Download S. epidermidis - UTCOMClass2015

Clinical Case 2
• 12-year-old boy was admitted to the hospital because of fever, chills,
sweats, productive cough, nausea, and vomiting.
• recurrent pneumonias since the age of 5 years.
• physical exam:
•febrile, tachycardic, and tachypneic;
•diffuse rhonchi in both lungs.
•finger clubbing, splenomegaly
• Blood cultures grew Staphylococcus aureus.
• Dx: Chronic granulomatous disease
Clinical Manifestations
• Disease from S. aureus occurs in one of
several ways
– toxin formation
– localized infection (pyogenic disease)
– systemic infection (disseminated infection)
Clinical Manifestations
• Staph food poisoning
– occurs through ingestion of a preformed enterotoxin
(usually staph enterotoxin A or B) in contaminated food
– meats, potato salad, custards, ice cream - partially cooked
or come to room temperature and then refrigerated
– usually the food appears normal
– abrupt onset of salivation, N/V, abdominal pain, diarrhea
occurring 2 - 6 hours after ingestion
– usually occurs in community outbreaks
– self-limited: resolves in a few hours
Clinical Manifestations
• Toxic shock syndrome
– associated with toxigenic staph strains producing
TSST-1
• TSST-1: related to the enterotoxins and is a
superantigen
– patients are colonized with the staph strain and
under certain conditions (low oxygen tension, low
magnesium concentration, etc), toxin production
begins
Clinical Manifestations
• Toxic shock syndrome - 2 scenarios clinical
picture looks the same
– Non-menstrual
• usually occurs 48 hours after a surgical procedure
• patient looks septic but wound looks good
– Menstrual
• young women age 15-25 using tampons during menses
Clinical Manifestations
• TSS - clinical picture
– abrupt onset of myalgias, fever, vomiting, diarrhea
– confusion without focal neurologic deficits
– severe hypotension, renal insufficiency, shock liver
– rash with desquamation of palms and soles within
a week - often conjunctival injection
Clinical Manifestations
• TSS - Treatment
– remove source of the staph (removes toxin
production) abscesses, fluid collections, tampons
– supportive measures, immunoglobulins,
antibiotics
• 3% mortality currently - long term neurologic
sequelae not uncommon
Clinical Manifestations
• Pyogenic disease
• Numerous types - clinical name used depends on
location and size of the S. aureus infection
• Examples:
– folliculitis
– furuncles/carbuncles • deep seated inflammatory mass that evolves from folliculitis
(zits) - a carbuncle is a coalescence of furuncles
– hidradenitis suppurativa
• chronic infections of axilla, pubic area associated with
apocrine sweat glands
Carbuncle
Furuncle
hidradenitis
Clinical Manifestations
• Pyogenic Diseases con’t
– impetigo
• Superficial infection of the skin
• begins as a vesicular lesion, then changes to a crusty
erosion
– cellulitis
• Infection of the dermal, subcutaneous tissues
associated with dolor, rubor, calor, tumor
– lymphangitis
• Dissemination of infection through lymphatics - can
be a complication of pyogenic infection
impetigo
cellulitis
lymphangitis
Clinical Manifestations
• SSSS (Staph Scalded Skin Syndrome)
– Ritter von Ritterschein disease (in newborns)
– Toxins act on the dermis
• Generalized
– Staph secretes a toxin systemically (usually can’t recover staph
from the involved site)
– Nikolsky’s sign: detachment of the skin by rubbing
• Localized
– Bullous impetigo
– Blistering around an infected area
– Treatment is antistaph agents/local wound care
Scalded Skin Syndrome
SSSS vs TEN
• TEN (Toxic Epidermal Necrolysis)
– Cleavage within the dermis or dermoepidermal
junction
• epidermal involvement
• High fatality rate
• Can be difficult to distinguish from SSSS
– May need biopsy
– Treatment with steroids (?)
Clinical Manifestations
• Disseminated infection
– “Staph goes where the blood goes”
– bacteremia/septicemia usually starts as a local
infection and overcomes host defenses
– manifestations include endocarditis, vasculitis,
pericarditis, pneumonia, osteomyelitis, brain
abscess
Treatment
• Remove foreign bodies if possible
• Drain pus if possible
• Duration of therapy depends on the
type of infection
– bone, foreign body, heart require at least
4 weeks of antibiotics
Treatment
• Antibiotic Therapy
– guided by local susceptibility data
– MSSA- methicillin sensitive S. aureus
• good drug choices are B-lactams
– Hospital Acquired MRSA (HA-MRSA)
• Most frequently due to altered penicillin binding
proteins (PBP2a)- mecA gene
• resistant to more drugs than CA-MRSA
• vancomycin best choice
Treatment
– Community acquired-MRSA (CA-MRSA)
• doxycycline, trim-sulfa, linezolid, vancomycin good
initial choices if CA-MRSA suspected
• rifampin resistance occurs rapidly and combination
therapy is useful
– VISA/VRSA
• MRSA that is Vancomycin Resistant
– vancomycin intermediate-susceptible MRSA
– vancomycin resistant MRSA
• consider linezolid or Synercid or daptomycin
Antibiotic Susceptibility Testing
Mueller-Hinton Agar Disk Diffusion
Vitek 2.0
CA-MRSA
Coagulase Negative Staphylococci
• Coagulase Negative staph
– 15 species are indigenous to man
– 4 are clinically important
• S. epidermidis (S. epidermidis)
• S. hemolyticus
• S. saphrophyticus
• S. lugdunensis (infrequent, but severe)
– Others: S. capitis, S. caprae, S. warneri, S. auricularis,
S. intermedius, S. simulans, S. cohnii, S. chormogenes
S. epidermidis
• normal resident bacteria on skin, mucous
membranes (S.epi - 65% - 90%)
• type, location, and amount of S.epi on skin
can be altered by many factors
• eg. - antibiotic use, S. aureus colonization
• Contains numerous plasmids coding for
antibiotic resistance and can easily transfer
them within or between species, genus
S. epidermidis
• usually highly antibiotic resistant
– >80% methicillin resistant
– >50% are resistant to: erythromycin,
clindamycin, Chloramphenicol, and tetracyclines
– Sensitive to: vancomycin, rifampin, and
ciprofloxacin
• Nearly all infections are nosocomial (hospital
acquired)
S. epidermidis
S. epidermidis
• Coagulase negative
• Catalase positive
• Growth on blood agar:
– Non-hemolytic (gamma
hemolysis)
– Whitish creamy color
– Grows readily (16 hours)
S. aureus
S. epidermidis
• no known pathogenic exoproteins or toxins
• mainly causes infection on “hardware” and is
introduced onto foreign body during
procedure from hospital environment, hands
of personnel
– eg - IVs, dacron grafts, CSF shunts, pacemaker
wires, artificial valves and joints, implants (breast,
eye)
S. epidermidis
• Exopolysaccharide layer produced by the
organism (biofilm) is the major reason it
causes infection on hardware
– Biofilm protects S. epidermidis from
host defenses such as opsonization and
decreases penetration of antibiotics
– some surface antigens produced by S.
epidermidis may promote its adherence
CoNS Pathogenesis
Von Eiff, et al. Lancet Infect Dis 2002;2:677-85
before inoculation
30 minutes
24 hours
12 hours
silicone ventricular catheter (Cordis®)
Clinical Manifestations
• DO NOT take blood cultures from Lines!
• Intravenous Catheter Infections
– S. epidermidis- most common associated
organism
– Can lead to bacteremia and can also be
associated with significant morbidity/mortality
(“line sepsis”)
– Infection can occur at the insertion site or the
tip
– Remove catheter + Vancomycin
Clinical Manifestations
• Bacteremia
– S. epidermidis often recovered from blood cultures
– most common blood contaminate and rarely causes native
valve endocarditis
• most common cause of “line sepsis”
• major cause of sternal osteomyelitis after
cardiothoracic surgery
• common cause of prosthetic joint infection
Clinical Manifestations
• Infective Endocarditis (IE)
– Native valve IE
• 5% of all cases are due to S. epidermidis
• occurs with seeding of damaged valves,
endocardium when S. epidermidis crosses skin
barrier
– Prosthetic valve IE
• 40% of all cases are due to S. epidermidis
• if it develops in the first months after valve
replacement, seeding probably occurred during
surgery
Clinical Manifestations
• IE (continued)
– Diagnosis
• Multiple sets of positive blood cultures
• echocardiography
• high level of clinical suspicion
– Treatment
• Vancomycin + gent + rifampin
• Removal & replacement of valve
Clinical Manifestations
• S. epidermidis
endophthalmitis:
– Most common cause after
cataract surgery/lens
implantation
– Also occurs in intravenous
drug abusers (IVDA)
– Dx - clinical exam
– Tx - vitrectomy or enucleation
with IV vancomycin
+intravitreal antibiotics
Clinical Manifestations
• Urinary Tract Infections
– S. epidermidis usually causes UTIs in elderly,
hospitalized patients with catheters in place
– Very different than clinical setting of UTIs
with S. saprophyticus
S. hemolyticus
• (2nd most common cause of CoNS infections)
• normal resident bacteria on skin, mucous
membranes
• Infections: similar to S. epidermidis– Line infections, endocarditis, septicemia
– Others: UTI, Wound, bone, and joint
• Lab: similar to S. epidermidis: catalase positive
coagulase negative, non-hemolytic on blood agar
S. saprophyticus
•
•
•
•
•
Catalase positive
Coagulase negative
Non-hemolytic on blood agar
Novobiocin resistant
True urinary pathogen (rarely a
contaminant)
• UTI clinical presentation similar
to that of infection with GNRs
such as E. coli: frequency, urgency,
dysuria: pyuria on UA
S. saprophyticus
• Infection occurs in healthy young women in an
outpatient setting
– 70% report sex within 24 hours preceding symptoms
– 2nd most common pathogen (after E. coli) in young
women
– can cause symptoms, pyuria, with <105 cfu/ml
– may be cause of acute urethral syndrome
– Tx - quinolones, Bactrim
• may recur in 10% of patients
S. lugdunensis
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•
•
•
Infrequent, but important cause of infections
Very aggressive endocarditis with frequent valve replacement, congestive heart
failure, and high mortality rate
Bacteremia, arthritis, UTI, central line infections, wound infections
Key lab features:
– Beta hemolytic on blood agar
– Coagulase negative
– pyrrolidonyl-α-naphthylamide hydrolysis (PYR) positive
•
•
•
Detects L-pyrrolidonyl arylamidase
Paper disk impregnated with reagent
(most staph are negative): good rapid screening test
– Rapid ornithine decarboxylase positive (all other staphylococci are negative)
PYR negative
PYR positive
Definitive ID to Species
Biochemical Reactions
Automated
Vitek 2.0
Manual Methods
Remel Staph RapID
BioMerieux API Staph
Definitive ID to Species
16S rRNA gene sequencing
Search Sequence Database of Organisms