Chp 19 pt 1

What are the sign and symptoms of pharyngitis

Pain, inflammation of the throat, reddened and/or swollen mucosa

Causative agents of pharyngitis

Same viruses that cause common cold

Streptococcus pyogenes, a group A streptococcus (cause most serious cases)

Pharyngitis-Streptococcus pyogenes

Gram-positive coccus, no endospores, nonmotile, forms capsule and slime layers

Pathogenesis of pharyngitis streptococcus pyogenes

Untreated can lead to serious complications

Scarlet fever is a result of an infection of S. pyogenes infected with a bacteriophage

Rheumatic fever is due too an immunologic cross-relation between streptococcal M proteins(resists phagocytosis, contributes to adherence) and the heart muscle

Virulence factors of pharyngitis S. pyogenes

Result of two phenomena: 1. ability of surface antigens to mimic host proteins and 2. possession of super antigens.

Specialized polysaccharides protect the bacterium from being dissolved by lysozyme

Lipoteichoic acid: contributes to the adherence of the cell wall to the epithelial cells of the pharynx

M protein: resists phagocytosis, contributes to adherence

Hyaluronic acid capsule: contributes to adhesiveness

Transmission of pharyngitis S. pyogenes

By respiratory droplets or direct contact with mucus secretions. Humans are the only significant reservoir. More than 80 serotypes exist; immunity is serotype specific

Culture and diagnosis of pharyngitis S. pyogenes

Rapid diagnostic test and culture method

Rapid diagnostic tests of pharyngeal specimens

Uses antibodies to detect Group A Streptococcus (S. pyogenes) directly from a pharyngeal swab.

Culturing of pharyngeal swab specimens

• Swab is plated on sheep blood agar.

• S. pyogenes shows beta-hemolysis (clear zones around colonies).

• Differentiate from Group B streptococci and enterococci using the bacitracin disc test —
  → S. pyogenes is sensitive to bacitracin.

Prevention of of pharyngitis S. pyogenes

No vaccine exists

Prevention through good hand washing after coughing, sneezing, and before preparing foods and eating

Treatment of of pharyngitis S. pyogenes

Penicillin is the antibiotic of choice

Cephalexin use for patients with penicillin allergy

Most sore throats can resolve on their own; antibiotic treatment used to prevent serious sequelae

Common cold

Over 200 viruses that cause this. Focused only on Covid (SARS-CoV-2) and RSV (Respiratory syncytial virus)

Pathogenesis of SARS-CoV-2 (Covid)

Highly pathogenic when initially crossing to humans, first identified as a pneumonia-causing virus. It triggers activation of bradykinins, which causes damage to lungs and other tissues

Transmission and epidemiology of SARS-CoV-2

Transmitted through droplet and airborne contact. Transmissible even in the absence of symptoms, so well people circulating between public spaces and home are reservoirs and carriers

What is the causative agent of RSV

Respiratory syncytial virus

Transmission of RSV

Droplet and indirect contact via fomite

Peak incidence in the winter and early spring

Premature babies and children 6 months or younger are susceptible (100,000 kids hospitalized every year in U.S.)

What is the virulence factor of RSV

Syncytia formation

How to prevent RSV

Passive antibody for high-risk children

Is influenza a type of pneumonia

No, the flu is not a type of pneumonia, but pneumonia can be a complication of the flu

Influenza causative agents

Influenza A, B, and C viruses of the Orthomyxoviridae family.

What are the influenza viruses (A,B,C) characterized by

• Spherical particles (80 to 120 nanometers in diameter)

• A lipoprotein envelope with glycoprotein spikes, including:

  • Hemagglutinin (H)

  • Neuraminidase (N)

Influenza pathogenesis and virulence facts

Virus binds to ciliated cells of the respiratory mucosa. Once the virus gets in, it infects and kills those cells quickly, and a lot of viruses are released as the cells break apart. Immune system reacts strongly, releasing chemicals called cytokines. Too many at once can cause a “cytokine storm”, which leads to severe inflammation and irritation in lungs.

Glycoproteins help the virus attach to cells and hide from immune system by changing shape

Transmission of influenza

Inhalation of virus-laden aerosols and droplets, indirect contact with fomites, transmission aided by crowding (poor ventilation), drier air of winter helps spread virus, 12,000 to 60,000 deaths annually, mainly affects very young and old

Culture and diagnosis of influenza

Culture and non culture based test to diagnose infection

RT-PCR is preferred method

Prevention of influenza

Vaccination- can be administered intramuscular or intradermally. vaccination might be inactivated (killed) or live attenuated

Treatment of influenza

One of first viral diseases where antiviral drugs are effective- must be taken early in infection

Zanamivir (Relenza)- inhaled drug that works against influenza A and B

Oseltamivir (Tamiflu)

Baloxavir

Otitis Media (Ear infection)

Viral infections of the upper respiratory tract that leads to inflammation of eustachian tubes, buildup of fluid in the middler ear, and bacterial multiplication in the fluid

Otitis Media causative agents

Strep pneumo, Candida auris, and other bacteria/viruses

Presentation of otitis media

Prevnar

Treatment of otitis media

“Watchful waiting”, antibiotics, tympanic membrane tubes

Community-acquired pneumonia

Inflammatory condition of the lung in which fluid fills the alveoli. Bacteria, fungi, and a wide variety of viruses can cause pneumonias. Can be deadly and across the globe more children under age 5 die from pneumonia than any other infectious disease

Pneumonia (Community acquired) streptococcus pneumoniae

Factors that favor the ability of the pneumococcus to cause disease are old age, seasonal factors (winter and early spring), diabetes, and chronic abuse of alcohol or narcotics

Community-acquired pneumonia: Legionella

Less common, serious cause of disease

Pneumonia Mycoplasma

Walking pneumonia

What causes tuberculosis

Mycobacterium tuberculosis

Mycobacterium tuberculosis

Slow-growing, acid-fast bacillus (due to a waxy, lipid-rich cell wall with mycolic acid), aerobic (require oxygen to grow), resistant to drying and disinfectants, cord factor (glycolipid) linked to virulence

What is the causative agent for whooping cough (pertussis)

Bordetella pertussis

Transmission for whooping cough

Droplet contact

Signs and symptoms for whooping cough

Incubation period is 3 to 21 days

Catarrhal stage- runny nose for 1 to 2 weeks

Paroxysmal stage- bout of sever coughing

Convalescent phase- bacteria decreasing, not causing ongoing symptoms

Prevention of whooping cough

DTaP vaccine (antibiotic treatment for contacts). Vaccine does not provide lifelong immunity