Microbiology Assignment Discussion

Abstract

Staphylococcus aureus is a Gram-positive bacterium. It causes multiple infections including Staphylococcal scalded skin syndrome (SSSS). It appears purple from gram staining due to the presence of a thick peptidoglycan which absorbs the stain. The thick layer also causes antibiotic resistance. Antibacterial activity focuses on destroying the peptidoglycan.Microbiology Assignment Discussion

Article Summary

The article is about staphylococcus diseases caused by Staphylococcus aureus strains of bacteria. According to Bass (2016), these pathogens strains produce digestive enzymes and toxins which influence the invasive potential and virulence. This results in the development of specific clinical diseases. The most common illnesses include exfoliative skin disorders, Staphylococcal scalded skin syndrome (SSSS), staphylococcal enterocolitis, staphylococcal food poisoning and toxic shock syndrome (Bass, 2016). In general, the author reviews the specific staphylococcal toxins mediated diseases.

Pathogen Information

Staphylococcus aureus is a round-shaped Gram-positive bacterium from the class Bacilli and Bacteria domain. It is a prokaryote meaning that it is single celled and lack a nuclear membrane as well as other cellular organelles. Notably, it belongs to the Staphylococcaceae family of facultative anaerobes and genus staphylococcus which appear spherical under a microscope and form in grape-like clusters.

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Cellular/ structural characteristics

1. aureus has a spherical, ovoid, or round shape. It is arranged systematically on the lateral end of the cell. When grown on blood agar plate, they grow as golden yellow colonies. The structure of the bacterial cell wall is composed of a Gram-positive bacterium have a thick, multilayered cell wall consisting of peptidoglycan (Center for Disease Control and Prevention, 2017). The genome is comprised of a single chromosome that is circular together with mobile elements, nonconjugative and conjugative plasmids, prophages and other assortment of extrachromosomal accessory gene elements. The staphylococcus species is suggested by the appearance of clusters of Gram-positive cocci. Microscopy staining of S.aureus gives a purple coloration because the crystal stain used is retained in the thick peptidoglycan cell wall layer. Consequently, the bacterium produces multiple virulent factors whose expression is tightly controlled during growth. These include immune-modulatory factors (11, 12, 21, 31), exfoliative toxins, proteases, enterotoxins, hemolysins and leukocidins (Cowan, 2018). Understanding this information is important in patient’s diagnosis and treatment.Microbiology Assignment Discussion

Susceptibility to antibiotics/ antiviral or antifungals

1. aureus is susceptible to beta-lactam antibiotics such as flucloxacillin, nafcillin, oxacillin, cephalosporin, and clindamycin antibiotics. A combined therapy is recommended due to the resistant nature of the pathogen particularly to penicillin. These drugs are effective since they prevent the peptidoglycan formation of cross links which provide strength and rigidity of the cell wall. This leads to imbalanced cell degradation and cell wall formation causing death.

Growth conditions

The hosts for S. aureus are both the phagocytic and nonphagocytic cells. In Staphylococcal scalded skin syndrome, the bacterium invades the epithelia cells of humans and releases toxins that cause skin blistering and peeling. They feed on N-acetylglucosamine, sucrose, glucose, mannose, beta-glucosides, lactose, galactose, and mannitol and hence are chemoorganotrophic heterotrophic. They grow in mesophilic conditions with moderate temperature. They reproduce rapidly through binary fission yielding yellow colonies. The life cycle involves five stages namely attachment, multiplication, exodus, maturation and dispersal.

Evasion of immune system

1. aureus evades the immune system through secretion of proteases and other molecules that cling to components of the innate immune system, disrupting the extracellular and intercellular tissue connections integrity. This inhibits the complement system proteases’ and neutrophil antibacterial functions allowing the survival of the pathogen. Microbiology Assignment Discussion

Disease(s) caused, symptoms, diagnosis, and therapeutic interventions.

1. aureus skin invasion causes Staphylococcal scalded skin syndrome (SSSS). Symptoms caused are Fever, redness of the skin, fluid Filled Blisters, peeling skin, irritability, weakness and lack of appetite (Bass, 2016). SSSS is diagnosed through skin biopsy, bacteria culture and Tzanck Smear followed by treatment using flucloxacillin, nafcillin, oxacillin, cephalosporin, and clindamycin.

References

Bass, J (2016). The spectrum of staphylococcal disease, Postgraduate Medicine retrieved from https://www.tandfonline.com/action/showCitFormats?doi=10.1080%2F00325481.1982.11716247

Center for Disease Control and Prevention. (2017) Staphylococcus aureus in Healthcare Settings retrieved from https://www.cdc.gov/hai/organisms/staph.html

Cowan, M.K. (2018). Microbiology: A Systems Approach (5th Edition). New York, NY: McGraw-Hill Education.

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Microbiology Assignment Discussion