[Microbiology] Atlas of Miscellaneous Body Fluids

Atlas of Miscellaneous Body Fluids, Miscellaneous Body Fluids, Graff's Textbook of Urinalysis and Body Fluids



The clinical laboratory has a role in providing the clinician with critical test results from a variety of body fluids. This chapter will cover miscellaneous testing and body fluids that have not been covered previously, or that are currently tested less frequently, but that yield crucial evidence of the patient’s status. In addition, laboratory medicine is constantly expanding its capabilities and thus, continually adding new tests and new types of specimens

URINE PREGNANCY TESTING

Urine pregnancy testing is widely performed and has not been covered in previous chapters. Pregnancy testing may be performed on urine or on blood. The substance tested in pregnancy is beta-human chorionic gonadotropin hormone ( -hCG), a hormone that is secreted in urine within 2–3 days after implantation of the embryo (or approximately 8–10 days after fertilization). Levels of this hormone rise rapidly after conception and remain elevated in pregnancy, peaking in the first trimester of pregnancy. Some tests performed on serum can detect pregnancy much earlier, within days of conception. One reason that serum is able to detect pregnancy earlier is that the levels of the hormone -hCG vary a great deal due to the concentration of the urine, yet the levels are relatively stable in serum. Still, collecting a urine specimen is easier and urine pregnancy test kits are available over the counter. The best specimen for urine pregnancy testing is the first morning urine, which is the most concentrated specimen. For optimal results, the specific gravity should be 1.015 or higher. False results may occur with large amounts of blood, pro- tein, or bacterial contamination. Enzyme immunoassays are the most popular type of test kit, but whatever the method, follow the manufacturer’s guideline. Results are reported as -hCG negative or as -hCG positive. These kits may show a positive result in a urine sample in as little as 10 days after conception.

AMNIOTIC FLUID

Amniotic fluid is found around the developing fetus, inside a membranoussac, called the amnion. This fluid serves to cushion and protect the developing fetus and also serves a key role in the exchange of water and molecules between the fetus and the maternal circulation. The laboratory performs several crucial tests on amniotic fluid to assess the status of the fetus. These tests can be divided into these groups: (a) tests to diagnose genetic and congenital disorders before birth, (b) tests to detect fetal distress from hemolytic disease of the newborn (HDN) or from infection, (c) tests to assess fetal lung maturity, and (d) assessment of the ability of the fetus to survive early delivery.

ANATOMY AND PHYSIOLOGY OF AMNIOTIC FLUID FORMATION
The amniotic fluid is formed from the placenta. Amniotic fluid has a composition similar to that of the maternal plasma with a small number of cells from the skin, urinary tract, and digestive tract of the newborn and biochemical substances produced by the fetus. The volume of amniotic fluid increases steadily throughout the pregnancy up to a maximum of 1100–1500 mL at 36 weeks of gestation.
When fetal urine production begins, the chemical composition of the amniotic fluid changes. This change corre- sponds to the increased production of creatinine at about  36 weeks of gestation. Prior to 36 weeks of gestation, the amniotic fluid creatinine level is 1.5–2.0 mg/dL and after 36 weeks, it rises greater than 2.0 mg/dL.
At the commencement of fetal urine production, fetal swallowing of amniotic fluid begins and this regulates the formation of fetal urine. Decreased fetal swallowing results in an increase in amniotic fluid volume, known as hydramnios. Abnormally decreased amounts of amniotic fluid, oligohydramnios, can occur with premature rupture of the membranes and with congenital malformations. The fetus also secretes lung liquid and fetal pulmonary substances into the amniotic fluid through fetal breathing movements that circulate amniotic fluid. Exchange between amniotic fluid and the maternal plasma circulation equals the amount of amniotic fluid every 2–3 hours (Fig. 14-1).

AMNIOCENTESIS, SPECIMEN COLLECTION AND HANDLING
Amniotic fluid is obtained by needle aspiration into the amniotic sac, usually transabdominally with simultaneous use of ultrasound. The addition of ultrasound has helped make this procedure safer especially if performed after 14 weeks of gestation. Amniocentesis is generally performed between 15 and 18 weeks of gestation for genetic studies although it may be used later in the pregnancy in cases of fetal distress. The amount collected is usually 10–20 mL (maximum 30 mL), with collection into several different syringes to prevent the contamination of all specimens with the blood from initial puncture. 
Immediately after collection, the fluid is dispensed into sterile plastic specimen containers. Glass containers are less desirable as cells have more of a tendency to adhere to the glass surface. Normal amniotic fluid is colorless to pale yellow and slightly turbid due to fetal cells, vernix, and hair. Specimens for cell culture and chromosomal studies must be stored at body or room temperature to keep fetal cells alive. Specimens for phospholipid analysis should be transported on ice and centrifuged at 500g and the supernatant
Schematic drawing of the amniotic cavity.
Figure 14-1. Schematic drawing of the amniotic cavity.

saved for testing. If blood is present, the specimen should be centrifuged to prevent hemolysis from altering the test results. All amniotic fluid samples for chemical analysis that must be stored for any length of time must be centrifuged. If samples for chemical analysis need to be stored more than 24 hours, they must be stored frozen

DIFFERENTIATION OF AMNIOTIC FLUID FROM MATERNAL URINE
In case of possible premature membrane rupture or maternal bladder puncture or rupture, it may be necessary to differentiate amniotic fluid from urine. To differentiate these two fluids, chemical levels of creatinine, urea, glucose, and protein can be of assistance. Levels of creatinine and urea are much higher in urine than in amniotic fluid. Glucose and protein levels tend to be higher in amniotic fluid than in urine. 
A microscopic test, the fern test, is also used to differentiate amniotic fluid from maternal urine. With this test, vaginal fluid is spread out on a glass slide and allowed to dry at room temperature. This slide is observed for fernlike crystals that are a positive screen test for amniotic fluid.

PHYSICAL AND MICROSCOPIC EXAMINATION OF AMNIOTIC FLUID
Normal amniotic fluid is colorless to pale yellow and slightly cloudy. A dark yellow or amber color is associated with bilirubin, whereas a green color indicates meconium, the newborn’s first fecal bowel movements. Blood canappear as pink or red and the source of the blood, whether fetal or maternal, can be distinguished by the Kleihauer- Betke test for fetal hemoglobin. A very dark red-brown amniotic fluid is associated with fetal death. 
Microscopic cytological examination of the amniotic fluid may yield information on the diagnosis of ruptured membranes or chorioamnionitis. Cytogenetic studies are also a common reason for performing amniocentesis

TESTING AMNIOTIC FLUID FOR GENETIC AND CONGENITAL DISORDERS
Valuable cytogenetic information related to the sex of the fetus and to genetic abnormalities can be obtained via amniocentesis. Congenital neural tube disorders can also be detected by amniotic fluid analysis. Amniocentesis is often performed to detect Down syndrome and anencephaly prior to birth.


Testing for Neural Tube Defects—Alpha Fetoprotein and Acetylcholinesterase 
Fetal neural tube defects such as anencephaly and spina bifida cause elevated alpha fetoprotein (AFP) in amniotic fluid and in the maternal circulation. AFP is present in the fetal serum and is secreted in the fetal urine and thus appears in the amni- otic fluid. In normal fetal development, AFP peaks at about 
16 weeks of gestation and then declines gradually to term. With neural tube disorders, the neural tube is open and AFP is released from the cerebrospinal fluid directly into the amniotic fluid, resulting in amniotic AFP levels that are muchhigher than normal. AFP is also typically elevated in the maternal serum with fetal neural tube disorders 
Acetylcholinesterase (AChE) is also tested, usually in conjunction with AFP, in neural tube disorders. AChE testing is more specific than AFP testing for neural tube disorders. Because blood interferes with AChE testing, amniotic fluid must be free of blood or hemolysis for this test to be accurate, however

FETAL DISTRESS TESTING
HDN, also known as erythroblastosis fetalis, is caused when mother develops antibodies to an antigen on the fetal erythrocytes and these maternal antibodies cross the placenta to destroy many fetal red blood cells (RBCs). Most frequently, HDN is caused by the sensitization of an Rh-negative mother to fetal Rho[D] antigen, although rarely, other antigens are involved. The destruction of these fetal RBCs results in the appearance of elevated unconjugated bilirubin in the amniotic fluid. With this hemolytic disease process, the high unconjugated bilirubin triggers early production of fetal hepatic glucuronyl transferase activity and this unconjugated bilirubin is converted to conjugated bilirubin. The conjugated bilirubin is not cleared by the placenta, and variable amounts of the conjugated bilirubin are found in the amniotic fluid. Modern preventive measures such as prenatal screening and the administration of RhoGam (Rho[D] immune globulin) to mother during pregnancy have dramatically lowered the incidence of this disease but have not totally eliminated HDN.

Measurement of amniotic fluid bilirubin is performed through spectrophotometric analysis. The absorbance spectrum of amniotic fluid is measured between 365 and 

550 nm. The amount that the curve deviates from a straight line at 450 nm (the ΔA450) is directly proportional to the amount of bilirubin in the amniotic fluid. The ΔA410 corre- sponds to oxyhemoglobin, which is the major contaminant of concern. This constituent can be minimized by centrifu- gation to remove blood upon receipt. The bilirubin concen- tration correlates to the severity of HDN.2,3 (Fig. 14-2).


Infection 
Evidence is mounting of the importance of microorgan- isms in the amniotic fluid contributing to the incidence of preterm delivery and spontaneous abortion. Even bacterial vaginosis and trichomoniasis have been linked to preterm birth. Gram stain, wet mount, culture, and molecular tests may be used on amniotic fluid to look for potential infec- tious agents.


Respiratory Distress Syndrome 
Respiratory distress syndrome is the most common cause of death in the premature newborn and is of particular

Figure 14-2. Spectrophotometric scan of amniotic fluid indicating bilirubin and oxyhemoglobin peaks. Note the near linearity of the normal curve in A. In B, note the elevated bilirubin peak (at 450 nm) and the oxyhemoglobin peak (at 410 nm). The base is drawn from 550 nm to 365 nm.

concern in the premature birth. When fetal lungs are imma- ture, they lack sufficient lung surfactant to allow the alveoli of the lungs to function throughout the normal cycle of inhalation and exhalation. Surfactant prevents the alveoli from collapsing by decreasing the surface tension enough to allow them to inflate with air. The surfactant is packed by the cell in structures called lamellar bodies which extend into the alveolar air-spaces. The lamellar bodies then unfold into a complex lining of the alveolar space. This layer reduces the surface tension of the fluid that lines the air-space. There is a correlation between the levels of lung sur- factants and fetal lung maturity and lung stability. Several fetal lung tests are available to assess fetal lung maturity before birth in order to prevent respiratory distress syndrome by determining the best time for preterm delivery

FETAL LUNG MATURITY TESTS

Lecithin:Sphingomyelin Ratio and Phosphatidylglycerol
Fetal lung surfactants include these three phospholipids: lecithin (also known as phosphatidylcholine), sphingomyelin, and phosphatidyl glycerol. Lecithin is the major lung surfactant. The role of sphingomyelin is not estab- lished. The ratio of lecithin to sphingomyelin is used to assess fetal lung maturity. Up until the 33rd week of gestation, the levels of these two phospholipids are relatively equal. After 34 weeks of gestation, the level of sphin- gomyelin decreases, whereas the level of lecithin increases significantly. A lecithin:sphingomyelin (L/S) ratio of 2.0 or greater is associated with fetal pulmonary system maturity.

Phosphatidyl glycerol is another lung surfactant that is measured to assess fetal lung maturity. Phosphatidyl glyc- erol is not normally detectable in the amniotic fluid unti 35 weeks of gestation. Phosphatidyl glycerol production is delayed in cases of maternal diabetes. An advantage to testing for phosphatidyl glycerol is that the presence of blood and meconium in the amniotic fluid does not invalidate this test result.


Amniostat-FLM
The Amniostat-FLM (Irving Scientific of Santa Ana, Cali- fornia) is a commercial product that uses antibodies to phosphatidyl glycerol to detect this fetal lung surfactant. An advantage to this immunological test is that it is not affected by blood or meconium that might be present in the amniotic fluid.

Foam Stability
This is a screening test for fetal lung surfactant in amniotic fluid. In this test, a fixed amount of amniotic fluid is mixed with an increasing volume of 95% ethanol in a series of tubes with alcohol concentrations ranging from 0.43 to 0.55. The mixtures are shaken vigorously for 30 seconds, and the contents are allowed to settle for 15 seconds and the samples are examined for an uninterrupted ring of foam in the tube. The highest concentration of 95% ethanol that is able to support a ring of foam is known as the foam stability index. The principle of the test is that more surfactant is needed to maintain the foam in greater concentrations of ethanol and more fetal lung surfactant is needed to support fetal lung function at birth. An index of 0.47 or higher is considered to indicate enough fetal lung surfac- tant for fetal lung maturity.


Microviscosity Fluorescence Polarization Assay
Another measure for fetal lung surfactant is the Abbott TDx/TDxFLx Fetal Lung Maturity II (FLM II) Assay. This assay provides a fluorescence polarization (P) surfactant: albumin ratio. Phospholipids decrease the microviscosity of amniotic f luid and this change in microviscosity is measured through fluorescent polarization. In this test, a fluorescent dye that binds to both albumin and surfactant is added to the amniotic fluid sample. The addition of this fluorescent dye gives the sample a measurable fluorescent polarization (P) intensity value. Dye bound to surfactant has a longer fluorescence lifetime and exhibits a low polar- ization. The P value is high in amniotic fluid with low lev- els of surfactant and the P value is low in amniotic fluid with high levels of surfactant. The degree of fluorescence polarization is inversely proportional to the quantity of pulmonary surfactant present. The Abbott TDx/TDxFLx assay provides a standard curve with a range from 0 to 160 mg/g of phosphatidyl glycerol.


Lamellar Bodies 
Fetal lung surfactants are produced by fetal type II pneu- mocytes of the fetal lung and are stored as lamellar bodies after about 20 weeks of gestation. Lamellar bodies are about the size of small platelets. Lamellar bodies are storage forms of lung phospholipids and they enter the fetal lungs and the amniotic fluid at about 20–24 weeks of gestation. They reach levels of about 50,000–200,000 lamellar bodies/microliter of amniotic fluid by the third trimester of pregnancy. Amniotic fluid samples must be free of hemoglobin and meconium for accurate lamellar body testing. 

Lamellar bodies affect the optical density of amniotic fluid and a measurement of the optical density of 0.150 at 650 nm has been shown to correlate with an L/S ratio of 2.0 and to correlate with the presence of phosphatidyl glycerol.

Lamellar body counts provide a reliable estimate of fetal lung maturity. Lamellar body counts can be performed easily with many hematology analyzers using the platelet count channel. As the methods employed by each hematology system vary considerably, sample preparation and lamellar body count cutoff values vary for assessment of fetal lung maturity. Lamellar body counts of approximately 35,000 per microliter correspond to adequate fetal lung surfactant levels.


Assessment of Fetal Risk and Survivability with Premature Delivery 
Of paramount importance to the ability of the preterm infant to survive after delivery is the fetal lung maturity. The risk of death from respiratory distress syndrome can be reduced greatly if delivery is delayed until fetal lung tests show sufficient lung surfactant to support lung function. If the fetus is in danger in utero and needs intervention, the risk they face must be weighed against the risk of early delivery. Tests for fetal lung surfactants and amniotic fluid creatinine level are most helpful to establish fetal maturity and fetal survival risk.


In 1961, Liley proposed testing of amniotic fluid to assess fetal risk in cases of HDN. He developed a graph that is still used today to assess fetal risk in these cases (Fig. 14-3). In Liley graph, a semilogarithmic plot of the amniotic fluid ΔA450 against fetal gestational age, three zones are designated to assign disease severity: zone I—normal val- ues, zone II—moderate hemolysis, and zone III—severe hemolysis with risk of death. Using this graph can guide

Liley graph for assessment of fetal risk
Figure 14-3. Liley graph for assessment of fetal risk. The Liley graph is a three-zone chart with modification for the interpretation of amniotic fluid change in absorbance at 450 nm versus weeks of gestation. The graph divides the patient’s readings into three zones of gestational risk, with zone III posing the greatest risk for the developing infant

physicians in decisions of whether to induce labor or to uti- lize intrauterine blood transfusion exchanges in cases of HDN. Measures of fetal lung maturity can also assist in these treatment decisions

VAGINAL SECRETIONS

Glands in the cervix normally produce a clear mucus that may turn slightly white or pale yellow upon exposure to air. The amount of vaginal secretions may vary throughout the menstrual cycle. Noticeable changes in the color, consistency, or amount of vaginal secretions may be linked to various conditions and infections. Examination of vaginal secretions may provide the caregiver with helpful informa- tion on the patient’s condition.

FEMALE GENITAL DISORDERS DETECTED BY VAGINAL SECRETIONS
Infections and sexually transmitted diseases can be detected via testing of vaginal secretions. Some testing may be performed in the microbiology department whereas other test- ing may be performed in the urinalysis department. Below are some conditions that can be detected by examining vaginal secretions.


Bacterial Vaginosis
Bacterial vaginosis is the most common vaginal infection in women. In bacterial vaginosis, the vaginal f lora is altered. Normally, Lactobacillus predominates in the healthy vaginal f lora. In vaginosis, other bacteria such as Gardnerella vaginalis, or Mobiluncus species, or the anaer- obic Prevotella species predominate. The overgrowth of other anaerobic bacteria is also associated with bacterial vaginosis. Studies of women with vaginosis have shown a correlation of bacterial vaginosis with an increased risk for premature birth and low–birth weight infants.8 In bacterial vaginosis, the vaginal discharge is gray or off-white and thin, with characteristics of a transudate. There is a characteristic lack of white blood cells (WBCs) as there is no invasion of the subepithelial tissue, but there is an increase in exfoliation of epithelial cells. To diagnose bacterial vaginosis, three of the following char- acteristics should be seen: (a) “clue cells,” sloughed off squamous epithelial cells covered with numerous small thin, curved gram-variable bacilli, (b) a vaginal pH greater than 4.5, (c) a positive amine or “whiff ” test, and (d) a malodorous, homogenous vaginal discharge. 

Wet mount and Gram stain of “clue cells
Figure 14-4. Wet mount and Gram stain of “clue cells.” These are squamous epithelial cells that are literally covered with numerous small curved bacilli. These cells slough off because of bacterial alteration in bacterial vaginosis


Of these tests, the most reliable indicator of bacterial vaginosis is the characteristic microscopic appearance of “clue cells,” together with an altered microbial f lora, with a reduction in the typical long, thin Lactobacillus and an overgrowth of the small, thin, curved gram-variable bacilli of species such as Gardnerella, Mobiluncus, and Prevotella2 (Figs. 14-4 and 14-5).

Trichomonas Vaginalis
Trichomonas vaginalis is a common parasitic infection of the vaginal mucosa in females and of the urogenital tract of males. Women usually complain of yellow green vaginal dis-
Gram stain
Figure 14-5. Gram stain (1000x). Lactobacillus predominating 
in a healthy vagina with squamous epithelial cells

charge, although women can be asymptomatic and men are usually asymptomatic. In pregnant women, Trichomonas is a risk factor for preterm rupture of membranes and preterm labor and delivery. The wet mount is helpful to detect the majority of cases of Trichomonas, but culture or DNA probe for Trichomonas are useful when the wet preparation is nega- tive and trichomoniasis is strongly suspected. In Tri- chomonas, the bacterial flora is also altered and the pH is abnormally elevated to 5.0 or 6.0. The amine or “whiff ” test may also be positive with Trichomonas due to the altered bacterial flora and vaginal pH. WBCs are also frequently seen in the wet preparation of trichomoniasis. See Figure 14-6 for the characteristic appearance of these organisms.
Figure 14-6. Trophozoites of T. vaginalis obtained from in vitro culture, stained with Giemsa

Figure 14-7. Wet preparation of C. albicans yeast and pseudohyphae 
with WBCs. Yeast (including pseudohyphae), RBCs, and WBCs (200x).


Candidiasis
Candida albicans causes the majority of cases of vulvovaginal candidiasis, a common vaginal fungal infection in women. Again, this infection occurs when there is an alteration in the normal bacterial flora and the normal vaginal environ- ment. While C. albicans can be found normally in the vagina, it is generally in small numbers but greatly overgrows in candidiasis. This is frequently caused by antibiotic treatment and can occur in celibate as well as sexually active women. It is also more common in immunosuppressed patients. Women with candidiasis frequently complain of a whitish, curdlike vaginal discharge. Microscopic examina- tion reveals an increased number of yeast cells and pseudo- hyphae with a concomitant increase in WBCs2 (Fig. 14-7).

GROSS VAGINAL SECRETION EXAMINATION

pH
Normally, vaginal secretions have a pH of 3.8–4.5, due to the growth of Lactobacillus species and its acidic byprod- ucts. With the alterations of bacterial flora that occur in bacterial vaginosis and in Trichomonas, the pH goes up and Lactobacillus numbers decrease. The vaginal pH also rises in postmenopausal women due to decreased Lactobacillus species that can occur with atrophic vaginosis. In candidia- sis, the pH is largely unchanged, between 3.8 and 4.5.

MICROSCOPIC EXAMINATION OF VAGINAL SECRETIONS
Vaginal secretions are examined in the wet mount under low and high dry powers for various microbes and cells. In the microbiology laboratory, the Gram stain is also useful to detect some of these agents when performed by the trained technologist.

Wet Mount
The saline wet mount is frequently used to examine vaginal secretions for “clue cells,” that are seen in bacterial vaginosis or for trichomonads. A preparation is made of vaginal secretions with a drop of isotonic saline and a coverslip and the slide is examined under low power and high dry power. “Clue cells” are squamous epithelial cells that are covered with numerous bacteria, such as G. vaginalis or Prevotella bivia that are overgrown in bacterial vaginosis. A saline wet mount of vaginal secretions can also be used to find T. vaginalis trophozoite parasites. Trichomonad trophozoite forms are associated with vaginal infections and are motile flagellate protozoans in the saline wet preparation. These organisms are also sometimes seen in urinalysis wet preparations. Trichomon- ads are readily identifiable by their characteristic jerky movement due to both their five flagella and their undulating membrane. When these cells die, they ball up and become difficult to distinguish from WBCs, so it is important to process and read all specimens for wet preparation examination immediately, within 1⁄2 hour, to avoid missing these organ- isms. The yeast and pseudohyphae of candidiasis can also be seen in wet mounts. The presence of squamous epithelial cells and leukocytes should be reported as well.


KOH Preparation and Amine Test
A KOH preparation is a slide prepared for examination by adding one drop of 10% KOH to vaginal secretions with a coverslip. As the KOH slide is prepared, if the microbial flora of the vaginal secretions are altered due to bacterial vaginosis, a foul-smelling trimethylamine odor is given off when the KOH is added and the pH of the sample changes. Detection of this characteristic odor associated with bacterial vaginosis is sometimes referred to as a positive amine or “whiff” test. KOH is added to digest cellular elements and this is particularly helpful in order to detect yeast and pseudohyphae fungal elements which do not digest in KOH as readily as do other vaginal cells.

Other Examinations
Gram stain, culture, and molecular probes are used to detect a wide variety of infectious agents that can infect the reproductive tract. The appropriate specimens should be submitted to the microbiology department for this testing.

BRONCHOALVEOLAR LAVAGE AND BRONCHIAL WASHINGS

Bronchoalveolar lavage (BAL) and bronchial washings are body fluids that are generally collected to assess the cellular composition and to detect any infectious agents present in the lower respiratory tract.

SPECIMEN COLLECTION
These specimens are obtained in surgery. A lighted optical instrument, the bronchoscope, is used to examine the tracheobronchial tree and can help detect obstructions, pneumonia, carcinoma, hemoptysis, foreign bodies, or abscesses. These instruments can be equipped with suction catheters, brushes, or biopsy attachments for specimen collection. For washings, 20–60 mL of saline are infused and then recollected by aspiration. Bronchial washings obtain material from the more proximal areas of the bronchoalveolar tree. The BAL is used at more distal sites to retrieve material more representative of the alveoli and to obtain more cellular alveolar material.


DISEASE CORRELATIONS
These specimens are obtained for routine bacterial, fungal, and mycobacterial examination and culture, and for cytological studies. Cell counts are performed with a hemacytometer.

As with most body fluids, cytocentrifugation gives the best cellular preparations for staining for cellular differentiation. Cytological and microbiological stains are used on these specimens. Cells seen in bronchial washings and BAL include macrophages, lymphocytes, neutrophils, eosinophils, ciliated columnar epithelial cells, and squamous epithelial cells. A variety of microorganisms, bacteria, fungi, and mycobacteria, can be found in these samples in lower respiratory tract infections.

The BAL is particularly helpful for immunocompro- mised patients to look for Pneumocystis jiroveci or Aspergillus species or other fungi that are found in the alveolar cellular layer. Immunocompromised hosts are susceptible to many organisms that normally do not cause infection as well as being susceptible to the generally recognized pathogens of the lower respiratory tract.

TESTING
Culture, stains, wet mounts, and molecular tests are used to look for infectious organisms. A variety of histological stains can also be performed in the pathology laboratory to find these organisms as well.


Wet Mounts, Calcofluor White Stain, and Other Stains

Wet mounts are useful to detect fungal elements and cells that may be present in these samples. Stains can be used along with wet mounts or stains can be used on smears.

A technique that is particularly helpful to detect P. jiroveci, C. albicans, and other fungi is the calcofluor white wet preparation. The calcofluor white stain is a fluorescent

C. albicans with germ tube development in a calcofluor white preparation
Figure 14-8. C. albicans with germ tube development in a calcofluor white preparation


stain that has increased sensitivity in the detection of these organisms and detection of fungi. It can be combined with KOH to dissolve cells in order to see fungal structures more easily. Histologic stains such as Gomori methenamine silver are also helpful in detecting these organisms (Figs.14-9–14-10).

OTHER BODY FLUIDS

A variety of other body fluids are tested less frequently but still yield important clinical information. For example, saliva is increasingly used in human immunodeficiency virus testing. Just about any body fluid can be received in cytology or microbiology for analysis for the cellular changes of malignancy or for microbial infections

Cell block preparation of BAL showing cysts of P. jiroveci, GMS-P stain
Figure 14-9. Cell block preparation of BAL showing cysts of P. jiroveci, GMS-P stain (1000x).



Figure 14-10. Cell block preparation of BAL showing cysts of P. jiroveci, GMS-P stain (1000x).


REFERENCES 
Lillian A. Mundt and Kristy Shanahan, Graff's Textbook of Urinalysis and Body Fluids, Second Edition 2011





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