Staphylococcus/Streptococcus

Staphylococcus/Streptococcus
And Aerobic Gram-positive Cocci
Chapters 9 & 10
Microbiology for Surgical Technologists

Review
Staphylococcus
And Aerobic Gram-positive Cocci
Staphylococcus
Clusters of spherical organisms
Two bacteria to be discussed
Staphylococcus aureus
Staphylococcus epidermidis
Both are Gram-positive
Stain purple in Gram stain test
Nosocomial Infections
Hospital-acquired infection
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Types of patients that are prone
Immunologically suppressed
Surgical pts
Areas of the body that are susceptible:
UTI, surgical sites, URS and the blood
Staphylococcus aureus
Termed a “super bug”
Common in boils, impetigo, TSS, osteomyelitis, and postoperative wound infections
Usually localized
Controlled by host defenses
Portals of entry
Brake in skin
Respiratory tract
Serious infection can follow prosthetic placement

Staphylococcus aureus
(continued)
Initial response
Inflammation, heat, swelling, and pus
Fibrin clot may form to protect the infection
Abscess
Can become systemic and cause recurring boils (carbuncles)
If it becomes systemic the septicemia can be fatal
Second most common type of nosocomial infections
Staphylococcus aureus
(continued)
Facultative anaerobe
aerobic on skin
Anaerobic in the pores
Primarily colonizes in the nasal passages
Multiplies rapidly in moist places
Nose, axilla, anus
Lab culture is yellow

Staphylococcus aureus

Staphylococcus aureus
(continued)
Antibiotic Resistance
90% of nosocomial infections are untreatable with penicillin
MRSA (methicillin-resistant S.aureus)
Represents about 45% of nosocomial infections
Resistant to most antibiotics
Vancomycin is drug of choice
No longer restricted to hospitals
Resistant strains are considered a medical emergency
Staphylococcus aureus
(continued)
Virulence Factors
Some release exoenzymes
Increase the ability of the pathogen to invade tissue
The exoenzyme produces coagulase
Clots plasma to form a coat of fibrin for protection
Staphylococcus aureus
(continued)
Diseases
Food poisoning
Caused by the enterotoxins
Symptoms usually appear in 2 to 6 hours
Lives on skin and mucous membranes
Result of improper food handling and storage
Cannot be killed by cooking
Food looks and smell normal
Cannot be treated by antibiotics
Prevention is the key
Staphylococcus aureus
(continued)
Toxic Shock Syndrome (TSS)
Caused by exotoxin (a superantigen)
Commonly infects menstruating women
Can also be caused by pneumonia, wound infection and abscess
Toxin producing strains are part of normal flora of the vagina
If left untreated, can be fatal
Nafcillin is drug of choice
Staphylococcus aureus
(continued)
Impetigo
Highly contagious superficial skin infection
Nonbullous
Small red macules that turn into pus filled vesicles that break open
Forms thick yellow crust
Bullous
Vesicle is thin walled and ruptures
Forms thin clear crust
Treated with cephalosporins or erythormycin
Impetigo
Staphylococcus aureus
(continued)
Folliculitis
Infection of the hair follicle that causes pustules
Can lead to furunculosus and carbuncles
Furunculosis
Found on faces of men with beards, eyelids (styes), and arms and legs of children
Hard painful pustules that rupture and spread the disease
Folliculitis
Staphylococcus aureus
(continued)
Osteomyelitis
Chronic bone and bone marrow infection
Occurs at one site and travels to bone
Long bones in children
Vertebrae and pelvis in adults
Pt’s have persistent localized pain that increases
Treated with bed rest and IV antibiotics
In some cases an I&D is performed to remove necrotic bone
Osteomyelitis
Staphylococcus aureus
(continued)
Endocarditis
Travels from initial site, through bloodstream, to endocardium and heart valves
Destroys valve tissue
Symptoms – heart murmur, chronic fever, splenomegaly, and embolism
Treatment
IV penicillin, cephalosporin, or gentamicin
Sometimes may require valve replacement
Staphylococcus epidermidis
Lab culture is white
Found on the skin, but can be found in eyes, ears, mouth and nose
Most frequent cause of IV catheter infections, urinary infections, prosthetic infection and subacute bacterial endocarditis
Can be introduced in surgery
Staphylococcus epidermidis
(continued)
Signs and symptoms of endocarditis often do not develop for up to one year after surgery
The percentage of reinfection in artificial joints is high
Most strains are methicillin resistent (MRSE)
75% of S. epidermidis infections are caused by MRSE
Vancomycin is the drug of choice
Streptococcus
And Aerobic Gram-positive Cocci
Streptococcus
Streptococcus
Gram-positive
Non-motile
Non-spore forming
Facultative or obligate anaerobe
Identified by sensitivity to optochin
Causes cell to lyse
Streptococcus
(continued)
Classifications
Beta hemolytic (β-hemolytic)
Complete lysis of erythrocytes
Alpha hemolytic
Partial lysis of erythrocytes
Gamma hemolytic
Do not lysis erythrocytes
Streptococcus
(continued)
Groups
Group A streptococci
Beta hemolytic
Spread by respiratory secretions and fomites
Group B streptococci
Gamma hemolytic
Normal vaginal flora
Streptococcus pneumoniae
In the eyes, ears, mouth, and nose
Causes:
Pneumonia, meningitis, and otitis media
Most common cause of bacterial pneumonia
One of three most common causes of bacterial meningitis
Streptococcus pneumoniae
(continued)
Two pneumonia causing strains
Capsulated
Shiny, mucoid appearance
More virulent
Non-capsulated
Dry pitted appearance
Frequent cause of pneumonia in children and elderly
Streptococcus pneumoniae
(continued)
Diseases
Pneumococcal pneumonia
Caused by inhaling infected droplets
To not produce toxins, bacterial cells cause inflammation
Becoming more virulent over time
Resistant to many antibiotics
Vaccine – Pneumovax
Protects from 23 of the 84 known strains
The 23 strain account for 90% of the known virulent strains that cause the infection
Streptococcus pneumoniae
(continued)
Bacterial ear infection
Responsible for most cases of otitis media
Most occur in children ages 1 – 8
Usually in conjunction with cold, nose or throat infection
Treatment
Penicillin, amoxicillin, or erythromycin
Myringotomy
Otitis media
Streptococcus pneumoniae
(continued)
Meningitis
S. pneumoniae is the primary cause in the elderly
Is also common cause in children
Symptoms similar to cold
Cause death if untreated
5% to 10% will die anyway
Can cause permanent brain damage
Streptococcus pyogenes
Group A, beta hemolytic
Causes strep throat, rheumatic fever, scarlet fever, and necrotizing fasciitis (the flesh eating disease)
Cell envelope contain antigenic protein M
Prevents phagocytosis
Help to adhere to pharyngeal cells
Identified with fluorescent staining
Streptococcus pyogenes
(continued)
Diseases
Streptococcal pharyngitis
Pharyngitis is strep throat
Causes fever, pain, difficulty swallowing, and inflammation of the tonsils and pharynx
Streptococcal pharyngitis
Streptococcus pyogenes
(continued)
Scarlet fever
Associated with strep throat
The pathogen is invaded by a bacterial virus that deposits it’s genetic information into it
This strain produces erythrogenic toxin
The toxin causes a red skin rash, and red spots on the tongue
The skin and tongue eventually shed their cells
Streptococcus pyogenes
(continued)
Necrotizing Fasciitis
The cell surface is mucoid and has a large amount of M protein
Infects the fascia and may penetrate the underlying muscle
Produces an enzyme called protease, that destroys proteins
Also produces a pyrogenic toxin, that causes a type of TSS
Streptococcus pyogenes
(continued)

Necrotizing Fasciitis (continued)
The disease has been around for a while, but the number of cases has increased in recent years
Treatment
Heavy doses of penicillin, cephalosporin, or vancomycin
Surgical I&D of necrotized flesh to pervent secondary infections
Necrotizing Fasciitis
Streptococcus agalactiae
Better known as group B strep (GBS)
Found in lower GI tract, GU tract and vagina
20% of women have GBS
Naturally acquired antibodies protect the host

Streptococcus agalactiae
(continued)
Neonate born without the antibodies 1% -2% are at risk of contracting systemic infections
Can be contracted in utero, during birth or during the first few weeks of life
Early onset – infection occurs in within seven days
Late onset – infection occurs from one week to three months
Streptococcus agalactiae
(continued)
Pregnant women are at risk of developing UTIs, amnionitis, endometritis, and wound infections
Men and non pregnant females develop skin infections, bacteremia, and pneumonia
Cancer, alcoholism and diabetes predispose individuals to infection
Treated with penicillin and vancomycin
Streptococcus viridans
Similar to S. pyogenes
Alpha hemolytic
Named for the green colonies that grow in the lab
Viridis is Latin for green
Normal flora of the upper respiratory tract, GI and GU tracts
Streptococcus viridans
(continued)
Cause subacute endocarditis, dental caries, and suppurative abdominal infections
Adhere to tooth enamel and heart valves that have already been damaged by rheumatic fever
Treated with penicillin