Week 10: Gram-Negative Pathogenic Bacteria and Associated Diseases

Vocabulary practice flashcards covering Gram-negative pathogenic enterics, respiratory infections, meningitis, pyrogenic endotoxin response, reproductive tract pathogens, and urinary tract infections.

Shigella sonnei

The most common Shigella species in the United States, which causes a mild form of shigellosis.

Shigella dysenteriae

A Shigella species not common in the United States that causes a much more severe disease characterized by bloody diarrhea.

Salmonellosis

A gastrointestinal infection caused by Salmonella enterica, which inhabits the intestinal tract of humans and animals (including birds) and is transmitted via contaminated food or handling certain pets.

Infection Process of Salmonella enterica

A three-step progression: 1. Salmonella enters an epithelial cell; 2. It multiplies within a vesicle inside the cell; 3. It multiplies in mucosal cells, triggering an inflammatory response that results in diarrhea, occasionally crossing into the lymphatic system and bloodstream.

Pseudomonas aeruginosa

A Gram-negative, aerobic rod common in the environment that can cause opportunistic infections, particularly in burn victims and individuals with otitis externa.

Pyocyanin

A pigment produced by Pseudomonas aeruginosa that generates a distinct blue-green pus.

Otitis externa

An ear infection commonly known as "swimmer's ear," frequently caused by Pseudomonas aeruginosa.

Bronchitis

Inflammation of the bronchi caused by bacteria, viruses, or fungi.

Bronchiolitis

Inflammation of the bronchioles caused by bacteria, viruses, or fungi.

Pneumonia

An infection of the lungs that affects the alveoli, most commonly caused by bacteria such as Streptococcus pneumoniae.

Bordetella pertussis

A Gram-negative rod that causes pertussis, or "whooping cough," by attaching to and multiplying on the respiratory epithelium from the nasopharynx to the bronchi and bronchioles.

Transmission of Bordetella pertussis

Strictly human-to-human transmission via exposure to aerosol droplets; the infection is highly contagious and occurs most often in late summer and early fall.

Haemophilus influenzae (Meningitis)

A Gram-negative rod with a capsule that protects it from phagocytosis in the bloodstream, allowing rapid replication and potential entry into the cerebrospinal fluid (CSF).

Haemophilus influenzae (Pneumonia)

A Gram-negative, non-encapsulated coccobacillus causing pneumonia primarily in individuals with predisposing factors (alcoholism, poor nutrition, cancer, diabetes), treated with cephalosporins.

Neisseria meningitidis

A Gram-negative, encapsulated diplococcus that causes meningococcal meningitis, carried asymptomatically in the nasopharynx by $10\%$ of healthy individuals and prevented through vaccines recommended for college students.

Sepsis

A condition occurring when bacteria gain access to the bloodstream, become widely disseminated, and reproduce rapidly.

Pyrogenic Response to Endotoxins

A four-step pathway: 1. Macrophage ingests a Gram-negative bacterium; 2. Bacterium is degraded in a vacuole, releasing endotoxins that stimulate cytokine production (IL-1 and TNF); 3. Cytokines travel via blood to the hypothalamus; 4. Hypothalamus produces prostaglandins, resetting the thermostat to a higher temperature to cause fever.

Neisseria gonorrhoeae

A Gram-negative diplococcus responsible for gonorrhea, spread through intimate sexual contact or vertically during childbirth.

Clinical Presentations of Gonorrhea

Infections manifest primarily in the lower genital tract as male urethritis and female cervicitis; infections of the pharynx, rectum, and female urethra often present asymptomatically or minimally symptomatically.

Urethral Length Differences

The female urethra measures approximately $4\,\text{cm}$ in length, whereas the male urethra measures approximately $17.5\,\text{cm}$ in length.

Female UTI Predisposition

An increased susceptibility to urinary tract infections caused by a short urethra and close proximity to the anus.

Normal Urethral Microbiota

Microorganisms that normally colonize the urethra, including species of Lactobacillus and Staphylococcus, while the rest of the urinary organs remain sterile.

Urethritis

An inflammation of the urethra classified as a lower urinary tract infection.

Cystitis

A common lower urinary tract infection characterized by inflammation of the urinary bladder.

Pyelonephritis

An uncommon and serious upper urinary tract infection characterized by inflammation of one or both kidneys.

Catheter-Associated Nosocomial UTIs

Hospital-acquired urinary tract infections accounting for about $900{,}000$ cases annually, approximately $90\%$ of which are linked to urinary catheters.

Cystitis Causative Agents

The primary bacterial agents responsible for bladder inflammation: Escherichia coli (Gram-negative) and Staphylococcus saprophyticus (Gram-positive).

Dysuria

Difficult or painful urination, which serves as a common symptom of cystitis.

Pyuria

The presence of pus in the urine, indicative of a urinary tract infection.

Cystitis Diagnosis and Treatment

Diagnosed by laboratory isolation of $> 100\,\text{CFU/mL}$ of potential pathogens in urine, and commonly treated with trimethoprim-sulfamethexazole.