Staphylococcus epidermidis (MRSE)

Structure and Physiology

This bacteria is a Gram-positive, cocci-shaped, facultative anaerobe which is resistant to the penicillin-derivative antibiotic methicillin. S. epidermidis is part of normal human bacterial flora and is mostly located on skin.

Transmission and Disease

 It is an opportunistic and pathogenic; infections caused by this bacteria can be very difficult to treat.


Most Staphylococcus species are hardy microorganisms capable of surviving on surfaces and under dry conditions.


Staphylococcus aureus (MRSA)

Structure and Physiology

Methicillin-resistant Staphylococcus aureus (MRSA) is a Gram-positive, coccal-shaped, facultative anaerobic bacterium that is responsible for many difficult to treat infections. MRSA is any strain of Staphylococcus aureus that has developed a resistance to beta-lactam antibiotics through the process of natural selection. Beta-lactam antibiotics include penicillin, methicillin, dicloxacillin, nafcillin, oxacillin, and cephalosporins. Resistance does not increase the virulence of the microbe but does make it more difficult to treat.

Enterococcus faecalis (VRE)

Structure and Physiology

Enterococcus faecalis is a Gram-positive, nonmotile, facultative anaerobic microbe.  Vancomycin Resistant Enterococcus (VRE) are strains that are resistant to the antibiotic vancomycin. There are six different types of vancomycin resistance shown by Enterococcus: Van-A, Van-B, Van-C, Van-D, Van-D, Van-E, Van-F. Van-A, Van-B, Van-C have been tested in clinical trials and have shown to be resistant to vancomycin and teicoplanin. The current treatment in the U.S for VRE is linezolid.

Acinetobacter baumannii

Structure and Phisiology

This bacteria is a Gram-negative, rod-shaped aerobe. A. baumannii can be responsible for infections such as pneumonia and septicemia in immunodeficient patients. The natural reservoir of this organism remains to be determined. These are among a class of bacteria that are "naturally transformable" - meaning that the incorporation of exogenous genetic material can occur due to a special physiological state incorporated by the bacteria, which may be the reason for the prevalence of antibiotic resistance in some strains of A. baumannii.

Enterobacter aerogenes

Structure and Physiology

This bacteria is Gram-negative, rod-shaped, and radially surrounded by flagellum. It can be found in dairy products, soil, and the gastrointestinal tract of animals. E. aerogenes is closely related to a wide range of other common microorganisms including Escherichia, Klebsiella, Shigella, and Serratia.   

Enterobacter cloacae

Structure and Physiology

This bacteria is a Gram-negative, rod shaped, facultative anaerobe commonly found in the gastrointestinal tract of humans. It is not usually a primary pathogen although it is sometimes associated with urinary and respiratory tract infection.