3 - BACTERIOLOGY: Gram Negative Bacteria 2025

Neisseria meningitidis

Gram negative diplococci that can ferment glucose and maltose

Waterhouse-Friedrichsen syndrome

Most severe form of meningococcemia which leads to bilateral hemorrhagic destruction of the adrenal glands

None that’s why it is not significant

Function of the capsule of Neisseria gonorrhea

Complement 5-9 deficiency

Deficiency of what component of the immune system predisposes a patient to Neisseria infection

Brudzinski’s sign

A 12-year-old male presents with flexion of legs and thighs with passive flexion of neck. What sign of meningeal irritation is this?

Penicillin G

Treatment of choice for Meningococcemia

A, C,Y and W-135

Prevention is better than cure that’s why vaccine against N. meningitidisis available. This vaccine contains capsular polysaccharide of what strains of N. meningitidis?

Lipooligosaccharide

A 19-year-old male came in due to septic arthritis. Gram stain of the synovial fluid showed gram negative diplococci. Toxicity of this organism is mostly due to what toxin?

Neisseria gonorrhea

Most common cause of urethritis and PID. Also the most common cause of septic arthritis in sexually active adults.

Ceftriaxone + Doxycycline

Treatment of choice for infections with N. gonorrhea

Nucleic acid amplification test (NAAT)

Gold standard for the diagnosis of gonorrheal infection

Haemophilus influenzae type b

A gram-negative rod with polyribitol phosphate capsule that can be cultured using chocolate agar. It causes epiglottitis.

X (Hemin) and V (NAD)

H. influenzae requires what factors to be able to grow?

Staphylococcus aureus

Satellite phenomenon of H. influenzae can be observed around colonies of what bacteria?

Catarrhal phase

What phase of pertussis infection are antibiotics most effective?

-Causes ADP ribosylation

-Activates G protein leading to increase cAMP

Mechanism of action of pertussis toxin

Legionella pneumophila

A 36yr old male was admitted due to pneumonia associated with non-bloody diarrhea and hyponatremia. What is the most likely causative agent?

Legionella pneumophila

Causative agent of Pontiac fever

Charcoal yeast extract agar

Agar used for the isolation of Legionella pneumophilla

Escherichia coli

Most common cause of urinary tract infection

Enterotoxigenic E. coli

A 28 year old male who went to travel to a local region in the Philippines went to the ER due to persistent watery diarrhea. Culture on EMB agar showed greenish metallic sheen. What strain of this bacteria is most likely the culprit?

E. coli 0157:H7

A 40yr old male was brought to the ER due to persistent bloody diarrhea after eating hamburger which he bought from the street. He was noted to have hemolytic anemia, thrombocytopenia and uremia. What is the most likely causative agent?

E. coli

What is the facultative organism that is predominant in the large intestine and can be used as an index of fecal contamination of a water sample?

Bacteroides fragilis

What is the most predominant organism of the large intestine? This organism is considered as anaerobic.

Widal test

Tests used to detect antibodies against Salmonella in patient’s serum

Vi antigen

Capsular antigens for bacteria are labeled as K antigen except for Salmonella which is labeled as _________.

Patients with sickle cell anemia

Who are at greater risk of developing osteomyelitis due to S. cholerasuis?

Bone marrow culture

The most sensitive diagnostic modality for Salmonella infections

Gallbladder

In cases of chronic carriers of Salmonella, the microorganism can usually be isolated at ______.

Shigella dysenteriae

A 30yr old male was brought to the ER due to bloody-diarrhea, abdominal pain and confusion. Culture of the stool showed non-lactose fermenting gram negative rods which are non-motile and does not produce H2S. What is the causative agent?

ADP ribosylation leading to stimulated Gs protein which increases cAMP

Mode of action of Subunit A of Cholera toxin

Thiosulfate Citrate Bile Salt Sucrose agar

Agar of choice for the isolation of Vibrio cholerae

Fluid and electrolyte replacement

Treatment of choice for Cholera

Vibrio cholerae 01 biotype El Tor

The strain of Vibrio that led to a pandemic of Cholera in the past is _________

Vibrio vulnificus

A 30-year-old male came to the ER due to watery diarrhea associated with abdominal cramps, vomiting, and low grade fever. Upon taking detailed history, it was noted that symptoms develop after eating raw seafood. What is the causative agent?

Campylobacter jejuni

Small, motile, non-spore forming curved microaerophilic bacilli that is associated with GBS

Skirrow agar

Agar of choice for C. jejuni

Urethritis, Uveitis and Arthritis

Triad of Reiter Syndrome

Amoxicillin + Clarithromycin + PPI

Triple therapy for H. pylori includes:

Proteus mirabilis

Klebsiella pneumoniae

Helicobacter pylori

Ureaplasma urealyticum

Bacteria's that are considered as Urease positive

Gastric carcinoma

MALT lymphomas

Cancers that are associated with H. pylori

Klebsiella pneumoniae

A 59-year-old alcoholic male came to the ER due to productive cough with mucoid bloody sputum. Gram stain revealed large capsules. What is the most likely etiologic agent?

Magnesium-ammonium-phosphate

Struvite stones formed by Proteus mirabilis are mainly composed of ______________.

Proteus mirabilis

A 29-year-old female came in due to recurrent urinary tract infection. Diagnostics revealed she has nephrolithiasis. Culture was done which showed gram negative rods urease positive with swarming motility. What is the most likely etiologic agent?

Pseudomonas aeruginosa

Soft tissue infection on burn patients is most likely caused by?

Tissue necrosis and inactivation of elongation factor 2

Mechanism of action of exotoxin A of P. aeruginosa

Acinetobacter baumanii

Pleomorphic aerobic gram-negative bacillus that is multi-drug resistant and is commonly isolated from hospital environment and hospitalized patients

Rabbits

Most common reservoir of F. tularensis

Yersinia pestis

A 30-year-old male came in due to sudden onset of fever, chills and multiple painful lymph nodes. Gram stain showed a gram-negative rod with safety appearance

Oriental rat flea (Xenopsylla cheopis)

What is the vector for the transmission of Y. pestis

Pasteurella multocida

A 28 year old male develops cellulitis after he was bitten by his neighbor's cat. What is the most likely dominant organism involved in the infection?

Bartonella henselae

Causative agent of cat scratch fever is

Eikenella corrodens

A gram-negative rod that causes skin and bone infections associated with human bites.

Treponema carateum

Causative agent for the disease called Pinta

VDRL

What test is useful for CNS syphilis?

Condyloma Lata

Which of the following can be seen in secondary syphilis?

Vasa vasorum

What part is usually affected in aortitis caused by syphilis?

RPR, VDRL

Which test can be used for monitoring of treatment of syphilis and can also be used a test of cure?

Jaundice, bleeding and uremia

Triad of Weil Syndrome

Jarisch-Herxheimer reaction

Influenza like symptoms few hours after receiving Penicillin for treatment of Leptospirosis is called _______.

Doxycycline

Treatment of choice for mild leptospirosis

Snow-flake lesions

Characteristic finding in chest Xray if there is pulmonary involvement in a patient diagnosed with leptospirosis

Borrelia burgdorferi

Largest medically important spirochete that is the causative agent of Lyme disease

Erythema chronicum migrans

Characteristic dermatologic finding in patients on stage 1 of Lyme disease

Cord factor

Most important virulence factor of Mycobacteria

Lymph node

(Scrofula)

The most common site of extrapulmonary tuberculosis

Choroidal tubercles

Pathognomonic finding of Miliary tuberculosis

Interferon Gamma Release Assays

Diagnostic tool for latent tuberculosis that is not affected by prior BCG vaccination or infection with nontuberculous mycobacteria

rpoB gene mutation

Mechanism of resistance against rifampicin

Delayed (Type 4)

Tuberculin skin test demonstrates what type of hypersensitivity reaction?

Mouse foot pad or in the armadillo

M. leprae can be cultured using

Tuberculoid Leprosy

Lepromin skin test would be positive on_____.

Thalidomide

Treatment of choice for Erythema nodosum leprosum

Mycoplasma pneumoniae

Most common cause of atypical pneumonia. This is bacteria has sterol in membrane and can cause for the body to form cold agglutinins.

Halberstadter-Prowazek inclusion

Round to oval cytoplasmic inclusion bodies near the nuclei of conjunctival epithelial cells in trachoma

Chlamydia trachomatis types L1-L3

A 22 year old sexually active female presented with unilateral painful inguinal lymphadenopathy. Extensive enlargement of chains of inguinal nodes are noted above and below the inguinal ligament. What is the most likely etiologic agent?

Doxycycline 100mg BID for 7 days

Treatment for Chlamydia

Types A-C

Types of C. trachomatis associated with trachoma

Types D-K

Types of C. trachomatis that causes genital tract infections and is associated with Reiter syndrome

Types L1-L3

Types of C. trachomatis associated with Lymphogranuloma venereum

Q fever (caused by Coxiella burnetii)

A type of rickettsial disease that does not present with fever or rash, has a chronic onset and has the highest mortality

Doxycycline

Treatment of choice for Rickettsial infections

Sulfonamides

Drug that is contraindicated in patients with Rickettsial infection because they stimulate Rickettsial growth

Bacterial Vaginosis

A 40-year-old female with grayish vaginal discharge where wet mount showed stippled epithelial cells being covered by microorganism. The condition most likely described is_______.

Haemophilus ducreyi

A gram-negative rod that is associated with painful genital ulcers.