My gram negative unknown identification Bacteria is enterobacter arogenes and my

Question

My gram negative unknown identification Bacteria is enterobacter arogenes and my Gram positive unknown identification is staphylococcus epidermis HOW TO WRITE AN UNKNOWN LAB REPORT IN MICROBIOLOGY GENERAL Unknown reports in microbiology are written in scientific format. Scientific writing is written differently from other types of writing. The results of the exercise or experiment are what are bein showcased, not the writing. The purpose of scientific writing is not to entertain, but to inform. Th writing should be simple and easy to understand. There is a specific style that must be followed when writing scientific reports. Scientific writing is typically written in the passive voice. The pronouns "I", "We" and "They" are not typically used.. For example, instead of writing "I used a TSA agar plate to isolate my unknown," it is customary to write, "A trypticase soy agar (TSA) plate was used to isolate the unknown." It is also customary to write in the past tense for most of the report. This includes the introduction, the summary, the description of the materials and methods and the results. The present tense is reserved for the conclusions about the results. See the examples given below. Some other general rules that should be followed are: Microbial nomenclature: The name of the bacterium should written and spelled correctly. The name should be italicized or underlined. Italicized is preferred. For example, Staphylococcus aureus The genus is capitalized but the species is not. After the full genus name is given in the paper, it can be written as S. aureus, but still italicized. This is as long as there in no other genera in the paper that starts with the same letter

Explanation / Answer

Aim: Identification of bacteria, from given unknown sample.

Introduction:

Bacteria are ubiquitous, but each species is associated with specific habitat, as per their biochemical and physiological preferences.

Identification of microorganisms from unknown samples is very important to characterize the bacteria as useful (beneficial bacteria, like those used in breweries, diaries etc.) or harmful, to associate the bacteria with a specific environment (like food, water, human flora), relation and condition that may allow the bacteria to cause disease, sensitivity or resistance of the bacteria towards antimicrobial agents (like antibiotic) and other criteria.

Several theoretical and practical techniques may be implemented to identify and characterize bacteria. This is based on the physical parameters like shape, size, motility, or biochemical properties, like types of metabolic pathways opted, biochemical properties of membranes etc.

Materials and method:

Two unknown labelled samples are given to be identified, designated as sample 1 and sample 2.

Each sample is separately inoculated on sterilized Trypticase Soy Agar plates using T-streak method.

Each plate is incubated at 37 ° Celsius for 24 to 48 hours.

The growth pattern and type of colonies formed are observe for sample 1 and sample 2.

Each sample is separately stained using Gram stain technique.

Sample 1 was Gram positive cocci in clusters.

Sample 2 was Gram negative rods.

Biochemical tests for sample 1:

The bacterial sample 1 was Gram positive cocci in clusters indicating genus Staphylococcus.

The sample was tested on:

1. Mannitol salt agar (MSA).

2. Blood agar.

3. Coagulase test.

4. Urease test.

Biochemical tests for sample 2:

The bacterial sample 2 was Gram negative rods, to identify the species, following tests were performed:

1. Catalase test.

2. Oxidase test.

3. IMViC

4. BCP test with sugars.

5. Urease

5. Motility.

Observation and Results:

For sample 1

Tests

Observation

Result

MSA

Negative, Medium remains natural orange-pink, does not turn yellow

Does not ferment mannitol to generate organic acids.

Blood agar

Non-haemolytic white colonies

Gamma-haemolytic

Coagulase

negative

Does not produce coagulase

Urease

Positive, neutral to neon-pink color

Produces urease, break down urea to give positive results

For sample 2

Tests

Observation

Result

Catalase

Positive

Produce catalase

Oxidase

Negative

Does not produce oxidase

IMVic

No ring for indole.

No change with methyl red indicator

Brown color with Barrett’s reagent.

Growth and blue color on citrate.

Indole- negative

Methyl red (MR) negative

Voges Proskauer (VP) positive

Citrate positive

BCP test

Purple to yellow color change with glucose, maltose, sucrose, no color change or late color change with lactose

Positive with glucose, maltose, sucrose,

Negative or late with lactose

Urease

No color change

Negative

motility

Shows motility

positive

Conclusion and discussion:

Sample 1:

Since sample 1 comprises of Garam positive cocci in clusters, it may be concluded to belong to Staphylococcus species. The tests which distinguishes different species of Staphylococcus sp. Indicate that the given organism is MSA and coagulase negative, shows non-hemolytic growth on blood agar, nut is urease positive. Thus, the organism may be identified as Staphylococcus epidermidis.

Staphylococcus epidermidis form a part of normal skin flora. They are associated with the upper skin layer or the epidermis and remains under normal state as non- infectious carriers.

If an individual is immunocompromised under circumstances like, extensive drug/ addictive use, wounds, burns, etc. the bacteria may penetrate into deeper skin layers or blood and cause infections.

Sample 2.

Since sample 2 comprises of Gram negative rods, it may belong to Enterobacteriaceae.

The biochemical; tests results indicate that the organism is motile, indole, MR negative, VP, citrate positive, late lactose fermenters, catalase positive, urea and oxidase negative. Thus, the species may be identified as Enterobacter aerogenes.

Enterobacter aerogenes are nosocomial present in soil water, wastes, fecal contaminants, also in gastrointestinal tracts of humans. They cause opportunistic infections in immunocompromised people, or poor living conditions. They are sensitive to most antibiotics.

Tests

Observation

Result

MSA

Negative, Medium remains natural orange-pink, does not turn yellow

Does not ferment mannitol to generate organic acids.

Blood agar

Non-haemolytic white colonies

Gamma-haemolytic

Coagulase

negative

Does not produce coagulase

Urease

Positive, neutral to neon-pink color

Produces urease, break down urea to give positive results

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