gram stains

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Sink used for Acid Fast Bacilli Kinyoun stain. This is at the lab I’m currently doing my rotations at and I thought it was pretty.
Mycobacterium tuberculosis, the causative agent for Tuberculosis or TB, has a cell wall that’s high in lipid content. So, it doesn’t stain with regular gram stain; thus, they used acid fast staining techniques with carbolfuchsin.

2

Streptococcus pyogenes

Streptococcus pyogenes (also known as the flesh eating bacteria) is a gram-positive bacterium that usually grows in pairs or chains. It has been classified as a beta-hemolytic streptococcus because when cultured on a blood agar plate all the red blood cells are ruptured by the bacteria. Furthermore, it has been classified using Lancefield serotyping as group A, because it displays antigen A on its cell wall. Therefore, this bacterium is commonly called the beta-hemolytic group A streptococcus, or GAS.

This bacterium is responsible for a wide array of infections. It can cause streptococcal sore throat which is characterized by fever, enlarged tonsils, tonsillar exudate, sensitive cervical lymph nodes and malaise. If untreated, strep throat can last 7-10 days. Scarlet fever (pink-red rash and fever) as well as impetigo (infection of the superficial layers of skin) and pneumonia are also caused by this bacterium. Septicaemia, otitis media, mastitis, sepsis, cellulitis, erysipelas, myositis, osteomyelitis, septic arthritis, meningitis, endocarditis, pericarditis, and neonatal infections are all less common infections due to S. pyogenes

There are at least 517,000 deaths globally each year due to severe S. pyogenes infections and rheumatic fever disease alone causes 233,000 deaths. 

Key characteristics: Gram(+), beta-hemolytic, bacitracin(+), PYR(+), facultatively anaerobic.

Urinary Tract Infections

Definition of UTI

  • Pathologic bacteria in urine
    • Asymptomatic patients: growth of > 10^5 (100,000) CFU/mL
    • Symptomatic patients: 10^2 (100) CFU/mL

Classification of UTI

  • Lower tract infections: urethritis, cystitis
  • Upper tract infections: pyelonephritis, prostatitis
  • Community-acquired
  • Nosocomial: catheter-related

Etiology

  • E. coli - most common
  • Gram negative rods
  • Adenovirus - children

Pathophysiology

  • Colonization of external genetalia
  • Bacteria can ascend into the urinary tract 
  • Upper tract infection most common complication of lower tract infection
  • Hematogenous spread - S. aureus

Who gets UTIs?

  • Females > males
  • Increased incidence with sexual activity
  • Childhood: M > F

Female Patients

  • Vaginal introitus and distal urethra normally colonized by gram positive organisms
  • Female urethra more prone to gram negative infection 
    • Close to anus
    • Short length 
  • Risk factors
    • Hygiene issues
    • Sexual activity
      • Void after intercourse decreases this risk

Male Patients

  • Rare
  • > 50 years of age, BPH is main cause

Other Risk Factors

  • Pregnancy
  • Unsterile or prolonged catheterization
  • Obstruction
  • Vesicourethral reflux

Cystitis

  • Most common manifestation of UTI
  • Infection/inflammation of bladder
  • Most commonly E. coli, can be adenovirus
  • Clinical presentation
    • Irritative voiding 
    • Supraspubic discomfort
    • Other urinary complaints?
  • PE
    • Unremarkable
    • No CVA tenderness
  • Lab
    • Urinalysis
      • (+) LES
      • (+) Nitrites
    • Urine gram-staining
      • E. coli
      • Contamination possible
  • Acute urethral syndrome
    • “Painful voiding syndrome”
    • Dysuria with sterile culture
    • Irritants, trauma, etc.
  • Management
    • Antimicrobials
      • Short-term (< 7 days) for uncomplicated cases
      • Longer therapy (7-10 days) for DM, recurrent UTI, over 65, Men
    • Symptomatic treatment
  • Follow-up
    • Repeat urine C&S 3-5 days after antibiotics finished

Pyelonephritis

  • Infection/inflammation of renal parenchyma and pelvis
  • Most commonly E. coli or Proteus sp. 
  • Presentation
    • Flank pain
    • Fever
    • Chills
    • Toxic appearance
    • CVA tenderness
  • Lab
    • Urinalysis
      • (+) LES
      • (+) Nitrites
      • WBC casts
    • Urine gram stain
      • E. coli
      • Contamination possible
    • CBC
      • Leukocytosis with left shift
  • Imaging
    • Only done in complicated cases
  • Complications
    • Sepsis/shock
    • Scarring/fibrosis
      • Chronic pyelonephritis
  • Management
    • Usually treated as outpatient
    • Empiric therapy
      • Broad-spectrum antibiotics
        • IV 
        • PO quinolone
        • No nitrofurantoin
        • Watch resistance for Augmentin and Bactrim 
      • 14+ days
        • Inpatient: 24 hours after fever resolves
        • Outpatient: 14 days
  • Follow-up
    • Repeat urine C&S 1-2 weeks after treatment completed
    • Treatment failure
      • Imaging or referral

UTIs in Pregnancy

  • Asymptomatic bacteriuria very common - treat due to risk of complications to fetus
  • Cystitis
    • No fluoroquinolones
    • Recheck urine C&S
  • Pyelonephritis
    • Hospitalization
    • Empiric IV therapy, then PO
    • No fluoroquinolones
    • Recheck urine C&S

Nosocomial UTIs

  • Foley catheters 
  • Care for UTIs not reimbursed by Medicare/Medicaid 

Recurrent Infections: more than 2-3 per year

Vesicoureteral reflux (VUR)

  • Reflux of urine from bladder into ureters/renal pelvis
  • Common cause of UTI in children
  • Renal scarring due to volume and duration of reflux
  • Presentation
    • Weight loss
    • Nocturnal enuresis
    • Failure to thrive
  • Labs
    • Urinalysis
      • (+) LES
      • (+) Nitrites
    • Urine gram stain
      • E. coli
    • Cast formation
  • Imaging
    • Voiding cystourethrogram (VCUG)
    • Management of VUR
      • Mild
        • Spontaneous resolution usually
        • Antibiotics until puberty
      • Severe
        • Surgical intervention
        • Antibiotics into condition corrected
2

Yersinia pestis

Yersinia pestis is the causative agent of the systemic invasive infectious disease often referred to as the plague. The Y. pestis is an extremely virulent pathogen that is likely to cause severe illness and death upon infection unless antibiotics are administered. In the past, Y. pestis has caused devastating epidemics during three periods of modern history; the Justinian Plague spread from the Middle East to the Mediterranean during the 6th-8th centuries AD and killed approximately 25% of the population below the Alps region. Perhaps the most famous incidence of any disease was the devastating Black Plague of 8th-14th century Europe that eradicated 25 million people (nearly 25% of the population) and marked the end of the Dark Ages. The third endemic began in 1855 in China and was responsible for millions of deaths.

Plague is a very serious illness, but is treatable with commonly available antibiotics. The earlier a patient seeks medical care and receives treatment that is appropriate for plague, the better their chances are of a full recovery.

Yersinia pestis is a Gram-negative bacillus member of the Enterobacteriaceae family, and is an obligate intracellular pathogen that must be contained within the blood to survive. It is also a fermentative, motile organism that produces a thick anti-phagocytic slime layer in its path. 

Key characteristics: Gram(-), catalase(+), oxidase(-), indole(-), urease(-)

anonymous asked:

I have a cockatiel and he's been sitting on the ground poofed up and not really eating or drinking but he's not displaying any other symptoms. I'm going to take him to the vet as soon as I can but can you give me an idea of how the examination will go and what tests they might run/how much they usually cost?

It does sound like your baby is sick so I’m glad you are taking him in to be seen. I would for sure get a poop gram stain to check for bacteria or infections. They might also do an x-ray. The price usually depends on the actual vet. I’ve had vet bills range from 30$ - 400$. If it does come out a little pricey you should ask if they can put you on a payment plan so you can pay over time. 

Bacterial Taxonomy 1 - Classification Based on Morphology and the Gram Stain. 

Taxonomy, is literally the science of classification. Look at the picture above, and imagine that all those little divisions, like “firmicutes” are different phyla under the kingdom of bacteria. Then those phyla are further subdivided into different classes, then orders, then families, then genera, and then finally species! Take a look at how this works for one particular bacteria, called streptococcus mutans. 

Wow, there’s a lot to classify, probably why it’s taxonomy: it’s such a taxing job.

Ahem, right, so. As you’ve probably noticed, Streptococcus mutans is named using its Genera and its Species name. Similarly, all organisms have a scientific name comprising of two parts: The genus, followed by the species. It is very important to classify organisms in this way because: 

  1. It establishes criteria for identifying organisms. 
  2. Allows arrangement of related organisms into groups. 
  3. Provides important information on how organisms evolved.  

Bacteria are classified, usually, according to their morphological, metabolic and biochemical differences, although genetic and immunologic factors are also now being considered. 

One of the earliest, and most fundamental methods of classifying bacteria depended on the use of the Gram Stain. 

Gram Stain

Unlike large organisms like humans, parrots and dra-, erm, Komodo Dragons, which are easy to spot and have a distinct appearance to the eye, bacteria are colourless and invisible to light microscopy. Thus, gram staining had to be developed to give bacteria a colour, and visualize them. Since bacteria would either respond to the stain, or not, all bacteria were subsequently classified into gram-positive and gram-negative bacteria. 

There are 4 steps to the Gram Stain Procedure. 

  1. Pour crystal violet stain (a blue dye) and wait for 60 seconds. 
  2. Wash off with water and flood with iodine solution. Wait for 60 seconds. 
  3. Wash off with water and then “decolourize” with 95% alcohol solution. 
  4. Counter-stain with safranin (a red dye). Wait 30 seconds and then wash off with water. 

Basically, when viewed under the microscope, cells that absorb the crystal violet dye and hold on to it become blue: These are gram-positive. Alternatively, if the crystal violet is washed off by the 95% alcohol, the cells absorb the safranin and appear red. These are gram-negative. 

Gram Positive = Blue 

Imagine yourself sitting by the beach, opposite crystal blue waters, or kayaking across deep waters, or even river tubing across the bluest of rivers.. won’t you say yes to that? So, Blue = Positive. Note that Gram-Positive bacteria may also appear purple if the red safranin is not effectively washed off. This is because blue + red is purple. 

Gram Negative = Red

Now you’re sitting in sweltering red heat, sweat pouring down your body, the sun red in the sky. You don’t want that, do you? Or for comic book fans, you can picture Superman’s face when he sees a Red Sun in the sky. NOPE, thinks Superman. So Red = Negative. 

This difference occurs due to a difference in morphology of the bacteria. 

Gram Positive vs Gram Negative Bacteria 

Unlike eukaryotic animal cells which contain only one cell membrane composed of phospholipid separating the nucleus from the ECF, both gram-positive and gram negative bacteria contain more than 1 layer: the layer outside the bacterial cytoplasmic membrane is the peptidoglycan layer. 

Keep reading

@barbellsandbetasheets soo… microbio? what a joke. We had a practical on basic gram staining and my professor told me that on my first slide that I had no specimen. That the specimen or organism I did find was incorrect because it should not reflect light. Then I made a new slide in the 10 minutes we had left and asked her to find it because I was not about to waste anymore time. When she did find it, guess what? IT WAS THE SAME DAMN THING THAT I FOUND THE FIRST TIME!!!!!! The oil immersion showed that i was right. I wasted over 20 minutes trying to find something else on my first bacterial smear because she told me I was wrong. WTF? I CANNOT TAKE THIS LAB ANYMORE.

2

Neisseria meningitidis

Neisseria meningitidis, often referred to as meningococcus, is a gram negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. The bacterium is referred to as a coccus because it is round, and more specifically, diplococcus because of its tendency to form pairs. About 10% of adults are carriers of the bacteria in their nasopharynx. As an exclusively human pathogen it is the main cause of bacterial meningitis in children and young adults, causing developmental impairment and death in about 10% of cases. It causes the only form of bacterial meningitis known to occur epidemically, mainly in Africa and Asia. N. meningitidis is spread through saliva and respiratory secretions during coughing, sneezing, kissing, and chewing on toys.

Persons with confirmed N. meningitidis infection should be hospitalized immediately for treatment with antibiotics. Because meningococcal disease can disseminate very rapidly, a single dose of intramuscular antibiotic is often given at the earliest possible opportunity, even before hospitalization, if disease symptoms look suspicious enough. Third-generation cephalosporin antibiotics (i.e. cefotaxime, ceftriaxone) should be used to treat a suspected or culture-proven meningococcal infection before antibiotic susceptibility results are available. Empirical treatment should also be considered if a lumbar puncture, to collect CSF for laboratory testing, cannot be done within 30 minutes of admission to hospital. Antibiotic treatment may affect the results of microbiology tests, but a diagnosis may be made on the basis of blood-cultures and clinical examination.

Key characteristics: Gram(-), diplococci, oxidase(+), glucose(+), maltose(-), lactose(-), sucrose(-), grows best at 35-37°C with ~5% CO2

2

Pseudomonas aeruginosa

Pseudomonas aeruginosa is a nonfermentative gram-negative bacillus. This bacterium is ubiquitous in soil and water, and on surfaces in contact with soil or water. Pseudomonas aeruginosa is an opportunistic pathogen, meaning that it exploits some break in the host defenses to initiate an infection. It causes urinary tract infections, respiratory system infections, dermatitis, soft tissue infections, bacteremia, bone and joint infections, gastrointestinal infections and a variety of systemic infections, particularly in patients with severe burns and in cancer and AIDS patients who are immunosuppressed.

Key characteristics: Gram(-), catalase(+), oxidase(+), motility(+), aerobic, produces pigments (green and blue), grows at 42°C.

We Know When You're Lying (Most of the Time)

Recently admitted a young person with horrific orbital cellulitis- like dripping pus down their face, can’t even see the pupil when we pried open their eyelids level horrible.

And the gram stain from their eye came back gram negative diplococci… And their STI test came back positive for gonorrhea. So we think they have gonorrhea in their eye too.

However, (after kicking parents out of the room) they furiously denied having ever come in contact with any person’s genitals, boy or girl. They told three different doctors the same story.

The next day they shyly admitting to kissing their partner.

Then today we sat down with them and said, “So, our tests show that you have a sexually transmitted disease.” Finally they fessed up to having unprotected sex a few times. Luckily we were already treating them with an antibiotic that covered gonorrhea because we didn’t believe the never-had-sex story.

So! If a doctor asks you a question, tell the truth the first time, because it just makes things easier for everyone. We’re not going to judge you or tattle on you, we have to know the truth so we can provide proper care.

Also use a condom!!