Sharq Elneil CollegeSchool of Medical Laboratory Sciences Department of Microbiology Medical Bacteriology course Enterococci Dr.Mahadi Hassan Mahmoud email@example.com Bsc, Msc, MIBMS Microbiology
The Natural habitatNormal components of the flora of: Intestinal tract Oral cavity Vaginal canal of humans and animals
Morphology Gram-positive cocci (0.5 and1.25 micrometers in diameter)usually occur in pairs or shortchainsNon-capsulateNon-motile.
General properties:production of gas from glucose(most enterococci are negative)Have ability to grow at both45°C and 10°C temperatures).Can grow on media containingBile aesculin,
Medically Important speciesAt least 12 different species havebeen associated with various illnessesEnterococcus faecalis and E.faecium — have emerged as a majorcause of nosocomial infections
Culture &chaacteristics:Enterococci are aerobic organismscapable of growing over a widetemperature range,10–45 ºCOn blood agar,Enterococci are mainly nonhaemolyticbut some strains show alpha or beta-haemolysis
ON MacConkey &CLEDFerments lactose, producing small dark-red magenta colonies on MacConkey agasmall yellow colonies on CLED (cysteinelactose electrolyte-deficient) agar
Enterococcus species are alsoable to grow in the presence of 6.5%sodium chloride and 40% bile. When grown on media containingaesculin, enterococci hydrolyze theaesculin, producing black colonies.
Virulence Factor Polysaccharides on the surface ofenterococci represent an effective way toprevent phagocytosis. Secreted factors (cytolysin/hemolysin,gelatinase and serine protease) cell surface-located proteins oradhesins (Esp) and the adhesin ofcollagen Adhesins (Acm and SagA)
Pathogeicity:Enterococcus faecalis, causing about 95% ofenterococcal infections including infectionsof theUrinary tract infection Biliary tract,ulcers (e.g. bed sores) Wounds (particularly abdominal) Occasionally endocarditis or meningitis
Laboratory diagnosisspecimens:Collection of SpacimenDirect ExamCultureIdentificaionSerologyMolecular characterization
Biochemical TestsCatalase negativeFerment lactose (alsomannitol and other sugars).Hydrolyze aesculinReduce litmus milk
grow on reduce sorbitol glycerol, D- L- melibios 0.4% tetrazol tagatose arabinos e telluride ium to e formaz anE. yes Yes Acid Acid Acid No Acid No AcidfaecalisE. No No No Acid No Acid No Acid Acid Acidfaecium
Lancefield GroupingEnterococci possess LancefieldGroup D antigen (as also somestreptococci).The Group D antigen of enterococciis unlike that of other Lancefieldgroups.It is not extracted by traditional acidextraction techniques. Enzymetechniquesbased on Maxted’s enzymeare required.
Antibiotic ResistantMost enterococci are susceptible toampicillin and resistant tocephalosporins.Resistance is shown againstpenicillin. Vancomycinand ampicillinresistance appear to beemerging,associated particularly withhospital infections.
Penicillin or AmpicillinVancomycinFor urine isolatesFluoroquinolonesNitrofurantoinFosfomycinVancomycin-resistant strains(VRE)