Gram Positive Cocci Flashcards by Emily Barker

List four prototypic diseases associated with Streptococcus pneumoniae

Otitis media
Sinusitis
Pneumonia
Meningitis

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Describe treatment for Strep pneumoniae meningitis

Widespread penicillin resistance

tx with vancomycin and cefriaxone or dexamethasone

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Describe Streptococcus pneumonia morphology

Gram positive, lancet shaped diplococci
a-hemolytic on blood agar
opaque mucoid colonies

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Describe how to distinguish Streptococcus pneumoniae from Streptococcus viridans

Strep pneumoniae has + bile solubility and + optochin sensitivity

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The most important virulence factor for Streptococcus pneumoniae is the ___________, which is antiphagocytic and stimulates an intense hose inflammatory response

capsular polysaccharide

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Outcomes from septic shock may be improved by the addition of ________ to treatment regime

corticosteroids- block inflammatory events at subcellular level

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True or false: Streptococcus pneumoniae remains highly susceptible to penicillin

FALSE.

high levels of penicillin resistance due to altered PBPs

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List populations that are highly susceptible to Streptococcus pneumoniae

Alcoholics (aspiration)
COPD, heart failure
Influenza A (airway damage, predisposes to aspiration)
Diseases that cause inability to mobilize antibody response
Sickle cell disease
Asplenics
CSF leaks ex following head trauma
People living in close quarters (ex prison)

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True or false: most influenza-related deaths are due to direct effects of the influenza virus

FALSE

Deaths often due to decompensation, secondary bacterial infection, pneumonia

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True or false: Streptococcus pneumoniae is spread by airborne respiratory droplets but is not highly contagious

TRUE

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True or false: the vaccine for Streptococcus pneumoniae is not recommended to be routinely administered in children

FALSE

is one of standard vaccines of childhood

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A new ______ pneumococcal vaccine has been shown in trials to be 89% effective against any serotype of S. pneumoniae

conjugate

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Children with otitis media more than ____ times for year should receive antibiotic prophylaxis against S. pneumoniae

4x per year

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List treatment regime for the common diseases caused by S. pneumoniae

Otitis media: Amoxicillin 80 mg/kg/d or erythromycin Sinusitis: Amoxicillin-clavulinate or FQ
Pneumonia: Ceftriaxone + Macrolide or FQ
Meningitis: Ceftriaxone + Vancomycin

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List prototypic diseases associated with Group A Streptococcus

Pharyngitis
Impetigo
Erysipelas
Cellulitis
Toxic shock syndrome

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List the prototypic diseases associated with Group B Streptococcus

Pueperal and neonatal sepsis

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List the prototypic diseases associated with Group D Streptococcus

Urinary tract infection
Surgical wound infection
Endocarditis

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List prototypic diseases associated with viridans a Streptococcus

Dental caries
Bacteremia
Subacute endocarditis

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List the prototypic diseases associated with Peptostreptococcus (anaerobic strep)

Peritonitis

Intraabdominal abscess

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Describe the morphology of Streptococci

Gram positive cocci in pairs and chains

Convex, opaque colonies

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Streptococcus pneumoniae are __-hemolytic. Group A and B Streptococcus are ___- hemolytic, Group D are often ___- hemolytic

S. pneumoniae: a-hemolytic
Group A and B: B-hemolytic
Group D: y-hemolytic

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The __ polysaccharide is an important antigen of many Streptococcus and is the basis of the Lancefield grouping scheme

C polysaccharide

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The __ protein is a virulence factor specific to Group A Streptococcus and is the basis of the Lancefield typing scheme

M protein

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M protein is antiphagocytic, promotes binding to surface fibronectin, and plays a role in post-streptococcal sequelae including _______ and ________

Rheumatic fever and glomerulonephritis

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Organisms that are a-hemolytic can be Strep ____ or Strep _____; the two are distinguished on the basis of the _________test

Viridans or pneumoniae | Copper disc test

Group D Streptococcus includes two subgroups:

Enterococci and non-enterococci

Enterococci (do/do not) grow on 6.5% salt and (are/ are not) penicillin sensitive

Do grow on 6.5% salt | Not penicillin sensitive

Community acquired infections caused by enterococci include ________. Nosocomial infections caused by enterococci include __________

Community: endocarditis, UTI Nosocomial: catheter associated UTI, bacteremia, surgical site infections

______ toxin of Group A Streptococcus causes Scarlet fever and is produced by _______ phage

Erythogenic toxin; lysogenic phage

List some extracellular enzymes and toxins produced by B-hemolytic Streptococci

``` Streptolysin O, S Diphosphopyridine nucleotidase Streptokinases Deoxyribonucleases Hyaluronidase Proteinase ```

There are two forms of toxic shock syndrome: the Staphylococcus aureus form is mostly associated with tampon use and has (high/low) mortality. The form associated with Group ___ Streptococcus a necrotizing infection with (high/low) mortality in healthy people

S. aureus: low mortality | Streptococcal: high mortality

The treatment for Streptococcal TSS includes:

Penicillin | Surgical debridement

Rheumatic fever and glomerulonephritis are _______ sequelae of Group A Strep infection and are mediated by ____ protein

non-suppurative; M protien

True or false: clinical features alone are highly diagnostic for Strep pharyngitis

false, only 50-75% acurate

True or false: most sore throats are due to Streptococcus

False, most due to viral infection or mycoplasma

List suppurative complications of Group A Strep pharyngitis

Peritonsillar abscess Pneumonia with empyema Bacteremia, distant metastatic infection (rare)

Differentiate rheumatic fever from glomerulonephritis on the basis of pathogenesis, precipitating infection, antibiotic prevention, treatment

``` Rheumatic fever: Autoimmune cause, heart and joints Precipitated by pharyngitis Is preventable with antibiotics Tx= aspirin ``` ``` Glomerulonephritis: Immune complex mediated Precipitated by skin infection Not preventable with antibiotics Tx= supportive only ```

Group ___ Strep is transferred from mother to neonate during parturition. Group __ is usually nosocomial. Group ___ Strep is transmitted by airborne droplets or contact

B D A All others- autochthonous

List susceptible hosts for Group A Strep

College students, military recruits, prisoners Neonates and post-partum women Damaged skin Post-surgery

List preferred treatment for Streptococcal infections

Penicillin | Erythromycin or vancomycin if penicillin allergy

List preferred treatment for enterococcal infections

Ampicillin Penicillin AND gentamicin Vancomycin

What is the reservoir of Staphylococcus aureus?

Nares, skin, mucosal surfaces

Describe modes of transmission of Staphylococcus aureus

- individual's endogenous flora spreads to normally sterile site - spread person to person by fomites, contact, respiratory droplets - ingestion of food contaminated with toxin

List general categories of Staphylococcus aureus virulence factors

- surface proteins - toxins - enzymes - antibiotic resistance genes

Describe two surface proteins of Staphylococcus aureus that act as virulence factors

- teichoic acid- aids in attachment by binding fibronectin | - protein A- inhibits antibody-mediated clearance by phagocytes

Describe toxins of Staphylococcus aureus that act as virulence factors

- cytotoxins: ex PVL- damage mammalian cell membranes, alpha/beta/delta/gamma toxins - exfoliative toxins- desquamation - enterotoxins- GI symptoms - TSST-1- activation of T cells, cytokine storm, superantigen

List two major enzymes of Staphylococcus aureus that act as virulence factors

- coagulase: converts fibronectin to fibrin, protects from phagocytosis - catalase: breaks down H2O2

List the major cutaneous infections caused by S. aureus

``` Impetigo Cellulitis Folliculitis Furuncle, carbuncle Wound infection Mastitis ```

Food poisoning caused by S. aureus is mediated by a _____-stable toxin; illness occurs (soon/late) after food ingestion.

heat stable | soon

Toxic shock syndrome caused by S. aureus is commonly associated with _____ use or surgical packing. Mortality is (high/low). ________ is critical.

tampon low mortality fluid resuscitation

Scalded skin syndrome is more common in (young children/ adults) and mortality is (high/low)

young children | low mortality

List the major risk groups for S. aureus infection and S. epidermidis infeciton

S. aureus: - menstruating women (TSS) - neonates (scalded skin) - young children (impetigo) - implanted medical devices (bacteremia, endocarditis) - immunocompromised, post-viral (pneumonia) - IV drug users (bacteremia, endocarditis) - burn/ post-op patients (soft tissue infection S. epidermidis: mostly associated with implanted medical devices

Describe lab diagnostics to differentiate S. aureus from S. epidermidis

S aureus is coagulase positive and positive mannitol fermenter, most colonies yellow-gold and hemolytic S. epidermidis is coagulase negative, does not ferment mannitol, colonies are nonhemolytic and white

List important measures to prevent Staphylococcal infections

Hand hygiene, proper wound cleaning, proper food handling, limiting long term use of catheters, chemoprophylaxis to prevent post-op surgical site infections

Describe the normal reservoir of Staphylococcus epidermidis infection

skin, mucous membranes

Describe Staphylococcus epidermidis virulence

Largely associated with ability to form biofilms, which act as barrier to antibiotics and host immunity, form on implantable medical devices

List major diseases associated with Staphylococcus epidermidis

``` Hospital acquired bacteremia Endocarditis Catheter infections Implanted medical device infection Surgical site infection (could develop up to 3 yrs post-op) ```

Staphylococcus saprophyticus is a coagulase negative staph that may cause ____, typically in adolescent, newly sexually active females

UTI

True or false: staph described as "methicillin resistant" can be treated with other beta lactam antibiotics and semi-synthetic penicillins

FALSE Resistance mechanism imparts resistance to more than methicillin- applies to all beta lactams, semi-synthetic penicillins, most cephalosporins, monobacams, carbapenems.

______ and ________ are antibiotics that were developed in response to the threat of vancomycin resistant S. aureus

Linezolid and daptomycin

True/ false: when staphylococci infect an implanted medical device, appropriate treatment involves long term IV antibiotics and leaving the device in to sterilize it

False, rarely able to resolve coagulase - infection without removing the infected device due to biofilm formation