2026 1st Seattle Japanese Research Community Date: Jan 31 (Sat) Venue: Fred Hutchinson Cancer Center

Event Report: From Micro-Evolution to Macro-Waves

This page reorganizes the January 31 event content for clarity and readability. Use the tabs below to switch between Naoya Nishiyama's talk (infectious diseases / bacterial evolution) and Takuya Miyashita's talk (tsunami engineering / disaster mitigation).

Naoya Nishiyama (Infectious Disease Physician / Researcher)

Theme: Pneumonia, Pseudomonas Evolution, and the Fight Against Antimicrobial Resistance

This talk connected frontline clinical infectious disease practice with basic microbiology research, spanning from real pneumonia cases to adaptive evolution in Pseudomonas. It reframed the everyday question, “Why must we complete an antibiotic course?” through the lens of AMR and evolutionary biology.

🩺 Clinical Entry: Pneumonia Is a Close and Serious Risk

Using a case of a 30-year-old man, Nishiyama showed how CT can reveal pneumonia not clearly visible on plain X-ray, and emphasized that even younger adults can worsen when immune balance is disrupted.

Why Finishing Antibiotics Matters

Prevent relapse: stopping early can allow infection to rebound.
Reduce resistance pressure: incomplete courses can promote AMR selection.

Multi-Layer Human Defense System

Invading microbes are removed step by step through the following defense layers.

1. Nose/Mouth (Physical Barrier)

Traps foreign particles at the entry and lowers lower-airway invasion.

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2. Pharynx/Tonsils (Capture)

Lymphoid tissues in the throat capture microbes and provide local defense.

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3. Bronchi (Ciliary Clearance)

Mucus and ciliary motion move foreign material upward, limiting lung reach.

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4. Alveoli (Macrophages)

Immune cells phagocytose and process microbes that reach deep lung tissue.

Smoking particularly impairs ciliary clearance, increasing pneumonia risk.

Evolutionary Trade-Offs in Pseudomonas

Comparison of Wild-Type (Offensive) vs Adapted-Type (Defensive)

Wild Type

Highly motile and toxin-producing, dominant in early acute infection but more visible to host immunity and antibiotics.

During adaptation, bacteria reduce motility and toxin output while strengthening resistance and biofilm formation for long-term persistence.

Details

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Naoya Nishiyama (Infectious Disease Physician / Researcher)
Theme: Pneumonia, Pseudomonas Evolution, and the Fight Against AMR
1. Background and Career Path
Nishiyama graduated from the University of the Ryukyus School of Medicine and spent about ten years in clinical practice.
His specialty is infectious diseases, with practical work in infection control and antimicrobial stewardship in hospital settings.
His team monitored resistant organisms, reviewed antibiotic prescriptions, and intervened when treatment optimization was needed.
He is currently conducting basic research at the University of Washington Department of Microbiology, focusing on Pseudomonas evolution.

2. Pneumonia as a Real-World Threat
A clinical case of a 30-year-old man with fever and chest pain was presented.
Plain X-ray findings were subtle, but CT clearly identified left-sided pneumonia.
This illustrated that even younger, generally healthy adults can develop serious pneumonia when host defense is disrupted.
In Japan, pneumonia remains one of the major causes of death, despite changes in reporting categories over time.

Why should patients finish prescribed antibiotics?
Common question: “Can I stop once symptoms improve?”
Nishiyama’s answer was clear: no.
Risk of relapse: stopping too early can leave viable bacteria and trigger recurrence.
Risk of resistance: incomplete treatment can increase selective pressure for antimicrobial resistance.
Following dose and duration is important for both personal recovery and public AMR control.

3. Pneumococcus and Multi-Layer Host Defense
The most common cause of community-acquired bacterial pneumonia is Streptococcus pneumoniae.
Pneumococcus has a capsule that helps it evade phagocytosis and increases virulence.
The classic Griffith experiment was discussed as an example of bacterial adaptation through genetic transformation.

Multi-layer human defense system:
Physical barrier: nasal hair and saliva reduce microbial entry.
Tonsillar tissue: lymphoid structures in the throat capture invading organisms.
Ciliary clearance: bronchial cilia and mucus transport particles upward toward the mouth.
Alveolar macrophages: immune cells in distal lungs phagocytose bacteria that pass earlier barriers.

Pneumonia develops when this defense system weakens relative to pathogen pressure.
Smoking is a key risk factor because it impairs ciliary function and raises pneumonia risk.

4. Pseudomonas as a Difficult Nosocomial Pathogen
Pseudomonas aeruginosa is widely present in environmental water and soil.
It is often low-virulence in healthy hosts, but can become life-threatening in vulnerable patients.
It is intrinsically difficult to treat because many antibiotics are less effective.
It also thrives in moist environments and can colonize medical devices.

Why does it spread in healthcare settings?
Poorly maintained humidifiers or nebulizers can become reservoirs.
The organism forms biofilms on devices such as ventilator tubing and catheters.
Inside biofilm communities, bacteria are more protected from both antibiotics and host immunity.

5. Evolutionary Adaptation in Chronic Infection
Early or environmental strains are often motile and toxin-producing (“wild type” behavior).
During chronic airway disease, long-term lung colonization selects for adapted phenotypes.
These adapted populations tend to show:
Increased diversity within one patient.
Reduced motility.
Reduced toxin production.
Slower growth.
Enhanced biofilm/mucoid behavior.

This shift reflects strong in-lung environmental stress:
immune pressure, antimicrobial exposure, inflammation-related tissue damage, oxygen limitation, and nutrient limitation.
In such conditions, strains with lower offensive traits but stronger persistence traits are favored by natural selection.

Nishiyama’s research asks why slower-growing, less overtly virulent phenotypes are repeatedly selected in lungs.
Approaches include experimental evolution, genome analysis, and game-theory-based interpretation.
Understanding this process may enable therapies that not only kill bacteria, but also constrain maladaptive evolution and chronicity.

Takuya Miyashita (Coastal Engineering / Tsunami Research)

Theme: Tsunami Mechanisms and the Future of Disaster Mitigation from an Engineering Perspective

Starting from field surveys after the Noto Peninsula earthquake, Miyashita explained tsunami propagation physics (c = √gh) and probabilistic hazard/risk assessment. The emphasis was not “perfect prediction,” but practical uncertainty management for loss reduction.

🌊 Tsunami Speed Calculator (c = √gh)

Tsunami phase speed increases with water depth. As the wave enters shallow water, speed decreases and energy is converted into greater wave height nearshore.

Depth 4000m

Coast Open Ocean

Computed Speed

713 km/h

Analogy

✈️ Jet Aircraft

High Waves, Tsunami, and Storm Surge

High Waves (Wind Waves)

Generated by strong wind. Surface-particle orbital motion dominates, and coastal overtopping/erosion risk rises in storms.

Tsunami (Long Wave)

A long wave that displaces the full water column, often from earthquakes. Speed scales with depth (c = √gh), with shoaling amplification near coastlines.

Storm Surge

A broad sea-level rise driven by low pressure and wind setup during storms. Compound impact with high waves can significantly increase inundation.

Japan's Two-Level Mitigation Framework (L1 / L2)

Level 1 Tsunami (Higher Frequency)

Protect communities and assets with hard infrastructure (e.g., seawalls).

Level 2 Tsunami (Maximum Class)

Hard infrastructure alone is insufficient; survival depends on evacuation plans, routes, and hazard communication.

Multi-Hazard Perspective

Risk evaluation must integrate tsunami with high waves, storm surge, fire, and infrastructure disruption.

Details

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Takuya Miyashita (Coastal Engineering / Tsunami Research)
Theme: Tsunami Mechanisms and the Future of Disaster Mitigation from an Engineering Perspective
1. Background and Noto Peninsula Earthquake Field Survey
Miyashita is affiliated with the Disaster Prevention Research Institute, Kyoto University, and has worked as a visiting researcher with NOAA and the University of Washington.
His core field is coastal engineering, particularly risk assessment for tsunami and storm surge hazards.
He described rapid post-event survey work after the January 1, 2024 Noto Peninsula earthquake, including measurements of tsunami trace heights.

Researcher dilemma and role:
Tsunami traces fade quickly, so early field surveys are scientifically critical.
At the same time, researchers must be mindful of local communities under severe stress in rescue and recovery phases.
Survey timing therefore requires balancing urgency with social and logistical realities.

Field observations:
Road disruption and major uplift were observed in affected areas.
He also highlighted the speed and effectiveness of emergency road restoration by local civil engineering teams.

2. Physics of Tsunami: High Waves, Tsunami, and Storm Surge
In coastal hazard science, these three should be clearly distinguished.

High waves (wind waves):
Generated by wind forcing at the sea surface.
Water-particle motion is concentrated near the surface and wavelengths are relatively short.
They can cause overtopping and erosion under storm conditions.

Tsunami (long wave):
Generated by large-scale water-column displacement, often due to earthquakes.
Typical wavelengths are much longer, from kilometers to hundreds of kilometers.
They are treated as shallow-water long waves in many engineering applications.

Storm surge:
A broad sea-level rise driven by low pressure and wind setup.
When combined with high waves, inundation impacts can become more severe.

Tsunami speed and propagation:
Tsunami phase speed can be approximated by c = √(gh), where g is gravity and h is water depth.
This means deeper water gives faster propagation.
In deep ocean, speed can approach jet-aircraft scale while wave height may remain modest.
Near coast, depth decreases, speed drops, and shoaling can amplify wave height significantly.
Arrival time is often estimated reasonably once source location is known, but real-time height prediction remains harder due to source complexity.

3. Simulation and Uncertainty
A key research focus is how to treat uncertainty in practical hazard analysis.
Numerical models based on long-wave equations are useful, but real environments are not perfectly modeled.
Unresolved processes include structural damage, debris, sediment effects (multiphase behavior), and small-scale turbulence.
Therefore, modern practice relies on probabilistic approaches rather than a single deterministic scenario.
Thousands of plausible earthquake scenarios are evaluated to estimate hazard and risk ranges.

4. Japan's Two-Level Tsunami Mitigation Framework
Future large events such as Nankai Trough earthquakes are a major concern in Japan.
Historical records and geological studies indicate recurrence, but exact timing and scale are uncertain.
Japan distinguishes two planning levels:

Level 1 tsunami (more frequent):
Order of decades to about a century.
Mitigation focus: protect communities and assets with hard infrastructure.

Level 2 tsunami (maximum class):
Rare but potentially catastrophic.
Mitigation focus: life safety through evacuation planning, routes, hazard maps, and preparedness.

Miyashita emphasized that hazard occurrence itself cannot be controlled.
The realistic objective is damage reduction through integrated science and policy.

5. Q&A Themes and Multi-Hazard Perspective
Discussion topics included shelter safety under compound hazards, including tsunami-related fire.
Questions also addressed regional differences in seismic-tsunami risk, including the Cascadia subduction zone on the U.S. West Coast.
Risk differs among subduction systems due to factors such as convergence rate, 3D plate geometry, and thermal structure.

On hazard-map reliability:
He noted that real events can still exceed or differ from representative scenarios.
Even so, hazard maps remain valuable for identifying relatively higher-risk areas and informing long-term planning.

Conclusion:
No place is absolutely risk-free.
However, understanding local hazard characteristics, infrastructure fragility, and evacuation constraints can substantially reduce societal impact.
Preparedness at both individual and community levels remains essential.