing a new paradigm for how the microbiota can influence the severity of disease caused by bacterial pathogens. Because T3SSs are employed by many pathogens, this phenomenon has broad implications to commensal-pathogen relationships.IMPORTANCEThe gut microbiota is usually regarded as providing colonization resistance against enteric pathogens. However, some pathogens evolved to thrive with the aid of certain members of the microbiota. Several Gram-negative bacteria employ type three secretion systems (T3SSs), which are molecular syringes that deliver effector proteins to host cells, hijacking host cell function. Here we show that the T3SS of enterohemorrhagicE. coli(EHEC) is cleaved by self and microbiota-derived proteases. Self-cleavage limits effector translocation, while cleavage by the microbiota memberBacteroides thetaiotamicron(Bt) exacerbates effector translocation and lesion formation on epithelial cells.

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The Biochemistry of Sensing: Enteric Pathogens Regulate Type III Secretion in Response to Environmental and Host Cues

mBio ◽

10.1128/mbio.02122-17 ◽

2018 ◽

Vol 9 (1) ◽

Cited By ~ 11

Author(s):

Nicole J. De Nisco ◽

Giomar Rivera-Cancel ◽

Kim Orth

Keyword(s):

Type Iii Secretion ◽

Chemical Signals ◽

Enteric Pathogens ◽

Transcriptional Networks ◽

Secretion Systems ◽

Gram Negative ◽

Type Iii ◽

Tract Infections ◽

Physical And Chemical ◽

Host Cues

ABSTRACTEnteric pathogens employ sophisticated strategies to colonize and infect mammalian hosts. Gram-negative bacteria, such asEscherichia coli,Salmonella, andCampylobacter jejuni, are among the leading causes of gastrointestinal tract infections worldwide. The virulence strategies of many of these Gram-negative pathogens rely on type III secretion systems (T3SSs), which are macromolecular syringes that translocate bacterial effector proteins directly into the host cytosol. However, synthesis of T3SS proteins comes at a cost to the bacterium in terms of growth rate and fitness, both in the environment and within the host. Therefore, expression of the T3SS must be tightly regulated to occur at the appropriate time and place during infection. Enteric pathogens have thus evolved regulatory mechanisms to control expression of their T3SSs in response to specific environmental and host cues. These regulatory cascades integrate multiple physical and chemical signals through complex transcriptional networks. Although the power of bacterial genetics has allowed elucidation of many of these networks, the biochemical interactions between signal and sensor that initiate the signaling cascade are often poorly understood. Here, we review the physical and chemical signals that Gram-negative enteric pathogens use to regulate T3SS expression during infection. We highlight the recent structural and functional studies that have elucidated the biochemical properties governing both the interaction between sensor and signal and the mechanisms of signal transduction from sensor to downstream transcriptional networks.

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A Freeze-Etch Study of Acinetobacter SP. Grown on a Hydrocarbon Substrate

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100050883 ◽

1974 ◽

Vol 32 ◽

pp. 174-175

Author(s):

C. L. Scott ◽

W. R. Finnerty

Keyword(s):

Membrane System ◽

Structural Distortion ◽

Intracytoplasmic Membrane ◽

Gram Negative ◽

Sectioned Material ◽

Acinetobacter Sp

Acinetobacter sp. HO-1-N, a gram-negative hydrocarbon oxidizing bacterium previously designated Micrococcus cerificans, has been shown to sequester the hydrocarbon into intracytoplasmic pools as a result of growth on this substrate. In hydrocarbon grown cells, an intracytoplasmic membrane system was also observed along with a doubling of cellular phospholipids (Z). However, using conventional dehydration and embedding procedures in preparing thin sectioned material, the hydrocarbon is extracted from the cells. This may lead to structural distortion, consequently, the freeze-etch technique was applied to preserve the integrity of the cell.

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Bacterial-Mucosal Cell Junctional Complexes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100050731 ◽

1974 ◽

Vol 32 ◽

pp. 144-145

Author(s):

Roger C. Wagner

Keyword(s):

Intestinal Wall ◽

Rat Colon ◽

Mucosal Cell ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Mucosal Cells ◽

Mucosal Lining ◽

Degenerative Alterations ◽

Junctional Complexes ◽

Intestinal Mucosal Cells

Bacteria exhibit the ability to adhere to the apical surfaces of intestinal mucosal cells. These attachments either precede invasion of the intestinal wall by the bacteria with accompanying inflammation and degeneration of the mucosa or represent permanent anchoring sites where the bacteria never totally penetrate the mucosal cells.Endemic gram negative bacteria were found attached to the surface of mucosal cells lining the walls of crypts in the rat colon. The bacteria did not intrude deeper than 0.5 urn into the mucosal cells and no degenerative alterations were detectable in the mucosal lining.

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