Infectious Disease: Bacterial Morphology, Cell Structure, and Key Pathogens

Bacteria can exist in various shapes:

cocci (spherical), bacilli (rod-shaped), and spiral (helical).

Spiral-shaped organisms

can be further classified into spirilla (rigid) and spirochetes (flexible).

Morphology vs arrangement

morphology refers to the shape of the bacteria,

while arrangement refers to how they group together (e.g., chains, clusters).

Cocci arrangements

include diplococci (pairs), streptococci (chains), and staphylococci (clusters).

Bacilli arrangements

can be single, in pairs (diplobacilli), or chains (streptobacilli).

Microorganisms are categorized into three main types:

eukaryotic cells (e.g., fungi, protozoa), prokaryotic cells (e.g., bacteria), and viruses.

Eukaryotic cells are generally

larger and more complex than prokaryotic cells, which lack a nucleus.

Viruses are

the smallest, requiring a host cell to replicate and are not classified as living organisms.

Size Comparison

Eukaryotic cells

typically range from 10-100 micrometers in diameter

Viruses

can be as small as 20-300 nanometers, making them significantly smaller than both eukaryotic and prokaryotic cells.

SOAP

stands for Subjective, Objective, Assessment, and Plan, which are the four components of a clinical note.

Subjective:

Patient's reported symptoms and history.

Objective:

Clinician's observations and findings during examination

Assessment:

Diagnosis based on subjective and objective data.

Plan:

Proposed treatment and follow-up actions.

HPI

(History of Present Illness)

OPQRST(U) is a mnemonic for HPI questions:

Onset, Provocation, Quality, Radiation, Severity, Timing, and Understanding.

SAMPLE is another mnemonic for gathering patient history:

Signs/Symptoms, Allergies, Medications, Past medical history, Last oral intake, Events leading to the present illness.

The nucleoid

is the region in prokaryotic cells where the bacterial DNA is located, typically in a single circular chromosome.

Bacteria replicate their DNA through a process called

binary fission, which is a form of asexual reproduction.

Plasmids are

small, circular DNA molecules that can carry genes beneficial for survival, such as antibiotic resistance.

Prokaryotic ribosomes

are smaller (70S) compared to eukaryotic ribosomes (80S) and are composed of rRNA and proteins.

prokaryotic ribosome,

showing its 30S small subunit, 50S large subunit, and the complete 70S ribosome formed by their combination.

Fimbriae and pili

are hair-like structures on the surface of prokaryotic cells that aid in attachment to surfaces and other cells.

Flagella

are long, whip-like structures that enable motility; they can be arranged in various ways (monotrichous, lophotrichous, amphitrichous, and peritrichous).

Environmental triggers

can influence flagellar movement, directing bacteria toward nutrients (positive chemotaxis) or away from harmful substances (negative chemotaxis).

Sporulation

is the process by which certain bacteria form endospores in response to adverse environmental conditions.

Common endospore formers

include Bacillus and Clostridium species.

These bacteria can survive extreme conditions like heat, desiccation, and chemical exposure. (sporulation)

Sporulation allows

bacteria to survive extreme conditions, such as heat, desiccation, and nutrient depletion.

Sporulation is activated..

The process is activated when environmental stressors are detected, prompting the cell to enter a dormant state.

Giardiasis is caused by

protozoan Giardia lamblia, leading to changes in the intestinal lining and symptoms like diarrhea and steatorrhea (fatty stools).

Steatorrhea occurs due to

malabsorption of fats, which can significantly affect a patient's nutritional status.

Rat-bite fever is caused by

Streptobacillus moniliformis and can lead to fever, rash, and joint pain.

Cholera, caused by

Vibrio cholerae, results in severe diarrhea and dehydration, requiring prompt treatment to prevent mortality.

Dracunculiasis, or Guinea worm disease,

is characterized by painful blisters and can be prevented through clean water initiatives.

Ascariasis is caused by

the roundworm Ascaris lumbricoides, leading to gastrointestinal symptoms and malnutrition, as seen in the case of Jordan Casey.

Strep throat, caused by

Streptococcus pyogenes, presents with sore throat, fever, and swollen lymph nodes, requiring throat culture for diagnosis.

Differentiating between strep throat and oral candidiasis

involves assessing symptoms and conducting appropriate tests

prokaryotic cells

range from 0.2-10 micrometers.