Microorganisms and Infection Control: Precautions, Pathogens, and Diseases

Universal precautions

All handlers must treat all samples known or unknown as potentially hazardous or pathogenic material; guidelines implemented in response to the AIDS epidemic, to prevent healthcare worker exposure to infected blood and body fluids that could transmit the disease.

Standard precautions

Termed by CDC to be used with all patients because infection status is not known; includes: hand hygiene, wearing gloves, barrier gowns and face shields for splash risk, and disinfection of surfaces, laundry and tools.

Contact Precautions

Limit spread via hands or fomites when patient has drug resistant infection, wound, or C. diff; limit patient transport, give private room, extra attention to hand washing, always wear gloves and barrier gowns removing immediately after interaction, single use fomites.

Droplet precautions

When infection does not suspend in air requiring closer contact for transmission; respiratory infections like flu, diphtheria, mumps, pertussis, plague, strep, and pneumonia; wear mask.

Airborne precautions

When microbe spreads through fine respiratory aerosol and can remain suspended in air; TB, measles, chickenpox, COVID; patient placed in airborne infection isolation rooms (AIIR); workers wear N95 respirator.

Pathogenicity

Ability of microorganism to cause disease.

Virulence

Severity of disease it causes.

Steps of infection

Entry, attachment, invasion, evasion, exit and transmission.

Direct contact

Between source of pathogen and host includes person to person, animal bites or scratches, environment, and vertical from mother to child.

Indirect contact

Airborne, vehicle with contaminated object such as foodborne, contaminated needles or water, through biological vector such as mosquito bite, tick bite, flea bite, or mechanical vector such as flies and cockroaches.

Portals of entry

Skin, mucous membrane (most common), placenta, parenteral (through puncture wound).

Streptococcus

Gram-positive, round, links in chain like structure; catalase negative; cultured on BAP.

Strep. Pneumonia

Identified by alpha hemolysis.

Strep. Pyogenes

Identified by beta hemolysis.

Enterococcus faecalis

Identified by gamma hemolysis.

Beta hemolytic strep

Divided into groups known as Lancefield groupings; catalase and coagulase negative; differentiate by carbohydrate composition of bacterial antigens located in cell wall.

Catalase

Enzyme that protects against free radicals; for catalase test organism placed in hydrogen peroxide solutions, if makes catalase, hydrogen peroxide is broken down and bubbles up; catalase negative = no bubbles.

Streptococcal pharyngitis

Group A; fever, enlarged lymph node, pharyngeal erythema causing soreness and discomfort; if untreated becomes rheumatic fever.

Rheumatic fever

Symptoms are inflammation of joints, involuntary jerking movements, development of pea sized nodules beneath skin, reddened areas with raised edges over surface of skin; most serious = damage to heart valves because bacteria targets heart.

Streptococcal septicemia

Blood poisoning caused by Group B strep infection of blood and secondarily infects surrounding tissues; can arise from infections in the lungs, abdomen, or urinary tract and may precede or accompany meningitis or endocarditis.

Sepsis

Bodywide inflammatory response to an infection and/or toxins released by pathogen; most common is from pneumonia.

Staphylococcus

Gram positive, round that forms grape-like clusters with other bacteria; catalase and coagulase positive; facultative anaerobe meaning it is capable of growth both aerobically and anaerobically.

Folliculitis

Affects hair follicles causing lesions called pustules; larger pus-filled skin lesions like boils also develop anywhere on surface of skin.

Scalded skin syndrome

Caused by Staph aureus; young children and infants; causes pustules to rupture yielding a scalded appearance due to the peeling of the skin.

Impetigo

Contagious childhood skin disease that presents as fluid-filled red sores near the mouth and/or nose; when ruptured, scratched, or rubbed the infection can be spread to other parts of the body.

Conjunctivitis

Infection of the conjunctiva, the thin transparent layer of tissue that covers the white part of the eye (sclera) as well as the inner surface of the eyelid; can be bacterial or viral.

Ophthalmia neonatorum

Severe form of bacterial conjunctivitis that occurs in newborn babies and can lead to permanent eye damage unless it is treated immediately.

Chlamydia and Gonorrhea

Antibiotic ointment containing neomycin applied to newborns' eyes for prevention.

Mycobacterium tuberculosis

Gram positive and bacillus shaped.

Active TB Diagnosis

Staining sputum coughed up from respiratory tract smear is a quick and cheap way to diagnose an active infection.

TB Acid-Fast Stain

Stains red while background is blue.

TB Transmission

Spread from person to person through air or mucosal emissions, must be inhaled to be infectious.

TB Symptoms

Primary symptoms include a bad cough for about three weeks, pain located in the chest, and coughing up blood or heavy sputum.

TB Skin Test

A small fluid sample of tuberculin is placed under the skin of your arm or via a direct blood test.

Positive Induration 5 mm

Positive for immune compromised, patients with a history of prior TB, or those in close contact with someone who has TB.

Positive Induration 10 mm

Positive for patients who visit, live, or work in TB endemic areas, patients younger than 4, or residents of long-term facilities.

Positive Induration 15 mm

Positive for anyone with or without risk for TB.

TB Treatment Duration

Treatment lasts 6-9 months with a combination of drugs INH, rifampin (RIF), ethambutol (EMB), and pyrazinamide (PZA).

TB Infection Steps

Transmission -> alveolar macrophage engulf bacteria but resists lysis -> bacteria survive and multiply -> immune cells alerted.

Leprosy

Caused by Mycobacterium leprae, a small rod-shaped, acid-fast bacterium.

Leprosy Transmission

Spread from person to person via airborne fluid droplets from the nose and/or mouth.

Leprosy Treatment

Multiple drug therapy regimen consisting of dapsone, rifampin, and clofazimine.

Botulism

Caused by Clostridium botulinum, a Gram-positive, anaerobic, spore-forming bacillus.

Botulism Causes

Foodborne from improperly canned or contaminated low acidic foods, infant botulism occurs when infants consume honey.

Tetanus

Caused by Clostridium tetani, a Gram-positive, anaerobic, spore-forming bacillus.

Tetanus Toxin

The tetanospasmin toxin produced by C. tetani causes illness, not the bacteria itself.

Tetanus Symptoms

Causes systemic muscle stiffness and spasms, often seen initially in the masseter muscle of the jaw.

Gas Gangrene

Caused by Clostridium perfringens, a Gram-positive, anaerobic, spore-forming bacillus.

Gas Gangrene Symptoms

Characterized by muscle necrosis, swelling of infected areas, fever, and intense gas production.

C. diff

Clostridioides difficile, bacillus, gram positive, spore-forming anaerobe.

C. diff Transmission

Occurs via the fecal-oral route, and is an opportunistic infection that colonizes after antibiotic use.

C. diff Symptoms

Causes antibiotic-associated infectious diarrhea and deadly colitis.

C. Diff Sx's

Mild/moderate diarrhea, dehydration, colitis leading to bowel perforation, sepsis, and hemorrhage

C. diff Diagnosis

Culturing bacteria from stool samples and use molecular method to detect bacteria's genes or enzymes

C. diff Treatment

Rehydration, antibiotics, fecal transplants

Transmission of C. diff

1. Normal microbiota, 2. Antibiotic therapy, 3. C. diff exposure, 4. Dysbiosis

Legionella

A Gram-negative, aerobic, motile (single flagellum) bacterium

Legionella pneumophila

A fastidious bacteria that needs iron salts and the amino acid cysteine, can grow on buffered charcoal yeast extract agar

Legionella Transmission

Can only be transmitted through droplets small enough to be breathed in like hot water mist or vaporized

Legionella Symptoms

Developing pneumonia as well as fever, headaches, muscle aches, coughs, and shortness of breath

Plague

Yersinia pestis, a Gram-negative, facultative anaerobe, rod-shaped bacterium capable of infecting both humans and animals

Bubonic plague

Best characterized by painfully swollen lymph nodes

Pneumonic plague

Affects the respiratory system (lungs) and is a highly virulent form

Septicemic plague

Targets the blood system and can develop into a life-threatening illness

Plague Symptoms

Headache, fever, seizures, bleeding, difficulty breathing, low blood pressure, and organ failure

Plague Treatment

Antibiotics such as streptomycin, tetracycline, fluoroquinolones, gentamicin, and doxycycline

Anthrax

Bacillus anthracis, a Gram-positive, aerobic, rod-shaped, spore-forming bacterium commonly found in soil

Anthrax Transmission

Spores are ingested or inhaled near an open wound, germinate, colonize, and disseminate throughout the host

Forms of Anthrax

Cutaneous, pulmonary, and gastrointestinal

Lyme disease

Borrelia burgdorferi, a motile (multi-flagellated), anaerobic spirochete bacterium

Lyme disease Transmission

Transmitted through a tick bite containing B. burgdorferi in its saliva

Lyme disease Symptoms

Bulls-eye rash, fever/chills, headache, muscle and joint pain, fatigue

Gonorrhea

Neisseria gonorrhoeae, a Gram-negative, diplococci, and fastidious bacterium

Gonorrhea Symptoms

Inflammatory responses in the urethra, throat, prostate, anus, testes, uterus, and fallopian tubes

Gonorrhea Treatment

Currently treated with an intramuscular dose of ceftriaxone and co-treatment for Chlamydia trachomatis

Chlamydia

Chlamydia trachomatis, a Gram-negative, nonmotile rod bacterium and obligate parasite

Chlamydia Symptoms

Often indistinguishable from gonorrhea; can cause PID in women and urethritis in men

Chlamydia Treatment

Antibiotics like doxycycline and azithromycin

Syphilis

Treponema pallidum, a Gram-negative spirochete

Syphilis Stages

Primary, Secondary, Latent, Tertiary

Syphilis Treatment

Penicillin

Candidiasis

Caused by an overgrowth of Candida albicans due to drug therapy or conditions like HIV/AIDS

Candidiasis Symptoms

Vaginal itching, discharge, soreness, and oral thrush

Candidiasis Diagnosis

Diagnosed by wet prep