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)

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

Hepatovirus

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

Filoviridae

• Family: Filoviridae

  Ebola virus

• Type: RNA virus, single-stranded, enveloped

• Disease: Hemorrhagic fever

Morbillivirus

• Family: Paramyxoviridae (Genus: Morbillivirus)

• Measles virus

• 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

• infect a wide range of mammals and birds

• mostly humans

• human and swine, rarely cause disease

enveloped , strain is id by differences in spikes on protein coats

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

contains reverse transcriptase

lentivirus

HIV human immunodeficiency virus 1 and 2 aids-acquired immunodeficiency syndrome

*RNA virus that produce DS DNA

hemagglutinin HA

needed for entry 16 subtypes

neuraminidase NA

needed for release 9 subtypes

coronavirdiae

RNS enveloped

coronavirus