Chapters 4 + 19-24: Pathogenic Prokaryotes, Gram Positive Bacteria (Not Done)

General Characteristics of Prokaryotic Organisms

• Gram Stain

• Shape

• Arrangement

• Endospores

Prokaryotes

This microbe is made up of the most numerous and diverse group of cellular microbes with only a few capable of colonizing humans and causing disease

• Bacteria and Archaea (do not cause disease)

Gram Stain

This is typically the first type of stain used to identify bacterial pathogens, differentiating two types of microorganisms (gram + and gram -)

Gram Positive Bacteria

This type of bacteria shows up as purple in a gram stain and has a thick peptidoglycan layer

Gram Negative Bacteria

This type of bacteria shows up as red/pink in a gram stain with a thin peptidoglycan layer and has an additional liposaccharide layer

Endospore

A highly resistant structure which contains a defensive strategy against unfavorable conditions; very difficult to destroy and needs a high level disinfection

• Produced by gram-positive Bacillus and Clostidrium

Types of Gram-Positive Bacteria

• Staphylococcus

• Streptococcus

• Clostridium

• Listeria

• Mycobacterium

• Actinomyces

Staphylococcus General Characteristics

This type of gram-positive bacteria contains normal members of a microbiota, but can be opportunist

• Gram + cocci, grapelike clusters

• Tolerant to salt and desiccation

• Human pathogen: Staphylococcus aureus

Staphylococcus Pathogenicity

• Structures that enable it to evade phagocytosis

  • Protein A coat prevents phagocytosis

  • Forms capsule for attachment and escape from immune system

• Production of enzymes

  • Coagulase triggers blood clotting around bacteria

  • Staphylokinase allows for escape from clots to spread further

  • Hyaluronidase allows for easy spread through intracellular matrix

  • Lipases allow for bacteria to grow in oil glands of skin

  • B-lactamase (penicillinase) breaks down penicillin

• Production of toxins

  • Cytolytic toxins disrupt cell membranes

  • Exfoliative toxins cause skin to separate and slough off

  • Toxic shock toxin causes immune response overreaction

  • Enterotoxins  stimulate symptoms of food poisoning

Pathogenicity

The potential of a pathogen to cause a disease

Staphylococcus Epidemiology

This gram positive bacteria is found on human skin and does not become pathogenic until it breaches the body’s physical barriers

• Can colonize upper respiratory GI, urinary and genital tracts

• Virulent strains transmitted through direct contact or fomites

Food Poisoning

This non-invasive staphylococcus disease is one of the most common causes of this “disease” and is caused by enterotoxins

• Impacted products include processed meats, potato salad, custard type desserts

• Symptoms: nausea, vomiting, diarrhea, headaches, abdominal pain

• Clears in 24 hours

Scalded Skin Syndrome

This type of cutaneous staphylococcal disease includes reddening of the skin near the mouth which spreads to the entire body which is followed by large blisters containing clear fluid

• Within two days, the outer layer of the skin peels off in sheets

Impetigo

This type of cutaneous staphylococcal disease includes small, red, flat patches on the face and limbs that form pus filled lesions

Toxic Shock Syndrome

This systemic staphylococcal disease causes a strain to produce TSS toxin in which the toxin is absorbed into the blood leading to symptoms including fever, vomiting, red rash, extremely low blood pressure, and loss of sheets of skin

• Enters through skin wounds, surgical sites, improper tampon use

Bacteremia

Bacteria in the blood

Endocarditis

Infection of the heart lining or valves

Pneumonia

Infection of the lungs

Osteomyelitis

Infection of the bone

Staphylococcus aureus

This type of bacteria may enter the blood via a would and cause

• bacteremia

• endocarditis

• pneumonia

• osteomyelitis

Staphylococcus Diagnosis

This type of bacteria is detected as gram-positive bacteria in a grape-like arrangement

• ability to clot blood

Staphylococcus Treatment

This type of bacteria is sensitive to methicillin an vancomycin(MRSA)

Staphylococcus Prevention

Methods such as hand washing helps to prevent nosocomial infections, but there is not vaccine available for this bacteria

Streptococcus

This type of bacteria is gram positive and made up of cocci arranged in pairs or chains

Streptococcus Human Pathogens

• Streptococcus pyogenes (group A)

• Streptococcus agalactiae (group B)

• Streptococcus pneumoniae

Streptococcus pyogenes

This pathogen is present when Group A Streptococcus is detected

Group A Streptococcus Epidemiology

This bacteria group causes disease when normal microbiota is depleted, when immunity is impaired ,or a large inoculum is introduced

• Virulent strains spread via respiratory droplets

Group A Streptococcus Diseases

• Pharyngitis (“strep throat”)

• Scarlet fever

• Rheumatic fever

• Pyoderma and erysipelas

• Streptococcal toxic shock syndrome

• Necrotizing fasciitis

Pharyngitis (Strep Throat)

Symptoms of this group A streptococcus disease include

• Sore throat, painful swallowing

• Fever, fatigue, and headache

• Red and swollen tonsils

• Swollen lymph nodes

• Tiny red spots on roof of mouth

Scarlet Fever

This group A streptococcus disease results from complications due to pharyngitis in which toxins released by the bacteria trigger rash that begins as the chest and spreads across the body

• Rash disappears after one week, followed by sloughing(shedding) of the skin

Rheumatic Fever

This group A streptococcus disease results from untreated pharyngitis

• Autoimmune response —> antibodies against streptococcus cross react with the body’s own healthy tissue

• Leads to inflammation of the skin(rash), joints(migratory), heart(damage of heart valves)

Pyoderma (Impetigo)

This streptococcal skin infection is a pus-producing lesion on exposed skin of the face, arms, or legs

• Highly contagious

Erysipelas

This streptococcal skin infection is a pyoderma condition that involves superficial lymphatics; localized

• Pain and infection

Cellulitis

This streptococcal skin infection occurs in deeper tissue, more diffuse, pus forming

• Can involve/occur in the muscles and tendons

Necrotizing Fascilitis

This infection is known as “flesh eating bacteria” in which is enters the body through breaks in the skin and produces enzyme + toxins that destroy muscle and fat tissue

• Disproportionate pain at injury site, red/ purplish area that spreads rapidly, fever, fatigue

• Involves toxemia, organ failure & death in 30% of patients

Strepotococcus Pyogenes Diagnosis

This type of streptococcus bacteria diagnosis includes gram positive bacteria in short chains or pairs in skin specimens

• Antibody tests for group A antigens

Strepotococcus Pyogenes Treatment

Penicillin is effective in treating this type of bacteria; necrotizing fascitis must be treated with surgical removal of infected tissue as well as antimicrobials

Strepotococcus Pyogenes Prevention

Preventing infections from this bacteria includes handwashing, good personal hygiene

• No widely available vaccines

Streptococcus agalactiae

This bacteria is present in Group B streptococcus

Streptococcus agalactiae Epidemiology and Pathogenicity

This type of bacteria can infect the normal microbiota of the lower GI, genital, and urinary tracts

• Can be passed to newborns during birth or by healthcare workers

• Can be passed to elderly through wound infections

Streptococcus agalactiae Disease

Newborn diseases from this bacteria include

• Puerperal

• Childbirth fever

• Bacteremia

• Meningitis

• Pneumonia

• Blindness

• Deafness

Elderly/Immunocompromised diseases include

• Skin and join infections

• UTI’s

Streptococcus agalactiae Diagnosis

This bacteria can be diagnosed using the ELISA test

Streptococcus agalactiae Treatment

Penicillin is the drug of choice for this bacteria type

Streptococcus agalactiae Prevention

This type of bacteria can be prevented through prophylactic administration of penicillin to newborns of infected mothers

• Maternal vaccination research in progress

Streptococcus pneumoniae Epidemiology and Pathogenicity

This type of bacteria is diplococci, with a large capsule which is found in mouths and pharynges

• This bacteria causes disease when the virulent strains travel to the lungs

Streptococcus pneumoniae Diseases

Diseases of this bacteria include

• Pneumococcal pneumonia (productive cough with blood)

• Sinusitis and otitis media

• Pneumococcal meningitis

Streptococcus pneumoniae Diagnosis

This type of bacteria can be diagnosed through a gram stain of sputum smears and a quellung reaction for a capsule

Streptococcus pneumoniae Treatment

Treatment for this bacteria includes penicillin but many gram stains are becoming resistant making it difficult to diagnose

Streptococcus pneumoniae Prevention

This bacteria type is prevented only through a vaccine

Clostridia General Characteristics

This type of bacteria is gram positive, anaerobic, and has endospore-forming bacillus

Clostridia Human Pathogens

• C. perfringens

• C. botulinum

• C. tetani

• C. difficile

Clostridium perfringens epidemiology and pathogenesis

This bacteria type grows in the digestive tracts of animals and humans and are transmitted by eating contaminated foods(meat) or through open wound

• Vegetative cells can produce up to 20 toxins

Clostridium perfringens Diseases

Food borne illnesses of this bacteria include diarrhea and stomach cramps, but are quick to start and end

• Gas gangrene is another disease and is self-diagnosed (foul smell, swelling, discoloration)

Clostridium perfringens Treatment

Treatment for this bacteria type is self limiting when it comes to foodborne illnesses, but requires removal of dead tissues and antimicrobials if severe (such as gas gangrene)

Clostridium perfringens Treatment

Prevention of this bacteria is difficult because this organism is so common

Clostridium botulinum Epidemiology and Pathogenesis

This bacteria type is commonly found in soil, water food (home canned goods) and are transmitted by ingestion or contamination of a wound

• Toxins inhibit neuromuscular actions (paralysis)

Clostridium botulinum Diseases

• Foodborne botulism

• Wound botulism

• Infant Botulism

Foodborne Botulism

Symptoms of this disease include descending weakness, blurred vision, dry mouth, slurred speech, abdominal pain, death can result from asphyxiation, no fever

Wound botulism

This disease is similar to foodborne botulism where a fever is present but there is no abdominal pain

Infant botulism

This disease can result in harm to an infant if they are given honey under 1 years old and can result in constipation, floppy muscle tone, and poor feeding

Clostridium botulinum Diagnosis

This bacteria is diagnosed by culturing organisms from food, feces, or wounds but symptoms are diagnostic

Clostridium botulinum Treatment

In order to treat this bacteria type, antimicrobial drugs and neutralizing antibodies are administered to fight against the botulism toxin

Clostridium botulinum Prevention