Alpha & Non-hemolytic Streptococcus Flashcards
What indicates inflammation from Strep pneumoniae?
C substance in the cell wall can elicit a C-reactive protein in the patient
Non-specific & only indicates inflammation
What is Streptococcus pneumoniae referred to & what is it?
Pneumococcus
Pathogen that causes pneumocccoccal pneumonia & meningitis
What is S. pneumoniae famous for?
A capsule - virulence factor
50 types
What is used to serotype the bacteria S. pneumoniae?
The Neufield test
Antisera & capsule will cause a swelling in the Quellung reaction
What does S. pneumoniae cause?
Pneumonia, sinusitis, otitis media, bacteremia, & meningitis
Ear infections in children over 3
Pneumonia in the elderly
How does one get pneumonia & what are their risk factors?
Patient must already by colonized & not have an antibody to the strain
Immunosuppressed - alcoholism, anesthesia, viral infections
Can lead to lobar pneumonia
What is effusion & pleural effusion?
Collection of serous fluid between an organ & the lining of the body cavity
Pleural effusion is effusion around the lungs
What can pneumonia be accompanied by?
A pleural effusion
Pneumonia can have several effusions which are?
Exudate
Transudate
Empyema
What is exudate?
Effusion that is caused by infection or malignancy & has pus (WBC)
Increased LD - lactate dehydrogenase
Increased protein
What is transudate?
Effusion that is caused by hydrostatic pressure Watery Low WBC Low LD Low protein
What is empyema?
Collection of purulent fluid in the pleural space between the lung & chest wall
Sterile empyema has no bacteria in it
Fluid may be infected or sterile
What are the characteristics of pneumococcal pneumonia, meningitis, & septicemia?
Mortality rates are high if untreated & still can be fatal if treated
Meningitis can follow otitis media & pneumonia
CSF gram stain reveals WBC & characteristic gram positive pairs - “lancet shaped pairs”
Blood cultures are positive & performed when sputum & CSF are collected
Penicillin is the drug of choice - some strains are resistant
What are the types of vaccinations for pneumococcal pneumonia, meningitis, & septicemia?
PCV7
PS23
What is PCV7?
Pneumococcal conjugate vaccine 7
Approved for children & part of normal pediatric care
13 valent product for children
What is PS23?
23-valent vaccine used for adults
Recommended for elderly with cardiac or pulmonary disease & for asplenic individuals
What are the laboratory diagnosis of Strep pneumoniae?
Specimens - sputum, blood, CSF
Sputum is cultured to BAP in CO2, MAC & CNA, & gram stained
Beta hemolytic
Colonies - umbilicate or mucoid
MAC - no growth
CNA - growth
Distinguishes from other alpha strep using optochin & bile solubility
Where are the oldest colonies of S. pneumoniae?
In the center
How do we differentiate green streps (what tests)?
Optochin - P disk; ethylhydrocupreine HCl
Bile solubility - sodium desoxycholate
Colony morphology
Gram stain - gram positive lancet shaped pairs & chains (capsule)
What is endocarditis?
Infection of the valves of the heart
Associated with transient bacteria
Those at risk have hematologic malignancies, damaged heart valves (rheumatic fever)
What are the characteristics of Viridans Streptococci?
Normal flora in the URT, female genital tract, & GI tract
Many require CO2 for growth
Are oropharyngeal normal flora which can be opportunistic pathogens
Viridans strep is the most common cause of bacterial endocarditis
What does capnophilic mean?
Grows better in carbon dioxide
Strep viridans is not S. pneumoniae because of?
It’s green strep without Lancefield group antigens
What are oropharyngeal commensals of Strep viridans?
Sub acute bacterial Endocarditis Meningitis Abscesses Osteomyelitis Epyema
What are the species of S. viridans?
Angiosus group Mitis group Mutans group Salivarius group Bovis group
What are the types of oral infections that are caused by S. viridans?
Gingivitis
Dental caries - cavaties
Oropharyngeal abscess
What are the laboratory tests for S. viridans?
All viridans are PYR positive & LAP positive
Multitest panels can be used to speciate them
What is the most commonly isolated viridans group?
S. mutans
Usually from oral cavity
Primary contributor to dental caries & bacteremia
What will viridans strep be seen as in cultures?
Throat culture as small green colonies in the background
Normal flora
What two types of strep bacteria are not green?
Enterococcus & group D strep
What are enterococci?
Normal flora in the intestines
Frequent causes of nosocomial infection, especially UTI, then bacteremia, & endocarditis
What are common species of enterococcus & group D strep?
E. faecalis & E. faecium
What type of lancefield antigen do enterococcus & group D strep have?
Antigen D
What type of hemolysis do enterococcus & group D strep have?
Usually hemolytic
Can be alpha or beta
What type of pseudo-catalase reaction do enterococcus & group D strep?
Weak
What type of conditions do enterococcus & group D strep grow under?
Bile
High salt
High temperature
Alkaline conditions
What group are group D strep a part of?
Streptococcus bovis
What are the strep members of the strep bovis group?
S. equinus
S. gallolyticus
S. infantarius
S. alactolyticus
What are the laboratory diagnosis for Enterococcus?
Urine cultures on BAP & MAC with calibrated loop to count colonies
Colonies grow in CO2 but don’t require it
Blood cultures are their own collection media
Bile esculin - positive
Grow in high salt broth
PYR - positive
What is esculin hydrolysis?
Ability to hydrolyze esculin
Characteristic of enterococci & group D strep
Some S. viridans do this
What are the two results of bile esculin?
Black - positive
Growth - positive
No growth - negative
What does 6.5% NaCl broth do?
Distinguishes between enterococcus & group D strep
Tubes will get cloudy or stay clear
No color is used for evaluation
How are enterococcus species differentiated?
Based on carbohydrate & amino acid usage
Motility
Ability to grow in the presence of tellurie
What are the motile forms of enterococcus?
E. faecalis - UTI
E. faecium
E avium
E. durans
What type of enterococcus is the only one to grow in the presence of tellurite?
E. faecalis
What are the components of antimicrobial resistance to aminoglycosides?
Enterococcus is resistant to several antibiotics
6 vancomycin resistant phenotypes VanA - VanE & VanG
˜2% of E. faecalis & 60% E. faecium found in blood are vancomycin resistant - VRE
What is Van A?
Inducible
Carried on a transposon & confers a high level of resistance to vancomycin & teicoplanin
What is VanB?
Chromosomal
Has variable levels of resistance to vancomycin
Susceptible to teicoplanin
What are two types of nutritionally variant strep?
Abiotrophia & granulicatella spp.
Not typeable by lancefield typing
Growth as satellites & require SH for growth
What do nutritionally variant strep cause?
Bacteremia, endocarditis, otitis media
Very antibiotic resistant, may require surgery
What is the typical presentation of nutritionally variant strep?
Fever Collect blood cultures Tubes monitored under CO2 for growth Gram positive S. aureus is streaked to see if they grow in satellites around it
What types of nutritionally variant strep organisms are grown from supplemented media?
Pyridoxal-dependent
Vitamin B6 dependent
Thiol dependent
Staph aureus streak plates
What are some strep like organisms?
Aerococcus
Gemella
Lactococcus
What is LAP leucine aminopeptidase?
Enzyme that cleaves peptide bonds, especially leucine
Substrate is leucine-B-napthylamide which is hydrolyzed to B-napthylamine
Red - positive
PYR similar
What are characteristics of aerococcus?
Gram-positive cocci that form tetrads Alpha hemolytic - resemble viridans group Usually a contamininant PYR - positive Salt tolerant - 6.5% NaCl Bile esculin variable LAP - negative
What are lactococcus?
Similar to enterococci
Pattern of carbohydrate fermentation is used to identify & distinguish them from enterococci
What are characteristics of gemella?
Similar to viridans
Decolorize easily
May look gram negative cocci in pairs, tetrads, clusters or chains
