Pathogenic bacteria

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Pathogenic bacteria are bacteria that cause infectious diseases. This article deals with human pathogenic bacteria.

Although the vast majority of bacteria are harmless or beneficial, a few bacteria are pathogenic. The most common bacterial disease is tuberculosis, caused by the bacterium Mycobacterium tuberculosis, which kills about 2 million people a year, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis and leprosy.

## Contents

* 1 History
* 2 Diseases
* 3 Treatment
* 4 Pathogenic genuses
* 5 Pathogenic species
* 6 See also
* 7 References

## History

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Koch's postulates, proposed by Robert Koch in 1890, are criteria designed to establish a causal relationship between a causative microbe and a disease. A pathogenic cause for a known medical disease may only be discovered many years after, as was the case with Helicobacter pylori and peptic ulcer disease.

## Diseases

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Each pathogenic species has a characteristic spectrum of interactions with its human hosts. Some organisms, such as Staphylococcus or Streptococcus, can cause skin infections, pneumonia, meningitis and even overwhelming sepsis, a systemic inflammatory response producing shock, massive vasodilation and death.[1] Yet these organisms are also part of the normal human flora and usually exist on the skin or in the nose without causing any disease at all. Other organisms invariably cause disease in humans, such as the Rickettsia, which are obligate intracellular parasites able to grow and reproduce only within the cells of other organisms. One species of Rickettsia causes typhus, while another causes Rocky Mountain spotted fever. Chlamydia, another phylum of obligate intracellular parasites, contains species that can cause pneumonia, or urinary tract infection and may be involved in coronary heart disease.[2] Finally, some species, such as Pseudomonas aeruginosa, Burkholderia cenocepacia, and Mycobacterium avium, are opportunistic pathogens and cause disease mainly in people suffering from immunosuppression or cystic fibrosis.[3][4]

## Treatment

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Main article: Antibiotics

Bacterial infections may be treated with antibiotics, which are classified as bacteriocidal if they kill bacteria, or bacteriostatic if they just prevent bacterial growth. There are many types of antibiotics and each class inhibits a process that is different in the pathogen from that found in the host. For example, the antibiotics, chloramphenicol and tetracyclin inhibit the bacterial ribosome, but not the structurally-different eukaryotic ribosome, and so exhibit selective toxicity.[5] Antibiotics are used both in treating human disease and in intensive farming to promote animal growth. Both uses may be contributing to the rapid development of antibiotic resistance in bacterial populations.[6] Infections can be prevented by antiseptic measures such as sterilizating the skin prior to piercing it with the needle of a syringe, and by proper care of indwelling catheters. Surgical and dental instruments are also sterilized to prevent contamination and infection by bacteria. Disinfectants such as bleach are used to kill bacteria or other pathogens on surfaces to prevent contamination and further reduce the risk of infection. Most bacteria in food are killed by cooking to temperatures above 60 °C (140 °F).

## Pathogenic genuses

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The following Genuses contain the most important human pathogenic bacteria species: [7]

Clinically most important human pathogenic bacteria genuses[8] and species  Genus  | Important species  | Gram staining | Shape  | Capsulation  | Bonding tendency  | Motility  | Respiration  | Growth medium | Intra/Extracellular

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Bacillus |

* Bacillus anthracis

| Gram-positive  | Blunt-ended bacilli  | Antiphagocytic capsule  | singly, in pairs or frequently in long chains  | Nonmotile  | Facultative or strictly aerobic  | Blood agar | extracellular
Bordetella |

* Bordetella pertussis

| Gram-negative  | Small coccobacilli | Encapsulated  | singly or in pairs  |  | aerobic  | Regan-Lowe agar | extracellular
Borrelia |

* Borrelia burgdorferi

| Gram-negative, but stains poorly  |  |  | Long, slender, flexible, spiral- or corkscrew-shaped rods  | higly motile  | (difficult to culture)  | extracellular
Brucella |

* Brucella abortus
* Brucella canis
* Brucella melitensis
* Brucella suis

| Gram-negative  | Small coccobacilli | Unencapsulated  | singly or in pairs  |  | aerobic  | Blood agar | intracellular
Campylobacter |

* Campylobacter jejuni

| Gram-negative  | Curved, spiral, or S-shaped
with single, polar flagellum  |  |  | characteristic darting motion  | microaerophilic | Blood agar inhibiting other fecal flora | extracellular
Chlamydia |

* Chlamydia pneumoniae
* Chlamydia psittaci
* Chlamydia trachomatis

| (not Gram-stained)  | Small, round, ovoid  |  |  |  | motile  | Facultative or strictly aerobic  | Obligate intracellular
Clostridium |

* Clostridium botulinum
* Clostridium difficile
* Clostridium perfringens
* Clostridium tetani

| Gram-positive  | Large, blunt-ended rods  |  | mostly motile  | Obligate aerobic  | Anaerobic blood agar | extracellular
Corynebacterium |

* Corynebacterium diphteriae

| Gram-positive (unevenly)  | Small, slender, pleomorphic rods  | unencapsulated  | clumps looking like Chinese characters or a picket fence | nonmotile  | Mostly facultative anaerobic  | Aerobically on Tinsdale agar | extracellular
Enterococcus |

* Enterococcus faecalis
* Enterococcus faecum

| Gram-positive  | Round to ovoid  |  | pairs or chains  |  | 6.5% NaCl, bile-esculin agar | extracellular
Escherichia |

* Escherichia coli

| Gram-negative  | Short rods  |  |  |  | Facultative anaerobic  | MacConkey agar | extracellular
Francisella |

* Francisella tularensis

| Gram-negative  | Small, pleomorphic coccobacillus  |  |  |  | strictly aerobic  | (rarely cultured)  | Facultative intracellular
Haemophilus |

* Haemophilus influenzae

| Gram-negative  | Ranging from small coccobacillus to long, slender filaments  |  |  |  |  | Chocolate agar with hemin and NAD+ | extracellular
Helicobacter |

* Helicobacter pylori

| Gram-negative  | Curved or spiral rods
pultiple polar flagella  |  |  | rapid, corkscrew motility  |  | Medium containing antibiotics against other fecal flora  | extracellular
Legionella |

* Legionella pneumophila

| Gram-negative, but stains poorly  | Slender rod in nature, cocobacillary in laboratory.
monotrichious flagella  | unencapsulated  |  | motile  |  | Specialized medium  | facultative intracellular
Leptospira |

* Leptospira interrogans

| Gram-negative, but stains poorly  | Long, very slender, flexible, spiral- or corkscrew-shaped rods  |  |  | highly motile  |  | Specialized medium  | extracellular
Listeria |

* Listeria monocytogenes

| Gram-positive, darkly  | Slender, short rods  |  | diplobacilli or short chains  | Distinct tumbling motility in liquid medium  |  | enriched medium  | intracellular
Mycobacterium |

* Mycobacterium leprae
* Mycobacterium tuberculosis

| (none)  | Long, slender rods  |  |  | nonmotile  | aerobic  | M. tuberculosis: Lowenstein-Jensen agar
M. leprae: (none)  | extracellular
Mycoplasma |

* Mycoplasma pneumoniae

| (none)  | Plastic, pleomorphic  |  | singly or in pairs  |  |  | (rarely cultured)  | extracellular
Neisseria |

* Neisseria gonorrhoeae
* Neisseria meningitidis

| Gram-negative  | Kidney bean-shaped  |  | diplococci  |  | aerobic  | Thayer-Martin agar | Gonococcus: facultative intracellular
N. meningitidis: extracellular
Pseudomonas |

* Pseudomonas aeruginosa

| Gram-negative  | rods  | encapsulated  |  | motile  | Obligate aerobic  | MacConkey agar | extracellular
Rickettsia |

* Rickettsia rickettsii

| Gram-negative, but stains poorly  | Small, rod-like coccobacillary  |  |  |  |  | (rarely cultured)  | Obligate intracellular
Salmonella |

* Salmonella typhi
* Salmonella typhimurium

| Gram-negative  |  |  |  |  | Facultative anaerobic  | MacConkey agar | acellular
Shigella |

* Shigella sonnei

| Gram-negative  | rods  |  |  |  | Facultative anaerobic  | Hektoen agar | extracellular
Staphylococcus |

* Staphylococcus aureus
* Staphylococcus epidermidis
* Staphylococcus saprophyticus

| Gram-positive, darkly  | Round cocci  |  | in bunches like grapes  |  | Facultative anaerobic  | enriched medium (broth and/or blood)  | extracellular
Streptococcus |

* Streptococcus agalactiae
* Streptococcus pneumoniae
* Streptococcus pyogenes

| Gram-positive  | ovoid to spherical  |  | pairs or chains  | nonmotile  | Facultative anaerobic  | blood agar | extracellular
Treponema |

* Treponema pallidum

| Gram-negative, but stains poorly  | Long, slender, flexible, spiral- or corkscrew-shaped rods  |  |  | highly motile  |  | none  | extracellular
Vibrio |

* Vibrio cholerae

| Gram-negative  | Short, curved, rod-shaped with single polar flagellum  |  |  | rapidly motile  | Facultative anaerobic  | blood- or MacConkey agar. Stimulated by NaCl  | extracellular
Yersinia |

* Yersinia pestis

| Gram-negative, stains bipolarly  | Small rods  | encapsulated  |  | nonmotile  |  | MacConkey or CIN agar | extracellular

## Pathogenic species

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This is a further description of the species presented in the previous section, containing transmission, diseases, treatment, prevention and laboratory diagnosis, which all can differ substantially among the species of the same genus.

Species of human pathogenic bacteria [8] Species  | Transmission | Diseases  | Treatment  | Prevention  | laboratory diagnosis

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Bacillus anthracis |

* Contact with sheep, goats and horses
* Inhalation or skin penetration through abrasions of spor-contaminated dust

* Cutaneous anthrax
* Pulmonary anthrax
* Gastrointestinal anthrax

| In early infection:

* Penicillin
* Doxycycline
* Ciprofloxacin

* Anthrax vaccine
* autoclaving of instruments

* Large, grayish, nonhemolytic colonies with irregular borders on blood agar
* Direct immunofluorescence

Bordetella pertussis |

* Contact with respiratory droplets expelled by infected human hosts.

* Whooping cough

Complications:

* Secondary bacterial pneumonia

| Macrolide antibiotics

* Azithromycin
* Erythromycin
* Clarithromycin

* Pertussis vaccine, DTP

* Direct immunofluorescence
* PCR amplification

Borrelia burgdorferi | Ixodes ticks
reservoir in deer, mice and other rodents  |

* Lyme disease

* Early stages:
* cephalosporins
* amoxicillin
* doxycycline
* If arthritic symptoms have appeared:
* Longer courses of antibiotics

* Lyme vaccine
* wearing clothing that limits skin exposure to ticks
* insect repellent

* Microscopy using Giemsa or Wright stain
* PCR
* serology (low precision rate)

Brucella abortus |  |  |  |  |
Brucella canis |  |  |  |  |
Brucella melitensis |  |  |  |  |
Brucella suis |  |  |  |  |
Campylobacter jejuni |  |  |  |  |
Chlamydia pneumoniae |  |  |  |  |
Chlamydia psittaci |  |  |  |  |
Chlamydia trachomatis |  |  |  |  |
Clostridium botulinum |  |

* Botulism

|  |
Clostridium difficile |  |  |  |  |
Clostridium perfringens |  |  |  |  |
Clostridium tetani |  |

* [Tetanus]]

|  |
Corynebacterium diphteriae |  |

* Diphtheria

|  |
Enterococcus faecalis |  |  |  |  |
Enterococcus faecum |  |  |  |  |
Escherichia coli |  |  |  |  |
Francisella tularensis |  |

* Tularemia

|  |
Haemophilus influenzae |  |  |  |  |
Helicobacter pylori |  |  |  |  |
Legionella pneumophila |  |

* Legionnaire's Disease

|  |
Leptospira interrogans |  |  |  |  |
Listeria monocytogenes |  |  |  |  |
Mycobacterium leprae |  |  |  |  |
Mycobacterium tuberculosis |  |  |  |  |
Mycoplasma pneumoniae |  |  |  |  |
Neisseria gonorrhoeae |  |  |  |  |
Neisseria meningitidis |  |  |  |  |
Pseudomonas aeruginosa |  |  |  |  |
Rickettsia rickettsii |  |  |  |  |
Salmonella typhi |  |  |  |  |
Salmonella typhimurium |  |  |  |  |
Shigella sonnei |  |  |  |  |
Staphylococcus aureus |  |  |  |  |
Staphylococcus epidermidis |  |  |  |  |
Staphylococcus saprophyticus |  |  |  |  |
Streptococcus agalactiae |  |  |  |  |
Streptococcus pneumoniae |  |  |  |  |
Streptococcus pyogenes |  |  |  |  |
Treponema pallidum |  |  |  |  |
Vibrio cholerae |  |  |  |  |
Yersinia pestis |  |

* Plague

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## See also

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* Pathogenic viruses

## References

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1. ↑ Fish D. "Optimal antimicrobial therapy for sepsis". Am J Health Syst Pharm. 59 Suppl 1: S13–9. PMID 11885408.
2. ↑ Belland R, Ouellette S, Gieffers J, Byrne G (2004). "Chlamydia pneumoniae and atherosclerosis". Cell Microbiol. 6 (2): 117–27. PMID 14706098.CS1 maint: Multiple names: authors list (link)
3. ↑ Heise E. "Diseases associated with immunosuppression". Environ Health Perspect. 43: 9–19. PMID 7037390.
4. ↑ Saiman, L. "Microbiology of early CF lung disease". Paediatr Respir Rev. volume = 5 Suppl A: S367&ndash, 369. Unknown parameter `|yar=` ignored (help)CS1 maint: Missing pipe (link)  PMID 14980298
5. ↑ Yonath A, Bashan A (2004). "Ribosomal crystallography: initiation, peptide bond formation, and amino acid polymerization are hampered by antibiotics". Annu Rev Microbiol. 58: 233–51. PMID 15487937.
6. ↑ Khachatourians G (1998). "Agricultural use of antibiotics and the evolution and transfer of antibiotic-resistant bacteria". CMAJ. 159 (9): 1129–36. PMID 9835883.
7. ↑ Fisher, Bruce; Harvey, Richard P.; Champe, Pamela C. Lippincott's Illustrated Reviews: Microbiology (Lippincott's Illustrated Reviews Series). Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 0-7817-8215-5.CS1 maint: Multiple names: authors list (link)
8. ↑ 8.0 8.1 Unless else specified then ref is: Fisher, Bruce; Harvey, Richard P.; Champe, Pamela C. Lippincott's Illustrated Reviews: Microbiology (Lippincott's Illustrated Reviews Series). Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 0-7817-8215-5.CS1 maint: Multiple names: authors list (link)  Pages 332 to 353

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