Microbiology - Bacteriology

Bacterial Structure and Function

• Prokaryotes are characterized by a lack of membranous organelles.
• Key structural components of bacteria include the nucleoid, flagella, pili, and fimbriae.
• The bacterial cell wall's main function is to protect against osmotic lysis and mechanical damage.
• The bacterial cell wall is primarily a peptidoglycan layer.
• The Gram stain differentiates bacteria based on their cell wall structure, Gram-positive bacteria appear purple after staining.
• Staphylococcus is a Gram-positive coccus.
• Escherichia coli is a Gram-negative bacillus.
• The four phases of the bacterial growth curve are lag, log, stationary, and death.
• The log phase of the bacterial growth curve features the most rapid cell division.
• Ribosomes in bacterial cells are responsible for protein synthesis.
• An outer membrane is a structure unique to Gram-negative bacteria.
• Glycocalyx is the primary component of the bacterial capsule.
• Flagella primarily function in motility.
• Pili or fimbriae's main role is attachment to host tissues.

Bacteria-Specific Terminology & Classification

• A microorganism that causes disease upon colonizing a host is a pathogen.
• An obligate pathogen must infect a host and cause disease to multiply and transmit.
• An opportunistic pathogen becomes pathogenic under certain conditions, not ordinarily causing disease.
• Pathogenicity describes a microorganism's ability to cause disease, while virulence is the degree of pathogenicity.
• The capacity of a bacterium to survive and multiply inside and outside host cells is best described as facultative intracellular.
• A small, circular DNA molecule capable of replicating independently of the bacterial chromosome is called a plasmid.
• Cell-to-cell communication in bacteria is known as quorum sensing.
• Bactericidal agents kill bacteria.
• The minimum inhibitory concentration (MIC) measures the highest dilution of an antibacterial agent that inhibits growth.
• Transformation is the process by which bacteria acquire and incorporate DNA fragments.
• Phylogeny refers to the evolutionary history of organisms.
• Taxonomy is the study of bacterial identification, nomenclature, and classification.
• Phylum reflects a broader classification of bacteria than genus or species.
• Genus is the basic taxonomic unit.
• Infection is the establishment and multiplication of pathogens in a host.

Bacterial Pathogenesis

• Mutation is not a step in bacterial pathogenesis.
• Virulence factors are bacterial traits that make them pathogenic.
• Capsule, flagella, and toxins are bacterial virulence factors.
• Endospores are not a type of bacterial toxin.
• Endotoxins are located in the outer membrane of Gram-negative bacteria.
• Protection against phagocytosis is a function of the bacterial capsule.
• Flagella play a role in bacterial pathogenesis.
• Quorum sensing is the process of bacterial cell-to-cell communication using signaling molecules.
• Biofilm is a structured community of microorganisms attached to a surface.
• Virulence factors transfer between bacteria through conjugation, transduction, and transformation.

Treatment of Bacterial Diseases

• An antimicrobial agent kills microbes or prevents their pathogenic effect via natural, semisynthetic, or synthetic origins.
• A broad-spectrum antimicrobial agent is effective against both Gram-positive and Gram-negative bacteria.
• Bactericidal antimicrobial agents kill bacteria.
• To alter bacterial DNA is NOT a mode of action of antibacterial agents.
• Beta-lactams are a class of antibiotics that inhibits cell wall synthesis.
• Beta-lactam antibiotics' mechanism is to Inhibit peptidoglycan synthesis.
• Aminoglycosides inhibit the 30S subunit of bacterial ribosome.
• Quinolones inhibit DNA synthesis.
• Sulphonamides interfere with folic acid formation.
• AST stands for Antimicrobial Susceptibility Testing.
• Antimicrobial susceptibility testing determines the sensitivity of bacteria to antibiotics in vitro.
• Broth dilution test measures the minimum inhibitory concentration (MIC) of an antibiotic.
• Over-prescribing of antibiotics, patients not finishing treatment, and overuse in livestock farming are causes of antimicrobial resistance.
• Increased drug absorption is NOT a mechanism of antimicrobial resistance.
• Activation of drug efflux pumps enables bacteria to pump out antibiotics.

Microbial Control

• Sterilization eradicates all viable microorganisms, including spores.
• Autoclaving is a sterilization method.
• Sterilization kills all microorganisms, but disinfection does not kill spores.
• Heat, radiation, and filtration are physical methods of microbial control.
• Carbolic acid (phenol) is used as an antiseptic in surgery.
• Pasteurization kills heat-susceptible organisms in food and beverages.
• Liquid is a chemical method of microbial control.
• Type/number of microorganisms and temperature/pH affect microbial control.
• Bacterial spores are the most difficult to kill, while vegetative bacteria are the easiest.

Bacterial Vaccines

• Vaccines work by stimulating the body's natural defenses to develop immunity.
• The initial response when the body encounters an antigen for the first time is the primary immune response.
• IgM is the main antibody of the primary response and fixes complement.
• IgA is secreted into mucous, saliva, tears, and colostrum.
• Safeguarding animal health/welfare, ensuring safe food, and protecting human health are goals of vaccinating animals.
• Live-attenuated, inactivated, and subunit vaccines are all vax types.
• Live, attenuated vaccines contain a weakened version of the pathogen.
• An adjuvant stimulates and enhances the immune response of a vaccine.
• Intranasal is a route of vaccine administration.
• Intranasal vaccination avoids limitations of parentals i.e. no injection pain or risks with sharp needles use and waste management
• Animal/vaccine-related factors and incorrect administration cause vaccine failure.
• Enterisol Ileitis is a vaccine to target Lawsonia intracellularis.
• Periovac vaccines target Porphyromonas gulae, P. denticanis, and P. salivosa.
• Streptococcus equi vaccines are Equilis StrepE.
• Enterisol Ileitis is a live oral vaccine.