Reaction–diffusion theory explains hypoxia and heterogeneous growth within microbial biofilms associated with chronic infections

Stewart, Philip S.; Zhang, Tianyu; Xu, Ruifang; Pitts, Betsey; Walters, Marshall C.; Roe, Frank L.; Kikhney, Judith; Moter, Annette

doi:10.1038/npjbiofilms.2016.12

Cited by 140 publications

(112 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In other words, the average growth rate of S. aureus at a depth of 1.5 mm was 41 times lower than the average growth rate near the nutrient-and oxygen-fed interface. Physiological heterogeneity is a well-established characteristic of biofilms (44) that derives from reaction-diffusion interactions on metabolic substrates (42,45). The S. aureus-agarose biofilm system displayed the antibiotic tolerance that is characteristic of microbial biofilms (46).…”

Section: Discussionmentioning

confidence: 99%

Gel-Entrapped Staphylococcus aureus Bacteria as Models of Biofilm Infection Exhibit Growth in Dense Aggregates, Oxygen Limitation, Antibiotic Tolerance, and Heterogeneous Gene Expression

Pabst

Pitts

Lauchnor

et al. 2016

Antimicrob Agents Chemother

Self Cite

View full text Add to dashboard Cite

An experimental model that mimicked the structure and characteristics of in vivo biofilm infections, such as those occurring in the lung or in dermal wounds where no biomaterial surface is present, was developed. In these infections, microbial biofilm forms as cell aggregates interspersed in a layer of mucus or host matrix material. This structure was modeled by filling glass capillary tubes with an agarose gel that had been seeded with Staphylococcus aureus bacteria and then incubating the gel biofilm in medium for up to 30 h. Confocal microscopy showed that the bacteria formed in discrete pockets distributed throughout the gel matrix. These aggregates enlarged over time and also developed a size gradient, with the clusters being larger near the nutrientand oxygen-supplied interface and smaller at greater depths. Bacteria entrapped in gels for 24 h grew slowly (specific growth rate, 0.06 h ؊1 ) and were much less susceptible to oxacillin, minocycline, or ciprofloxacin than planktonic cells. Microelectrode measurements showed that the oxygen concentration decreased with depth into the gel biofilm, falling to values less than 3% of air saturation at depths of 500 m. An anaerobiosis-responsive green fluorescent protein reporter gene for lactate dehydrogenase was induced in the region of the gel where the measured oxygen concentrations were low, confirming biologically relevant hypoxia. These results show that the gel biofilm model captures key features of biofilm infection in mucus or compromised tissue: formation of dense, distinct aggregates, reduced specific growth rates, local hypoxia, and antibiotic tolerance.

show abstract

Section: Discussionmentioning

confidence: 99%

Gel-Entrapped Staphylococcus aureus Bacteria as Models of Biofilm Infection Exhibit Growth in Dense Aggregates, Oxygen Limitation, Antibiotic Tolerance, and Heterogeneous Gene Expression

Pabst

Pitts

Lauchnor

et al. 2016

Antimicrob Agents Chemother

Self Cite

View full text Add to dashboard Cite

show abstract

“…Since FISH‐probes hybridize ribosomal RNA, the signal intensity correlates to the ribosome content and consequently activity of the cells. This allows both visualization and identification of the microorganisms, and also provides information about their spatial distribution and activity in situ (Fig. ).…”

Section: Bacteriological Aspects Of Odri Studiesmentioning

confidence: 99%

Recommendations for design and conduct of preclinical in vivo studies of orthopedic device‐related infection

Moriarty

Harris

Mooney

et al. 2019

Journal Orthopaedic Research

Self Cite

View full text Add to dashboard Cite

Orthopedic device-related infection (ODRI), including both fracture-related infection (FRI) and periprosthetic joint infection (PJI), remain among the most challenging complications in orthopedic and musculoskeletal trauma surgery. ODRI has been convincingly shown to delay healing, worsen functional outcome and incur significant socio-economic costs. To address this clinical problem, ever more sophisticated technologies targeting the prevention and/or treatment of ODRI are being developed and tested in vitro and in vivo. Among the most commonly described innovations are antimicrobial-coated orthopedic devices, antimicrobial-loaded bone cements and void fillers, and dual osteo-inductive/antimicrobial biomaterials. Unfortunately, translation of these technologies to the clinic has been limited, at least partially due to the challenging and still evolving regulatory environment for antimicrobial drugdevice combination products, and a lack of clarity in the burden of proof required in preclinical studies. Preclinical in vivo testing (i.e. animal studies) represents a critical phase of the multidisciplinary effort to design, produce and reliably test both safety and efficacy of any new antimicrobial device. Nonetheless, current in vivo testing protocols, procedures, models, and assessments are highly disparate, irregularly conducted and reported, and without standardization and validation. The purpose of the present opinion piece is to discuss best practices in preclinical in vivo testing of antimicrobial interventions targeting ODRI. By sharing these experience-driven views, we aim to aid others in conducting such studies both for fundamental biomedical research, but also for regulatory and clinical evaluation.

show abstract

“…These result in heterogeneous growth patterns forming a complex structural and chemical landscape (3)(4)(5)49). In such in vitro biofilms, bacterial growth rate has been estimated to rapidly drop with distance from the biofilm surface reaching quasi-static growth at 40-50 lm depth (49,50). As illustrated in Fig.…”

Section: Growth and Biofilm Structurementioning

confidence: 99%

Microenvironmental characteristics and physiology of biofilms in chronic infections of CF patients are strongly affected by the host immune response

Jensen

Kolpen

Kragh

et al. 2017

APMIS

View full text Add to dashboard Cite

Jensen PØ, Kolpen M, Kragh KN, K€ uhl M. Microenvironmental characteristics and physiology of biofilms in chronic infections of CF patients are strongly affected by the host immune response. APMIS 2017; 125: 276-288.In vitro studies of Pseudomonas aeruginosa and other pathogenic bacteria in biofilm aggregates have yielded detailed insight into their potential growth modes and metabolic flexibility under exposure to gradients of substrate and electron acceptor. However, the growth pattern of P. aeruginosa in chronic lung infections of cystic fibrosis (CF) patients is very different from what is observed in vitro, for example, in biofilms grown in flow chambers. Dense in vitro biofilms of P. aeruginosa exhibit rapid O 2 depletion within <50-100 lm due to their own aerobic metabolism. In contrast, in vivo investigations show that P. aeruginosa persists in the chronically infected CF lung as relatively small cell aggregates that are surrounded by numerous PMNs, where the activity of PMNs is the major cause of O 2 depletion rendering the P. aeruginosa aggregates anoxic. High levels of nitrate and nitrite enable P. aeruginosa to persist fueled by denitrification in the PMN-surrounded biofilm aggregates. This configuration creates a potentially long-term stable ecological niche for P. aeruginosa in the CF lung, which is largely governed by slow growth and anaerobic metabolism and enables persistence and resilience of this pathogen even under the recurring aggressive antimicrobial treatments of CF patients. As similar slow growth of other CF pathogens has recently been observed in endobronchial secretions, there is now a clear need for better in vitro models that simulate such in vivo growth patterns and anoxic microenvironments in order to help unravel the efficiency of existing or new antimicrobials targeting anaerobic metabolism in P. aeruginosa and other CF pathogens. We also advocate that host immune responses such as PMN-driven O 2 depletion play a central role in the formation of anoxic microniches governing bacterial persistence in other chronic infections such as chronic wounds.

show abstract

Reaction–diffusion theory explains hypoxia and heterogeneous growth within microbial biofilms associated with chronic infections

Cited by 140 publications

References 50 publications

Gel-Entrapped Staphylococcus aureus Bacteria as Models of Biofilm Infection Exhibit Growth in Dense Aggregates, Oxygen Limitation, Antibiotic Tolerance, and Heterogeneous Gene Expression

Gel-Entrapped Staphylococcus aureus Bacteria as Models of Biofilm Infection Exhibit Growth in Dense Aggregates, Oxygen Limitation, Antibiotic Tolerance, and Heterogeneous Gene Expression

Recommendations for design and conduct of preclinical in vivo studies of orthopedic device‐related infection

Microenvironmental characteristics and physiology of biofilms in chronic infections of CF patients are strongly affected by the host immune response

Contact Info

Product

Resources

About