Antimicrobial Drugs Overview
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Questions and Answers

What defines selective toxicity in antimicrobial drugs?

  • Requiring higher doses to affect pathogens
  • Killing all cells indiscriminately
  • Interfering with the growth of all microorganisms
  • Attacking specific microbial cells while leaving host cells unharmed (correct)

    • Which type of antimicrobial drug directly kills bacteria?

  • Broad-spectrum agents
  • Narrow-spectrum agents
  • Bacteriostatic agents
  • Bactericidal agents (correct)

    • What is an advantage of broad-spectrum antibiotics?

  • They only target Gram-positive bacteria
  • They do not affect the body's normal flora
  • They have a narrow range of action
  • They are effective against a wide range of pathogens (correct)

    • What may result from the use of broad-spectrum antibiotics?

    <p>Inhibition of both harmful and beneficial bacteria</p> Signup and view all the answers

    What characterizes semi-synthetic antimicrobials?

    <p>They undergo chemical alterations to improve efficacy</p> Signup and view all the answers

    What is a key limitation of antimicrobial drugs targeting Gram-negative bacteria?

    <p>The presence of a lipid bilayer that restricts drug entry</p> Signup and view all the answers

    What is the primary purpose of antibiotic substances produced by microorganisms?

    <p>To inhibit the growth of competing microorganisms</p> Signup and view all the answers

    What can result from the disruption of normal flora caused by some antibiotics?

    <p>Development of superinfections</p> Signup and view all the answers

    What is a significant risk associated with the use of chloramphenicol?

    <p>Aplastic anemia and suppression of bone marrow activity</p> Signup and view all the answers

    For which condition are aminoglycosides primarily used today?

    <p>Lung infections with Pseudomonas aeruginosa in cystic fibrosis</p> Signup and view all the answers

    What is a major side effect of using tetracyclines?

    <p>Suppression of normal flora leading to superinfections</p> Signup and view all the answers

    Which statement about macrolides is true?

    <p>They inhibit the continuation of protein synthesis.</p> Signup and view all the answers

    What is the consequence of prolonged use of aminoglycosides?

    <p>Toxicity and potential permanent damage to the kidneys</p> Signup and view all the answers

    What is a potential advantage of monobactams?

    <p>They are synthetic and take longer for pathogens to develop resistance.</p> Signup and view all the answers

    Which statement about cephalosporins is true?

    <p>They inhibit cell wall synthesis like penicillin.</p> Signup and view all the answers

    What is the primary effect of isoniazid?

    <p>It interferes with mycolic acid synthesis.</p> Signup and view all the answers

    Why can protein synthesis inhibitors have toxic effects on humans?

    <p>They affect 70S ribosomes that resemble those in mitochondria.</p> Signup and view all the answers

    Which antibiotic is used to treat leprosy by inhibiting nucleic acid synthesis?

    <p>Dapsone</p> Signup and view all the answers

    What is the main mechanism of action of aminoglycosides?

    <p>They cause misreading of mRNA and block initiation.</p> Signup and view all the answers

    What type of bacteria does ethambutol primarily target?

    <p>Mycobacteria</p> Signup and view all the answers

    Chloramphenicol prevents which of the following during protein synthesis?

    <p>Peptide bond formation</p> Signup and view all the answers

    What is a significant side effect of rifampin?

    <p>Orange-red urine</p> Signup and view all the answers

    Which class of antibiotics is effective against intracellular bacteria such as Chlamydia?

    <p>Macrolides</p> Signup and view all the answers

    What mechanism do fluoroquinolones utilize to eliminate bacteria?

    <p>Inhibiting bacterial DNA replication</p> Signup and view all the answers

    How do sulfonamides work in bacterial infections?

    <p>They block the production of nucleic acids by mimicking PABA.</p> Signup and view all the answers

    What is the principle behind the synergistic effect of combining penicillin and streptomycin?

    <p>Streptomycin enhances penicillin's efficacy by damaging the cell wall.</p> Signup and view all the answers

    Which antifungal class blocks the synthesis of fungal sterols?

    <p>Azoles</p> Signup and view all the answers

    Why are fluoroquinolones not recommended for children and pregnant women?

    <p>They affect cartilage development.</p> Signup and view all the answers

    What type of bacteria is polymyxin B primarily effective against?

    <p>Gram-negative bacteria</p> Signup and view all the answers

    What is a potential risk associated with the use of amphotericin B?

    <p>Kidney toxicity</p> Signup and view all the answers

    What is the primary mode of action for penicillin?

    <p>Interfering with cell wall synthesis</p> Signup and view all the answers

    What is the common structure found in all penicillins?

    <p>A β-lactam ring</p> Signup and view all the answers

    Which type of penicillin is most commonly susceptible to β-lactamases?

    <p>Natural Penicillins</p> Signup and view all the answers

    Which antibiotic is commonly used to treat MRSA infections?

    <p>Vancomycin</p> Signup and view all the answers

    What characteristic differentiates semisynthetic penicillins from natural penicillins?

    <p>The addition of an R-group in the laboratory</p> Signup and view all the answers

    What is a major mechanism through which bacteria develop resistance to penicillin?

    <p>Inactivation of penicillin by β-lactamase</p> Signup and view all the answers

    What type of bacteria does Vancomycin primarily target?

    <p>Gram-positive bacteria</p> Signup and view all the answers

    What feature of Staphylococcus aureus contributes to its resistance against methicillin?

    <p>Genetic mutation preventing penicillin binding</p> Signup and view all the answers

    What is the main function of the buccopharyngeal fascia?

    <p>Coating the outside of the muscle wall</p> Signup and view all the answers

    Killian's dehiscence is a weak spot in the pharyngeal wall found between which structures?

    <p>Thyropharyngeal and cricopharyngeus</p> Signup and view all the answers

    Which nerve primarily supplies the stylopharyngeus muscle?

    <p>Glossopharyngeal nerve</p> Signup and view all the answers

    What type of epithelium lines the paranasal air sinuses?

    <p>Pseudostratified ciliated columnar epithelium</p> Signup and view all the answers

    Which part of the external nose is referred to as the apex?

    <p>The tip</p> Signup and view all the answers

    What does the nasal cavity primarily separate into?

    <p>Two halves</p> Signup and view all the answers

    Which artery is NOT involved in the blood supply to the external nose?

    <p>Temporal artery</p> Signup and view all the answers

    What structure forms the roof of the nasal cavity?

    <p>Cribriform plate of the ethmoid</p> Signup and view all the answers

    Which component contributes to the lateral wall of the nasal cavity?

    <p>Ethmoid bone</p> Signup and view all the answers

    Which type of innervation provides sensory functions to the external nose?

    <p>Infraorbital nerve</p> Signup and view all the answers

    What is the approximate length of the nasal cavity?

    <p>5 cm</p> Signup and view all the answers

    Which feature characterizes the vestibule of the nasal cavity?

    <p>Close to nostrils and lined by skin</p> Signup and view all the answers

    What is the primary composition of the nasal septum?

    <p>An osseocartilaginous partition</p> Signup and view all the answers

    Which structure is NOT part of the formation of the nasal septum?

    <p>Frontal bone</p> Signup and view all the answers

    What is the main purpose of Kiesselbach’s plexus?

    <p>To provide arterial supply</p> Signup and view all the answers

    Which nerve is responsible for the sensory innervation of the nasal septum's olfactory zone?

    <p>Anterior ethmoidal nerve</p> Signup and view all the answers

    What is the role of vibrissae found in the vestibule of the lateral wall of the nose?

    <p>To filter larger particles from entering</p> Signup and view all the answers

    What type of tissue composes the cuticular formation of the nasal septum?

    <p>Fibro-fatty tissue with skin</p> Signup and view all the answers

    Which of the following best describes the venous drainage of the nasal septum?

    <p>It drains into both facial vein and pterygoid plexus</p> Signup and view all the answers

    Which part of the nasal cavity is lined by modified skin containing glands?

    <p>Vestibule</p> Signup and view all the answers

    Which of the following statements about the inferior concha is true?

    <p>It is a separate bone</p> Signup and view all the answers

    Which structure is primarily involved in lymphatic drainage from the nasal cavity?

    <p>Pterygoid venous plexus</p> Signup and view all the answers

    Which structure opens into the inferior meatus?

    <p>Nasolacrimal duct</p> Signup and view all the answers

    Which sinus opens into the posterior part of the hiatal semilunaris?

    <p>Maxillary sinus</p> Signup and view all the answers

    What is the shortest concha in the lateral wall of the nose?

    <p>Superior concha</p> Signup and view all the answers

    What nerve supplies the anterior part of the lateral wall of the nasal cavity?

    <p>Maxillary nerve</p> Signup and view all the answers

    Which sinus opens through the sphenoethmoidal recess?

    <p>Sphenoidal sinus</p> Signup and view all the answers

    What causes nasal congestion in case of septal deviation?

    <p>Reduced airflow through the transverse plane</p> Signup and view all the answers

    Which artery is NOT associated with the arterial supply of the lateral wall of the nose?

    <p>Occipital artery</p> Signup and view all the answers

    Which type of infection can spread through the cribriform plate?

    <p>Sinusitis</p> Signup and view all the answers

    Which structure serves as a passage for the anterior ethmoidal and frontal sinus drainage?

    <p>Ethmoidal infundibulum</p> Signup and view all the answers

    Which nerve provides special sensory fibers for the sense of smell?

    <p>Olfactory nerve</p> Signup and view all the answers

    What is the significance of Kiesselbach's plexus in the nasal cavity?

    <p>It is a common site of epistaxis.</p> Signup and view all the answers

    What defines a nasal fracture?

    <p>A break or crack in the bone or cartilage of the nose.</p> Signup and view all the answers

    Which structure serves as the communication pathway between the nasal cavity and the pharynx?

    <p>Pharyngeal isthmus</p> Signup and view all the answers

    Which part of the pharynx lies in front of the C2 and upper part of C3 vertebra?

    <p>Oropharynx</p> Signup and view all the answers

    What anatomical feature is formed by the anastomosis of four arteries in the nasal septum?

    <p>Kiesselbach's plexus</p> Signup and view all the answers

    What term describes the hypertrophy of mucosa over the inferior nasal concha?

    <p>Allergic rhinitis</p> Signup and view all the answers

    Which feature of the nasopharynx is responsible for equalizing pressure in the ear?

    <p>Auditory tube</p> Signup and view all the answers

    Which structure is located at the upper boundary of the laryngopharynx?

    <p>Inlet of the larynx</p> Signup and view all the answers

    In what part of the pharynx would you find palatine tonsils?

    <p>Oropharynx</p> Signup and view all the answers

    Which part of the pharynx extends from the cranial base to the lower border of the cricoid cartilage?

    <p>Nasopharynx</p> Signup and view all the answers

    What is the main role of the pharyngeal branch of the vagus nerve?

    <p>Innervates all constrictor muscles of pharynx</p> Signup and view all the answers

    Which structures does Killian's dehiscence lie between?

    <p>Thyropharyngeal and cricopharyngeus muscles</p> Signup and view all the answers

    What type of epithelium lines the paranasal air sinuses?

    <p>Pseudostratified ciliated columnar epithelium</p> Signup and view all the answers

    What constitutes the blood supply to the pharynx?

    <p>Ascending pharyngeal and maxillary arteries</p> Signup and view all the answers

    Which of the following muscles is classified as a longitudinal muscle of the pharynx?

    <p>Stylopharyngeus</p> Signup and view all the answers

    Which part of the external nose is named for its tip?

    <p>Apex</p> Signup and view all the answers

    How is the nasal cavity anatomically divided?

    <p>By the nasal septum</p> Signup and view all the answers

    What is the primary function of the vestibule of the nasal cavity?

    <p>Filter particles</p> Signup and view all the answers

    Which artery is NOT listed as supplying blood to the external nose?

    <p>Maxillary artery</p> Signup and view all the answers

    What structure primarily forms the roof of the nasal cavity?

    <p>Cribriform plate</p> Signup and view all the answers

    What is the average width of the nasal cavity near the floor?

    <p>1.5cm</p> Signup and view all the answers

    Which of the following provides motor innervation to the external nose?

    <p>Facial nerve branches</p> Signup and view all the answers

    What is the approximate length of the nasal cavity as stated?

    <p>5cm</p> Signup and view all the answers

    What structure forms the bony part of the nasal septum?

    <p>Vomer</p> Signup and view all the answers

    Which part of the nasal cavity is covered by a mucous membrane?

    <p>Lateral wall</p> Signup and view all the answers

    What is the primary venous drainage of the nasal septum?

    <p>Facial vein</p> Signup and view all the answers

    What type of cartilage is primarily involved in the formation of the nasal septum?

    <p>Hyaline cartilage</p> Signup and view all the answers

    Which nerve supplies the olfactory zone of the nasal septum?

    <p>Ophthalmic nerve</p> Signup and view all the answers

    What anatomical feature separates the concha in the lateral wall of the nose?

    <p>Meatuses</p> Signup and view all the answers

    Which nerve is not involved in the sensory supply of the nasal septum?

    <p>Hypoglossal nerve</p> Signup and view all the answers

    Which anatomical structure is described as a mucocutaneous ridge in the lateral wall of the nose?

    <p>Limen nasi</p> Signup and view all the answers

    What is the role of Kiesselbach's plexus in the nasal cavity?

    <p>Anastomosis of arteries</p> Signup and view all the answers

    What does the inferior concha specifically refer to in terms of anatomical classification?

    <p>A separate bone</p> Signup and view all the answers

    What is the primary structure that opens into the inferior meatus of the nasal cavity?

    <p>Nasolacrimal duct</p> Signup and view all the answers

    Which structure opens into the middle meatus of the nasal cavity?

    <p>Frontal sinus</p> Signup and view all the answers

    What is the function of the sphenoethmoidal recess in the nasal cavity?

    <p>It allows drainage of the sphenoidal sinus.</p> Signup and view all the answers

    Which artery does NOT typically supply the lateral wall of the nose?

    <p>Carotid artery</p> Signup and view all the answers

    Which nerve supplies the anterior part of the lateral wall of the nasal cavity?

    <p>Maxillary nerve</p> Signup and view all the answers

    Where does the middle ethmoidal air sinus typically open?

    <p>Above the bulla</p> Signup and view all the answers

    What anatomical feature leads to congestion when misaligned?

    <p>Septum</p> Signup and view all the answers

    Which structure drains into the posterior part of the hiatius semilunaris?

    <p>Maxillary sinus</p> Signup and view all the answers

    Which of the following nerves is responsible for special sensory functions in the nose?

    <p>Olfactory nerve</p> Signup and view all the answers

    What is the anatomical significance of the cribriform plate?

    <p>Allows the spread of infection</p> Signup and view all the answers

    What region in the nasal septum is known as a common site for nosebleeds?

    <p>Kiesselbach's area</p> Signup and view all the answers

    Which structure forms the base for the pharynx?

    <p>Cricoid cartilage</p> Signup and view all the answers

    What is the anatomical term for the division between the nasal and oral cavities?

    <p>Pharyngeal isthmus</p> Signup and view all the answers

    Which condition is characterized by hypertrophy of the mucosa over the inferior nasal concha?

    <p>Allergic rhinitis</p> Signup and view all the answers

    Which part of the pharynx is primarily located in front of the C2 to upper part of the C3 vertebrae?

    <p>Oropharynx</p> Signup and view all the answers

    Which structure is not a feature of the nasopharynx?

    <p>Palatine tonsil</p> Signup and view all the answers

    What is the upper boundary of the pharynx defined by?

    <p>Base of the skull</p> Signup and view all the answers

    Which feature is found in the oropharynx?

    <p>Tonsillar sinus</p> Signup and view all the answers

    Which part of the pharynx is primarily associated with the inlet of the larynx?

    <p>Laryngopharynx</p> Signup and view all the answers

    Which arteries are involved in the vascular plexus of Kiesselbach's area?

    <p>Four specific arteries including the anterior ethmoidal</p> Signup and view all the answers

    Study Notes

    Antimicrobial Drugs

    • Antimicrobial drugs are used to treat infectious diseases by interfering with the growth of microorganisms
    • The ideal drug will kill pathogens without harming the host
    • Selective toxicity: attacks some cells but not others, refers to a drug's ability to attack specific microbial cells but leaves other cells unharmed
    • Most drugs available are antibacterial, fewer are anti-fungal, anti-protozoan, or anti-helminthic. Anti-viral drugs are the least common.

    Definitions and Classification of Antimicrobials

    • Antibiotic: substance that inhibits the growth of a microorganism
      • Technically, antibiotics are produced by microorganisms but synthetic drugs are also commonly called antibiotics
    • Antibiotics can be:
      • Bacteriostatic agents, which stop bacterial replication and prevent growth; the host's immune system then eliminates the bacteria
      • Bactericidal agents, which kill bacteria directly

    Spectrum of Activity

    • Range of microbes that an antimicrobial drug can affect
    • Narrow-spectrum: works against a limited number of pathogens
    • Broad-spectrum: affects a wide range of Gram+ and Gram- bacteria
      • Advantages: treats unknown infections and infections caused by different organisms, such as bacterial meningitis
      • Disadvantages: can destroy the normal flora of the host, leading to overgrowth of other species (superinfection)
        • Examples: C. difficile diarrhea, C. albicans overgrowth, opportunistic growth of antibiotic-resistant strains
    • Semi-synthetics: chemically altered antibiotics more effective than naturally occurring ones
    • Synthetics: antimicrobials completely synthesized in a lab

    Gram Negative Outer Membrane Limits Drug Penetration

    • Most antibacterial drugs have polar properties
    • Gram Negative bacteria have an outer membrane, composed of a "lipid bilayer" with fatty acid tails, which prevents the passage of polar molecules
    • Small, water-filled "pores" allow entry only by compounds soluble in water
    • If a drug can’t reach its specific target, it is useless

    Type 1: Inhibition of Cell Wall Synthesis

    • Bacterial cell walls are distinct from eukaryotic cell walls
    • prokaryotic cells have peptidoglycan
    • These drugs interfere with synthesis of the cell wall, only affecting actively growing cells
      • Weakened cell wall exposes the plasma membrane and leads to lysis

    Penicillin

    • "Family" of over 50 chemically related antibiotics
    • Common core structure: a β-lactam ring found in all penicillins
      • Penicillins also called “β-lactam antibiotics”
    • Penicillin V was the first penicillin discovered
    • Different types of penicillin vary in their R-group

    β-lactam Ring Required for Penicillin Activity

    • Some bacteria produce β-lactamase, an enzyme that breaks the β-lactam ring and inactivates penicillin
    • β-lactamase is also called “penicillinase”
    • This is the most common form of penicillin resistance

    Natural vs Semisynthetic Penicillin

    • Natural penicillins:
      • Extracted directly from Penicillium cultures
      • Narrow spectrum (G+); useful against most Staphylococci, Streptococci & spirochetes
      • Often susceptible to β-lactamases
      • Pen G & Pen V are the most common natural penicillins
    • Semisynthetic penicillins:
      • β-lactam core made by Penicillium
      • R-group is added in the lab
      • Engineered for specific characteristics:
        • Can be designed to be more resistant to β-lactamase (methicillin)
        • Can be designed to have a broader specificity: Gram+ & some Gram- (ampicillin, amoxicillin)

    Antibiotic Resistance

    • Antibiotic resistance is a growing problem:
      • MRSA: methicillin-resistant Staphylococcus aureus
      • Penicillins usually interact with bacterial cell walls through penicillin binding proteins in the peptidoglycan layer
      • MRSA has a genetic mutation that prevents penicillin binding
      • MRSA also produces beta-lactamase
      • Patients with MRSA infections must be isolated
      • MRSA can be treated with vancomycin

    Vancomycin

    • Named for the word “vanquish”
    • Glycopeptide antibiotic: completely different structure than penicillin
    • Naturally produced by a species of Streptomyces
    • Inhibits cell wall synthesis
    • Very narrow spectrum
      • Mostly used to treat MRSA
      • Recently strains of S. aureus and certain Enterococci species resistant to vancomycin have been discovered
    • Toxicity used to be a problem but improved manufacturing procedures have corrected this

    Monobactams

    • Synthetic and semisynthetic antibiotics
      • Potential advantage: not found in nature, therefore takes more time for pathogens to develop resistance
    • Structure is similar to penicillin but different enough that it is not sensitive to β-lactamase
    • Spectrum of activity:
      • Affects certain Gram negative bacteria (E. coli, H. influenzae, P. aeruginosa); effective in treating these infections in Cystic Fibrosis patients

    Cephalosporins

    • Similar chemical structure to penicillin (β-lactam ring)
    • Examples: cephalothin, cefixime
      • Comes from the fungus Cephalosporium
    • Inhibit cell wall synthesis in the same way as penicillin, but tend to be more broad-spectrum than natural penicillin
    • Susceptible to a different group of β-lactamases

    Mycobacteria

    • Have different cell walls from other bacteria
    • M. tuberculosis, M. leprae: cause tuberculosis, leprosy
    • Cell walls contain mycolic acids and a small amount of peptidoglycan
    • Anti-mycobacterial antibiotics interfere with mycolic acid incorporation or synthesis
      • These drugs have minimal to no effect on other bacteria
    • Isoniazid: inhibits mycolic acid synthesis
    • Ethambutol: inhibits the incorporation of mycolic acid
      • Fairly weak on its own, so administered as part of a "cocktail" to prevent development of resistance
    • Dapsone (tx Leprosy): inhibits nucleic acid synthesis

    Type 2: Inhibition of Protein Synthesis

    • Ribosomes are the sites of protein synthesis
    • Eukaryotic and prokaryotic ribosomes are different:
      • Eukaryotic: 80S ribosomes (40S + 60S subunits)
      • Prokaryotic: 70S ribosomes (30S + 50S subunits)
    • Targeting 70S ribosomes directs action against bacteria
      • Problem: mitochondria have 70S ribosomes, some drugs in this group may have toxic effects on humans
    • Protein synthesis inhibitors: drugs in this category all have slightly different modes of action with the same end result

    Examples: Mechanisms of Action of Protein Synthesis Inhibitors

    • Chloramphenicol: prevents peptide bond formation [50S subunit]
    • Aminoglycosides: block initiation and cause misreading of mRNA [30S subunit]
    • Tetracyclines: block attachment of tRNA to the ribosome [30S subunit]
    • Macrolides: prevent continuation of synthesis (translocation from A site to P site) [50S subunit]

    Chloramphenicol

    • Broad spectrum
    • Simple structure: small size allows it to diffuse into areas inaccessible to many other drugs
    • Inexpensive to manufacture, often used where low cost is essential
    • Down side: serious toxicity problems
      • Suppression of bone marrow activity: aplastic anemia, potentially fatal, affects formation of blood cells, 1 in 40,000 users affected (normal: 1 in 500,000)
      • Teratogenic in neonates: causes grey baby syndrome

    Aminoglycosides

    • Among the first antibiotics found to have activity against Gram- bacteria
    • Bactericidal
    • Can be toxic, therefore use is declining
      • Permanent damage to the auditory nerve (Ototoxicity) and kidneys
    • Current use:
      • Cystic fibrosis where lung infections with Pseudomonas aeruginosa are common (G-, difficult to treat)
      • Tobramycin is delivered as an aerosol to control these infections

    Tetracyclines

    • Broad spectrum: effective against Gram+ and Gram-, intracellular bacteria
      • Able to penetrate tissues and cells well
    • Natural protein synthesis inhibitor, but semisynthetics have longer retention in the body (doxycycline, minocycline)
    • Uses:
      • UTI, Mycoplasma, Chlamydia, and Rickettsia infections
      • Alternatives for syphilis and gonorrhea instead of penicillins
    • Problems:
      • Suppress normal flora (broad spectrum)
        • GI upsets leading to superinfections, often by C. albicans
      • May cause brown teeth discoloration in children younger than 8 years old
      • May cause liver damage in pregnant women

    Macrolides

    • Narrow spectrum (G+)
      • Alternative to penicillin
      • Too big to enter G- cells
    • Inhibit protein synthesis
    • Oral administration:
      • Orange-flavored suspension often used to treat streptococcal and staphylococcal infections in children
      • Useful to treat people who are allergic to β-lactams
      • Erythromycin
      • Azithromycin, clarithromycin
        • Broader specificity, better tissue penetration
        • Important for treatment of intracellular bacteria such as Chlamydia

    Type 3: Injury to Plasma Membrane

    • Change permeability of the plasma membrane
    • Essential metabolites leave the cell
    • Probably not the best choice: eukaryotic plasma membrane is very similar to bacteria
    • Example: Polymyxin B
      • First drug active against gram(-) Pseudomonas
      • Attaches to phospholipids, causes disruption
      • Host toxicity: significant internally
      • Used as a topical treatment for superficial infections
      • Available in non-prescription antibiotic ointments: Polysporin

    Type 4: Nucleic Acid Synthesis Inhibitors

    • May interfere with replication or transcription
    • May cause harm to the human host, but useful drugs in this class are more harmful to the bacteria than the host (selective toxicity)
    • Rifamycins: most common is rifampin
      • Inhibits mRNA synthesis, bactericidal
      • Side effect: orange-red urine, feces, tears, sweat, saliva
    • Can penetrate tissues:
      • Therapeutic levels in CSF and abscesses
      • Useful for treatment of TB along with isoniazid & ethambutol - Tissue penetration required

    Quinolones & Fluoroquinolones

    • Bactericidal, broad spectrum
      • Specifically inhibit bacterial DNA replication
    • Quinolones: early drug (1960’s), limited use
      • Only application: UTI
    • Fluoroquinolones: developed in the 1980’s
      • Norfloxacin, ciprofloxacin (Cipro)
    • Safe for adults, but not recommended for children, adolescents, or pregnant women:
      • Affects cartilage development
    • New synthetic versions being developed that are broader spectrum, but adversely affect some drugs that control heart rhythm

    Type 5: Drugs that Inhibit Metabolic Pathways & Enzymatic Activity

    • It is possible to block the activity of essential enzymes within a cell using specifically designed drugs
    • Competitive inhibition: a drug with a very similar structure to the normal substrate can "block" the active site of an enzyme, preventing it from carrying out its normal function

    Sulfonamides

    • Sulfa drugs (among the first synthetic antimicrobials)
    • PABA (para aminobenzoic acid): required to make nucleic acids in pathogens, but not in humans
    • Most widely used today:
      • TMP-SMZ (trimethoprim & sulfamethoxazole): synergistic combo
      • Broad spectrum
      • Used for control of pneumonia caused by Pneumocystis carnii
      • Effective in penetration of the brain & CSF

    Things to Consider in Combining Drugs

    • Synergism: when 2 drugs used together are more effective than either one alone
      • Penicillin (damage cell wall) + streptomycin (inhibit protein synthesis at the ribosome)
        • Damage by penicillin allows entry by streptomycin
    • Antagonism: when the activity of one drug works against the activity of another when they are used together
      • Penicillin (inhibits ACTIVE cell wall synthesis) + tetracycline (stops bacterial growth) - Bacteria that are not making a cell wall are not affected by penicillin

    Antifungals

    • Fungal infections are increasing in frequency: opportunistic infections, immunosuppression, AIDS
    • Toxicity problem since fungi are eukaryotes
    • Azoles: block fungal sterol synthesis
      • Clotrimazole, miconazole (Monistat): topical treatment of athlete’s foot, yeast infection
      • Triazoles: less toxic, but still some liver damage - Fluconazole, ketoconazole: treatment of systemic mycoses
    • Polyenes: kills fungal cells via sterol recognition
      • Amphotericin B commonly used treatment for systemic mycoses
      • Toxicity in the kidney limits use

    Antivirals & Antiviral Targets

    • In the developed world many of the most serious infections are caused by viruses, but there are few antiviral drugs
      • Ideally, drugs that kill pathogens without harming the host, but this is difficult when dealing with cellular hijackers

    Respiratory Tract Anatomy

    • Introduction
      • The respiratory tract facilitates gas exchange, bringing oxygen into the body and removing carbon dioxide.
      • Divided into an upper and lower respiratory tract:
        • Upper respiratory tract: the nose, pharynx, and larynx
        • Lower respiratory tract: the trachea, bronchi, bronchioles, and alveoli
    • Structure and Function
      • Nose:
        • The external nose is made of bone and cartilage.
        • The nasal cavity is divided into two halves by the nasal septum.
        • The nasal cavity warms, humidifies, and filters air.
        • The olfactory epithelium, responsible for smell, is located in the roof of the nasal cavity.
        • The lateral wall of the nose contains three turbinate bones (conchae) that increase the surface area of the nasal cavity.
        • The space between the concha are called meatuses:
          • Inferior meatus: receives drainage from the nasolacrimal duct.
          • Middle meatus: receives drainage from the frontal, maxillary, and anterior ethmoidal sinuses.
          • Superior meatus: receives drainage from the posterior ethmoidal sinuses.
          • Sphenoethmoidal recess: receives drainage from the sphenoidal sinuses.
      • Pharynx:
        • A muscular tube that connects the nasal and oral cavities to the larynx.
        • Divided into three regions:
          • Nasopharynx: the upper portion, located behind the nasal cavity.
          • Oropharynx: the middle portion, located behind the oral cavity.
          • Laryngopharynx: the lower portion, located behind the larynx.
    • Innervation
      • The respiratory tract is innervated by the olfactory nerve (for smell), the trigeminal nerve (for general sensation), and the vagus nerve (for motor function).
      • The vagus nerve also provides parasympathetic innervation, controlling secretions.
      • The sympathetic system also innervates the respiratory tract, controlling bronchodilation.

    Pharynx

    • Location
      • Musculomembranous tube extending from the base of the skull to the level of the sixth cervical vertebra.
      • Connects the nasal and oral cavities to the larynx.
    • Divisions
      • Nasopharynx: Posterior to the nasal cavity
      • Oropharynx: Posterior to the oral cavity
      • Laryngopharynx: Posterior to the larynx.
    • Muscles
      • Three constrictor muscles: Superior, Middle, Inferior constrictors
      • Longitudinal muscles: Stylopharyngeus, Palatopharyngeus, Salpingopharyngeus
    • Nerve Supply
      • Vagus Nerve: All constrictors and salpingopharyngeus
      • Glossopharyngeal Nerve: Stylopharyngeus
      • Cranial Part of the Accessory Nerve: Palatopharyngeus

    Paranasal Sinuses

    • Air filled spaces in bones that surround the nasal cavity.
    • Communicate with the nasal cavity and are lined by mucous membrane
    • Four groups:
      • Maxillary sinuses (Antrum of Highmore)
      • Ethmoid sinuses
      • Frontal sinus
      • Sphenoid sinus

    Applied Anatomy

    • Septal Deviation : A crooked septum can cause nasal obstruction, and may require a submucosal resection.
    • Epistaxis : Bleeding from the nose, often from Kiesselbach's plexus (a vascular network in the anterior nasal septum).
    • Nasal Fractures : Broken bones or cartilage of the nose.
    • Allergic Rhinitis : Inflammation of the nasal mucosa, commonly due to allergic reactions, can cause hypertrophy of the inferior nasal concha, leading to nasal congestion.
    • Killian's Dehiscence: A triangular area in the pharyngeal wall, which represents a weak spot where a pharyngoesophageal diverticulum (Zenker's diverticulum) can develop.
    • Spread of Infection : Infections of the sinuses or nose can spread easily due to close proximity to the brain and other delicate structures (e.g., through cribriform plate, nasolacrimal duct).
    • Nasal Polyps : Non-cancerous growths that can block the nasal cavity, leading to difficulty breathing.

    Respiratory Tract Anatomy

    • The respiratory tract is responsible for breathing and gas exchange in the body. It’s divided into upper and lower portions. The upper portion of the respiratory tract is the part of the airway outside of the chest: the nose, pharynx, and larynx.
    • The nasal cavity is divided into two halves by the nasal septum and has several parts, including the vestibule, roof, floor, and lateral wall.
    • The lateral wall of the nasal cavity has concha, which are bony projections and meatuses, which are spaces between the concha. The concha are lined with a mucous membrane, which helps to warm and humidify the air that is breathed in.
    • Kiesselbach's plexus is a vascular area in the anteroinferior part of the nasal septum; it is a common site for nosebleeds, or epistaxis.
    • The pharynx is a musculomembranous tube that connects the nasal and oral cavities to the larynx and esophagus as well as extending from the base of the skull to the level of the sixth cervical vertebra. It is divided into three parts: nasopharynx, oropharynx, and laryngopharynx.
    • The larynx is a cartilaginous structure that connects the pharynx to the trachea. It houses the vocal cords.
    • The trachea is a cartilaginous tube that connects the larynx to the bronchi.
    • Killian's dehiscence, or Killian's triangle, is a triangular area in the wall of the pharynx that is susceptible to the development of a pharyngoesophageal diverticulum, also known as Zenker's diverticulum.
    • Paranasal sinuses are air-filled spaces within the skull that connect to the nasal cavity and are found in the maxillary, frontal, sphenoid, and ethmoid bones. They are lined with mucous membrane and are filled with air.

    Nasal Cavity

    • The nasal cavity is the part of the respiratory system that is responsible for breathing and filtering air.
    • The nasal cavity is lined with a mucous membrane, which moistens and warms the air before it enters the lungs.
    • The nasal mucosa has olfactory receptors, which allow us to smell.
    • The nasal cavity is divided into two halves by the nasal septum, a bony and cartilaginous partition.
    • The inferior, middle, and superior conchae are bony projections that extend from the lateral wall of the nasal cavity and divide the nasal cavity into meatuses, which are spaces between the concha.
    • The nasal cavity has three meatuses: superior, middle, and inferior. Each meatus has openings from specific paranasal sinuses.
    • Structures that open into the inferior meatus: nasolacrimal duct
    • Structures that open into the middle meatus: frontal sinus, maxillary sinus, anterior ethmoidal cells, middle ethmoidal cells
    • Structures that open into the superior meatus: posterior ethmoidal cells
    • Structure that opens into the sphenoethmoidal recess: sphenoidal sinus
    • The nasal cavity receives its blood supply from branches of the ophthalmic, maxillary, and facial arteries.

    Blood Supply and Innervation of the Nasal Septum

    • Arteries:*
    • Dorsal nasal branch - ophthalmic artery
    • Infraorbital artery - maxillary artery
    • Alar and septal branches - facial artery
    • Innervation (sensory):*
    • External nasal nerve
    • Alar nerve
    • Septal nerve
    • Inferior trochlear nerve - ophthalmic artery
    • Infraorbital nerve - maxillary artery
    • Innervation (motor):*
    • Facial nerve branches

    Blood Supply and Innervation of the Lateral Wall of the Nose

    • Arteries:*
    • Anterior ethmoidal artery
    • Posterior ethmoidal artery
    • Sphenopalatine artery
    • Facial artery
    • Greater palatine artery
    • Innervation:*
    • Anterior ethmoidal nerve - ophthalmic nerve
    • Posterior superior lateral nasal nerve - pterygopalatine ganglion (maxillary nerve)
    • Anterior superior alveolar nerve - maxillary nerve
    • Anterior palatine nerve - pterygopalatine ganglion (maxillary nerve)
    • Olfactory nerve (special sensory for smell)

    Pharynx

    • The pharynx connects the nasal and oral cavities to the larynx and esophagus.
    • The pharynx consists of three parts: the nasopharynx, the oropharynx, and the laryngopharynx.
    • The nasopharynx is the superiormost part of the pharynx and connects the nasal cavity to the pharynx. It has the opening of the auditory tube, as well as the tubal elevation, salpingopharyngeal fold, and salpingopalatine fold. The nasopharynx also contains the tubal tonsil and pharyngeal tonsil (adenoids).
    • The oropharynx lies posterior to the oral cavity and is the middle part of the pharynx. It has the palatopharyngeal folds/arches and contains the palatine tonsil and tonsillar sinus.
    • The laryngopharynx is the inferior part of the pharynx and connects the oropharynx to the larynx and esophagus. It contains the inlet of the larynx and is formed by the arytenoid and cricoid cartilages.
    • The pharynx is lined with a mucous membrane and is supplied by the pharyngeal plexus, which is formed by branches of the glossopharyngeal, vagus, and cranial accessory nerves.
    • The pharynx has three constrictor muscles—superior, middle, and inferior—that encircle the pharynx and constrict the lumen during swallowing.
    • It has three longitudinal muscles—stylopharyngeus, palatopharyngeus, and salpingopharyngeus—that elevate the pharynx and larynx during swallowing.
    • The blood supply to the pharynx is provided by the ascending pharyngeal, lingual, facial, and maxillary arteries.

    Applied Anatomy of the Respiratory System

    • Septal deviation: Deviation of the nasal septum can cause congestion and obstruction.
    • Epistaxis: Epistaxis is bleeding from the nose.
    • Dangerous area: The nose is considered a “dangerous area” due to the proximity of the nasal cavity to the cranial cavity, which can be infected via spread along the olfactory nerves.
    • Allergic rhinitis: Allergic rhinitis is inflammation of the nasal mucosa due to an allergic reaction. It can be caused by exposure to pollen, dust mites, mold, pet dander, or other allergens.
    • Nasal polyps: Nasal polyps are noncancerous growths that hang from the lining of the nose or sinuses. They are often caused by chronic inflammation.
    • Killian's dehiscence: Killian's dehiscence may be the site for a Zenker's diverticulum, which is a pouch-like protrusion of the pharyngeal wall.

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