Microbiology Lecture Exam Flashcards

50 Question and Answer style flashcards designed for reviewing key microbiology concepts, diagnostic tests, pathogen characteristics, and clinical findings.

What are the motility and biochemical test results for pathogens causing Enteric fever?

They are motile, gram-negative bacilli that test catalase positive and oxidase negative.

Which non-specific serological test detects Rickettsial antibodies against Proteus OX 19, OX 2, and OX K antigens?

Weil-Felix test.

Which biphasic culture medium is used for isolating Brucella from blood specimens?

Castaneda's biphasic media (BHI broth/agar).

How soon after infection can the p24 antigen be detected as a confirmatory marker for HIV?

After 12-26 days of infection.

Which nonstructural antigen in blood is detected via ELISA and ICT for the diagnosis of Dengue virus?

NS1 (nonstructural antigen 1).

What characteristic ring and gametocyte forms are seen inside RBCs on a thin blood smear in Plasmodium falciparum malaria?

Multiple ring forms, accole forms, headphone-shaped ring forms, and crescent (banana) shaped gametocytes.

Which culture media are used to detect promastigotes in Visceral Leishmaniasis?

NNN medium and Schneider's liquid medium.

How do the tail tips of microfilariae differ between Wuchereria bancrofti and Brugia malayi on blood smears?

W. bancrofti microfilariae have a pointed tail tip free of nuclei, whereas B. malayi microfilariae have a blunt tail tip with nuclei extending up to the tip.

Which rapid morphologic test yields a positive result specifically for identifying Candida albicans?

Germ tube test.

What classic morphology is exhibited by Leptospira under dark ground or phase contrast microscopy?

Spirally coiled bacilli (tightly and regularly coiled) with characteristic hooked ends like an umbrella handle.

What special culture medium is required for the isolation of Borrelia burgdorferi in Lyme disease?

BSK medium (Barbour-Stoenner-Kelly).

Which enterotoxin serotype of Staphylococcus aureus is most commonly responsible for food poisoning?

Type A.

What is the characteristic appearance of Shigella colonies grown on highly selective XLD agar?

Red colonies without a black center.

What characteristic colony appearance does Yersinia produce on CIN agar within 24 hours?

Typical dark red bull's eye appearing colonies.

What type of motility is demonstrated by Vibrio cholerae in a hanging drop preparation?

Darting motility.

What noninvasive test measures labeled $CO_2$ in breath samples to detect active Helicobacter pylori infection?

Urea breath test (using urea labeled with nonradioactive $^{13}C$).

What are the morphological features of Entamoeba histolytica cysts on stool microscopy?

Round shape, measuring 1-4 nuclei.

Which test is currently considered the gold standard for diagnosing cryptosporidiosis?

Direct fluorescent antibody (DFA) staining using fluorescent-labeled monoclonal antibody directed against cyst wall antigens.

How does the Entero-test (String Test) sample the duodenum to detect Giardia trophozoites?

The patient swallows a weighted gelatin capsule attached to a thread; the dissolved capsule releases the thread into the duodenum, where it collects duodenal fluid and trophozoites for microscopic detection.

What staining property distinguishes eggs of Taenia saginata from eggs of Taenia solium?

Eggs of T. saginata are acid fast, whereas eggs of T. solium are non-acid fast.

What are the dimensions and key structural feature of Schistosoma mansoni eggs seen in stool microscopy?

They measure $114-180\,\mu m \times 45-73\,\mu m$, are non-operculated, and possess a characteristic lateral spine.

Why is floatation concentration not recommended for detecting Ascaris unfertilized eggs in stool?

Unfertilized eggs of Ascaris do not float in saturated salt solution.

What are the characteristic features of a hookworm egg observed on a saline mount?

Oval-shaped, measures $60 \times 40\,\mu m$, non-bile stained, surrounded by a thin eggshell, with a clear space between the shell and a segmented ovum containing 4-32 blastomeres.

Which antigenic marker is the first to appear in the serum during a Hepatitis B infection?

HBsAg.

Why do amoebic liver abscesses appear as cold lesions on nuclear imaging, in contrast to pyogenic liver abscesses?

Amoebic liver abscesses contain necrotic hepatocytes without leukocytes (cold lesions), whereas pyogenic liver abscesses contain leukocytes (hot lesions).

What specific ultrasonographic finding is characteristic of hydatid cyst disease?

Water lily sign.

What colony appearance and hemolytic property does Staphylococcus aureus demonstrate on blood agar?

Golden yellow pigmented colonies with a narrow zone of $\beta$-hemolysis.

What are the biochemical characteristics that define Streptococcus pyogenes (Group A)?

Catalase negative, bacitracin sensitive, and CAMP test negative.

What diagnostic phenomenon is observed around the streak line of Clostridium perfringens on egg yolk agar in Nagler's reaction?

Opalescence.

What distinct growth pattern is produced by Bacillus anthracis in gelatin stab agar?

Inverted fir tree appearance growth.

What concentration of sulfuric acid is used for decolorization in the Ziehl-Neelsen staining of Mycobacterium leprae?

5% sulfuric acid.

What histopathological appearance is observed in tissue sections stained with Gomori's stain for actinomycosis?

Sun-ray appearance (eosinophilic clubs surrounding basophilic filaments).

What specific subspecies of Treponema pallidum is the causative agent of Yaws?

Treponema pallidum subspecies pertenue.

What type of inclusion bodies are seen in skin scrapings of Molluscum contagiosum lesions?

Molluscum bodies (intracytoplasmic eosinophilic inclusions).

What cytological finding on a Tzanck preparation is diagnostic for Herpes Simplex Virus (HSV) infection?

Multinucleated giant cells (Tzanck cells) and Lipschultz inclusion bodies.

Which viral strain is utilized in the live attenuated Varicella-Zoster Virus (VZV) vaccine?

Oka strain.

Which vaccine strains are currently used to manufacture the live attenuated measles vaccine?

Schwartz strain, Edmonston-Zagreb strain, and Moraten strain.

What are the conidial characteristics of Trichophyton species upon microscopic culture examination?

Abundant small unicellular microconidia and rare, thin-walled, smooth, pencil-shaped macroconidia.

What serological marker is measured to retrospectively diagnose streptococcal pharyngitis or establish rheumatic fever?

Anti-streptolysin O (ASO) titer.

What staining technique is used to reveal green bacilli with bluish-black metachromatic granules in Corynebacterium diphtheriae?

Albert's stain.

What morphological arrangement is characteristic of Streptococcus pneumoniae on direct microscopic smear examination?

Lanceolate-shaped gram-positive diplococci surrounded by a clear halo (capsule).

What culture phenomenon occurs when Haemophilus influenzae is grown on blood agar near a streak line of Staphylococcus aureus?

Satellitism.

Which automated molecular method provides identification of Mycobacterium tuberculosis and detects rifampicin resistance within 2 hours?

CBNAAT (GeneXpert) or Truenat.

What colony morphology is exhibited by Bordetella pertussis on Regan-Lowe medium or Bordet-Gengou agar?

Mercury drops or bisected pearls colony appearance.

Which selective medium is used to isolate Burkholderia pseudomallei, producing wrinkled purple colonies?

Ashdown's medium.

What live attenuated strain is universally recommended and used in mumps vaccines worldwide?

Jeryl Lynn strain.

What heterophile agglutination test uses sheep RBCs to diagnose Epstein-Barr Virus (EBV) infectious mononucleosis?

Paul-Bunnell test.

What is the preferred staining method for demonstrating Pneumocystis jirovecii cysts in lung tissue specimens?

Gomori's methenamine silver (GMS) staining.

What microscopic feature is characteristic of Clostridium tetani on Gram stain?

Gram-positive bacilli with terminal and round spores giving a drumstick appearance.

What non-treponemal standard tests are commonly utilized to detect reagin antibodies in syphilis screening?

VDRL (Venereal Disease Research Laboratory) test, RPR (Rapid Plasma Reagin), TRUST, and USR.