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Microbes, Transmission Routes and Survival Outside the Body

  • Bjørg Marit Andersen
Chapter
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Abstract

Microbes like bacteria, virus, parasites and fungi may naturally colonize skin and mucous membranes without any sign of illness, for a longer or shorter period, in all humans, animals, fish, parasites, plants and all other living beings. Some types may be more invasive in human tissue than others. Many microbes are free-living in the environment—in water, soil and air and on equipment—as a part of the normal microbial flora on the Earth. Most of them are not dangerous and live in peaceful symbiosis with other living beings and may also be transferred between living species, from man to animal or man to plants and environment—and vice versa. New and old human pathogenic microbes are increasing all over the world. Some agents, like drug-resistant bacteria and highly pathogenic viruses, are more dangerous than others, and some microbes may cause chronic devastating diseases. Transmission routes depend on the robustness of the microbe in the environment, virulence, infectious dose, anatomical site in the body, etc. Pathogenic microbes are spread by contact, air, water, food, beverages, contaminated equipment and environment and are more seldom vector-borne, by insects or animals. The following chapter is focused on the most frequent pathogenic microbes, their preselected localization in the body, transmission routes and survival in the environment.

Keywords

Microbes Pathogenic microbes Virulence Predilection Biological material Anatomical site Environment Survival Transmission Spread of infection 

3.1 Microbes are Mostly Normal, Nonpathogenic Flora

Microbes like bacteria, virus, parasites and fungi may naturally colonize skin and mucous membranes without any sign of illness, for a longer or shorter period, in all humans, animals, parasites, plants and all other living being [1, 2, 3, 4, 5, 6]. Some types may be more invasive in human tissue than others, partly via mucous membranes and lesions in the skin.

Many microbes are free-living in the environment—in water, soil and air and on equipment—as a part of the normal microbial flora on the Earth. Most of them are not dangerous and live in peaceful symbiosis with other living beings and may also be transferred between living species, from man to animal or man to plants and environment—and vice versa [1, 2, 3, 4, 5, 6]. Microbes, like bacteria, may outnumber us by a factor of 1022, are heavier than us by a factor of 108, have existed on Earth more than 1000 times longer than us and may undergo 500,000 generations in just one of our generations [7].

The existence of humans and animals is dependent on a rich and active bacterial flora in the gut, participating in the decomposition of food substances to energy and growth. Large amounts of bacteria in the gut (1–2 kg) and on the skin is a normal condition. Humans are releasing microbes into the environment and air wherever they move and—at the same time—are picking up new microbes from the environment.

3.2 Pathogenic Microbes: New and Old

Pathogenic microbes cause illness in most humans if introduced into sterile tissue. “Opportunistic” microbes may cause problems in people with reduced immune defence and/or if large amounts are introduced in sterile tissue. Nonpathogenic microbes nearly never cause illness in humans [1, 2, 3]. Human pathogenic microbes often survive for a long time outside the body—in the environment [1, 2, 3, 4, 5, 6]. Therefore, they are special threats to patients, personnel and visitors in healthcare institutions where there often is an accumulation of infectious diseases.

New and old human pathogenic microbes are increasing all over the world. Some agents, like drug-resistant bacteria (methicillin-resistant Staphylococcus aureus, MRSA, multidrug-resistant tubercle bacilli and others) and highly pathogenic viruses (Ebola, SARS and others), are more dangerous than others. Other viral agents may cause chronic devastating diseases like HIV and hepatitis B and C.

Microbes may have preselected locations and tissues in the host, like influenza virus, pneumococci and tuberculosis mostly in lungs, hepatitis viruses in the liver and blood, Clostridium difficile and norovirus in the gut, coagulase negative staphylococci on the skin, etc.

3.3 Transmission Routes: Spread of Infection

The transmission routes of microbes are many and different and depend on the robustness of the microbe in the environment, climate and temperature, virulence, infectious dose, etc. Pathogenic microbes are spread by contact, air, water, food, beverages, contaminated equipment and environment and are more seldom vector-borne, by insects or animals. Drug-resistant microbes and/or resistance genes are common on the global food market for humans, animals and fish [8, 9, 10, 11]. In addition, increased mobility, climatic changes, overcrowding, war and disasters, poor hygiene and poor infection control are increasing the transmission rate. Prudent use of antimicrobial drugs, proper hygiene and good infection control for humans, animals and fish are essential for stopping spread of infections [12, 13, 14, 15, 16, 17, 18, 19].

Microbes: pathways and survival outside the body—in environment

Biological material—location/microbes

Transmission routes

Lifetime in the environment1

 

Wound

 

Staphylococcus aureus

C/A [2]

3–10 months

 

Methicillin-resistant S. aureus (MRSA)

C/A

3–10 months

 

Gram-negative rods (Escherichia coli, Klebsiella, Enterobacter, Serratia, Proteus, Pseudomonas, Acinetobacter, etc.)

C/(A)

2 days–16 months

 

Multidrug-resistant gram-negative rods

C/A

2 days–16 months

 

 – ESBL: E. coli, Enterobacter, Citrobacter, Klebsiella, Serratia, etc.

   

 – Others: Pseudomonas, Acinetobacter, Stenotrophomonas maltophilia

 – New multidrug-resistant with NDM-1 gene; resistant to carbapenem and most other antibiotics

 

Klebsiella > 2.5 years

 

Enterococci, including VRE

C

2 months–4 years

 

Groups A, B, C, G streptococci

C

1–7 months

 

Prosthesis, foreign body

 

Coagulase-negative staphylococci

C/A

3 months

 

S. aureus and MRSA

C/A

3–10 months

 

Gram-negative rods

C

2 days–16 months

 

Enterococci, including VRE

C

2 months–4 years

 

Candida

C

Several months

 

Blood and tissue fluids

 

Hepatitis A, B, C, D, E

B (C) [3]

3 days–year

 

HIV

B (C) [3]

3–14 days

 

Other retroviruses (HTLV-I, HTLV-II)

B

Days

 

Parvovirus B19 and others

B

> 1 year

 

Cytomegalovirus

B/C

Hours to days

 

Prions

B 4

Infinite?

 

Malaria and other blood parasites

B, insects

Varies

 

Yellow fever virus

B, mosquito

Varies

 

Haemorrhagic fever virus

B/C/A, insects

Varies—long?

 

Respiratory tract infections

 

Pneumococci, including penicillin resistant

C/A

Hours–20 d

 

Gram-negative rod bacteria (E coli, Klebsiella, Enterobacter, Acinetobacter, Serratia, Pseudomonas, Morganella, etc.)

C/A

2 days–16 months

 

Haemophilus influenzae

C/A

Hours–12 days

 

S. aureus

C/A

3–10 months

 

Chlamydia pneumoniae/Mycoplasma pneumoniae

C/A L

Hours–days

 

Legionella pneumophila, etc.

A/C/water

Water: infinity

 

Mycobacterium tuberculosis (tuberculosis)

C/A

1 year

 

Neisseria meningitidis; meningococcus

C/A

Hours

 

Pertussis; Bordetella pertussis

C/A

3–5 days

 

Influenza viruses A, B, parainfluenza, adeno, rhino, entero, corona

C/A

Hours–20 d

 

RSV (respiratory syncytial virus)

C/A

Hours–3 d

 

Metapneumovirus

C/A

Unknown

 

Coronavirus OC43 (cold virus)

Human bocavirus (Parvoviridae)

C/A

Unknown

 

Avian influenza

A/C/B

Days to 6 weeks

 

SARS, MERS

A/C/B

3–4 weeks

 

Haemorrhagic fever virus

A/C/B

Varies prolong

 

Faeces/gastrointestinal tract

 

Intestinal pathogenic bacteria (Salmonella, Shigella, Campylobacter, Yersinia, Enteropathogenic E. coli, Helicobacter, Vibrio cholerae)

C/food/water

4–14 days–4.2 years

 

Clostridium difficile (spores)

C

Years

 

Listeria monocytogenes

C/food/water

Long, chilled

 

Bacterial toxins (E coli, S. aureus, Clostridium perfringens, Salmonella, etc.)

C/food

Hours to days

 

Rota/adeno/norovirus (Norwalk)

C/food/water

60–90 days

 

Hepatitis A, hepatitis E

C/food/water

14 days–2 months

 

SARS, MERS and avian influenza virus

C/A/B

3–6 weeks

 

Parasites

Giardia lamblia, Cryptosporidium parvum, Entamoeba histolytica, schistosomiasis, Ascaris, hookworm, trichuriasis, strongyloidiasis, etc.

C/water/food

Weeks–months–year

 

Urinary tract infections

 

E. coli

C

Hours–16 months

 

Other gram-negative rods (Proteus, Klebsiella, Citrobacter, Enterobacter, Pseudomonas, etc.)

C

Hours to 16 months

 

Enterococci

C

2mndr–4 years

 

Resistant bacteria (VRE, ESBL, CRE, MRSA, etc.)

C/A

days–4 years

 

Others

Borrelia burgdorferi, Ehrlichia sp. and less frequent bacteria

Ticks/insects, etc.

Varies

Varicella zoster virus

A/C

Hours–days

Herpes simplex virus

C

Hours–2 months

(Measles, rubella, parotitis virus)

A/C

Hours–days

Highly pathogenic microbes

Multidrug-resistant Mycobacterium tuberculosis

A/C

1 year

SARS, MERS virus

A/C/B

2–6 weeks ++

Haemorrhagic fever virus

A/C/B

2–3 weeks

(Lassa, Ebola, Sabia, Marburg virus, etc.)

A/C/B

Weeks

Avian influenza

A/C/B

Days–6 weeks ++

From Refs. [1, 2, 3, 4, 5, 6]

1. Lifetime in the environment, outside the body. Most gram-negative rod bacteria live almost infinite in water; some also multiply rapidly in water (Klebsiella, Enterobacter, Pseudomonas, Proteus, etc.).

2. C = contact transmission, A = airborne transmission (including droplets), B = blood-borne infection, v = variable, k = short life outside the body, ++ can be long life in optimal environment.

3. May be transmitted by mucous membrane contact, especially lesions of the mucosa.

4. Infectious protein molecules; spongiform encephalopathy.

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Bjørg Marit Andersen
    • 1
    • 2
  1. 1.Department of Hospital InfectionsOslo University HospitalOsloNorway
  2. 2.Faculty of Health and Social ScienceUniversity of South-Eastern NorwayOsloNorway

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