Chapter 14 Principles of Disease and Epidemiology

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Ko lectures slides 2016 1

Chapter 14 Principles of Disease

and Epidemiology

Microbiology, An Introduction Tortora, Funke, Case

Instructor: Yuan-Tih Ko, Ph.D.

Food Science Dept. NTOU



Disease (疾病)

• Pathogen (致病菌) Disease-causing microorganism

• Pathology (病理學) Study of disease

• Etiology (病因學) Study of the cause of a disease

• Pathogenesis(發病) Development of disease

• Effect (作用) Structural and functional changes

of disease

Epidemiology (流行病學) Study when and where disease occur and how they are transmitted in populations.

Definitions (定義)



Pathology (病理學)

• Pathology is the study of disease

• (pathos = suffering; logos = science)

• Pathology is concerned with

• (1) the etiology (cause),

• (2) pathogenesis (development), and

• (3) effects (structural and functional changes) of disease.

• 病理學是關注於(探討)與病因學、發病機制、對身體結構與功能改變

之效應(作用, 影響)的科學



Infection vs. Disease (兩者不同)

• Infection (感染) Colonization (invasion) of the body by pathogens

• Disease (疾病) An abnormal state in which the body is not functionally normally

• An infection may exist in the absence of detectable disease.(感染時可能沒有)

• The body may be infected with the virus that cause AIDS, but there may be no symptom of disease.

• The presence of a particular type of microb in a part of the body where it is not normally found is also called an infection. (菌存在於異常部位)



Microbiota

(微生物相 or 微生物群)

瞭解微生物和健康人體的關係



• Transient microbiota (短暫 or過渡微生物相) may be present for days, weeks, or months and then disappear

• Normal microbiota (human microbiome, 俗稱 normal flora) (正常微生物群/相) permanently colonize the host

Microbiota 微生物相分類



Normal Microbiota (正常微生物相)—人類出生之第一菌是?

• Animals, including humans, are usually germ-free in utero (子宮).

• Microorganisms begin colonization in and on the surface of the body soon after birth

• Just before a woman gives birth, lactobacilli in mother’s vagina (陰道)multiply rapidly. It becomes the newborne’s first contact and become predominant in baby’s intestine.

• After birth, E. coli then inhabit the large intestine



• Microorganisms that establish permanent (永久) colonies (聚落) inside or on the body without producing disease make up the normal microbiota.

• A typical human body contains 1 x 1013 body cells, yet harbors an estimated 1 x 1014 bacterial cells.

正常微生物相數目是人體細胞數10倍

• The Human Microbiome Project (HMP): 2007開始分析住在人體表面及內部之微生物聚落, 了解其與人類健康與疾病的關係

Normal Microbiota-2 正常微生物相數目?



•身體不同區域的代表性正常菌相



鼻腔表皮細胞上的金黃色葡球菌



胃內壁上的幽門桿菌



小腸內的菌相



正常微生物相在人類宿主的位置-1

• Locations of normal microbiota

on and in the human body



正常微生物相在人類宿主的位置-2

• Locations of normal microbiota

on and in the human body



(1)皮膚上正常菌相已克服角質, 酸性,乾燥而存在

初油酸桿菌 , 表皮葡萄球菌, 金黃色葡萄球菌, 棒狀桿菌,

--, 念珠菌

Table 14-1 Keratin, low pH, low moisture content



(結膜)

類白喉桿菌

眼淚, 眨眼 as barrier

(2) 眼結膜正常菌相原和皮膚相同, 但眼淚, 眨眼抑制他們聚集

Propionibacterium, Corynebacterium, Streptococci, Micrococcus

初油酸桿菌棒狀桿菌雙球菌微球菌



(3) 上呼吸道系統的正常菌相多致病菌

鼻: 葡球菌, 類白喉菌

喉:葡球菌, 類白喉菌, 肺炎雙球菌, 嗜血桿菌, 雙球菌



(4) 口腔內的活動影響正常菌相

雙球菌,

乳酸菌, 放線菌,類桿菌,

梭形桿菌, 密螺旋體,

棒狀桿菌, 念珠菌



(5) 大腸的正常菌相數目最多

類桿菌,梭形桿菌,乳酸菌,

腸球菌, 比菲德桿菌, 大腸菌,

腸桿菌, 檸檬酸桿菌, 變形桿菌,

克雷白氏桿菌, 志賀氏桿菌,念珠菌



(6) 泌尿系統菌相耐酸環境

陰道滴蟲

表皮葡萄球菌

腸球菌,乳酸菌,

類白喉, 假單胞桿菌

克雷白氏桿菌, 變形桿菌

雙球菌,類桿菌,梭狀芽胞桿菌,

念珠菌



• >300 species in mouth (106/mL saliva)

• stomach and small intestine have few resident microorganisms

• No microbiota in liver

• Large numbers in large intestine, assist in degrading food and synthesizing vitamins including:

• Up to 40% of fecal mass is microbial cells (106/g feces)

• .

正常菌相比較



• Involves competition (競爭)among microbes

• (1) Compete for nutrients

• (2) Physical and chemical factors

• (3) Defense of the host, Mechanical factors

Germfree animals are unusually susceptible to infection and serious disease, also require more calories and vitamins than normal animals

影響正常菌相分佈與組成因子



• Secretary and excretory products of cells

• Substance in the body fluid

• Dead cells

• Food in the gastrointestinal tract

(1) Compete for nutrients 競爭營養源



(2) Physical and chemical factors 物化因子

• Temperature

• pH

• Available oxygen

• Available carbon dioxide

• Salinity

• sunlight



(3) Defense of the host, Mechanical factors 宿主防禦性機械因子

• Chewing action of teeth

• Tongue movement

• dislodge microbe attached to tooth and mucosal surface

• Saliva flow

• Digestive secretion

• Muscular movement (throat, esophagus, stomach, intestine)

• remove attached microbe

• Flushing and action of urine

• remove unattached microbe

• Mucus trap microbe

• Cilia propel toward the throat



Relationship between Microbiota and the Host

正常菌相和宿主的關係



• Symbiosis (共生)

• the relationship between normal microbiota and the host

• “Symbiont” (共生菌)

• Microbial antagonism (頡抗).

• the normal microbiota can prevent pathogens from causing an infection

正常菌相和宿主的關係



微生物之間頡抗作用平衡得以保持健康

Microbial Antagonism

Normal microbiota protect the host against colonization

by potentially pathogenic microbe

Compete for nutrient, produce substance harmful to

the invading microbe, and affect pH and oxygen.

When the balance upset, disease can result.



• Normal microbiota protect the host by:

• occupying niches that pathogens might occupy

• producing acids

• producing bacteriocins (細菌素), an antimicrobial peptide produced by bacteria that kills other bacteria

Normal microbiota protect the host from pathogen 正常菌相保護宿主如何免於病菌感染 (頡抗)



正常菌相彼此頡抗例子

• Normal bacterial microbiota maintains pH in vagina 3.5-4.5 which inhibit growth of C. albicans. Antibiotic therapy, excessive douching, deodorant killed normal bacteria and revert pH to neutral vaginitis (陰道炎)

• Streptococci in mouth produce compound to inhibit most G(+) and G(-) cocci

• E. coli in large intestine produce bacteriocin (細菌素) to prevent growth of pathogens (Salmonella and Shigella)

• Microbiota in large intestine inhibit Clostridium difficiles. Following antibiotic therapy, this microbe cause diarrhea and fatal colitis ( 結腸炎)



Symbiosis (正常菌相和宿主共生的關係)



• The normal microbiota and the host exist in symbiosis (living together).

• Three types are

• (1) commensalism (片利共生) one organism benefits and the other is unaffected),

• (2) mutualism (both organisms benefit互利共生), and

• (3) parasitism (one organism benefits and one is harmed寄生).--pathogen

Three types of Symbiosis (三種共生關係)



Fig 14.2 Symbiosis

SYMBIOSIS



共生關係例子-片利共生

• Commensalism (片利共生) :

• Corynebacteria (棒狀桿菌)inhabit the surface of the eye

• Saprophytic mycobacteria (腐生性分枝桿菌) inhabit the ear and external genitals

• Some bacteria live on secretions and sloughed-off cells



(片利共生) :

共生關係例子



共生關係例子

Mutualism (互利共生):

E. coli in the large intestine synthesize Vit K

and Vit B. These vitamins are absorbed into

the blood stream and distributed for use by

body cells.

Parasitism (寄生):

Many disease-causing bacteria



(互利共生)



(寄生):



益生菌是共生關係

• Probiotics (pro = for, bios = life 益生菌)

• are live microbial cultures applied to or ingested into the body that are intended to exert a beneficial effect on health

• Probiotics may be administered with prebiotics (益生素), which are chemicals that selectively promote the growth of beneficial bacteria



乳酸菌群是益生菌

• LAB (lactic acid bacteria) such as Lactobacillus acidophilus and Bifidobacterium bifidum can alleviate diarrhea and prevent colonization by S. enterica and Staphylococcus aureus infection.

(嗜酸乳桿菌和雙歧桿菌可以減輕腹瀉和

防止由沙門氏菌和金黃色葡萄球菌感染的聚居。)

• Vaginal infection occur when normal LAB in vagina is disrupted…... (陰道內正常的LAB被打亂, 發生陰道感染)

基因重組乳酸菌治療應用價值:

Use of recombinant LAB to deliver vaccine, antimicrobials, and digestive enzymes, and their therapeutic value, risk assessment is under research development.



Opportunistic organisms

(共生關係中的伺機性生物)



Opportunistic Organisms -- 伺機性生物

• Opportunists (opportunistic pathogens伺機性病菌) do not cause disease under normal conditions but cause disease under special conditions.

• Normal microbiota symbiont E. coli –在不當位置

• gain access in urinary bladder, lungs, spinal cord or wounds, 引起 urinary infection, pulmonary infection, meningitis (腦膜炎), abscesses (膿瘡)

• Pneumocystis peumonia (肺囊蟲肺炎) cause secondary infection – 二次感染

• Infect AIDS immuno-compromised patient

• Present in and on the body or external environment in large amount



伺機性生物例子

• Many people carry pathogens but may not cause disease in those people

(攜帶病原菌但可能不致引起疾病)

• Echovirus (人類腸道細胞致病性病毒)cause intestinal disease

• Adenovirus (腺病毒)cause respiratory disease

• Neisseria meningitidis (腦膜炎雙球菌) reside in the respiratory tract and inflames the coverings of brain and spinal cord

• Streptococcus pneumonia (肺炎雙球菌)reside in nose and throat, cause pneumonia



Cooperation Among Microorganisms

微生物互助關係

導致致病的例子: 微生物引發periodontal disease(牙週病)and gingivitis (牙齦炎) Ch.25



• In some situations, one microorganism makes it possible for another to cause a disease or to produce more severe symptoms; this is called cooperation.

• 例子 :

• Over 700 species of bacteria have been isolated from teeth

• oral streptococci in teeth, pathogens cause periodontal disease (牙週病)and gingivitis (牙齦炎)have receptors for it, not on teeth

微生物互助關係導致致病的例子



Initiation of decay in the mouth (蛀牙開端)

• Streptococcus mutans G(+) Rod

cariogenic (caries-causing, 致蛀牙性的)

e.g. germ-free animal do not develop caries

• mouth sucrose

• Hydrolyze sucrose into glucose + fructose

• form dextran from glucose by glucosyltransferase

• Ferment into lactic acid from fructose.

• Accumulate bacteria and dextran plaque (牙斑) soften enamel



• The dextran capsule is produced when the S. mutans grow on sucrose.

• A sticky capsule enables the bacteria to adhere to teeth, forming dental plaque.

• These bacteria and others that become trapped in the dextran capsule. Acid produced during carbohydrate fermentation destroys tooth enamel at the site of the plaque.

• Gram-positive rods (S. mutans) and filamentous bacteria (Actinomyces) can penetrate into dentin and pulp.



Tooth Decay- Progressive decay

Figure 25.4

Dental caries begin when tooth enamel and dentin are eroded and the

pulp is exposed to bacterial infection.

牙齒: 琺瑯質, 象牙質, 瓍質, 骨, 根



Dental caries prevention (蛀牙預防)

• Carbohydrates such as

• starch

• mannitol

• sorbitol

are not used by cariogenic (致齲性) bacteria to produce dextran and do not promote tooth decay.

• Caries are prevented

• by restricting ingestion of sucrose (餐中間吃糖更易)

• by physical removal of plaque

• a vaccine against S. mutans is theoretically possible



• 如何瞭解 “感染性疾病”引起的原因?



The Etiology of Infectious Disease (感染性疾病之病因學– 柯霍假設)



Koch’s Postulates –德國醫生1877建立

• 1. Koch’s postulates are a method for establishing that specific microbes cause specific diseases.

• 2. Koch’s postulates have the following requirements:

(i) the same pathogen must be present in every case of the disease.

(ii) the pathogen must be isolated in pure culture.

(iii) the pathogen isolated from pure culture must cause the same disease in a healthy, susceptible laboratory animal.

(iv) the pathogen must be reisolated from the inoculated laboratory animal.



• Koch's Postulates are used to prove the cause of an infectious disease.

Koch’s Postulates-1

Figure 14.3.1



Koch’s Postulates-2

Figure 14.3.2

• Koch's Postulates are used to prove the cause of an infectious disease.



Koch’s Postulates –提供流行病學探討架構

• 德國醫生1877建立

• 設計一連串實驗步驟，推定出特定疾病與特定微生物，直接相關

• 決定出大部份細菌性疾病之 causative agent

• Demonstrate anthrax (炭疽病)與 Bacillus anthrax 有關

• 存在疾病動物血液中，健康動物則無

• Biological weapon



感染性疾病的病因 (Etiology)

病因已清楚

• polio (小兒麻痺)

• Lyme disease (萊姆病)

• tuberculosis (肺結核)

未知病因

• Alzheimer’s disease (阿茲罕默氏病)

• ulcers (潰瘍)

• Helicobacter pylori (幽門螺桿菌)

• Different from genetic disease, degenerative (變性) disease

• hemophilia (血友病) etc. 感染性疾病和遺傳性、變性疾病不同



Koch’s Postulates 的例外

• 1. Koch’s postulates are modified to establish etiologies of diseases caused by viruses and some bacteria, which cannot be grown on artificial media.

• 2. Some diseases, such as tetanus (破傷風), have unequivocal signs and symptoms.

• 3. Some diseases, such as pneumonia (肺炎)and nephritis(腎炎), may be caused by a variety of microbes.

• 4. Some pathogens, such as S. pyogenes (化膿鏈球菌), cause several different diseases.

• 5. Certain pathogens, such as HIV, cause disease in humans only.



Classifying Infectious Diseases (感染病的分類)

判別方式分類方式



Classifying Infectious Diseases-1

• Symptom (症狀-病人) A subjective(主觀) change in body

function that is felt by a patient as a result of disease

Pain (疼痛), malaise (不適)

• Sign (病徵-醫生診斷) A objective (客觀) change in a body

that the physician can be measured or observed

as a result of disease.

Lesions (損傷), swelling, fever, paralysis

• Syndrome (症候) A specific group of signs and symptoms that accompany a disease.



Classifying Infectious Diseases-2

• Communicable disease (可傳染) Any disease that spread from one host to another.

(chickenpox天花, measles麻疹, genital herpes龜頭泡疹, typhoid fever傷寒, tuberculosis肺結核)

• Contagious disease (易蔓延的、接觸性傳染的) A disease that is easily spread from one host to another.

• Noncommunicable disease (非傳染性) A disease that is not transmitted from one host to another. (by 擦傷, 傷口)

如由Clostridium tetani 引起的tetanus (破傷風)



Occurrence of Disease

•is reported by incidence (number of people contracting the disease) and prevalence (number of cases at a particular time).

•藉由發生率與流行率報告一種疾病的出現



• Incidence (發生率) Fraction of a population that contracts a disease during a specific time. As an indicator of the spread of a disease

在特定時段擴散指標, 新病例

• Prevalence (流行率) Fraction of a population having a specific disease at a given time.

It indicates how serious and how long

a disease affect a population指示影

響族群嚴重性和影響時間, 新舊病例都算

• For example, the incidence of AIDS in the US in 1999 was 45,000 while the prevalence in that same year was estimated o be about 700,000.

Occurrence of Disease-疾病的出現



Diseases are classified by frequency of occurrence

• Sporadic disease Disease that occurs

(零星性) occasionally in a population.

• Endemic disease Disease constantly present in a

(地方性) population-季節性感冒

• Epidemic disease Disease acquired by many

(流行性) hosts in a given area in a short time.

• Pandemic disease Worldwide epidemic.

(世界流行性, 大流行)

• Herd immunity Immunity in most of a population.

(群免疫力)


PowerPoint® Lecture Slide Presentation prepared by Christine L. Case

Microbiology

B.E Pruitt & Jane J. Stein

AN INTRODUCTION EIGHTH EDITION

TORTORA • FUNKE • CASE

Epidemiology: Occurrence of Disease

[insert Epidemiology_Occurrence.jpg]

file:///D:/Microbiology/EpidemiologyOccurrence/epidemiology_occurrence.html



感染病的分類--

嚴重性/持續時間、程度



Severity or Duration, and Extent of a Disease

• Acute, chronic, subacute, latent (持續時間分類)

• Extent of host involvement (宿主參與程度情形分類):

• Local infection (局部性) affect small area

• Systematic infection (系統性) spread throughout the body

• Primary infection (主) acute infection that causes the initial illness

• Secondary infection(二次) opportunistic infection occur after the host is weakened from a primary infection

• Subclinical infection(次臨床性) infection does not cause any (inapparent infection) signs of disease in host



• Acute disease Symptoms develop rapidly

急性 (e.g. influenza 流感)

• Chronic disease Disease develops slowly

慢性 (e.g. infectious mononucleosis, tuberculosis肺結核, hepatitis B)

• Subacute disease Symptoms between acute and

次急性 chronic (e.g. sclerosing parencephalitis)

• Latent disease Disease with a period of no

潛伏性 symptoms when the patient is inactive (e.g. shingles帶狀皰疹)

感染性疾病以持續性分類



• Local infection Pathogens limited to a small area (局部感染) of the body (燙傷, 膿瘡)

• Systemic infection An infection throughout the body

(系統性感染) (痲疹由血液、淋巴散佈)

• Focal infection Systemic infection that began as

(局部焦點感染) a local infection (由血液、淋巴散佈

到身體特定區域如牙齒、扁桃腺 )

感染疾病以程度分類-1



Bacteremia (菌血症 ) Bacteria in the blood

Septicemia (敗血症 ) Growth of bacteria in the blood

Toxemia (毒血症 ) Toxins in the blood

Viremia (病毒血症 ) Viruses in the blood

感染宿主的程度引發Sepsis (敗血)



• The state of host resistance also determines the extent of infection

• Primary infection (主感染): acute infection that causes the initial illness

• Secondary infection (二次感染): 2nd infection of the skin and respiratory tract are more dangerous than primary infection. Pneumocystis pneumonia (肺囊蟲肺炎) after AIDS, streptococcal bronchopneumonia (支氣管肺炎鏈球菌) after influenza

• Subclinical disease (次臨床): poliovirus (脊髓灰質炎病毒) and hepatitis A can be carried by people who never develop the disease

感染疾病以程度分類-2



Patterns of Disease (疾病模式) Predisposing Factors (前置因子)

• A predisposing factor is one that makes the body more susceptible to disease or alters the course of a disease.

使身體更容易受到疾病入侵或改變疾病過程的因子

• Examples include gender, climate, age, and level of fatigue and nutrition.



使身體更容易受到疾病入侵或改變疾病過程的因子

• Gender (性別)

• Short urethra that infect urinary tract infection in females

• Pneumonia and meningitis in male

• Inherited traits such as the sickle-cell gene

• Climate and weather

• Fatigue (疲勞)

• Age

• Lifestyle

• Chemotherapy

• Nutrition, occupation, emotional disturbance.

Predisposing Factors (前置因子)



The Development of Disease (疾病的發展)

• 1. The incubation (潛伏)period is the time interval between the initial infection and the first appearance of signs and symptoms.

• 2. The prodromal (前趨症狀) period is characterized by the appearance of the first mild signs and symptoms.

• 3. During the period of illness (生病), the disease is at its height and all disease signs and symptoms are present.

• 4. During the period of decline (衰退), the signs and symptoms decrease.<24 hrs to several days. Patients’ vulnerable to secondary infection

• 5. During the period of convalescence (康復), the body returns to its prediseased state, and health is restored.



The Stages of a Disease 疾病發展階段



潛伏期 (incubation)時間決定因素

• The time of incubation depends on

• The specific microbes involved

• Its virulence (毒力degree of pathogenicity)

• The number of infecting microbes

• The resistance of the host



• Period of illness exhibit overt symptoms and signs

• Fever, chill, muscle pain, photophobia, sore throat, lymphadenopathy, gastrointestinal disturbance

• The WBC increase or decrease

• The patient’s immune response and defense overcome or died

生病期 (ill) 有症狀與病徵



• The Spread of Infection

• The source of pathogens (reservoir, 儲主)

• How diseases are transmitted (傳染)

感染源散佈方式



• Reservoirs of infection are continual sources of infection.

•Human

•Animal

•Nonliving

Reservoirs of Infection (感染的儲主)-1



• Human —

• People who have a disease or are carriers (帶源者) of pathogenic microorganisms are human reservoirs of infection.

如 AIDS, gonorrhea(淋病), diphtheria(白喉), typhoid fever (傷寒)

• Carriers may have inapparent infections or latent diseases

帶源者可能有不顯性感染或潛伏的疾病




• Animal —

• Rabies (狂犬), Lyme disease (萊姆病)

• Zoonoses (zo a ’noses)人畜共通傳染病

• are diseases in wild and domestic animals that can be transmitted to humans

• Some zoonoses may be transmitted to humans

.

Reservoirs of Infection (感染的儲主) -2



• Nonliving —

• Botulism (肉毒中毒), tetanus (破傷風), cholera (霍亂),

trichinosis (旋毛蟲病)

• Soil (fungi, feces), water, food (improper stored)




Zoonoses-1 (人畜共通傳染病)

• Diseases that occur primarily in wild and domestic animals that can transmitted to human

• About 150 zoonoses are known

• By direct contact with infected animals

• By direct contact with domestic pet waste

• By contamination of food and water

• By air from contaminated hides, fur or feathers

• By consuming infected animals

• By insect vector



Zoonoses-2



-3



Zoonoses-4

蠕蟲



Transmission of Disease (疾病的傳播)



• Contact Direct, indirect, droplet (接觸性傳播)

• Vehicle Transmission by an inanimate reservoir

(媒介物傳播) (food, water, air)

• PM2.5 空氣污染

• Vectors Arthropods, especially fleas, ticks, and

(帶菌者傳播) mosquitoes

• Mechanical Arthropod carries pathogen on feet

• Biological Pathogen reproduces in vector

Transmission of Disease



Contact transmission-接觸性傳播方式

• Direct (直接) Requires close association between infected and susceptible host

• touching, kissing, sexual intercourse

• Viral respiratory tract disease, staphylococal, hep A, measles, scarlet fever, sex disease, pathogens

• Indirect (間接) Spread by fomites (病媒)

• Tissues, handkerchief, towels, bedding, diaper, drinking cup, toy, money, syringes,

• AIDS, hepB, tetanus

• Droplet (液滴) Transmission via airborne droplets



Transmission by direct contact (直接接觸性傳播)



手套、口罩、面罩避免直接接觸性感染



Indirect contact (間接接觸性傳播)

fomites (病媒)



Droplet transmission (液滴接觸性傳播)



• 20,000 droplets in one sneeze

• Influenza, pneumonia, pertussis (whooping cough)



Transmission by vehicle – (媒介物傳播)

Figure 14.6b, c

• By a medium (介質) such as water, food, air, blood, body fluid, drug

(由水、空氣、食物、血液、體液為介質之非動物性傳播)

• Waterborne transmission

• Foodborne transmission

• Airborne transmission



Waterborne transmission



Foodborne transmission



Airborne transmission



Mechanical transmission-Vectors - 帶菌者傳播

• By arthropods, animals, insect (flea, tick, mosquito)

• (1) Mechanical transmission- insect feet, house fly, contact food, swallowed, feces

• (2) Biological transmission- more complex; bite, blood, reproduce, pathogens, parasite, protozoan



Mechanical transmission-Vectors Figure 14.8 Mechanical transmission.



Microbiology



TORTORA • FUNKE • CASE Epidemiology: Transmission

[insert Epidemiology_Transmission.jpg]

file:///D:/Microbiology/EpidemiologyTransmission/epidemiology_transmission.html



Nosocomial (Hospital-Acquired) Infections (院內感染)



• Are acquired as a result of a hospital stay

• 5-15% of all hospital patients acquire nosocomial infections

• 2 million /yr in US, 100,000 die, 4th leading course of death

Nosocomial (Hospital-Acquired) Infections

(院內感染)



Factors for nosocomial infection (院內感染)



Compromised host (妥協的宿主)

• One whose resistance to infection is impaired by disease, therapy, or burns.

• Two conditions:

• (1) by broken skin or mucous membrane,

• (2) a suppressed system.

• Burns, surgical wounds, trauma, injections, invasive diagnostic procedure, ventilators, intravenous therapy, urinary catheters

• Administering anesthesia

• Drugs, radiation therapy, steroid therapy, burns, diabetes, leukemia, kidney disease, stress, and malnutrition can adversely affect the action of T and b lymphocytes and compromise the hosts.

• Table 14.5



醫院中的微生物引起感染

• Certain normal microbiota of the human body are opportunistic and present a particularly strong danger to hospital patients.

• Most of the microbes that cause nosocomial infections do not cause disease in healthy people but are pathogenic only for individuals whose defenses have been weakened by illness or therapy.

• Table 14.4

• Antibiotic resistance in nosocomial infection is a major concern.

• R-factors recombine, new and multiple resistance factors are produced

• If disease, surgery, or trauma (會留下永久性損傷的休克) has weakened the host’s defense, secondary infections may be difficult to treat.



(截肢)

(尿道)

(手術)

(尿導管)



(下呼吸道感染)

(菌血症)

(靜脈導管)



Relative frequency of nosocomial infections

(院內感染機會)



Microbiology



TORTORA • FUNKE • CASE

Nosocomial Infections: Overview

[insert Nosocomial_Overview.jpg]

file:///D:/Microbiology/NosocomialInfectionsOverview/nosocomial_infections.html



Chains of transmission in nosocomial infection 院內感染的傳播鏈

• Direct contact between hospital staff to patient, patient to patient,

• Indirect contact through fomites and hospital ventilation system

• Change a dressing, a kitchen worker

• Certain specialized care unit: burn, hemodialysis, recovery, intensive care, oncology unit

• Urinary catheter(導管), intravenous catheter

• Respiratory aids

• Needles

• Surgical dressing



Control of nosocomial infections (院內感染的控制)

• Reduce the number of pathogens to which patients are exposed.

• Use aseptic technique

• Handle contaminated material carefully

• Insist on frequent and thorough hand washing

• Educate staff member about basic infection control measures

• Use isolation rooms and wards

• Accredited hospitals should have an infection control committee-an epidemiologist

• Make periodic examination of hospital equipment to determine the extent of microbial contamination.



Microbiology



TORTORA • FUNKE • CASE Nosocomial Infections: Prevention

[insert Nosocomial_Prevention.jpg]

file:///D:/Microbiology/NosocomialInfectionsOverview/nosocomial_infections.html



Emerging Infectious Diseases (EIDs)



• Diseases that are new, increasing in incidence, or showing a potential to increase in the near future.

• Contributing factors:

• Evolution of new strains

• V. cholerae O139

• Inappropriate use of antibiotics and pesticides

• Antibiotic resistant strains, insects, ticks

• Changes in weather patterns (global warming)

• Hantavirus pulmonary syndrome, malaria

Emerging Infectious Diseases (EIDs)-1



• Contributing factors:

• Modern transportation

• Chloera, West Nile virus (travelers)

• Ecological disaster, war, expanding human settlement

• Coccidioidomycosis

• Animal control measures

• Lyme disease (deer increase, predator decrease)

• Public Health failure

• Diphtheria epidemic in Soviet Union, 1990

Emerging Infectious Diseases (EIDs)-2



• The study of where and when diseases occur

Epidemiology

Figure 14.11



10



Modern epidemiology began in the mid-1800s with three famous investigations

流行病學有名的三種探討方式之發源



Three famous investigations in epidemiology

John Snow 1848-1849 Mapped the occurrence of cholera in London

Ignaz Semmelweis 1846-1848 Showed the hand washing decreased the incidence of puerperal fever

Florence Nightingale

1858 Showed that improved sanitation decreased the incidence of epidemic typhus

* Provide the examples of descriptive, analytical and experimental

research model in epidemiology



• Descriptive

(描述性)

Collection and analysis of data regarding occurrence of disease

• Analytical

(分析性)

Comparison of a diseased group and a healthy group

• Experimental

(實驗性)

Study of a disease using controlled experiments

Three basic types of investigations in epidemiology



Descriptive Epidemiology

• Collecting all data that describe the occurrence of the disease under study.

• (1) Most are retrospective (回顧性)studies.

• Backtrack the cause the source of the disease.

• Snow’s search for the case of cholera outbreak in London is an example.

• (2) In contrast, a prospective (預料性) study, in which an epidemiologist choose a group of people who are free of a particular disease to study. The group’s subsequent disease experiences are then recorded for a given period.



Analytical epidemiology-兩種方式

(1) Case control method (病例控制性方法):

• look for factors that might have preceded the disease

• Compare groups of people w/ or w/o disease

• E.g. +/-meningitis vs. age, sex, socioeconomic status, locations

(2) Cohort method (伴隨性方法):

• Study two populations

• Two groups that has had contact w/ or w/o the agent causing the disease

• E.g. +/-blood transfusion vs. the incidence of hep B

• Nightingale’s search compare disease in soldiers and civilians is an example.



Experimental epidemiology

• Begins with a hypothesis (假設) use experiment to test the hypothesis.

• Assume the effectiveness of a drug

• A group of infected individuals is selected and divided randomly

• Some receive the drug, others receive a placebo

• All other factors keep constant

• Whether those who receive the drug (the variable) recover more rapidly than the placebo group to conclude



Case Reporting-to establish the chain of transmission

• Case reporting

(案例報告)

Health care workers report specified disease to local, state, and national offices

• Nationally Notifiable Diseases

(全國性法定具報病)

Physicians are required to report occurrence

* Provide the incidence and prevalence of the disease.

* Help officials decide whether or not to investigate a given disease



Case reporting provide valuable leads …

• Establish the origin and spread

• Discover the chain of transmission

• To isolate and identify the causative agent

• AIDS, measles, gonorrhea, tetanus, typhoid fever

• 協助官方決定是否重視與調查個案

• =>Apply control measurement

• Eliminate the source of infection

• Isolate and segregation of infected people

• Development of treatment (vaccines)

• Public education



Nationally Notifiable Diseases

(全國性法定具報病)



Table 14.11 -1



Table 14.11 Nationally Notifiable Infectious Diseases, 2013 -2



• Collects and analyzes epidemiological information in the U.S.

• Publishes Morbidity and Mortality Weekly Report (MMWR) www.cdc.gov

Morbidity(罹病率): incidence of a specific notifiable disease

Mortality: deaths from notifiable diseases

Morbidity rate = number of people affected/total population in a given time period

Mortality rate = number of deaths from a disease/total population in a given time

Centers for Disease Control and Prevention (CDC)

http://www.cdc.gov/



http://www.cdc.gov/mmwr/



http://www.cdc.gov.tw/

Chapter 14 Principles of Disease and Epidemiology

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Transcript of Chapter 14 Principles of Disease and Epidemiology