List of Pathogenic Bacteria

In clinical and public-health settings, having a clear, searchable list of bacterial threats makes it easier to prioritize surveillance, prevention, and treatment. Whether you’re scanning for hospital risks or studying zoonotic transmission, a compact reference saves time and reduces guesswork.

There are 92 Pathogenic Bacteria, ranging from Acinetobacter baumannii to Yersinia pestis. For each entry the columns are Scientific name,Main diseases,Transmission / reservoir, which you’ll find below.

Which bacteria on the list are most often linked to hospital-acquired infections?

Common hospital-associated pathogens include Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae and certain strains of Staphylococcus aureus; the list shows their main diseases and typical reservoirs so you can target infection-control measures like hand hygiene, environmental cleaning, and antimicrobial stewardship.

How can I use this list to assess local public health risk?

Use the columns to filter by transmission route and disease severity: prioritize organisms with airborne or vector-borne spread and high morbidity, compare against local surveillance data, and consult clinical labs for confirmation—this helps convert the list into practical actions for prevention and reporting.

Pathogenic Bacteria

Images and Descriptions

Staphylococcus aureus

Common human skin and nasal commensal that causes superficial to life‑threatening invasive infections; notable for toxin-mediated disease and frequent antibiotic resistance complicating therapy.

MRSA (methicillin-resistant Staph. aureus)

Methicillin-resistant strains are important hospital and community pathogens; resistance narrows antibiotic choices and MRSA causes outbreaks, severe invasive disease, and increased healthcare burden.

Streptococcus pyogenes (Group A Strep)

A common cause of pharyngitis and invasive soft tissue infections; post-infectious immune complications (rheumatic fever, glomerulonephritis) and toxin-related severe disease make it clinically significant.

Streptococcus pneumoniae

Leading cause of community-acquired pneumonia and bacterial meningitis; encapsulated strains vary in vaccine coverage and antibiotic resistance patterns affect treatment choices.

Streptococcus agalactiae (Group B Strep)

Colonizes vagina/rectum in many adults; causes severe neonatal disease during childbirth and invasive infections in older adults; screening and intrapartum antibiotics prevent newborn infections.

Enterococcus faecalis

Normal intestinal flora that causes hospital-acquired infections, especially with urinary catheters and prosthetic devices; notable for intrinsic and acquired antibiotic resistance.

VRE (vancomycin-resistant Enterococcus)

Vancomycin-resistant strains complicate treatment of enterococcal infections in hospitals; often associated with prolonged antibiotic exposure and invasive devices.

Escherichia coli (pathogenic strains)

Common gut bacterium with strains causing UTIs, bloodstream and wound infections; some produce toxins or extended-spectrum beta-lactamases that drive clinical concern.

E. coli O157:H7

A shiga-toxin producing strain causing bloody diarrhea and sometimes life-threatening kidney failure (HUS), often linked to foodborne outbreaks and person-to-person spread.

Klebsiella pneumoniae

Encapsulated Gram-negative pathogen causing hospital- and community-acquired infections; some strains carry carbapenemases causing multidrug resistance and severe disease.

Pseudomonas aeruginosa

Opportunistic pathogen thriving in moist niches and devices; causes severe infections in immunocompromised hosts and is notable for intrinsic resistance and biofilm formation.

Acinetobacter baumannii

Environmentally hardy hospital pathogen causing difficult-to-treat infections in ICUs; frequently multidrug-resistant and associated with outbreaks.

Enterobacter cloacae complex

Opportunistic Enterobacter species cause nosocomial infections and can acquire inducible beta-lactamases, complicating antibiotic therapy.

Proteus mirabilis

Motile Gram-negative commonly causing complicated urinary tract infections and struvite stone formation due to urease activity; often associated with catheters.

Serratia marcescens

Opportunistic pathogen causing nosocomial outbreaks; notable for red pigment production and multiple resistance mechanisms.

Neisseria meningitidis

Causes rapid-onset meningitis and systemic sepsis; carriage common, outbreaks in close communities, vaccines target major serogroups.

Neisseria gonorrhoeae

Sexually transmitted bacterium causing mucosal infection with rising antibiotic resistance; can disseminate causing arthritis and systemic illness.

Haemophilus influenzae

Encapsulated type b historically caused severe pediatric meningitis; vaccines have greatly reduced Hib disease; non-typeable strains cause otitis and bronchitis.

Bordetella pertussis

Highly contagious cause of prolonged coughing illness, severe in infants; vaccination prevents disease but waning immunity and outbreaks occur.

Legionella pneumophila

Environmental waterborne bacterium causing severe pneumonia when inhaled from contaminated aerosols; diagnosis often requires specialized tests and environmental control.

Mycobacterium tuberculosis

Obligate pathogen causing chronic pulmonary disease with significant global morbidity; long treatment courses required and drug resistance (MDR/XDR) complicates control.

Mycobacterium avium complex (MAC)

Nontuberculous mycobacteria causing chronic lung disease in vulnerable hosts and disseminated disease in immunocompromised people; requires prolonged combination therapy.

Listeria monocytogenes

Foodborne pathogen able to grow at refrigerator temperatures; causes severe fetal, neonatal, and elderly disease with high morbidity.

Salmonella enterica serovar Typhi

Cause of systemic enteric fever with prolonged bacteremia; transmission via contaminated food/water and chronic carriers; antimicrobial resistance is rising.

Non-typhoidal Salmonella

Common cause of foodborne diarrheal illness; invasive disease occurs in infants, elderly or immunocompromised hosts.

Shigella species

Highly infectious cause of severe, sometimes bloody diarrhea and cramps; outbreaks common in crowded settings and antimicrobial resistance is a clinical challenge.

Vibrio cholerae

Produces cholera toxin causing rapid watery diarrhea and severe dehydration; public health concern in outbreaks with need for rehydration therapy.

Vibrio vulnificus

Causes rapidly progressive wound infections and life-threatening sepsis, especially in patients with liver disease; associated with raw oyster consumption and seawater exposure.

Campylobacter jejuni

A frequent cause of foodborne diarrhea; postinfectious autoimmune sequelae (Guillain–Barré) can occur; commonly produces fever and bloody stools.

Helicobacter pylori

Colonizes stomach lining causing chronic gastritis and ulcers; long-term infection increases gastric cancer risk and requires combination antibiotic therapy for eradication.

Clostridioides difficile

Toxin-producing nosocomial pathogen causing severe antibiotic-associated diarrhea and colitis; spores persist in environment and recurrence is common.

Clostridium perfringens

Anaerobic spore-former causing rapid soft tissue necrosis (myonecrosis) and common foodborne illness from preformed toxins.

Clostridium tetani

Produces neurotoxin causing painful muscle rigidity and spasms; preventable by vaccination and treatable with antitoxin and supportive care.

Clostridium botulinum

Produces potent neurotoxins causing flaccid paralysis; foodborne, wound, and infant forms require antitoxin and supportive respiratory care.

Corynebacterium diphtheriae

Produces toxin causing throat pseudomembrane and systemic complications; rare where vaccination is routine, but severe when it occurs.

Bacillus anthracis

Spore-forming pathogen causing severe disease forms, historically linked to biothreat concerns; cutaneous anthrax most common, inhalational is often fatal without treatment.

Yersinia pestis

Cause of historic pandemics; still causes rural bubonic plague via flea transmission and severe pneumonic plague that can transmit person-to-person.

Francisella tularensis

Highly infectious zoonotic bacterium from rabbits/ticks causing varied clinical syndromes; inhalational tularemia can be severe and requires specific therapy.

Brucella species

Causes chronic febrile illness with bone/joint involvement often from unpasteurized dairy or livestock contact; intracellular organism requiring prolonged therapy.

Treponema pallidum

Spirochete causing multisystem disease over stages; diagnosis with serology and treatable with penicillin, important for congenital infection prevention.

Borrelia burgdorferi

Tick-borne spirochete causing early skin lesion and possible later joint, neurologic, or cardiac involvement; diagnosis often clinical plus serology.

Rickettsia rickettsii

Obligate intracellular bacteria causing febrile illness with rash and potential severe vasculitis; prompt doxycycline therapy critical.

Ehrlichia chaffeensis

Intracellular tick-transmitted pathogen causing febrile illness and hematologic abnormalities, diagnosed by PCR or serology and treated with doxycycline.

Chlamydia trachomatis

Obligate intracellular bacterium causing common sexually transmitted infections and ocular disease; often asymptomatic but causes reproductive complications if untreated.

Chlamydia pneumoniae

Causes community-acquired atypical respiratory infections; diagnosis via serology or PCR and treated with macrolides or doxycycline.

Mycoplasma pneumoniae

Small cell-wall–less bacterium causing mild to moderate atypical pneumonia, common in young adults; lacks a cell wall so beta-lactams are ineffective.

Mycoplasma genitalium

Emerging sexually transmitted pathogen causing persistent urethritis and cervicitis; increasing macrolide resistance complicates treatment.

Ureaplasma urealyticum

Small cell-wall–less organism colonizing genitourinary tract; can cause disease in neonates and contributes to obstetric complications in some settings.

Bacteroides fragilis

Anaerobic gut flora that causes intra-abdominal infections and abscesses; often involved in polymicrobial infections and may be beta-lactamase producing.

Gardnerella vaginalis

Associated with bacterial vaginosis from disrupted vaginal flora; causes discharge and odor and has implications for pregnancy and STI susceptibility.

Actinomyces israelii

Filamentous Gram-positive anaerobe causing chronic draining sinuses often after mucosal disruption; requires prolonged antibiotic therapy and sometimes surgery.

Nocardia asteroides complex

Weakly acid-fast branching rods causing pulmonary and disseminated disease mainly in immunocompromised patients; prolonged combination therapy needed.

Pasteurella multocida

Rapidly causes soft tissue infection after animal bites; clinical history of animal exposure guides early empiric therapy.

Haemophilus ducreyi

Causes sexually transmitted genital ulcers (rare in many regions); diagnosis clinical and by culture or molecular methods in endemic areas.

Streptococcus anginosus group

Part of oral and gut flora prone to cause purulent abscesses and invasive infections, often polymicrobial and requiring drainage plus antibiotics.

Streptococcus viridans group

Common oral commensals that can seed damaged heart valves causing subacute endocarditis; also implicated in dental disease and abscesses.

Gardnerella vaginalis

Associated with bacterial vaginosis from disrupted vaginal flora; causes discharge and odor and has implications for pregnancy and STI susceptibility.

Campylobacter fetus

Less common Campylobacter species causing systemic infections and complications in immunocompromised hosts and pregnant women.

Klebsiella granulomatis

Causes chronic genital ulcers (donovanosis) in endemic regions; diagnosis by Donovan bodies and treatable with antibiotics.

Bordetella parapertussis

Causes milder pertussis-like illness; similar transmission and clinical features but generally less severe than B. pertussis.

Gardnerella vaginalis

Associated with bacterial vaginosis from disrupted vaginal flora; causes discharge and odor and has implications for pregnancy and STI susceptibility.

Streptococcus suis

Zoonotic pathogen causing severe meningitis and sepsis in people with swine exposure; occupational risk for farmers and butchers.

Mycobacterium leprae

Slow-growing obligate pathogen causing chronic skin and peripheral nerve disease; treatable but can cause long-term disability and stigma.

Enterotoxigenic Bacteroides

Certain Bacteroides strains contribute to diarrheal illness and are common players in polymicrobial intra-abdominal infections, often requiring anaerobic coverage.

Chromobacterium violaceum

Rare environmental bacterium causing fulminant sepsis following wound contamination in tropical regions; high mortality without prompt treatment.

Leptospira interrogans

Spirochetal zoonosis causing a spectrum from mild fever to severe multi-organ failure; occupational and recreational exposure risks.

Capnocytophaga canimorsus

Oral commensal of dogs/cats causing fulminant sepsis in asplenic or immunocompromised people after bites or licks; early recognition important.

Tropheryma whipplei

Rare systemic disease caused by intracellular bacterium leading to chronic GI and multi-system symptoms; diagnosis by tissue PCR/biopsy and long-term antibiotics.

Eikenella corrodens

Part of normal oral flora causing infections after human bites or dental procedures; often mixed infections requiring specific antibiotic coverage.

Klebsiella oxytoca

Closely related to K. pneumoniae and implicated in nosocomial infections; can cause antibiotic-associated colitis and carries resistance determinants.

Providencia stuartii

Opportunistic Enterobacterales associated with complicated urinary tract infections and device-related outbreaks, often resistant to multiple antibiotics.

Sneathia spp.

Anaerobic vaginal bacteria associated with preterm birth and adverse pregnancy outcomes; emerging recognition in obstetric infections.

Eggerthella lenta

Anaerobic gut organism intermittently pathogenic in intra-abdominal and bloodstream infections, often in polymicrobial disease and difficult to culture.

Stenotrophomonas maltophilia

Opportunistic Gram-negative environmental pathogen causing hospital infections with intrinsic multi-drug resistance; treatment choices limited.

Providencia rettgeri

Opportunistic pathogen causing complicated UTIs and device-associated infections; capable of antimicrobial resistance that complicates therapy.

Bartonella henselae

Causes localized lymphadenopathy after cat exposure and vascular proliferative disease in immunocompromised people; diagnosed by serology or PCR.

Anaplasma phagocytophilum

Intracellular tick-transmitted pathogen causing febrile illness with hematologic abnormalities; early doxycycline treatment recommended.

Legionella longbeachae

Associated with exposure to contaminated soil and potting compost rather than water systems; causes Legionnaires’-type pneumonia, particularly in gardeners.

Chryseobacterium meningosepticum

Rare but serious cause of neonatal meningitis and nosocomial infections with intrinsic resistance; outbreaks linked to contaminated hospital equipment.

Pasteurella canis

Similar to P. multocida, can cause cellulitis and soft tissue infections following dog-related injuries; early wound management critical.

Mycobacterium marinum

Slow-growing nontuberculous mycobacterium causing chronic skin lesions after minor injuries in aquatic environments; requires prolonged targeted therapy.

Yersinia enterocolitica

Causes diarrheal illness often mistaken for appendicitis in children; can trigger reactive arthritis and is transmitted via contaminated food.

Campylobacter coli

Less common Campylobacter species causing diarrheal disease similar to C. jejuni; foodborne transmission predominates.

Kingella kingae

Common cause of bone and joint infections in young children, often following respiratory colonization; diagnosis benefits from molecular methods.

Enterococcus casseliflavus

Less common enterococcus species that can cause opportunistic infections and carries intrinsic low-level vancomycin resistance in some strains.

Actinobacillus actinomycetemcomitans

Oral pathogen implicated in periodontal disease and occasional endocarditis; associated with dental infections and systemic spread.

Coxiella burnetii

Intracellular pathogen transmitted from livestock causing acute febrile illness and chronic endocarditis; notable for environmental stability and occupational risk.

Legionella anisa

Environmental Legionella species occasionally cause pneumonia similar to L. pneumophila; identification important for source control.

Treponema pertenue

Nonvenereal treponemal disease causing chronic skin and bone lesions in tropical areas; treatable with antibiotics and targeted public health campaigns.

Brucella canis

Dog-associated Brucella species causing febrile illness in people with close canine exposure; less common than livestock-associated species.

Corynebacterium jeikeium

Opportunistic, multidrug-resistant skin commensal causing infections in immunocompromised and device-bearing patients; often needs targeted therapy.

Bartonella quintana

Louse-borne bacterium historically causing trench fever and currently linked to chronic bacteremia and endocarditis in vulnerable populations.

Bacteria of Other Types