BACTERIA SCREENSHOT PRESENTATIONStaphylococcus aureusEscherichia coliNeisseria meningiditis

K.Napper & S. SchemeryCollege of Southern Maryland

This presentation was prepared for MLT-2010, taught by Professor T. Gill

STAPHYLOCOCCUS AUREUS

STAPHYLOCOCCUS AUREUS

STAPHYLOCOCCUS AUREUS

Cellular Morphology• Gram positive cocci in grape like clusters.

Colony Morphology• Grows well on blood agar and abundant

growth in 18-24 hrs

• Large (6-8 mm) smooth, entire, slightly raised, translucent, and pigmented colonies

• Off-white, gray, cream-yellow, yellow, yellow-orange, or orange pigment

• Colonies surrounded by multiple zones of hemolysis, resembling targets

• On MSA plates colonies will have a yellow pigment and the pink medium will turn yellow

STAPHYLOCOCCUS AUREUSDistinguishing Media• Blood Agar – for hemolysis

detection

• Mannitol Salt Agar (MSA)-for mannitol fermentation

Differential and Susceptibility testing• Catalase positive

• Coagulase positive

• Commercial latex agglutination testing

STAPHYLOCOCCUS AUREUSIndigenous locations

• Often found in low numbers as indigenous microflora of the skin.

• 20% -30% of the population are “staph carriers” – nasal passages are colonized with S. aureus. As long as the S. aureus is localized to the nasal passages of the carrier it poses no threat, but the bacteria can be transmitted to others.

Infections caused by bacteria• Skin and soft tissue-Furnicle,

Cabuncles, Wound infections ( surgical/ traumatic), Cellulitis, Impetigo

• Musculoskeltal- Ostemyelitis, Arthritis

• Cardiovascular- Endocarditis

• Genitourinary Tract- Renal carbuncle, Lower urinary tract infection

• Other infections cause by toxins- Toxic shock syndrome (TSS), Scalded skin syndrome, Food poisoning (gastroenteritis)

ESCHERICHIA COLI

Figure 10 Water E. coli Lawsuit Settlement. (n.d.).

ESCHERICHIA COLI

ESCHERICHIA COLICellular morphology

• Gram negative bacilli motile by peritrichous flagella

Colony Morphology• On blood agar colonies are

smooth, dull gray, and 2-3 mm in diameter

• On MAC colonies are lactose-positive colonies producing pink to red, flat, dry, and 2-3 mm in diameter. The colonies are usually surrounded by a darker pink area of precipitated bile salts

• On HE and XLD agar colonies have a yellow pigment.

• Foul odor

ESCHERICHIA COLI

Distinguishing Media• Blood agar – for hemolysis

detection

• MAC – lactose fermentation detection

• HE

• XLD

Differential and Susceptibility testing

• A/A reaction on TSI and KIA slants with or without gas

• Indole positive

• MR positive

• Voges-Proskauer negative

• Citrate negative

• Oxidase negative

• Nitrate positive

• PYR negative

• MUG positive

ESCHERICHIA COLIIndigenous locations

• Commonly found in the indigenous gastrointestinal flora of humans and animals

Infections caused by bacteria• The strains and serotypes of E. coli

found in the GI tracts of humans and animals are opportunistic pathogens and can be problematic when entering other sites than the GI tract (bladder, bloodstream, wounds)

• Most common cause of UTIs and common cause of septicemia and nosocomial infections

• Enterovirulent E. coli or diarrheagenic E. coli serotypes cause GI disease when they are ingested by humans.

NEISSERIA MENINGITIDIS

NEISSERIA MENINGITIDIS

NEISSERIA MENINGITIDIS

Cellular morphology• Encapsulated gram negative diplococcus • Grows best at 35-37C in moist 5%-

7% CO2 environment

• On Blood agar, Chocolate agar, or Thayer-Martin medium colonies are gray, low, convex, and glistening, with a smooth, moist entire edge.

• Heavily encapsulated strains may be mucoid.

• N. meningiditis colonies are about 1 mm larger than N. gonorrhoeae after 18-24 hrs. of incubation.

• Older colonies become gummy due to autolysis and release of cellular DNA.

Colony morphology

NEISSERIA MENINGITIDIS

Distinguishing Media• Will grow on Blood agar incubated

in non-CO2 incubator where as N. gonorrhoeae will not.

• Thayer- Martin

Differential and Susceptibility testing• Carbohydrate utilization or

chromogenic enzyme substrate test

• Will acidify media containing glucose and maltose

• Oxidase positive

NEISSERIA MENINGITIDIS

Indigenous locations• Strict human pathogen

• Colonizes the nasopharyngeal mucosa of some individuals; N. meningiditis carriers

• May also colonizes the genital tract and conjunctiva

Infections causes by bacteria• N. meningiditis may be

transmitted from person to person by transfer of respiratory secretions or aerosolized droplets

• Menigococcemia (N. meningiditis in blood stream)

• Petechiae

• Meningococcus meningitis

• Rare types of infections- genital tract infection, proctitis, and conjunctivitis

REFERENCES• Bacteriainphotos.com (2014). Escherichia coli colonies on macconkey agar, e.coli lactose positive colonies. [online] Retrieved from:

http://www.bacteriainphotos.com/Escherichia%20coli%20on%20MacConkey%20agar.html [Accessed: 22 Jun 2014].

• Catalog.hardydiagnostics.com (2014). Tryptic soy agar (tsa). [online] Retrieved from: https://catalog.hardydiagnostics.com/cp_prod/Content/hugo/TrypticSoyAgar.htm [Accessed: 22 Jun 2014].

• Cdc.gov (2014). Cdc - meningitis - lab manual - identification and characterization of neisseria meningitidis - chapter 7. [online] Retrieved from: http://www.cdc.gov/meningitis/lab-manual/chpt07-id-characterization-nm.html [Accessed: 22 Jun 2014].

• E. Coli. CDC Retrived March 16, 2015,from http://www.cdc.gov/ecoli/

• Engelkirk, P. & Duben-Englekirk, J. (2008). Laboratory diagnostics of infectious diseases: essentials of diagnostic microbiolgy. Batlimore: Lippincott Williams & Wilkins, a Wolters Kluer business.

• Escherichia coli. Bacteriainphotos, Retrived June 25, 2014, from http://www.bacteriainphotos.com/bacteria%20photo%20gallery.html#ecoli

• Hogan, G. (2011). Staphylococcus aureus. [online] Retrieved from: http://www.microbeworld.org/index.php?option=com_jlibrary&view=article&id=7611 [Accessed: 22 Jun 2014].

• Neisseria Meningitidis. Bacteriainphotos. Retrieved June 25, 2014, from http://www.bacteriainphotos.com/Meningococcus.html

• Neisseria meningitidis. (n.d.). Bioquell. Retrieved June 22, 2014, from http://www.bioquell.com/technology/microbiology/neisseria-meningitidis

• News, B. (2014). Local food distributor might be behind e. coli outbreak at trader joe's. [online] Retrieved from: http://sfappeal.com/2013/11/local-food-distributor-might-be-behind-e-coli-outbreak-at-trader-joes/ [Accessed: 22 Jun 2014].

• Pictures.life.ku.dk (2014). Staphylococcus aureus. [online] Retrieved from: http://pictures.life.ku.dk/atlas/microatlas/food/bacteria/Staphylococcus_aureus/pop1.html [Accessed: 22 Jun 2014].

• Staphylococcus aureus. Bacteriainphotos . Retrieved June 25, 2014, from http://www.bacteriainphotos.com/beta_hemolysis_on_agar.html

• Staphylococcus aureus. (2014, June 19). Wikipedia. Retrieved June 22, 2014, from http://en.wikipedia.org/wiki/Staphylococcus_aureus

• Textbookofbacteriology.net (2014). The normal bacterial flora of humans. [online] Retrieved from: http://textbookofbacteriology.net/normalflora.html [Accessed: 22 Jun 2014].

• Web.cn.edu (2014). Physiological tests. [online] Retrieved from: http://web.cn.edu/stkarr/physiolo.htm [Accessed: 22 Jun 2014].