Staphylococcus Epidermidis and Citrobacter Freundii - Essay Example

Staphylococcus epidermidis and Citrobacter freundii Teacher           Staphylococcus epidermidis and Citrobacter freundii Staphylococcus epidermidis General Description Staphylococcus epidermidis is classified as gram-positive, coagulase-negative bacteria, which is a part of the human normal flora. However, it is also considered an opportunistic pathogen that is responsible for nosocomial infections particularly infections coming from foreign bodies. As normal flora, up to around 24 species are found in healthy individuals and thus the bacterial population make up around 65 to 90% of all staphylococci recovered from human flora. Moreover, as both normal flora and pathogen, the organism always chooses humans and warm-blooded animals as host (Bukhari, 2004). S. epidermidis is also characterized by a stronger cell wall containing techoic acids, which make up 30-50% of the dry parts of the bacterial cell. Moreover, the natural environment of this species of bacteria actually thrives in the human body and, as the name implies, it is the most common staphylococcus on the human skin. Moreover, the ability of the bacteria to form the biofilm make them attach themselves and grow on biomedical devices and therefore may contaminate the blood and spread the infection to new areas (Bukhari, 2004). Detailed Description of Diseases Caused and Transmission As a pathogen, the infection brought about by S. epidermidis is common among newborns, intravenous drug users, the elderly, and people using catheters and artificial appliances. One of the most important characteristics of this bacterial species is that it produces a “glycocalyx ‘slime’” that acts as an adhesive to plastics and cells, thus making the bacteria resistant to both phagocytosis and antibiotic action (Bukhari, 2004). As a pathogen, most infections of caused by S. epidermidis are usually associated with intravascular devices such as shunts and prosthetic heart valves. The disease also commonly occurs in prosthetic joints, wounds and catheters. The symptoms associated with this disease include fever, headache and fatigue. Complications include anorexia, dyspnea, septicemia especially among the newborn with very low birth weight, and endocarditis which occurs as an infection of the heart valves and the inside lining of the myocardium (Bukhari, 2004). Among newborns, bloodstream infections caused by S. epidermidis are actually more frequent and more problematic. Many neonates are susceptible to bacterial sepsis and this may be taken advantage of by S. epidermidis. The best way to prevent it is by increasing hygiene in the hospital setting (Cheung & Otto, 2010). One virulence factor of the organism is that it forms a hydrophobic biofilm, or the glycocalyx slime that was previously mentioned. This biofilm is actually adhesive to hydrophobic polymers of prosthetics thus it causes diseases like endocarditis. The formation of the biofilm genetically depends on gene icaADBC, which has been found to code for the capsule of polysaccharide as well as for the intracellular adhesion used in the formation of the biofilm. The clusters of cells that make up the biofilm is up to 160 µm thick, which is equivalent to the thickness of 50 cells. The biofilm of S. epidermidis acts as a block against the host defense and antibiotics (Bukhari, 2004). Another factor that accounts for the virulence of S. epidermidis is its fibrinogen binding, although this is still currently under scientific investigation. The protein in the bacterium known as Fbe can actually act like fibrinogen and promote adhesion of the host cells. If the bacteria adhere themselves to the same components of the biomaterial surfaces of the host, then it leads to infections and potential complications (Bukhari, 2004). Treatment and Vaccines Vancomycin or rifampin can be used to treat any infection since the bacterium has already developed resistance to other antibiotics like clindamycin, novobiocin and benzyl penicillin (Bukhari, 2004). Moreover, what is most recommended by some experts is the synthetic antimicrobial peptide bactericidal peptide 2, or BP2 (Kwakman et al., 2006). Possible vaccination with S. epidermidis surface exposed, or Ses, may actually reduce biofilm formation of the bacteria, thus ensuring a more effective treatment (Sharooei et al., 2012). Citrobacter freundii General Description Citrobacter freundii is an aerobic gram-negative bacillus that is usually 1-5µm long. Most bacterial cells have flagella for moving about while some are non-motile. The habitat of this bacterial species includes soil, water, sewage, food as well as the intestinal tracts of humans and animals such as amphibians, reptiles, mammals and birds, owing to the fact that it belongs to the Enterobacteriaceae family. Moreover, as gram-negative bacteria, C. freundii contains a double membrane, inner and outer, with the periplasmic space lying in the middle. The bacteria do not contain a thick cell wall, unlike the gram-positive bacteria (Chang, 2011). As a pathogen, C. freundii usually causes nosocomial infections of the respiratory tract, and may also affect parts of other systems of the body particularly the blood and the urinary tract. In particular, C. freundii makes up an estimated 29% of all cases of opportunistic infections. Moreover, as a pathogen, C. freundii produces the enzyme cephalosporinase, which can actually hydrolyze and inactivate the antibiotics cephamycin and cephalosporin, rendering them useless as treatment (Chang, 2011). Detailed Description of Diseases Caused and Transmission C. freundii is believed to be the reason behind neonatal meningitis. Neonatal meningitis is the inflammation of the meninges of the newborn due to bacterial infection and invasion. C. freundii causes a high mortality among those it infects with around 75% of the survivors developing neurological problems. The problem is that C. freundii can penetrate the blood-brain barrier, which therefore aggravates the whole situation (Chang, 2011). Symptoms of the disease aside from sepsis and meningitis include the development of brain abscesses. C. freundii may also cause infections of the urinary tract – which is the most common, respiratory tract, and the skin as well as soft tissues. There is also surgical wound infection, bloodstream infection and the possible development of pneumonia (Badger et al., 1999). Treatment and Vaccines Effective treatment for C. freundii infections include aminoglycosides, carbapenems, fluoroquinolones, and some cephems for these have the ability to stop the growth of C. freundii in vivo. Combination therapy is also possible especially using third-generation cephalosporins plus new oral cephems and tazobactam. However, in special situations, like bacteremia, aminoglycoside combined with β-lactam agent is recommended. Moreover, in the case of meningitis, it is an aminoglycoside combined with a third-generation cephalosporin. An example is using 300 mg/kg/day of cefotaxime for at least 21 days of antibiotic therapy (Chang, 2011). So far, no known vaccine has been stated in scientific investigations. References Badger, J. L., Stins, M. F. & Kim, K. S. (1999). Citrobacter freundii Invades and Replicates in Human Brain Microvascular Endothelial Cells. Infection and Immunity, 67(8), 4208-4215. Bukhari, M. (2004). Student presentation on Staphylococcus epidermidis. Retrieved from the University of Connecticut: http://web.uconn.edu/mcbstaff/graf/Student%20presentations/S%20epidermidis/sepidermidis.html Chang, S. (2011). Citrobacter species. Retrieved from Antimicrobe.org: http://www.antimicrobe.org/b93.asp Cheung, G. Y. C. & Otto, M. (2010). Understanding the significance of Staphylococcus epidermidis bacteremia in babies and children. Current Opinion in Infectious Diseases, 23(3), 208-216. Kwakman, P. H., Te Velde, A. A., Vandenbroucke-Grauls, C. M. J. E., Van Deventer, S. J. H. & Zaat, S. A. J. (2006). Treatment and Prevention of Staphylococcus epidermidis Experimental Biomaterial-Associated Infection by Bactericidal Peptide 2. Antimicrobial Agents and Chemotherapy, 50(12), 3977-3983. Shahrooei, M., Khodaparast, L., Stijlemans, B., Kucharikova, S., Burghout, P., Hermans P. W. & Van Eldere, J. (2012). Vaccination with SesC decreases Staphylococcus epidermidis biofilm formation. Infection and Immunity, 80(10), 3660-3668. Read More