Cultures and Other Microscopic Studies

Question 1

What are the reasons for performing Cultures and Other Microscopic Studies?

Answer 1

To evaluate hematologic disorders (bone marrow biopsy)
To detect STD
To evaluate dysfunctional uterine bleeding (endometrial biopsy)
To determine liver pathology (liver biopsy)
To detect lung cancer (lung biopsy)
To screen for cancer of vagina, cervix, and uterus (Papanicolaou smear)
To determine sensitivity of breast cancer to hormone therapy (estrogen and progesterone receptor assays)
To detect renal disease such as malignancy, glomerulonephritis, and transplant rejection (renal biopsy)
To detect TB (TB culture)
To evaluate and treat infections (wound and soft tissue culture and sensitivity)

Question 2

What are the Microscopic studies?

What do they determine?

Answer 2

Microscopic studies for infection include culture and sensitivity as well as Gram stain.

Gram stain determines whether the bacteria are gram positive or negative as well as the shape of the organism, which allows reasonable antibiotic treatment to be started prior to culture results

Question 3

What are Blood Culture and Sensitivity (Blood C & S) used for?

Answer 3

Obtained to detect presence of bacteria in the blood (bacteremia).

Bacteremia can be intermittent and transient and is usually accompanied by chills and fever, so the culture should be drawn when the patient is symptomatic to increase the chances of growing bacteria

Question 4

What are the interfering factors for a Blood Culture and Sensitivity (Blood C & S)?

Answer 4

Contamination by skin bacteria

Antibiotics altering test results

Question 5

What are the test results for a Blood Culture and Sensitivity (Blood C & S)?

Answer 5

Bacteremia – consider patient to be gravely ill and antibiotics should be started immediately after blood cultures are obtained

Question 6

What is Sputum Culture and Sensitivity used for?

Answer 6

Indicated with persistent productive cough, fever, hemoptysis, or CXR compatible with pulmonary infection.

Used to diagnose pneumonia, bronchiectasis, bronchitis, or pulmonary abscess.
Bacteria, fungus, or virus can be cultured

Question 7

What is done before the Sputum culture and sensitivity?

How does saliva affect the results?

What are possible positive results?

Answer 7

Gram stain is first step and may be used to guide initial antibiotic therapy until C&S report is done.
After gram stain, culture and sensitivity is done – this may take at least 48 hours, but cultures for fungus and Mycobacterium tuberculosis may take 6-8 weeks.

Saliva mixed with sputum will give a contaminated specimen - PROBLEM.

Test results – bacterial infection (pneumonia), viral infection, atypical bacterial infection (TB), fungal infection

Question 8

When is a wound and soft tissue culture and sensitivity indicated?

Answer 8

Indicated when a wound or soft tissue has signs of infection (redness, warmth, swelling, and pain).

In a postoperative patient with persistent fever of unknown origin, a wound may be probed and cultured even if signs of infection are not present.

Any drainage from a wound or soft tissue should be cultured to document infection for treatment, drug sensitivities, and to document appropriate skin and wound isolation precautions

Question 9

What are interfering factors for a wound and soft tissue culture and sensitivity ?

What is the best treatment?

Answer 9

Interfering Factors – antibiotics may alter test results.

Best treatment for a wound infection is incision and drainage. Antibiotics are secondary.

Question 10

What are wound infections most often cause by?

What wounds contain both aerobic and anaerobic?

Answer 10

Wound infections are most often caused by pus forming organisms.

Many wound infections contain more than one organism.

Deep space wounds, wounds with necrotic debris or gas, and postoperative wounds often contain both aerobic and anaerobic bacteria

Question 11

What is a Throat and Nose Culture used for?

Answer 11

Used to diagnose bacterial, viral, gonococcal, or candidal pharyngitis and are indicated in patients with sore throat, fever of unknown origin, or to identify chronic carriers of recurrent infection

Throat Culture serves only to isolate a few pathogens –streptococci, meningococci, gonococci, Bordetella pertussis, corynebacterium diphtheriae

Question 12

What is Group A beta-hemolytic streptococcal pharyngitis followed by?

Answer 12

Group A beta-hemolytic streptococcal pharyngitis may be followed by rheumatic fever or glomerulonephritis

Most frequently affects children ages 3-15.
Children with sore throat and fever should have throat culture done to identify the strep infection

Question 13

When are throat cultures indicated in adults?

Answer 13

In adults, fewer than 5% of pharyngitis has strep, so cultures are only indicated when patient has severe or recurrent sore throat, often with fever and lymphadenopathy

Question 14

What is the Rapid Strep Screen?

Answer 14

Rapid strep screen is an immunologic test and is very accurate.

The strep organism can be identified directly from the swab specimen.

Test can be performed in 15 minutes while the culture takes at least 2 days

Question 15

What do Nasal and pharyngeal cultures screen for?

What may interfere?

Answer 15

Screen for infections and carrier states caused by Staphylococcus aureus, Heamophilus influenza, Neisseria meningitides, respiratory syncytial virus (RSV), and influenza virus.

Antibiotic and antiseptic mouthwashes may affect the test results

Question 16

What are possible results of the Throat and Nose Culture?

Answer 16

Acute pharyngitis – throat cultures used to identify bacteria

Tonsillar infections

Chronic nasal carriers of bacteria – may chronically carry staphylococci, streptococci, influenza, or RSV

Question 17

What are the Vaginal Studies?

Answer 17

Papanicolaou Smear
Chlamydia
Herpes Simplex
Sexually Transmitted Disease Culture
Trichomonas Preparation
Bacterial Vaginosis
Vulvovaginal Candidiasis

Question 18

What is the Papanicolaou Smear (Pap smear)?

Who is it routinely performed on?

Answer 18

Main screening test for cancer of vagina, cervix, and uterus.
Done to detect neoplastic cells in cervical and vaginal secretions. Early cellular changes associated with premalignant conditions or an existing malignant condition can be detected.

Routinely performed on women older than 21 or on younger women who are sexually active. Until age 30, then if had 3 normal tests in a row, can change to screen every 2-3 years.

Pap smear is 95% accurate in detecting cervical carcinoma but only 40% accurate in detecting endometrial carcinoma

Question 19

What are the Contraindications for a Papanicolaou Smear (Pap smear)?

Interfering factors?

Answer 19

Contraindications – menses, vaginal infections

Interfering factors:
Delay in fixing a specimen allows cells to dry
Lubricating jelly on speculum can alter specimen
Douching or tub bathing before test can interfere with results
Menses
Infections

Question 20

What are positive test results for a Papanicolaou Smear (Pap smear)?

Answer 20

Cancer – suspicious Pap smears need more thorough exam with colposcopy, cone biopsy, and or dilation and curettage

STDs, fungal infection, parasite infection, herpes infection – cause cellular changes on Pap, need culture to make the diagnosis

Infertility – lack of estrogenic effect on Pap may indicate ovarian failure

Question 21

What is Chlamydia?

Answer 21

Most common form of pelvic inflammatory disease, presenting with pelvic pain and/or vaginal discharge

There are many species that can cause it, but C. trachomatis is the most frequently occurring STD in developing countries.

Most prevalent in patients younger than 20 years, in nulliparas, and in users of nonbarrier contraceptive methods

Also associated with gonorrhea in those with multiple or recent new sexual partners

Question 22

How are people evaluated for Chlamydia based on gender?

How treated?

Answer 22

Females are evaluated by cervical cultures, males with urethral cultures.

All affected patients should be treated with antibiotics and sexual partners should be evaluated

Question 23

What is the Herpes Simplex test used for?

Answer 23

Testing used to diagnose acute initial herpes infection.

Used on patients with suspected initial genital infection, in immunocompromised patients with aggressive oral mucosal or genital eruptions compatible with infection, and on patients, especially immunocompromised, who have a fever of unknown origin

Cultures are also used to identify genital herpes infections in women who are expecting to vaginally deliver a baby in the next 6-8 weeks

Question 24

What are the two types of HSV?

Answer 24

Type 1 mainly causes oral lesions (cold sores) with about half developing recurrent infections.

Type 2 is sexually transmitted and causes lesions on the penis, scrotum, vulva, perineum, perianal region, vagina, or cervix

Question 25

What are the Sexually Transmitted Disease cultures used for?

How are people evaluated based on gender?

Answer 25

Performed for patients who have a vaginal discharge, pelvic pain, urethritis, or penile discharge and are at risk for STDs.

If culture is positive then partners should be evaluated and treated.

Cervical cultures usually are done for women, urethral cultures for men.
Rectal and throat cultures are done when there has been anal or oral intercourse

Question 26

What are the Interfering factors for the Sexually Transmitted Disease cultures?

Answer 26

N. gonorrhoeae is very sensitive to lubricants and disinfectants.
Menses may alter test results.
Douching within 24 hours makes fewer organisms available for culture.
Male voiding within 1 hour of urethral culture washes secretions out of the urethra.
Fecal material may contaminate an anal culture

Question 27

How are Sexually Transmitted Disease cultures obtained?

Answer 27

Cervical – cervical mucus is removed with a cotton ball held in a ring forceps, then a sterile cotton tipped swab is inserted into the endocervical canal and moved from side to side to obtain the culture

Anal – insert sterile cotton tipped swab 1 inch into the anal canal. If stool contaminates the swab, repeat swab is done

Oropharyngeal – depress tongue with wooden tongue blade and touch posterior wall of throat with sterile cotton tipped swab

Urethral – insert sterile swab into anterior urethra with patient in supine position

Question 28

What is Trichomonas?

Answer 28

Trichomonas is a sexually transmitted protozoan infection.
It causes foamy, yellow drainage as well as petechiae and vaginal burning and itching in females.
In males, a persistent white urethral discharge may exist or no symptoms may be present.

Trichomonas vaginalis is transmitted by direct contact with the vaginal and urethral fluids of the infected patient.

Diagnosis is made by direct microscopic exam of wet mount of secretions

Question 29

What is Bacteria Vaginosis (Gardnerella)?

Answer 29

Not sexually transmitted, gardnerella vaginalis is a gram-variable rod that produces a malodorous vaginal discharge with clue cells, which are vaginal epithelial cells covered with bacteria.

The whiff test, which is done by treating the vaginal discharge with 10% KOH and smelling a pungent, fish odor, is often positive.

Trichomonas can also have a positive whiff test

Question 30

What is Vulvovaginal Candidiasis?

Answer 30

Produces itching, burning, or irritation and may have vulvar erythema, edema, fissures, and tenderness.

Will see a white vaginal discharge on exam with white thrush-like plaques or cottage cheese like curds adhering loosely to the vaginal mucosa.

Caused by candida albicans and is not an STD.

Diagnosis made by visualization of pseudohyphae or hyphae by microscopic exam of vaginal fluid mixed with saline or 1-% KOH or subjected to gram staining.