L 7Gram-Negative Bacterial Pathogens and Diseases

Comprehensive vocabulary flashcards covering the characteristics, toxins, disease mechanisms, and clinical presentations of medically important Gram-negative bacteria discussed in the lecture.

Neisseria gonorrhoeae

A Gram-negative diplococcus bacterium (commonly termed the gonococcus) that causes gonorrhea, the second most common bacterial STI, infection sites include: penis, vagina, anus. Known as “the drip”, & the “ The clap” causing localized pain, pus, and potential neonatal blindness.

Neisseria meningitidis

A Gram-negative, encapsulated diplococcus bacterium (meningococcus) that causes meningitis, spreading via person-to-person casual contact, especially in crowded settings like college dorms, prisons, and army barracks.

Can cause meningitis (inflammation of meninges, the protective membranes encasing the brain, & spinal cord). Origins include: bacterial species, viruses, and fungi. Symptoms: Bad headache, fever, neck stiffness & pain (esp when turning head due to inflamed cervical meninges surrounding the spinal cord), confusion, dizziness.

Meninges

The protective membranes that cover the central nervous system, including the brain and spinal cord.

Aseptic meningitis

Inflammation of the meninges that occurs without the presence of an infectious microbe.

Pseudomonas aeruginosa

A Gram-negative soil bacterium and obligate aerobe that causes opportunistic infections in burn victims (open wounds, compromised epithelium barrier, optimal conditions for obligate aerob colonization) and cystic fibrosis patients (point mutation in transmembrane cholride transporter gene→ disrupts fluid balance, =fluid accumulation in lung tissue→ perfect for P. aeruginosa (chronic pnumonia))

Pyocyanin

A blue-green pigment synthesized by Pseudomonas aeruginosa that gives characteristic greenish-blue coloration to pus and laboratory culture plates.

P. aeruginosa co-evolution competition

P. aeruginosa has access to carbon & energy sources, allowing it to break down complex substances, including antibiotics. It competes in the soil against antibiotic-producing microorganisms, and it withstands microbial warfare & can degrade antibiotics

Multidrug resistance pumps

Active transporters in bacterial cell membranes that utilize an energy source to actively pump antibiotics out of the cell, preventing lethal intracellular accumulation.

Vibrio cholerae

A Gram-negative, bent-shaped rod bacterium transmitted via contaminated water or food (fecal-oral route) that colonizes the intestine and produces cholera toxin.

Exotoxin

A bacterial toxin, typically a protein, synthesized by the cell and secreted into the surrounding environment; exotoxins are characteristically heat-labile ( unfold & denature when heatd)

AB toxin

A two-subunit bacterial exotoxin consisting of a binding (B) subunit that mediates attachment and cell entry, and an active (A) subunit that exerts enzymatic or toxic action inside the host cell.

Adenylate cyclase

A host enzyme targeted and irreversibly activated by cholera toxin's A subunit, leading to excessive intracellular production of cyclic AMP.

Rice water stool

The hallmark symptom of cholera characterized by profusely watery diarrhea containing flecks of dead, sloughed-off intestinal epithelial tissue resembling grains of rice.

Enterohemorrhagic E. coli (EHEC)

Strains of Escherichia coli that acquired the gene for Shiga toxin via transduction, causing severe intestinal tissue damage, bloody diarrhea, and potential kidney or liver failure.

Shiga toxin

An AB exotoxin produced by Shigella dysenteriae and EHEC that binds host epithelial cells and cleaves host ribosomes, halting protein synthesis and killing the cell.

Kauffman-White system

A serological scheme used to identify and distinguish bacterial serovars based on reactions with antibodies targeting O, H, and K antigens.

O antigen

The somatic antigen corresponding to a specific molecular structure on the lipopolysaccharide (LPS) layer of Gram-negative bacterial cells.

H antigen

The flagellar antigen corresponding to specific variations of the flagellin protein that makes up bacterial flagella.

K antigen

The capsular antigen evaluated in the Kauffman-White classification system, which is absent in Escherichia coli because it lacks a capsule.

Salmonella enterica

Salmonellosis: food poisoning (gastrointestinal infection)

Typhoid fever: prolonged high fever & temporary red spots on the skin

Food infection

Food poisoning that results from ingesting viable bacterial cells that multiply inside the gastrointestinal tract before symptoms appear.

Food intoxication

Food poisoning with rapid onset resulting from the direct consumption of pre-formed toxins produced by bacteria that grew in the food.

What is the first bacteria to have its entire genome fully sequenced?

E.coli

Dysentery

Severe diarrhea containing blood, mucus, or both, resulting from significant damage to the intestinal lining.

Typhoid fever

A systemic infection caused by specific strains of Salmonella enterica transmitted via the oral-fecal route, characterized by dangerously high fevers and occasionally a rash.

Mary Mallon (Typhoid Mary)

An asymptomatic carrier cook in Boston during the early 1900s who transmitted Salmonella enterica to multiple households through contaminated food.

Shigella dysenteriae

An obligate human Gram-negative pathogen spread via the oral-fecal route that natively synthesizes Shiga toxin(ribosome damage) and causes dysentery.

Yersinia pestis

A Gram-negative bacterium closely related to Escherichia coli that causes plague; it is naturally harbored by rodents and transmitted by flea bites.

Buboes

Swollen, infected, and blackened lymph nodes characteristic of bubonic plague following the bite of an infected flea.

Septicemic plague

A systemic form of plague resulting from Yersinia pestis invading the bloodstream (often after a bubo bursts), causing extremity tissue necrosis; historically known as the Black Death (fingers, toes & nose turn black)

Pneumonic plague

The most lethal form of plague, characterized by a Yersinia pestis lung infection with an untreated mortality rate of approximately $85\%$, and the only form transmissible person-to-person via respiratory droplets.

Justinian Plague

The first major global pandemic of Yersinia pestis, occurring in the 700s.