Teach Cough Hygiene Everywhere/Pathogenic bacteria

Pathogenic bacteria are bacteria that cause bacterial infectious disease|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.

Diseases

Each pathogenic species has a characteristic spectrum of interactions with its human host (biology)|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.

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

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 (bacterium)|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.

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:

• Bacterial vaginosis is a disease of the vagina caused by an imbalance of naturally occurring bacterial flora and is often confused with yeast infection (candidiasis), or infection with Trichomonas vaginalis (trichomoniasis), which are not caused by bacteria.
• Bacterial meningitis is a bacterial inflammation of the meninges, that is, the protective membranes covering the brain and spinal cord.
• Bacterial pneumonia is a bacterial infection of the lungs.
• Urinary tract infection is almost exclusively caused by bacteria. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli. Although urine contains a variety of fluids, salts, and waste products, it does not usually have bacteria in it, but when bacteria get into the Urinary bladder|bladder or kidney and multiply in the urine, they may cause a UTI.
• Bacterial gastroenteritis is caused by pathogenic enteric bacteria. Such pathogenic enteric bacteria are generally distinguished from the usually harmless bacteria of the normal gut flora, but the distinction is often not fully clear, and Escherichia, for example, can belong to either group.
• Bacterial skin infections include:
  • Impetigo is a highly contagious bacterial human skin|skin infection most common among pre-school children. It is primarily caused by Staphylococcus aureus, and sometimes by Streptococcus pyogenes.
  • Erysipelas is an acute streptococcus bacterial infection of the deep epidermis with lymphatic spread.
  • Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters, burn (injury)|burns, insect bites, surgical wounds, intravenous drug injection or sites of intravenous catheter insertion. Skin on the face or lower legs is most commonly affected by this infection, though cellulitis can occur on any part of the body.

Treatment

Main article: Antibiotics

See also Pathogenic bacteria#Clinical characteristics|overview list below

Bacterial infections may be treated with antibiotics, which are classified as bacteriocide|bacteriocidal if they kill bacteria, or bacteriostatic if they just prevent bacterial growth. There are many types of antibiotics and each class enzyme inhibitor|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. 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. 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 Sterilization (microbiology)|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 clinical characteristics

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

Species of human pathogenic bacteria

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: 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, DPT vaccine	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 stain|Giemsa or Wright stain polymerase chain reaction|PCR serology (low precision rate)
Brucella abortus Brucella canis Brucella melitensis Brucella suis	Direct contact with infected animal Oral, by ingestion of unpasteurized milk or milk products	Brucellosis	Combination therapy of: doxycycline streptomycin or gentamicin	-	Culture (difficult and time consuming) Agglutination (biology)|Agglutination serology
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	Doxycycline Erythromycin	None	None for routine use
Chlamydia trachomatis	Sexual (Lymphogranuloma venereum|NGU, lymphogranuloma venereum|LGV) Direct or contaminated surfaces and flies (trachoma) Passage through birth canal (Inclusion conjunctivitis of the newborn|ICN)	Nongonococcal urethritis (NGU) Lymphogranuloma venereum (LGV) Trachoma Inclusion conjunctivitis of the newborn (ICN)	Azithromycin Erythromycin Tetracyclines Doxycycline	No vaccine Erythromycin or silver nitrate in newborn's eyes Safe sex	Cellular cytoplasmic inclusions by immunofluorescence DNA hybridization ELISA for lipopolysaccharides
Chlamydophila psittaci	Inhalation of dust with secretions or feces from birds (e.g. parrots)	Psittacosis	Tetracycline Doxycycline Erythromycin (less efficient)	-	Rise in antibody titre Complement fixation indirect immunofluorescence
Clostridium botulinum	Spores from soil and aquatic sediments contaminating vegetables, meat and fish	Botulism	Antitoxin (horse antiserum)	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	Pseudomembranous colitis	Discontinuing predisposing antibiotic Fluid and electrolyte replacement Vancomycin or metronidazole if severe	None	ELISA for Clostridium_difficile#Toxin ELISA|Toxin ELISA for toxin A or B Endoscopy for pseudomembrane
Clostridium perfringens	Spores in soil Human flora in vagina and GI tract	Gas gangrene Acute food poisoning Anaerobic cellulitis	Gas gangrene: Debridement or amputation Hyperbaric medicine High doses of penicillin G or doxycycline Food poisoning: Self-limiting; Supportive care is sufficient	Appropriate food handling	Microscopically Blood agar culture, forming double-zone beta hemolysis|β-hemolysis Sugar fermentation Organic acid production
Clostridium tetani	Spores in soil infecting puncture wounds, severe burns or surgery	Tetanus	Tetanus immune globulin Horse antitoxin, alternatively Sedatives Muscle relaxants Mechanical ventilation	DPT vaccine	(difficult)
Corynebacterium diphtheriae	Respiratory droplets Part of human flora	Diphtheria	Horse serum antitoxin Erythromycin Penicillin	DPT vaccine	(no rapid) Culture on Tinsdale agar, followed by immunologic precipitin reaction
Enterococcus faecalis and Enterococcus faecium	Part of human flora, Opportunistic infection|opportunistic or entering through GI tract or urinary system wounds	Nosocomial infections	Penicillin and an aminoglycoside Vancomycin Quinupristin and dalfopristin	No vaccine Hand washing and other Nosocomial#Prevention|nosocomial prevention	Culture in 6.5% Sodium chloride|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) Co-trimoxazole Fluoroquinolone, e.g. ciprofloxacin Meningitis: Cephalosporin (e.g. cefotaxime) and gentamicin combination 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	Transmission_(medicine)#Vertical_Transmission|Vertical, in utero or at birth	Diarrhea in infants
E. coli O157:H7	Reservoir in cattle	Hemorrhagic colitis Hemolytic-uremic syndrome
Francisella tularensis	Vector (epidemiology)|vector-borne by arthropods Infected wild or domestic animals, birds or house pets	Tularemia	Streptomycin Gentamicin	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	Bacterial meningitis Upper respiratory tract infections Pneumonia, bronchitis	Meningitis: (resistance-tests are required first) Cephalosporin#Third_generation|Third generation cephalosporin, e.g. cefotaxime or ceftriaxone Ampicillin and sulbactam combination	Hib vaccine to infants Rifampin prophylactically	Culture on chocolate agar with hemin (factor X) and Nicotinamide adenine dinucleotide|NAD+ (factor V) Quellung reaction Immunofluorescence staining of capsule Detection of capsular antigen in Cerebrospinal fluid|CSF or other body fluids
Helicobacter pylori	Colonizing stomach Unclear person-to-person transmission	Peptic ulcer Risk factor for gastric carcinoma and gastric B-cell lymphoma	Tetracycline, metronidazole and bismuth salt combination	(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	Macrolides, e.g. erythromycin or azithromycin Fluoroquinolones	(no vaccine or preventive drug) Heating water	Culture from respiratory secretions on buffered charcoal yeast extract enriched with L-cysteine, iron and Alpha-ketoglutaric acid|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.	Leptospirosis	Penicillin G Tetracycline, e.g. doxycycline	(no vaccine) Doxycycline 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 Transmission_(medicine)#Vertical_Transmission|Vertical to newborn or fetus	Listeriosis	Ampicillin Co-trimoxazole	(no vaccine) Proper food preparation and handling	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	Leprosy (Hansen's disease)	Tuberculoid form: Dapsone and rifampin Lepromatous form: Clofazimine	Bacillus Calmette-Guérin|BCG vaccine shows some effects	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	Tuberculosis	(difficult, see Tuberculosis treatment for more details) Standard "short" course: First 2 months, combination: Isoniazid Rifampicin Pyrazinamide Ethambutol Further 4 months, combination: Isoniazid Rifampicin	Bacillus Calmette-Guérin|BCG vaccine Isoniazid	Ziehl-Neelsen stain showing acid-fast bacteria Hybridization probes for DNA, succeeded by Polymerase chain reaction|PCR Culture on Lowenstein-Jensen agar
Mycoplasma pneumoniae	Human flora Droplet contact	Mycoplasma pneumonia	Doxycycline and erythromycin		(difficult to culture) Serologic tests, e.g. complement fixation test DNA probes on sputum specimens
Neisseria gonorrhoeae	Sexually transmitted disease|Sexually transmitted Vertical transmission|vertical in birth	Gonorrhea Ophthalmia neonatorum Septic arthritis	Uncomplicated gonorrhea: Ceftriaxone Tetracycline, e.g. doxycycline if also chlamydia is suspected Spectinomycin for resistance or patient allergy to cephalosporin Ophthalmia neonatorum: Tetracycline or erythromycin into eyes	(No vaccine) Safe sex Tetracycline or erythromycin into eyes of newborn at risk	Gram-negative bacteria|Gram-negative diplococci in neutrophils from urethral exudates Oxidase test on culture on Thayer-Martin agar under increased oxygen tension Fermentation of glucose but not maltose
Neisseria meningitidis	Respiratory droplets	Meningococcal disease including meningitis Waterhouse-Friderichsen syndrome	Penicillin G Cefotaxime Ceftriaxone	NmVac4-A/C/Y/W-135 vaccine Rifampin	Microscopy showing gram-negative diplococci, often with polymorphonuclear leukocytes|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.	Aminoglycoside and anti-pseudomonal beta-lactam|β-lactam	(no vaccine) Topical silver sulfadiazine for burn wounds	Colourless colonies on MacConkey agar. Production of pyocyanine and fluorescein Positive oxidase test. No lactose fermentation.
Rickettsia rickettsii	Bite of infected Dermacentor variabilis|wood or Rhipicephalus sanguineus|dog tick	Rocky mountain spotted fever	Doxycycline Chloramphenicol	(no preventive drug or approved vaccine) Vector control, such as clothing Prompt removal of attached ticks	Serology Immunofluorescence against Rickettsia antigens
Salmonella typhi	Human-human Fecal-oral through food or water	Typhoid fever type salmonellosis (dysentery, colitis)	Ceftriaxone Fluoroquinolones, e.g. ciprofloxacin	Ty21a and Vi capsular polysaccharide vaccine|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	Salmonellosis with gastroenteritis and enterocolitis	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	Colourless colonies on MacConkey agar
Shigella sonnei	Fecal-oral Flies Contaminated food or water	Shigellosis|Bacillary dysentery/Shigellosis	Ciprofloxacin or azithromycin	Protection of water and food supplies Vaccines are in trial stage	Culture on Hektoen agar or other media for intestinal pathogens
Staphylococcus aureus	Human flora on Mucous membrane|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 Infective_endocarditis#Classification|Acute infective endocarditis Septicemia Necrotizing pneumonia Toxinoses Toxic shock syndrome Staphylococcal food poisoning	Incision and drainage of localized lesions Nafcillin and oxacillin Vancomycin for Methicillin-resistant Staphylococcus aureus|Methicillin-resistant (MRSA)	(no vaccine or preventive drug) Barrier precautions, washing hands and fomite disinfection in hospitals	Microscopy showing strongly positive Gram staining|Gram stained cells in grape-like clusters Positive Catalase#Catalase_test|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 Prosthesis|prostheses, e.g. heart valves and catheters	Vancomycin	None	Microscopy showing strongly positive Gram staining|Gram stained cells in grape-like clusters Positive Catalase#Catalase_test|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	Cystitis in women	Penicillin G	None
Streptococcus agalactiae	Human flora in vagina or urethral mucous membranes, rectum Vertical transmission by birth Sexually transmitted disease|Sexual	Meningitis and septicemia in neonates Endometritis in postpartum women Opportunistic infections with septicemia and pneumonia	Penicillin G Ampicillin Aminoglycoside in case of lethal infection	None	Culture showing large colonies with Hemolysis_(microbiology)#Beta|β-hemolysis Negative catalase test Hydrolyzes sodium hippurate
Streptococcus pneumoniae	Respiratory droplets Often human flora in nasopharynx (spreading in immunocompromised)	Acute bacterial pneumonia & meningitis in adults Otitis media and sinusitis in children	Penicillin G Vancomycin for resistant strains	23-serotype vaccine for adults (Pneumococcal polysaccharide vaccine|PPV) Heptavalent conjugated vaccine for children (Pneumococcal conjugate vaccine|PCV)	Microscopy showing gram-positive, encapsulated lancet-shaped diplococci Hemolysis_(microbiology)#Alpha|α-hemolysis on blood agar, bile-soluble, optochin-sensitive Positive Quellung reaction
Streptococcus pyogenes	Respiratory droplets Direct physical contact with impetigo lesions	Streptococcal pharyngitis Scarlet fever Rheumatic fever Impetigo and erysipelas Puerperal fever Necrotizing fasciitis	Penicillin G Macrolide, e.g. clarithromycin or azithromycin in penicillin allergy Drainage and debridement for Necrotizing fasciitis	No vaccine Rapid antibiotic treatment helps prevent rheumatic fever	Culture on sheep blood agar forming small, Opalescence|opalescent surrounded by large zone of Hemolysis_(microbiology)#Beta|β-hemolysis Serology for Anti-streptolysin O|ASO Very bacitracin-sensitive
Treponema pallidum	Sexual	Syphilis Congenital syphilis	Penicillin G Erythromycin or tetracycline if penicillin allergy	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 Dark field microscopy Serology, including nontreponemal (Venereal Disease Research Laboratory test|VDRL, Rapid plasma reagin|RPR) and treponemal tests (FTA-ABS, TPI test|TPI, Syphilis TPHA test|TPHA)
Vibrio cholerae	Contaminated water and food, especially raw seafood	Cholera	Fluid and electrolyte replacement e.g. doxycycline to shorten duration	Preventing fecal contamination of water supplies and food Adequate food preparation	Culture on blood agar|blood or MacConkey agar, enhanced by Thiosulfate citrate bile sucrose|TCBS Positive oxidase test
Yersinia pestis	Fleas from animals Ingestion of animal tissues Respiratory droplets	Plague: Bubonic plague Pneumonic plague	Streptomycin primarily Gentamicin Tetracyclin Supportive therapy for Shock (circulatory)|shock	Formalin-killed plague vaccine Minimize exposure to rodents and fleas	Gram-negative smear If pneumonic, culture from aspirate on MacConkey agar|MacConkey or blood agar