Staphylococcus aureusAbstract
One of the very familiar and universal bacterial infections is
caused by Staphylococcus aureus. So much so that it is the cause of
nearly 0.25 million afflictions, more than a thousand
hospitalizations, while 6 afflicted persons die due to S.aurues
each year. Staphylococcus aureus is a Gram-positive,
oxidase-negative, non-motile microorganism and facultative
anaerobic.Nearly 32 species of this genus is found so far and
Staphylococcus aureus is ofne of them. Other species are mostly
found in various other mammals but are found not to afflict humans.
Like most other un-solved riddles, origin of Staphylococcus aureus
is yet to be understood. However modern theories hint that it is a
decendent of the prehistoric soil bacteria. It was Anton Rosenbach,
a German physician, who in 1884 vindicated it. Growing like grapes,
the Staphylococcus aureus also grows in clusters but is immobile.
Staphyleis is a Greek word for bunch of grapes, and cocci, means
spherical bacteria." Aureus is Latin for gold, and so given as it
always grew in yellow colonies. S.aureus cells are of abou 1
micrometer in diameter; so 1,000 cells lined up next to each other
would cover a distance of only 1 millimeters. This experiment was
carried out for a comparison of the growth rate of S. Aureus grow
on soft (Camembert) & hard (cheddar) cheeses as well as to
assess the effect of the cheese handling, storage temperature
growth rate time of Staphylococcus aureus.Introduction
Staphylococcus aureus has been recognized and described only 125
years ago, but it almost certainly infected and killing humans for
thousands of years. As a nitrogen source, Staphylococcus aureus
needs thiamine, nicotic acid, salts inorganic in natureand amino
acids
B Vitamins is an important element for the growth of
Staphylococcus aureus. (nicotic acid, thiamine), amino acids and
inorganic salts as a nitrogen source, although Christian, Valine,
Glutamic acid, agrinine, and tyrosine are not helpful to its growth
but important source of enterotoxin production. Boils, which are
common S. Aureus skin infections, are mentioned in the Bible.
Staphylococcus aureus is extremely durable. It grows in a wide
temperature range, it's Mesophilic; 7- 47.8C (opt. 35C); pH: 4.5-
9.3 (opt. 7.0-7.5). Low levels of water activity (aw) 0.83 (Opt.
>0.99). If conditions for growth (i.e. Temperature or nutrient
supply) are not favorable, Staphylococcus aureus for a long time
even at a dormant state (essentially, being inactive and lying in
wait for a good time to begin growing). Later, the bacteria can
start growing again when conditions are more favourable (Gandhi, M
& Chikindas, ML 2006). Staphylococcus aureus is resilient
because its the walls of its cells are thicker in contrast to the
other bacterias cell walls. This thickness allows It exist with the
a very high internal pressure ever found in any type of bacteria.
S. Arrears' is nothing if not opportunistic. The biggest problem
with S. Areas wound infections is the manifold increase in the
quantity of such infections that occur due to antibiotic-resistant
S. aureus. These infections might be easily treated if the bacteria
were sensitive to the first antibiotic used, but they can become
much more serious before an appropriate antibiotic is found.
Because of this, many patients today die from infections that were
once easily cured.( Sumner, J, Ross, T, Jenson, I & Pointon, A
2005). Sometimes dairy products, like cheese also cause food
poisoning, which is due to the presence of S. aureus (Medveov A and
Valk L 2012). Dairy products like cheese, where the presence of
staphylococcal enterotoxins act, as causative agent of outbreaks of
staphylococcal food poisoning in humans. About 90% of S. aureus
strains are currently resistant to penicillin (Cynthia M. Stewart,
Martin B. Cole 2002). Many virulence factors are the result of
Staphylococcus aureus, proteins that help the bacteria damage human
host cells. These virulence factors help the bacteria attach to the
host cells, specifically attack and damage them, and resist the
immune system from any response to this bacteris. The
characteristics of S. aureus are mentioned as under:
Gram-positive
Non- motile
Facultative anaerobic
Catalase-positive Cocci in pairs, short chains, or bunched in
grape-like clusters
Ubiquitous
Usually found in foods due to environmental, animal and human
contamination.
Heat stable enterotoxins
Kousta et al. (51) studied that in both pasteurized and
unpasteurized milk cheeses did not meet the EU regulations for
Staphylococcus aureus where in 13-20% of samples or 35-45% and even
in 70-80%, its existence was documented. Cheese production has its
own critical factors of safety like the natural contamination in
milk, type of cheese and its nature, kind of starter culture. The
aim of this project is to study the comparison of the growth rate
of S. aureus growth of soft (Camembert) & hard (cheddar)
cheeses as well as to find out the effect of cheese handling,
storage temperature and period of time on rate of growth of
Staphylococcus aureus.Methods and Materials
Response of growth of Staphylococcus aureus as affected by NaCl
concentration, pH value and storage temperature, all studied in a
laboratoty. For the detection, enumeration and isolation of
Staphylococcus aureus the direct plating method was used, as it
allows the placement of cheese slices directly on solidified agar
media. This process was used an effective measure of inherent
Mycological quality was thus understood the presence of mycotoxins
were also assessed:
Two types: Soft Cheese (Camembert) and hard cheese (Cheddar)
Two replicates for each type of cheese
Staphylococcus aureus (strain)
Low concentration of soft cheese (103 cfu/ml)
High concentration of hard cheese (107 cfu/ml)
Two types of media for direct plating method:
Nutrient Agar (NA) as non-selective medium and
Baird-Parker (BP) as selective medium Storage temperature: 20
CAw has become a prodigy in the food science literature, this term
was used in the prediction of the microbial growth and to denote
relationship among food deterioration reactions. RH is a For the
past several decades, in the food science literature, the
phenomenon denoted by the term aw has been widely used to predict
microbial growth as well as the relationship between many common
food deterioration reactions and aw. Although RH happens to be an
improved indicator the constancy and protection of food than the
water content of a system (Kamal S, Rehman K, Zia A and Parvin
B).
Result
The results of the present study showed that the contamination
in cheese also can occur due to safety lacks in the production
process. For example at some stage during cheese production air
control points contain high mould counts. Thus it is proved that
the crucial factor that harms and contaminates cheese is air, if it
is clean then there are lesser chances of mould contamination.
ELISA based method: an immunological technique used to diagnose
various infectious diseases of human, animals as well as plants
which are more than 99% sensitive and specific than any other
serological test (Kemeny & Challacombe, 1989). ELISA is used
for the detection of Staphylococcus aureus which is Gram +ve
bacteria; exist in pairs, short chains, bunched or grape like
clusters and of golden yellow in color.
References
Cynthia M. Stewart, Martin B. Cole 2002, Staphylococcus aureus
Growth Boundariesto Applied and Environmental Microbiology, vol.
68, no. 12, pp. 6405-6409.
Gandhi, M & Chikindas, M (2006) Listeria: A foodborne
pathogen that knows how to survive, International Journal of Food
Microbiology, vol. 113, pp. 1-15.
Kamal S, Rehman K, Zia A and Parvin B (2006) International
journal of agriculture and biology, Pakistan, viewed 18 June 2013,
http://www.fspublishers.org/ijab/pastissues/IJABVOL_8_NO_1/17.pdfKousta,
ed (2008) Structure and Function of Food Engineering.
Medveov A and Valk L 2012, Staphylococcus aureus:
Characterisation and Quantitative Growth Description viewed 18 June
2013.
http://www.intechopen.com/books/structure-and-function-of-food-engineering/staphylococcus-aureus-characterisation-and-quantitative-growth-description-in-milk-and-artisanal-rawRyser,
ET & Marth, EH (eds) 2007, Listeria, listeriosis and food
safety, 3rd edn, CRC Press, US.
Sumner, J, Ross, T, Jenson, I & Pointon, A 2005,
'Staphylococcus aureus Growth', Applied & Environmental
Microbiology viewed on 18th June 2013
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC123857/6
