Biochemical Tests for Staphylococcus & Streptococcus | Legend Review Center

Summary

In this insightful review by Legend Review Center, we delve into biochemical tests crucial for identifying Staphylococcus and Streptococcus species. Starting with a Gram stain, learners progress through a series of tests—catalase, coagulase, and others—to differentiate key bacterial species. Understanding these tests aids in determining the species of Gram-positive cocci. Highlights include the role of catalase in distinguishing Staphylococcus from Streptococcus, methods for differentiating coagulase-negative staphylococci, and tests like novobiocin susceptibility to identify specific strains. Additionally, the session covers tests to differentiate beta and alpha hemolytic streptococci, including bacitracin sensitivity and the optochin test.

Highlights

• Gram stain is the starting point in identifying Gram-positive cocci 🦠.
• Catalase test: Watch for bubbles to tell if it's Staphylococcus! 🫧
• Coagulase test involves clotting to find Staphylococcus aureus 🤔.
• For coagulase-negative results, novobiocin susceptibility is next! 🚀
• Differentiate Streptococcus hemolytic groups with bacitracin and SXT tests 📊.
• Alpha-hemolytic streptococci need optochin testing for clarity! 🔎

Key Takeaways

• Begin with a Gram stain to identify if bacteria are Gram-positive cocci 🦠.
• The catalase test is essential to differentiate between Staphylococcus and Streptococcus ⛔️🟢.
• Coagulase test helps in distinguishing Staphylococcus aureus from other staphylococci 🎯.
• Use novobiocin susceptibility to differentiate Staphylococcus epidermidis from Staphylococcus saprophyticus 🔍.
• For beta-hemolytic streptococci, bacitracin sensitivity can differentiate Group A from Group B 💊.
• Optochin test distinguishes Streptococcus pneumoniae from other alpha-hemolytic streptococci 🔬.

Overview

The discussion kicks off with the fundamental Gram stain, a cornerstone method in microbiology, that sets the stage for identifying Gram-positive cocci. This is followed by the catalase test, a pivotal procedure that separates Staphylococcus (catalase-positive) from Streptococcus (catalase-negative). Watching for the appearance of bubbles can indicate the presence of catalase enzyme, a key differentiator!

Next up is the coagulase test, which further narrows down Staphylococcus strains. By checking for clot formation, students can pinpoint Staphylococcus aureus. For coagulase-negative strains, the novobiocin susceptibility test becomes essential to distinguish between Staphylococcus epidermidis and Staphylococcus saprophyticus, providing clarity on common clinical specimens.

As the session advances, the focus shifts to differentiating between beta and alpha hemolytic streptococci. Bacitracin sensitivity is highlighted as a go-to test for distinguishing Group A Streptococcus, while the optochin test is emphasized for identifying Streptococcus pneumoniae among alpha hemolytic strains. This comprehensive overview aids students in mastering the nuances of microbial identification.

Chapters

• 00:00 - 00:30: Introduction to Biochemical Tests The chapter begins with an introduction to using an algorithm to guide in identifying organisms. It emphasizes the importance of starting with a gram stain as the first step.
• 00:30 - 05:30: Catalase Test In this chapter titled "Catalase Test," the focus is on using biochemical tests after performing a Gram stain to determine the type of bacteria present. Specifically, the catalase test is highlighted, which is used to differentiate between the Gram-positive cocci Staphylococcus and Streptococcus, as these are the most common.
• 05:30 - 08:00: Coagulase Test The chapter discusses the Coagulase Test, which is crucial for differentiating Gram-positive cocci. The conversation also touches on the catalase test, used to distinguish between Staphylococcus and Streptococcus bacteria. The catalase test principle involves catalase catalyzing the breakdown of hydrogen peroxide, a key element in identifying bacterial species.
• 08:00 - 10:30: Differentiating Coagulase Negative Staphylococci The chapter discusses the differentiation of coagulase-negative staphylococci, focusing on the biochemical tests used for identification. A positive result in these tests is indicated by the rapid appearance of continuous bubbles, due to the production of oxygen. In contrast, a negative result is characterized by the formation of a lot of bubbles 30 seconds later. The transcript also provides a cautionary note on using inoculum from blood agar, as red blood cells (RBCs) contain peroxidase activity that can produce weak bubbles, potentially leading to false positives.
• 10:30 - 15:00: Staphylococcus Tests - DNase and Mannitol Salt Agar The chapter titled 'Staphylococcus Tests - DNase and Mannitol Salt Agar' covers two primary biochemical tests used in microbiology to identify Staphylococcus bacteria. The transcript snippet provided discusses observing positive results in these tests. It highlights the catalyst reactions, specifically mentioning the presence of effervescence or bubbles, which indicates a positive outcome. Further details would likely cover the methodology, expected results, and significance of these tests in identifying Staphylococcus species.
• 15:00 - 25:30: Streptococcus Tests - Beta Hemolytic The chapter focuses on tests related to Beta Hemolytic Streptococcus, specifically discussing the catalase test used for identification. The catalase test helps differentiate organisms, where Staphylococcus aureus serves as a negative control. Once a catalase-positive organism is identified, the coagulase test follows. The text references species such as Leptospira and different subtypes of Staphylococcus. The principal method revolves around using these tests to narrow down the specific bacteria present, although the transcript seems incomplete and references future tests.
• 25:30 - 30:30: Streptococcus Tests - Alpha Hemolytic This chapter delves into Streptococcus Tests, focusing on Alpha Hemolytic strains. It discusses the Congolese test, which is used to convert soluble elements into soluble fiber, preventing the appearance of floods in the plasma. The outcome of this test can either result in a smooth suspension (negative result) or a positive control case with Staphylococcus epidermidis. Two types of Congolese tests are mentioned: the slide test and the inner tube test. The slide test is emphasized as a screening test, which helps in the initial detection.
• 30:30 - 35:00: Streptococcus Tests - Gamma Hemolytic This chapter provides an overview of Streptococcus Tests, focusing specifically on gamma hemolytic types. It explains the differences between bound coagulase or clumping factor tests versus tube tests that detect coagulase. The chapter outlines what constitutes a positive result, which is clotting in this case. It also includes a reference to an algorithm used when dealing with catalase-positive gram-positive cocci and gives pointers on interpreting positive or negative coagulase test results.

Biochemical Tests for Staphylococcus & Streptococcus | Legend Review Center Transcription

• 00:00 - 00:30 [Music] let's begin with this for stuffing up okay so this is an algorithm for us to to guide us in identifying our organism screen so we always begin with your gram stream there so you begin with your gum
• 00:30 - 01:00 steam then beast from the Gram stain we will select what biochemical tests we will do so for if you have a gram positive cocci okay usually we start with the catalase test the catalyst will differentiate between Staphylococcus streptococcus which are the most common term positive cocci favored positive
• 01:00 - 01:30 catalase test if this is the field horse this is gram negative strapped to Ho Hos so let's begin with your cut the least positive gram positive cocci okay so the catalase test again differentiates the Philippakis from streptococcus the principle is the catalyst converts the religion represent hydrogen peroxide
• 01:30 - 02:00 into water and oxygen this is the reason why here positive result would be the appearance of rapid continuous bubbles this is due to the production of oxygen the negative result would be a lot of bubble formation 30 seconds later I have to be cautious when using the when collecting or when getting inoculum from blood agar since your RBC's also contain peroxidase activity which can produce weak bubbles thus causing a false
• 02:00 - 02:30 positive result pain so this is the positive result of your catalyst okay so you have here on the upper right corner today and repeat continues bubbles are effervescence okay so the positive control here for the
• 02:30 - 03:00 catalyst as yes Staphylococcus aureus negative controls Leptospira genus in the next test would be the coagulase test so once we are once you have isolated once you have identified your catalase positive organism the next that we would do is the coop beliefs test two different shades the fill hose or use from Kelly's negative stuff that would include stuff activities and stuff subroutine takus hey principal is the
• 03:00 - 03:30 congolese convert soluble 15 engine into soluble fiber in so this fibrin won't be seen as floods in the plasma a negative result would be smooth suspension a positive control stuff our use negative under staph epidermidis there are two types of Congolese test you have your slide test a inner tube test the slide test is a screening test it will detect
• 03:30 - 04:00 your bound coagulase or the clumping factor whereas your tube test will detect freako uglies either way the positive result would be clotting if so this is your algorithm again if you have a catalyst positive gram-positive cocci okay that stuff alahu sweetie your coagulase test if it is positive that stuff or use negative
• 04:00 - 04:30 you have your congolese negative stuff in Ho Hos so the next step if ever we get the hoggle is negative organism oh by the way this is just the slide the gluten even test first stuff or use this is for identification of stuff are you okay now if you have a coagulase negative stuff the next step would be the differentiate between staph epidermidis and stuff so prophetically but you can see here in our algorithm
• 04:30 - 05:00 okay so what we do is we do that novo bias in susceptibility test in your ANOVA bias in susceptibility test staph epidermidis would be susceptible where stuffs of profit equals would be resistant okay so for a susceptible result the zone the zone of inhibition should be greater than 60 millimeters resistant would be equal to degree less than 60 millimeters so again for the
• 05:00 - 05:30 novel by susceptibility test stuff epidermidis is susceptible so profit occurs is resistant an other test first stuff would include viennese test okay so what we are trying to detect here would be DNA's production there are only three organisms that you need to remember that produced DNA's this would be staph aureus stuff or use Marcella
• 05:30 - 06:00 huh Terry Harris and Sarah Shaw marisa-san's are in the 1x here would be s m/s okay now what is the principle the mid room that we use here contains DNA and methyl green the methyl green DNA complex is green in color in the presence of the enzyme DNA's
• 06:00 - 06:30 methyl green and DNA are broken down the complex is broken down and this will remove the green color so the positive result would actually be clear in okay so the positive result will be hydrolysis of the surrounding medium resulting in a clear zone because of the breakdown of the methyl green DNA complex the negative result would be no clear in positive control would be stuff or use negative would be stuff
• 06:30 - 07:00 epidermidis so when this remember there are only three organisms SMEs so if the question describes a gram positive cocci that this DNA is positive that's stuff aureus if the question is describing a gram-negative kohai that this DNA is positive that's what I said at the Harris if the question is describing a gram-negative bacilli that this DNA is positive that sarasu
• 07:00 - 07:30 marcescens ASMs another really the test for your Staphylococcus would be the mannitol salt agar this is a selective and differential culture medium first of in host species it is selective because it contains 7.5% salt hey so Philip our species are able to
• 07:30 - 08:00 grow in 7.5% so it is differential because it will test for manual fermentation if the organism ferments mannitol the products of fermentation will turn the phenol red indicator into a yellow holder okay so as you can see here in the top right diagram 3 so staph aureus will ferment mannitol converting the phenol red into a yellow holder okay so these are the results
• 08:00 - 08:30 growth without fermentation you will still have colonies but the surrounding color would be pink I read growth with fermentation like in the case of stuff or use colonies with surrounding yellow halos so this is another way to differentiate stuff are used from the other stuff you just like your novo I just like your coagulase test okay so going back this is our
• 08:30 - 09:00 algorithm so let's just look at the big picture so again catalase positive stuff Aloha hose congolese positive stuff our use if it's Pugliese negative do your anova biasing sensitivity to differentiate sub profit it goes from epidermidis okay now what if what if during the catalyst test you're able to
• 09:00 - 09:30 I sleep a gram positive cocci which is catalyst negative so if you scatter is negative we're thinking of strep toe co-hosts then the next step would be to check for the hemolytic pattern of the colonies on blood agar hey the base of the hemolytic pattern they we will now choose the biochemical tests that we will do next if the organism is beta hemolytic we would consider Group A and
• 09:30 - 10:00 Group B Strep Group A would be a strep pyogenes Group B would be step a galaxy so let's take a look at the test that we would do if we isolate the beta hemolytic catalyst negative gram positive cocci so again for your family t-strap we have Group A and Group me hey the first test that we could do to
• 10:00 - 10:30 differentiate Group A and Group B would be a massive Racine SXT susceptibility test okay group a strep or step by origin s would be susceptible to bacitracin but resistant to SXT whereas group b hey would be resistant to both vasopressin n SXT so this summarizes the results that we are trying to look for hey so again group a is susceptible to bus addressing our
• 10:30 - 11:00 mnemonics here would be bus a bus it Racine group a susceptible group B on the other hand is resistant to both okay so think of the be in Group B as both resistant to both if you have an organism which is resistant to bacitracin but this but susceptible to SXT that is neither group in or
• 11:00 - 11:30 droopy-eyed SXT is sulfamethoxazole try Metro trimethoprim another test that he could do the differentiate blue key from Group B is the B Y or a test in your P Y or a test group a strep are positive okay the principle is py r hydrolyzed by the enzyme by race forming bad enough deal
• 11:30 - 12:00 amide which produces a red color with your color developer which is paradigm 18 cinnamaldehyde so the positive result as you could see here in the picture in the bottom right is a red color in could share the red color okay so again in the py or a test group a is positive another Tessier can't test cap stands
• 12:00 - 12:30 for s stands for chris christie adkins munch peterson these are the names of the scientists who develop this test the cap test is used to identify Group B Strep Locos Tacos a galaxy a Group B Strep produces comfort or Group B Strep the juices can factor this camp factor
• 12:30 - 13:00 enhances the DVD of better Hamada seen which is produced by Staphylococcus aureus so how do we do the contest in the contest you use your blood agar then in the blood agar you will inoculate Staphylococcus aureus in a straight line as expected since your stuff aureus produces better medicine you will see clearing around this colonies of staph aureus okay group the
• 13:00 - 13:30 unknown the the organism that we're trying to identify would be strict perpendicularly to stuff our use okay then you will incubate this at the same time what you would look for what you would look for would be enhancement of the hemolysis of Staphylococcus for use this enhancement would produce a characteristic Arrowhead appearance okay
• 13:30 - 14:00 so this is the enhancement hey the negative result would be no enhancement there would still be hemolysis but there would be no enhancement please take note another organism known to cause a positive campus is Listeria monocytogenes okay so the recognition
• 14:00 - 14:30 positive for the contest is B Strep not Group a another test for group B a secret hydrolysis okay organisms that produce the enzyme habilities hydrolyze a sodium HIPAA rate to benzoate and glycine glycine reacts with min hye-rin
• 14:30 - 15:00 placing reacts with the ninhydrin reagent and this will form a purple color which is the positive result of your debrief hydrolysis test it organism that would be positive here will be Group B okay you can also do slightly gluttonous on tests and this is actually responsible or this is how we do your
• 15:00 - 15:30 Lance with grouping as you can see your group a your Lancefield group is your strep pyogenes then spheal group B strep agalactiae and under Group D you have your step obvious than other Andros and so on so going back again if you have a catalyst negative gram positive cocci you look at streptococcus then you examine the
• 15:30 - 16:00 hemolysis if you have a better Emily the coordination we are considering group B and Group A then how do you differentiate them you can do your bacitracin susceptibility you can also do your UI r side from your P Y or you can also do your come test and your people aid or you can also do your hypnotist okay now how about if we
• 16:00 - 16:30 isolate an alpha of elliptic organism for your alpha ability streptococcus we are considering very dense trap and streptococcus pneumoniae okay now how do you differentiate we didn't strip from Sirte focusing on yay we do the optics of touching sensitivity or your bile solubility tests so this is
• 16:30 - 17:00 the optic in test this is actually an antibiotic susceptibility test the antibiotic that we use is of the team which is also known as the pee disc alright the chemical names Green hydrochloride this is differentiate strep pneumonia which is susceptible from other family disturb which are resistant okay so this is the first test of the gene test not very
• 17:00 - 17:30 test is your bile solubility best this is also positive for strep pneumonia hey the strep pneumoniae colonies are known to produce autolysis strep pneumoniae colonies produce autolysis what does this mean and this is your strep pneumoniae colonies the first of many colonies this colonies over time tend to
• 17:30 - 18:00 digest themselves or the lysis or the digestion now if you add by insults to this colonies this will enhance the autolysis of this strep pneumoniae colonies so the positive result would absolutely be clearing of the broad disappearance of colonies positive control strep pneumoniae so there are just two tests so remember for your alpha hemolytic step up to gene test and
• 18:00 - 18:30 by solubility both are positive first step pneumonia both are negative first strip the events okay now let's go there gamma hemolytic strength forgot my Emily big strap you can do your BYU re test hey this different shades and Terra hocus species from not in their home species and as we have mentioned a while
• 18:30 - 19:00 ago group a step I also py are positive then we have also discussed the principle awhile ago positive result being to Cherry then now Delta C surveilence clean a girl the should differentiate group this trap and Enterococcus from other islands field groups okay the principal is here Group D grows in 480 percentile so this is selective through the forty percent male
• 19:00 - 19:30 then Group B Strep will hydrolyze eskalene to form escalating escalating reacts with ferric citrate and this forms a black brown black precipitating which is your positive result okay then another test is your six point five percent salt broth which also differentiates Group B Strep from nan antara how high you'll be entered or higher salt tolerant and to summarize the test for your gamma hemolytic step
• 19:30 - 20:00 you have this table you can see your Group D is comprised of Enterococcus and an interval of species okay all Group D whether they are intercourse or non tariff of host would be positive in nearby less given okay the other lands filled groups are negative now if you want to differentiate group the entire
• 20:00 - 20:30 focus from group did none and terror focused into our six point five percent soft broth a well in group the entire house is positive whereas Group B nine and Tara host would be negative the same result should be seen in their piracy piracy IRA test be positive for a group the entire focus but negative for Group B Nunn and arrow Cohoes so these are the three tests that you need to remember for your gamma Emily big step
• 20:30 - 21:00 [Music]