Pathogenic bacteria


Pathogenic bacteria
Clostridium tetani
Bacterial infection
Classification and external resources
MeSH D001424

Pathogenic bacteria are bacteria that cause bacterial infection. This article deals with human pathogenic bacteria.

Although the vast majority of bacteria are harmless or beneficial, quite a few bacteria are pathogenic. One of the bacterial diseases with highest disease burden 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.

Koch's postulates are criteria designed to establish a causal relationship between a causative microbe and a disease.

Contents

Diseases

Each pathogenic species has a characteristic spectrum of interactions with its human hosts.

Conditionally pathogenic

Conditionally pathogenic bacteria are only pathogenic under certain conditions, such as a wound that allows for entry into the blood, or a decrease in immune function.

For example, Staphylococcus or Streptococcus are also part of the normal human flora and usually exist on the skin or in the nose without causing disease, but can potentially cause skin infections, pneumonia, meningitis and even overwhelming sepsis, a systemic inflammatory response producing shock, massive vasodilation and death.[1]

Some species of bacteria, such as Pseudomonas aeruginosa, Burkholderia cenocepacia, and Mycobacterium avium, are opportunistic pathogens and cause disease mainly in people suffering from immunosuppression or cystic fibrosis.[2][3]

Intracellular

Other organisms invariably cause disease in humans, such as obligate intracellular parasites that are able to grow and reproduce only within the cells of other organisms. Still, infections with intracellular bacteria may be asymptomatic, such as during the incubation period. An example of intracellular bacteria is Rickettsia. 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.[4]

Mycobacterium and Brucella can exist intracellularly, though they are facultative (not obligate intracellular parasites.)

By location

Following is a list of bacterial infections classified by location in the body:

Treatment

See also overview list below

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.[13] 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.[14] Infections can be prevented by antiseptic measures such as sterilizing 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 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 73 °C (163°F).

List of pathogenic bacteria by basic laboratory characteristics

Following are the genera that contain the most important human pathogenic bacteria species:[15]

Genus Important species Gram staining Shape Capsulation Bonding tendency Motility Respiration Growth medium Intra/Extracellular
Bordetella Gram-negative Small coccobacilli Encapsulated singly or in pairs aerobic Regan-Lowe agar extracellular
Borrelia Gram-negative, but stains poorly Long, slender, flexible, spiral- or corkscrew-shaped rods highly motile (difficult to culture) extracellular
Brucella Gram-negative Small coccobacilli Unencapsulated singly or in pairs aerobic Blood agar intracellular
Campylobacter Gram-negative Curved, spiral, or S-shaped
with single, polar flagellum
characteristic darting motion microaerophilic Blood agar inhibiting other fecal flora extracellular
Chlamydia and Chlamydophila (not Gram-stained) Small, round, ovoid motile Facultative or strictly aerobic Obligate intracellular
Clostridium Gram-positive Large, blunt-ended rods mostly motile Obligate anaerobic Anaerobic blood agar extracellular
Corynebacterium 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 Gram-positive Round to ovoid pairs or chains Facultative Anaerobic 6.5% NaCl, bile-esculin agar extracellular
Escherichia Gram-negative Short rods Facultative anaerobic MacConkey agar extracellular
Francisella Gram-negative Small, pleomorphic coccobacillus strictly aerobic (rarely cultured) Facultative intracellular
Haemophilus Gram-negative Ranging from small coccobacillus to long, slender filaments Chocolate agar with hemin and NAD+ extracellular
Helicobacter Gram-negative Curved or spiral rods
pultiple polar flagella
rapid, corkscrew motility Medium containing antibiotics against other fecal flora extracellular
Legionella 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 Gram-positive, darkly Slender, short rods diplobacilli or short chains Distinct tumbling motility in liquid medium enriched medium intracellular
Mycobacterium (none) Long, slender rods nonmotile aerobic M. tuberculosis: Lowenstein-Jensen agar
M. leprae: (none)
extracellular
Mycoplasma (none) Plastic, pleomorphic singly or in pairs (rarely cultured) extracellular
Neisseria Gram-negative Kidney bean-shaped diplococci aerobic Thayer-Martin agar Gonococcus: facultative intracellular
N. meningitidis
: extracellular
Pseudomonas Gram-negative rods encapsulated motile Obligate aerobic MacConkey agar extracellular
Rickettsia Gram-negative, but stains poorly Small, rod-like coccobacillary (rarely cultured) Obligate intracellular
Salmonella
  • Salmonella typhi
  • Salmonella typhimurium
Gram-negative Facultative anaerobic MacConkey agar Facultative intracellular
Shigella
  • Shigella sonnei
Gram-negative rods Facultative anaerobic Hektoen agar extracellular
Staphylococcus Gram-positive, darkly Round cocci in bunches like grapes Facultative anaerobic enriched medium (broth and/or blood) extracellular
Streptococcus Gram-positive ovoid to spherical pairs or chains nonmotile Facultative anaerobic blood agar extracellular
Treponema Gram-negative, but stains poorly Long, slender, flexible, spiral- or corkscrew-shaped rods highly motile none extracellular
Vibrio Gram-negative Short, curved, rod-shaped with single polar flagellum rapidly motile Facultative anaerobic blood- or MacConkey agar. Stimulated by NaCl extracellular
Yersinia Gram-negative, stains bipolarly Small rods encapsulated nonmotile Facultative Anaerobe MacConkey or CIN agar Intracellular

List of pathogenic bacteria by clinical characteristics

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

Species of human pathogenic bacteria [15]
Species Transmission Diseases Treatment Prevention laboratory diagnosis
Bacillus anthracis
  • Contact with sheep, goats and horses
  • Inhalation or skin penetration through abrasions of spore-contaminated dust
  • Cutaneous anthrax
  • Pulmonary anthrax
  • Gastrointestinal anthrax
In early infection:
  • 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:

Macrolide antibiotics
Borrelia burgdorferi Ixodes ticks
reservoir in deer, mice and other rodents
  • Early stages:
  • If arthritic symptoms have appeared:
    • Longer courses of antibiotics
  • Lyme vaccine
  • wearing clothing that limits skin exposure to ticks
  • insect repellent
  • Direct contact with infected animal
  • Oral, by ingestion of unpasteurized milk or milk products
Combination therapy of: -
Campylobacter jejuni
  • Fecal/oral from animals (mammals and fowl)
  • Contaminated meat (especially poultry)
  • Contaminated water
  • Acute enteritis
  • Symptomatically by fluid and electrolyte replacement
  • Ciprofloxacin in severe cases
No available vaccine
  • Good hygiene
  • Avoiding contaminated water
  • Pasteurizing milk and milk products
  • Cooking meat (especially poultry)
  • Finding campylobacter in feces
Chlamydia pneumoniae
  • Respiratory droplets
Community-acquired respiratory infection None None for routine use
Chlamydia trachomatis
  • Sexual (NGU, LGV)
  • Direct or contaminated surfaces and flies (trachoma)
  • Passage through birth canal (ICN)
No vaccine
  • Erythromycin or silver nitrate in newborn's eyes
  • Safe sex
Chlamydophila psittaci Inhalation of dust with secretions or feces from birds (e.g. parrots) Psittacosis -
  • Rise in antibody titre
    • Complement fixation
    • indirect immunofluorescence
Clostridium botulinum Spores from soil and aquatic sediments contaminating vegetables, meat and fish
  • Proper food preservation techniques
  • Mouse inoculation detects toxin from food, intestinal contents or serum
  • Culture in standard aerobic culture
Clostridium difficile
  • Spores both indoors and outdoors
  • Human flora, overgrowing when other flora is depleted
None
Clostridium perfringens Gas gangrene:

Food poisoning:

  • Self-limiting; Supportive care is sufficient
Appropriate food handling
  • Microscopically
  • Blood agar culture, forming double-zone β-hemolysis
  • Sugar fermentation
  • Organic acid production
Clostridium tetani
  • Spores in soil infecting puncture wounds, severe burns or surgery
(difficult)
Corynebacterium diphtheriae
  • Respiratory droplets
  • Part of human flora
(no rapid)
  • Culture on Tinsdale agar, followed by immunologic precipitin reaction
Enterococcus faecalis and Enterococcus faecium
  • Part of human flora, opportunistic or entering through GI tract or urinary system wounds
  • Nosocomial infections
No vaccine
  • Hand washing and other nosocomial prevention
  • Culture in 6.5% NaCl
  • Can hydrolyze esculin in presence of bile
Escherichia coli (generally)
  • Part of gut flora, spreading extraintestinally or proliferating in the GI tract
  • Urinary tract infections (UTI)
  • Diarrhea
  • Meningitis in infants
UTI:

(resistance-tests are required first)

Meningitis:

Diarrhea:

  • Antibiotics above shorten duration
  • Electrolyte and fluid replacement
(no vaccine or preventive drug)
  • Food and water preparation
    • Cooking ground beef and pasteurizing milk against O157:H7
  • Hand washing and disinfection
  • Culture on MacConkey agar and study carbohydrate fermentation patterns:
    • Lactose fermentation (most E. coli strains)
    • Gas production in glucose fermentation
    • Mannitol fermentation
Enterotoxigenic Escherichia coli (ETEC)
  • Fecal-oral through food and water
  • Direct physical contact
  • Traveller's diarrhea
Enteropathogenic E. coli
  • Diarrhea in infants
E. coli O157:H7
  • Reservoir in cattle
Francisella tularensis
  • vector-borne by arthropods
  • Infected wild or domestic animals, birds or house pets
  • Avoiding insect vectors
  • Precautions when handling wild animals or animal products
(rarely cultured)
  • Serology
Haemophilus influenzae
  • Droplet contact
  • Human flora of e.g. upper respiratory tract
Meningitis:

(resistance-tests are required first)

Helicobacter pylori
  • Colonizing stomach
  • Unclear person-to-person transmission
(No vaccine or preventive drug)
  • Microscopically
    • Corkscrew movement
  • Urease-positivity by radioactively labeled urea
  • Serology by ELISA
Legionella pneumophila
  • Droplet contact, from e.g. cooling towers, humidifiers, air conditioners and water distribution systems
  • Legionnaire's Disease
  • Pontiac fever
(no vaccine or preventive drug)

Heating water

  • Culture from respiratory secretions on buffered charcoal yeast extract enriched with L-cysteine, iron and α-ketoglutarate
  • Serology, including direct immunofluorescence and radioimmunoassay for antigen in urine
  • Hybridization to ribosomal RNA using DNA probe
Leptospira interrogans
  • Food and water contaminated by e.g. urine from wild or domestic animals. Leptospira survives for weeks in stagnant water.
(no vaccine)

Prevention of exposure

  • Rodent control
  • Dark-field microscopy on fresh blood smear (but doesn't stain well)
  • Serologic agglutionation tests
Listeria monocytogenes
  • Dairy products, ground meats, poultry
  • Vertical to newborn or fetus
(no vaccine)
  • Proper food preparation and handling
Isolation from e.g. blood and CSF
  • Beta-hemolysis and catalase production on blood agar
  • Microscopy for morphology and motility
Mycobacterium leprae
  • Prolonged human-human contact, e.g. through exudates from skin lesions to abrasion of other person
Tuberculoid form:

Lepromatous form:

Tuberculoid form:
Hard to isolate (diagnosis on clinical findings and histology of biopsies)

Lepromatous form:

  • Acid-fast staining from e.g. skin scrapings
Mycobacterium tuberculosis
  • Droplet contact

(difficult, see Tuberculosis treatment for more details)

Standard "short" course:

Mycoplasma pneumoniae
  • Human flora
  • Droplet contact
(difficult to culture)
Neisseria gonorrhoeae Uncomplicated gonorrhea:

Ophthalmia neonatorum:

(No vaccine)
Neisseria meningitidis
  • Respiratory droplets
  • NmVac4-A/C/Y/W-135 vaccine
  • Rifampin
  • Microscopy showing gram-negative diplococci, often with PMNs
  • Culture on chocolate agar, giving positive oxidase test and fermentation of glucose and maltose in 5% CO2 in air
Pseudomonas aeruginosa Infects damaged tissues or people with reduced immunity.
  • Pseudomonas infection

Localized to eye, ear, skin, urinary, respiratory or gastrointestinal tract or CNS, or systemic with bacteremia, secondary pneumonia bone and joint infections, endocarditis, skin, soft tissue or CNS infections.

(no vaccine)
Rickettsia rickettsii
  • Bite of infected wood or dog tick
(no preventive drug or approved vaccine)
  • Vector control, such as clothing
  • Prompt removal of attached ticks
Salmonella typhi Human-human
  • Fecal-oral through food or water
  • Ty21a and ViCPS vaccines
  • Hygiene and food preparation
  • Isolation from blood, feces, bone marrow, urine or rose spots on skin
  • Colorless, non-lactose fermenting colonies on MacConkey agar
  • Serology for antibodies against O antigen
Salmonella typhimurium
  • Fecal-oral
  • Food contaminated by fowl (e.g. eggs), pets and other animals
  • Fluid and electrolyte replacement for severe diarrhea
  • Antibiotics (in immunocompromised to prevent systemic spread)
(No vaccine or preventive drug)
  • Proper sewage disposal
  • Food preparation
  • Good personal hygiene
Shigella sonnei
  • Fecal-oral
  • Flies
  • Contaminated food or water
  • Protection of water and food supplies
  • Vaccines are in trial stage[16]
  • Culture on Hektoen agar or other media for intestinal pathogens
Staphylococcus aureus
  • Human flora on mucosae in e.g. anterior nares and vagina, entering through wound
Coagulase-positive staphylococcal infections:
  • Localized skin infections
  • Diffuse skin infection (Impetigo)
  • Deep, localized infections
  • Acute infective endocarditis
  • Septicemia
  • Necrotizing pneumonia
  • Toxinoses
(no vaccine or preventive drug)
  • Barrier precautions, washing hands and fomite disinfection in hospitals
  • Microscopy showing strongly positive Gram stained cells in grape-like clusters
  • Positive Catalase test and coagulase test
  • Culture on enriched media producing deep yellow, hemolytic colonies
Staphylococcus epidermidis Human flora in skin and anterior nares
  • Infections of implanted prostheses, e.g. heart valves and catheters
None
  • Microscopy showing strongly positive Gram stained cells in grape-like clusters
  • Positive Catalase test but negative coagulase test
  • Novobiocin-sensitivity (S. epidermidis)
  • Novobiocin-resistance (S. saprophyticus)
  • Culture on enriched media producing white, nonhemolytic colonies
Staphylococcus saprophyticus Part of normal vaginal flora
  • Penicillin G
None
Streptococcus agalactiae Human flora in vagina or urethral mucous membranes, rectum None
  • Culture showing large colonies with β-hemolysis
  • Negative catalase test
  • Hydrolyzes sodium hippurate
Streptococcus pneumoniae
  • Respiratory droplets
  • Often human flora in nasopharynx (spreading in immunocompromised)
  • 23-serotype vaccine for adults (PPV)
  • Heptavalent conjugated vaccine for children (PCV)
  • Microscopy showing gram-positive, encapsulated lancet-shaped diplococci
  • α-hemolysis on blood agar, bile-soluble, optochin-sensitive
  • Positive Quellung reaction
Streptococcus pyogenes
  • Respiratory droplets
  • Direct physical contact with impetigo lesions
No vaccine
  • Rapid antibiotic treatment helps prevent rheumatic fever
Treponema pallidum
  • Sexual
No preventive drug or vaccine
  • Safe sex
  • Antibiotics to pregnant women at risk of transmitting congenital syphilis
Cannot be cultured or viewed in gram-stained smear
Vibrio cholerae
  • Contaminated water and food, especially raw seafood
  • Fluid and electrolyte replacement
  • e.g. doxycycline to shorten duration
  • Preventing fecal contamination of water supplies and food
  • Adequate food preparation
Yersinia pestis
  • Fleas from animals
  • Ingestion of animal tissues
  • Respiratory droplets
Plague:
  • Formalin-killed plague vaccine
  • Minimize exposure to rodents and fleas
  • Gram-negative smear
  • If pneumonic, culture from aspirate on MacConkey or blood agar

See also

References

  1. ^ Fish DN (February 2002). "Optimal antimicrobial therapy for sepsis". Am J Health Syst Pharm 59 (Suppl 1): S13–9. PMID 11885408. http://www.ajhp.org/cgi/pmidlookup?view=long&pmid=11885408. 
  2. ^ Heise E (1982). "Diseases associated with immunosuppression". Environ Health Perspect 43: 9–19. doi:10.2307/3429162. JSTOR 3429162. PMC 1568899. PMID 7037390. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1568899. 
  3. ^ Saiman L (2004). "Microbiology of early CF lung disease". Paediatr Respir Rev 5 (Suppl A): S367–9. doi:10.1016/S1526-0542(04)90065-6. PMID 14980298. http://linkinghub.elsevier.com/retrieve/pii/S1526054204900656. 
  4. ^ Belland R, Ouellette S, Gieffers J, Byrne G (2004). "Chlamydia pneumoniae and atherosclerosis". Cell Microbiol 6 (2): 117–27. doi:10.1046/j.1462-5822.2003.00352.x. PMID 14706098. 
  5. ^ Terri Warren, RN (2010). "Is It a Yeast Infection?". http://women.webmd.com/features/is-it-yeast-infection. Retrieved 2011-02-23. 
  6. ^ Ferris DG, Nyirjesy P, Sobel JD, Soper D, Pavletic A, Litaker MS (March 2002). "Over-the-counter antifungal drug misuse associated with patient-diagnosed vulvovaginal candidiasis". Obstetrics and Gynecology 99 (3): 419–425. doi:10.1016/S0029-7844(01)01759-8. PMID 11864668. 
  7. ^ "Urinary Tract Infections". http://www.medicinenet.com/urine_infection/page4.htm. Retrieved 2010-02-04. 
  8. ^ "Adult Health Advisor 2005.4: Bacteria in Urine, No Symptoms (Asymptomatic Bacteriuria)". Archived from the original on 2007-07-12. http://web.archive.org/web/20070712060000/http://www.med.umich.edu/1libr/aha/aha_asybac_crs.htm. Retrieved 2007-08-25. 
  9. ^ NHS Impetigo
  10. ^ Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; & Mitchell, Richard N. (2007). Robbins Basic Pathology (8th ed.). Saunders Elsevier. pp. 843 ISBN 978-1-4160-2973-1
  11. ^ "erysipelas" at Dorland's Medical Dictionary
  12. ^ "cellulitis" at Dorland's Medical Dictionary
  13. ^ 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. doi:10.1146/annurev.micro.58.030603.123822. PMID 15487937. 
  14. ^ Khachatourians GG (November 1998). "Agricultural use of antibiotics and the evolution and transfer of antibiotic-resistant bacteria". CMAJ 159 (9): 1129–36. PMC 1229782. PMID 9835883. http://www.cmaj.ca/cgi/pmidlookup?view=reprint&pmid=9835883. 
  15. ^ a b Unless else specified then ref is: Fisher, Bruce; Harvey, Richard P.; Champe, Pamela C. (2007). Lippincott's Illustrated Reviews: Microbiology (Lippincott's Illustrated Reviews Series). Hagerstown, MD: Lippincott Williams & Wilkins. pp. 332–353. ISBN 0-7817-8215-5. 
  16. ^ Institut Pasteur Press Office - Vaccine against shigellosis (bacillary dysentery):a promising clinical trial 15 January 2009. Retrieved on 27 February 2009

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