A SELECTION OF BACTERIA OF MEDICAL SIGNFICANCE

Bordetella pertussis

• Morphology: Gram-negative aerobic rod

• Disease: Pertussis (Whooping Cough)

• Common Sources: Respiratory droplets, human-to-human transmission

Neisseria gonorrhoeae

• Morphology: Gram-negative diplococcus

• Disease: Gonorrhea (STD)

• Common Sources: Sexual contact, vertical transmission (mother to baby during birth)

Neisseria meningitidis

• Morphology: Gram-negative diplococcus

• Disease: Meningococcal Meningitis (infection of the meninges of the brain/spinal cord)

• Common Sources: Respiratory droplets, close contact in crowded environments

Pseudomonas aeruginosa

• Morphology: Gram-negative rod, aerobic

• Disease: Opportunistic infections host, such as burn victims

• Common Sources: Soil, water, hospital environments, contaminated medical devices

Treponema pallidum

• Morphology: Gram-negative spirochete

• Disease: Syphilis (STD)

• Common Sources: Sexual contact, vertical transmission (mother to fetus)

Borrelia burgdorferi

• Morphology: Gram-negative spirochete

• Disease: Lyme Disease

• Common Sources: Tick bites (Ixodes species

Escherichia coli

• Morphology: Gram-negative facultative anaerobic rod

• Disease:

  • Diarrhea

  • UTIs

  • Neonatal meningitis

  • Sepsis in hospitalized patients

• Common Sources: Contaminated food/water, normal intestinal flora, fecal-oral transmission

• Special Strain: O157:H7 causes hemolytic uremic syndrome (renal failure)

Klebsiella pneumoniae

• Morphology: Gram-negative facultative anaerobic rod

• Disease:

  • Sepsis

  • Pneumonia (high mortality rate)

  • UTIs (hospital-acquired)

• Common Sources: Hospital environments, respiratory secretions, contaminated hands

Salmonella

• Morphology: Gram-negative facultative anaerobic rod

• Disease:

  • Typhoid fever

  • Sepsis

  • Gastroenteritis (food poisoning)

• Common Sources:

  • Contaminated food/water (especially undercooked poultry, eggs)

  • Handling reptiles (turtles, snakes)

S. typhi

• Morphology: Gram-negative rod

• Disease: Typhoid fever

• Common Sources: Contaminated water, food, fecal-oral transmission

S. enterica

• Morphology: Gram-negative rod

• Disease: Food poisoning

• Common Sources: Undercooked chicken, eggs, raw produce

Vibrio cholerae

• Morphology: Gram-negative curved rod

• Disease: Cholera (severe diarrhea, "rice water" stools)

• Common Sources: Contaminated water, raw shellfish

Haemophilus influenzae

• Morphology: Gram-negative coccobacillus

• Disease:

  • Upper respiratory infections

  • Epiglottitis

  • Sinusitis

  • Ear infections

  • Pneumonia

  • Meningitis

• Common Sources: Respiratory droplets, person-to-person contact

Streptococcus pyogenes (Group A Beta-Hemolytic)

• Morphology: Gram-positive cocci in chains

• Disease:

  • Strep throat

  • Scarlet fever

  • Folliculitis

  • Impetigo

  • Necrotizing fasciitis

  • Toxic shock syndrome

• Common Sources: Respiratory droplets, skin contact

Streptococcus agalactiae (Group B Strep)

• Morphology: Gram-positive cocci in chains

• Disease:

  • Neonatal meningitis

  • Pneumonia

  • Sepsis

• Common Sources:

  • Vaginal flora (transmitted to newborn during birth)

  • Respiratory secretions

Streptococcus mutans

• Morphology: Gram-positive cocci in chains

• Disease: Dental caries (cavities)

• Common Sources: Oral cavity, sugar-rich diets (biofilm formation

Streptococcus pneumoniae

• Morphology: Gram-positive lancet-shaped diplococcus

• Disease:

  • Pneumonia (most common cause in adults)

  • Bacterial meningitis (in adults)

  • Otitis media (ear infection in children)

• Common Sources: Respiratory droplets, normal flora of the upper respiratory tract

Staphylococcus aureus

• Morphology: Gram-positive cocci in clusters

• causes a broad range of human disease and can infect almost any organ system

• Diseases: broken into diseases caused by exotoxin release; skin infections, meningitis, acute bacterial endocarditis, sepsis pneumonia uti etc including MRSA

Staphylococcus epidermidis

• Morphology: Gram-positive cocci

• Diseases: Opportunistic/nosocomial infections: UTIs, IV catheter-related sepsis, prosthetic device infections

• Normal flora: Skin

• normally causes no disease

Enterococcus faecalis

• Morphology: Gram-positive cocci

• Diseases: UTIs, endocarditis

• Note: Common nosocomial infection; intrinsic resistance to many antibiotics

Bacillus anthracis

• Morphology: Gram-positive rod, spore-forming, aerobic

• Disease: Anthrax – cutaneous, GI, or pulmonary

• Notes: Zoonotic; bioweapon potential due to spore stability, size, high mortality

• primarily affects herbivores such as cows/sheep

• HUMAN exposure from contact with these animals, soils , animal products

Bacillus cereus

• Morphology: Gram-positive rod, spore-forming, aerobic

• Disease: Food poisoning from heat-stable toxins

• Common sources: Rice and starchy foods

clostridium tetani

• Morphology: Gram-positive rod, spore-forming, obligate anaerobe

• Disease: Tetanus – muscle spasms, "lockjaw"

• mortality is high

• Transmission: Soil, animal feces → wound entry

Clostridium botulinum

• Morphology: Gram-positive rod, spore-forming, obligate anaerobe

• Disease: Botulism – flaccid paralysis

• Mechanism: Neurotoxin

Clostridium difficile

• Morphology: Gram-positive rod, spore-forming, obligate anaerobe

• Disease: Antibiotic-associated diarrhea

• Note: Toxin-mediated

Mycobacterium tuberculosis

• Morphology: Acid-fast bacilli (not Gram-stained), obligate aerobe

• Disease: Tuberculosis (TB) (primarily lungs)

• Notes: Latent vs active; high mortality untreated; global #1 infectious disease killer

Human Papillomavirus (HPV)

• Family: Papovaviridae

• Type: DNA virus, double-stranded, non-enveloped

• Diseases: Warts (types 1,2,6,11), cervical cancer (oncoviruses 16,18)

• Replication: DNA-dependent DNA polymerase, nuclear replication

• Morphology: Icosahedral capsid

Herpesviridae

• Type: DNA virus, double-stranded, enveloped

• Diseases: Cold sores (HSV-1), genital herpes (HSV-2)

• Latency: Yes

• can remain latent

Varicella-Zoster Virus (HHV-3)

• Type: DNA virus, double-stranded, enveloped

• Diseases: Chickenpox, shingles

• Latency: Yes

• Replication: Nuclear

• Morphology: Enveloped icosahedral

orthoheadnavirus

• Type: DNA virus, double-stranded, enveloped

• Diseases: Hepatitis B, liver cancer (oncovirus)

• Transmission: Blood, needles, intercourse, birth

• Replication: Reverse transcription (unusual for DNA virus)

oncovirus ( liver cancer)

Rhinovirus

• Family: Picornaviridae

• Type: RNA virus, single-stranded, non-enveloped

• Diseases: Common cold, bronchitis

Hepatitis A Virus (HAV)

6. Hepatitis A Virus (HAV)

• Family: (Genus: Hepatovirus)

• Type: RNA virus, single-stranded, non-enveloped

• Transmission: Fecal-oral (contaminated food/water)

Norovirus (Norwalk virus)

• Family: Caliciviridae

• Type: RNA virus, single-stranded, non-enveloped

• Disease: Viral gastroenteritis, Norwalk virus

Ebola virus

• Family: Filoviridae

• Type: RNA virus, single-stranded, enveloped

• Disease: Hemorrhagic fever

Measles virus

• Family: Paramyxoviridae (Genus: Morbillivirus)

• Type: RNA virus, single-stranded, enveloped

• Disease: Measles

oronavirus (e.g., SARS-CoV-2)

• Family: Coronaviridae

• Type: RNA virus, single-stranded, enveloped

• Disease: Respiratory illnesses incl. COVID-19

• Morphology: Enveloped, crown-like spikes

• Replication: Cytoplasmic (positive-sense RNA)

Rotavirus

• Family: Reoviridae

• Type: RNA virus, double-stranded, non-enveloped

• Disease: Viral gastroenteritis (esp. children)

Influenza virus (Types A, B, C)

• Family: Orthomyxoviridae

• Type: RNA virus, segmented, single-stranded, enveloped

• Disease: Influenza

• Replication: Nuclear (unusual for RNA virus)

• Spikes: Hemagglutinin (HA), Neuraminidase (NA)

• Antigenic Drift: Minor mutations → epidemics

• Antigenic Shift: Major reassortments → pandemics

• Morphology: Enveloped, helical

antigenic drift

causes epidemics, minor changes based in random mutation

antigenic shift

more likely to cause pandemic assortment of viral genome; segments undergo recombination

Retroviridae

• Family:(Genus: Lentivirus)

• Type: RNA virus, enveloped

• Replication: Reverse transcriptase → dsDNA → integrates into host genome

• Disease: AIDS (Acquired Immunodeficiency Syndrome)