A 17-year-old female presented with worsening perineal and buttock lesions that were draining purulent discharge. Samples from the lesions were taken and incubated aerobically and anaerobically. Two organisms grew: coagulase-negative Staphylococcus on both plates and Bacteroides fragilis on the anaerobic plate. Tests identified B. fragilis as the causative pathogen through its antibiotic resistance profile and production of virulence factors like enzymes. B. fragilis is known to cause infections in areas like the perineum and buttocks when tissue barriers are breached.

1. Coagulase Negative Staphylococcus Essay.
Coagulase Negative Staphylococcus Essay. A 17 year old female with a one month history of
worsening perineal and buttock lesions. Two weeks prior to admission, she presented to
her family doctor for evaluation. At that time, the lesions were excoriated, inflamed and
indurated. The lesions were multiple and scattered over the perineum and buttocks. The
largest one measured approximately two centimetres in maximum dimension. The lesions
became more painful and began to drain a purulent discharge. The patient was admitted for
incision and drainage of the lesions. Fluid from the lesions was sent for investigation to the
Microbiology Lab.Coagulase Negative Staphylococcus Essay.ORDER A PLAGIARISM-FREE
PAPER HERETwo blood agar plates were inoculated and incubated – one aerobically and
one anaerobically at 37˚C.ResultsThe following are the results obtained for the organism
growing on the blood plate that was incubated aerobically and for the two organisms- A and
B, that were growing on the blood agar plate that was incubated anaerobically. Both plates
were incubated at 37˚C.The organism growing on the aerobic blood agar plate and also on
the anaerobic plate as Organism A was identified as a coagulase negative Staphylococcus.
Organism B that was growing on the anaerobic blood plate and that was the causative
pathogen was identified as Bacteroides fragilis.Table 1: Basic characterisation and further
identification test results carried out on the two blood agar plates, incubated both
aerobically and anaerobically at 37˚C for the patient in Case Study 1.Platename Blood
agar incubated aerobically Blood agar incubated anaerobically Controls:Positive
NegativeTest Organism A Organism B Colonial morphology
White, 0.5mm, convex, entire, circular, gamma haemolysis, no odour. White, 0.5mm,
circular, entire, gamma haemolysis, no odour. Grey, 1mm, mucoid, circular, entire, gamma
haemolysis, ++ odour. / /Gram stain Gram positive cocci in clustersGram positive
cocci in clusters Gram negative bacilli, pleomorphic / /Catalase +
/ + + –Oxidase – / – + –Preliminary
Identification Staphylococcus Staphylococcus Bacteroides /
/Further Identification Tests:Coagulase Test _ / / / /MTZ
/ / + / /An – ident / / + for Bacteroides
Fragilis/ /For the blood agar that was incubated anaerobically, there were two
different colonies growing on the agar. Organism A appears to be the same colony that was
growing on the aerobic blood agar plate and is also growing on the anaerobic plate.The
catalase and oxidase test was not carried out for Organism A as there were no colonies left
on the agar plate to carry out the testing.Legend:Catalase: + = positive for the enzyme

2. catalase- bubbles produced.- = negative for the enzyme catalase -no bubbles
producedOxidase: + = positive for the enzyme oxidase – purple colour formed- =
negative for the enzyme oxidase – no colour formedSmell: ++ = strong, slightly pungent
odourCoagulase test: + = positive for the coagulase enzyme. Agglutination observed.– =
negative for the coagulase enzyme. No agglutination observed.MTZ test: Positive = A zone of
clearance (inhibition) of growth around the MTZ discNegative = no zone of clearance
around the disc – the bacteria grows up to and around the MTZ disc.Table 2: Antibiogram
profile obtained for Organism B that grew on the anaerobic blood agar, for the An-ident
test.Coagulase Negative Staphylococcus Essay.Antibiotic E60 RD15 CT10 P2
K1000 VA5Result S S R R R RLegend: E60 =
Erythromycin 60µgRD15 = Rifampcin 15µgCT10 = Colistin 10µgP2 = Penicillin 2
unitsK1000 = Kanamycin 1000µgVA5 = Vancomycin 5µgS = SensitiveR = ResistantAn-ident
test: + = the bacteria is sensitive (zone of inhibition – no growth around these antibiotic
discs) to Erythromycin and Rifampicin and is resistant (no zone of inhibition – growth up to
and around the antibiotic discs) to Colistin, Penicillin, Kanamycin and Vancomycin. This
bacteria was identified as Bacteroides fragilis. DiscussionIt is more than likely apparent that
Organism A is a coagulase negative Staphylococcus. This organism was facultative as it grew
on both the aerobic and anaerobic blood agar plates. This organism appeared as white,
convex, circular, non-odorous, gamma haemolytic colonies on both agars. In the Gram stain
this organism appeared as Gram positive cocci in a clustered formation. Organism A
obtained a positive catalase test and a negative oxidase test. The coagulase test was then
carried out to further identify this organism. It tested negative for the coagulase enzyme,
hence leading to the identification of this organism as a coagulase
negative Staphylococcus.Coagulase Negative Staphylococcus Essay.From observing table 1,
it is evident that Organism B is Bacteroides fragilis. This organism only grew on the
anaerobic blood agar plate. It had a pungent smell, displayed gamma haemolysis, was
circular, convex, grey in colour and 1mm in size on the anaerobic blood agar plate. In the
Gram stain, this organism appeared as Gram negative bacilli that were pleomorphic in
shape. In Case Study 1, the female patient possesses lesions that are draining a purulent
discharge. A foul smell is associated with Bacteroides fragilis. This smell is due to the
production of gases by the bacteria. Organism B obtained a positive catalase test and a
negative oxidase test. An MTZ test was carried out on this organism and again, this
organism obtained a positive result, emphasising that this organism is indeed anaerobic, as
all anaerobic bacteria are sensitive to Metronidazole. In the An-ident disc antibiogram, the
organism was shown to be Bacteroides fragilis. This anaerobic organism is infecting the
patient. The site where the lesions are located – the perineum and buttocks are locations
that this bacteria are prone to infect. The lesions are inflamed, excoriated and indurated as
well as producing a purulent discharge are all indicative of tissue necrosis at the site of
infection. Bacteroides fragilis is prevalently found on mucosal surfaces in indigenous flora.
It initiates infection when tissue trauma or surgery occurs or when tumours are present on
the mucosal surface. This organism can also become displaced from its normal site and
hence, infect a site that is free from organisms. Bacteroides fragilis then penetrates host
tissues and establishes infection. A reduced blood supply and necrosis of tissue facilitate the

3. growth of this anaerobe due to them reducing the potential of oxidation-
reduction.Bacteroides fragilis possesses a wide array of virulence factors that aid in its
pathogenesis. These include the production of various enzymes including neuraminidase
that targets glycoproteins in the plasma of humans that contain neuraminic acid by altering
this acid. Another enzyme produced by this bacteria includes heparinase. This facilitates
clotting intravascularly. Hyaluronidase breaks down the hyaluronic acid between cells,
facilitating the spread of this pathogen. Bacteroides fragilis also produces beta-lactamase
that causes the destruction of the beta-lactam ring in beta-lactam antibiotics, initiating the
resistance to the organism. DNase enzyme degrades host DNA or RNA, by catalysing the
break-down of the phosphodiester bonds in the DNA backbone. This again is produced by
this organism. Phosphatase is another enzyme produced by this organism. It is involved in
signalling and the regulation of cells. The capsule is also a highly important virulent factor
in Bacteroides fragilis. Succinate and butyrate, which are responsible for respiration in cells
are produced by this organism and they possess a cytotoxic effect. This bacteria also
possesses fimbriae, enabling it to adhere to the host’s epithelial cells. As this organism is
Gram negative, it contains a Lipopolysaccharide layer (LPS) that activates coagulation via
the intrinsic pathway (Wexler, H., 2007).Bacteroides fragilis is one of the most resistant
anaerobic bacteria to antimicrobials. This is due to the production of beta-lactamase,
initiating resistance to the beta-lactam antibiotic family. This organism is resistant to many
antibiotics including amikacin and gentamicin, members of the aminoglycoside family of
antibiotics. Resistance is also shown to penicillin, vancomycin, colistin and kanamycin.
Metronidazole (MTZ) inhibits the nucleic acid synthesis by Bacteroides
fragilis, chloramphenicol, imipenem and antibiotics containing a mixture of both beta-
lactams and an inhibitor of beta-lactamase are most effective against this bacterial strain.
Rifampcin and erythromycin are also effective in treating infections by this organism
(Brook et al., 2013).This organism is responsible for a variety of infections throughout the
human body. Intra-abdominal, soft tissue, bacteraemia, dental, oral, bone and female genital
tract infections are among the most common infections caused by Bacteroides
fragilis. Abscesses, lesions and infections below the waist are also associated with this
bacteria. This organism can also play a virulent role in the pathogenesis of colon cancer and
periodontal disease due to the organism’s production of enzymes such as neuraminidase
and heparinase. These enzymes allow it to penetrate host tissues and cause infection
following surgery or trauma to the tissue (Wexler, H., 2007).In all, the two blood agar plates,
one that was incubated aerobically and the other that was incubated aerobically were
examined. Gram stains, colonial morphology, basic characterisation tests and further
identification tests were all carried out to decipher the organisms that were present. These
organisms were identified as Coagulase negative Staphylococcus – Organism A that was
growing on both plates and Organism B – Bacteroides fragilis that was growing on just the
anaerobic plate. Bacteroides fragilis is the principal organism that is causing the infection in
the female patient. The clinical details of the patient were discussed in conjunction to the
infecting pathogen. The virulence factors and pathogenesis of this organism were described,
along with the antimicrobials used to treat and the infections caused by Bacteroides
fragilis.Coagulase Negative Staphylococcus Essay. Practical Risk Assessment FormPractical

4. title: Anaerobic Case Study 1Practical description: Give a brief description of work to be
undertaken and the nature of the materials and techniques to be used.Working with two
organisms – Bacteroides fragilis and coagulase negative Staphylococcus.Colonial
morphology, Gram stains, catalase, oxidase, MTZ test, An-ident and Coagulase test will be
carried out on the organisms.Blood agar plates will be streaked/lawned with the organisms
and incubated anaerobically at 37˚C. Hazard High
Medium Low Current control measures for this hazard Options for
improved controlsBiological:Bacteroides fragilisOxidase positive and negative
controlsCatalase positive and negative controls XXX Good aseptic
techniques to control the exposure of this infectious agent.The use of gloves and laboratory
coat to avoid contamination of skin and clothes with these controls and bacteria.Cleaning
surface with disinfectant after working with these controls and the bacteria.Disposing of
gloves, slides and agar plates when they are finished with. Not touching face or mouth
with gloved hands to prevent contamination with the bacteria and controls.Chemical:Gram
stains – Crystal Violet, Gram’s iodine, acetone and Carbol FuschinHydrogen peroxide
XX Wearing gloves and laboratory coat to protect hands, clothes and skin from
being stained with these chemical agents.Wearing closed footwear and not sandals or open-
toed shoes.Not inhaling or ingesting the chemicals. Buttoning up laboratory coat
properly.Electrical:MicroscopeHot plate XX Correct handling of the
microscope.Not tangling the lead or have it hanging down on the floor.Turning it off when it
is not in use. Not leaving it at the edge of the benchtop.Physical:Glass slides
X Proper handling of slides.Disposing of them in the sharps bin when
they are finished with. Not dropping them or disposing of them in the biohazard
bins.Coagulase Negative Staphylococcus Essay.