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MicroB > Gram Negative Bacteria > Flashcards

Gram Negative Bacteria Flashcards

1
Q

Outline Neisseria meningitidis

A

GNDC
Polysaccharide capsule with groups A,B,C,Y, W135 (vaccine making except B)

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2
Q

Outline disease caused by meningococcus

A

Meningococcaemia - FULMINANT sepsis
Meningitis

Rashes that start as macular pink dots and progress into petechiae, purpura, ecchymoses. The rashes in later stages are non-blanching Conjunctival petechiae too!
Skin necrosis can also occur

Waterhouse-Friedrichsen Syndrome (Haemorrhagic adrenalitis)

Others - Pneumonia, urethritis, pericarditis, endocarditis, conjunctivitis, arthritis

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3
Q

Where does meningococcus have the highest incidence?

A

Young children with streptococcus pneumoniae / haemophilius influenzae

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4
Q

Notable meningococcus outbreaks?

A

Hajj pilgrims (need vaccine proof!)
Meningitis belt in Africa

Transmitted by respiratory droplets and carried in the nasopharynx!

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5
Q

How is meningococcus diagnosed?

A

BLOOD CULTURE!

Found in CSF, throa swab, joint fluid

Remember to take the sample BEFORE giving empirical therapy because they are susceptible to antibiotics!

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6
Q

How do you treat meningococcus?

A

Ceftriaxone as a first-line treatment. It also clears the nasal carriage!

Benzylpencillin as multi-day dosing

Surgery to remove dead / dying tissue

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7
Q

What do streptococcus pneumoniae and neisseria meningitidis have in common?

A

Both bacteria have capsules!
You should be worried in functional / anatomical asplenic pts

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8
Q

Prevention of meningococcus outbreaks?

A

Chemoprophylaxis - Rifampicin, ceftriaxone, ciprofloxacin

Vaccination:
Polysaccharide vaccine for infants

Conjugated (polysaccharide + protein) subdivided into Quadrivalent (A,C,Y,W135) and Monovalent (country-specific)

Protein based that works for group B!!! Uses a combination of SUBCAPSULAR proteins

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9
Q

Outline neisseria gonorrhoeae

A

LPS endotoxin in outer cell membrane

NO capsule, lots of antigenic variation in the fimbriae, opa

Causes gonorrhoea and has problems with AMR

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10
Q

Outline gonorrhoea in males, incl. diagnosis

A

Urethritis coupled with discharge and dysuria (painful urination). Epididymitis

Gram stain from the male urethra can be taken. GNDC under the microscope is diagnostic enough! Recall that you can’t do this as easily for females because of the background natural flora

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11
Q

Outline gonorrhoea in female patients

A

Endocervical infection that leads to vaginal discharge, dysuria, intermenstrual bleeding

Salpingitis that may lead to PID. This may cause infertility!

Fitz-Hugh-Curtis Syndrome => Perihepatitis (infection tracks up the RIGHT paracolic gutter and inflames the liver capsule

Some women may have gonorrhoea but be asymptomatic, and yet go on to become infertile

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12
Q

Outline common gonorrhoea symptoms

A

Proctitis from receptive anal sex

Conjunctivitis:
Ophthalmia neonatorum (pus-y discharge from eyes that can also be caused by other STIs like chlamydia so if mom has NG, test her for others!)

Disseminated gonococcal infection (DGI)

Gonococcal arhtritis (septic arthritis)

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13
Q

Outline the vaccine for gonorrhoea

A

There IS NO NEISSERIA GONORRHOEAE VACCINE

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14
Q

What is the main test used in Neisseria gonorrhoea?

A

Nucleic Acid Test - Urine samples! Easy to collect

Males can use a urethral swab, females can use an endocervical swab
Throat / rectal swabs can be done

Gram stain is ok in a male urethral swab, but not vaginal swab in women. Joint fluid can be collected too

To grow in culture, you NEED CHOCOLATE AGAR (Modified Thayer-Martin medium)

Bacteria can be identified with mass spectrometry

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15
Q

Treatment of gonorrhoea?

A

Rising penicillin and ciprofloxacin resistance

IM ceftriaxone +_ oral Azithromcyin !

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16
Q

What is moraxella catarrhalis?

A

Opportunisitc GNC, hits people with comorbs, results in chest infections

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17
Q

Treatment for moraxella catarrhalis

A

Coamoxiclav

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18
Q

Give 4 examples of enterobacterales

A

Eschirichia coli
Salmonella enterica
Shigella genus
Klebsiella pneumoniae

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19
Q

What is a common source of enterobacterales transmission?

A

Spreads through the feces because these bacteria are commonly found in the gut

They used to be called enterobacteria

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20
Q

How are serotypes defined in enterobacterales?

A

Somatic “O”
Flagellar “H”

Oxidase negative

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21
Q

What kind of agar enterobacterales grow on?

A

MacConkey agar - Grow as lactose fermenting (turn pink) or non-lactose fermenting (not pink) colonies

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22
Q

Enterobacterales is oxidase _

A

Negative! Pseudomonas is oxidase positive

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23
Q

What are the top 3 causes of bacteraemia

A

Streptococcus pneumoniae
Staphylococcus aureus
Escherichia coli

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24
Q

What diseases caused by E. Coli?

A

UTI caused by uropathogenic EC (UPEC). Increased susceptibility in congenital UG abnormalities, stones / BPH that blocks urinary flow, cystoceles, tumours, catheters, urethral valve formation, sexual activity in women due to their shorter urethras

Biliary infection. EC can track through biliary tree because of bile duct obstruction, tumours, even worms. Gut-related sepsis may occur

Neonatal septicaemia, meningitis, especially when the baby is exposed to faecal matter during delivery

Diarrhoea because of different EC strains that give different toxins (Most common bacterial cause is Enterotoxigenic EC, ETEC)

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25
Q

Name different strains of EC that cause different patterns of disease:

A

Enterotoxigenic EC - Infant gastroenteritis that leads to severe diarrhoea (dehydration and death). ORS really important!!! Spoonful of salt, handful sugar, jug of water

Enterohaemorrhagic (EHEC), Verocytotoxin (VTEC), Shigatoxin (STEC):
Low infectious dose
Causes Haemolytic Uraemia Syndrome (HUS) because of BV damage and platelet aggregation > Damage to glomerulus leading to renal failure and death

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26
Q

What are the two main serotypes of Salmonella enterica?

A

O-9, H-g = Salmonella enteritidis
O-9, H-d = Salmonella typhi

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27
Q

What is the main disease caused by Salmonella enterica?

A

Typhoid fever, caused by S. typhi and S. paratyphi A / B / C. Life-threatening condition causing constipation adn diarrhoea in the early stages due to Peyer’s patches infection

Transient ‘rose spots’ form in early infection and are often missed

Gastroenteritis is caused by most salmonella species and is the commonest salmonella presentation

Salmonella may also cause UTI, mycotic aneurysm

If immunocompromised, you can get bacteraemia even from non-typhoidal types

(Note - Every salmonella species that doesn’t cause typhoid fever is grouped as non-typhoidal salmonella)

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28
Q

What is the mode of transmission for Salmonella?

A

S. Typhi is always from another human, i.e. infected FnB workers / dirty water

NTS is usually poultry / other animal sources

Not very common in Singapore so ask about travel history

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29
Q

What is the go-to diagnostic for HIV?

A

Blood culture!

Stool isn’t very helpful and urine takes a while to become positive (may give a false negative)

A Widal test can be used but it is not optimal

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30
Q

What is the Widal test?

A

Checks if your body has made antibodies against Salmonella

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31
Q

Outline the vaccines for Salmonella

A

Prevention is best!

Conjugated vaccine is in the childhood schedule

Others:
Ty21(a) given orally - LIVE VACCINE. CAREFUL WITH IMMUNOCOMPROMISED

Vi (injectable)

Conjugated vaccine was introduced in 2018

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32
Q

Treatment of Salmonella?

A

Ceftriaxone / Azitrhomycin / Ciprofloxacin if salmonella is sensitive; Particularly for typhoid

Oral or IV ampicillin / amoxicillin, but rising BLase-mediated resistance (now >50%)

Fosfomycin and Nitrofurantoin given orally for a simple UTI

Co-amoxiclav is helpful to give orally / IV

Pip-tazo given intravenously

IV ceftriaxone and other cephalosporins, useful in CAI. HAI are a little harder because 30-70% of cases express ESBLase-mediated resistance

Oral / IV Co-trimoxazole (trimethoprim, sulphamethoxazole)

Aminoglycosides such as gentamicin and amikacin given parenterally.

Ciprofloxacins and other fluoroquinolones can be given Orally / IV but 50-70% resistance now

Imipenem / Meropenem (IV) - V broad spectrum but rising resistance

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33
Q

Outline the shigella spp.

A

Such as Shigella dysenteriae, Shigella flexneri, boydii, sonnei

Low infectious dose

Invades epithelial cells and produces toxins:
Causes dysentery, blood and mucus found in stools.

Virulence factors trasnmitted via plasmids and bacteriophages

Can induce / inhibit apoptosis by remodelling the host cytoskeleton!!!

34
Q

Outline Klebsiella pneumoniae

A

Type of Enterobacterales.
Very commonly CAI and invasive. If HAI, it is multi-resistant and causes UTI / wound infections / biliary issues / lung issues

Hyper-viscoid strains of the species exist and generally Klebsiella is quite virulent.

It causes UTI but not as commonly as in EC

Causes:
Friedlander’s pneumonia (sputum with a lot of GNB!)
Liver abscess

QUITE SUSCEPTIBLE to Antibiotics!

35
Q

What genus do you think of when you see renal stones?

A

PROTEUS! Proteus spp. such as proteus mirabilis, proteus vulgaris

It is a common cause of UTI associated with renal stones

36
Q

What are pseudomonas aeruginosa?

A

Gram negative Rods

Big cause of opportunistic infections in HAI (hospitalised / immunocompromised - THINK NEUTROPENIA!!!!!!!! As well as cancer, burn victims, ICU pts).

It also hits people who have been on prolonged antibiotics because of reduced colonisation resistance (UTI, Cystic Fibrosis, Bronchiectasis, Biliary infections)

CAI doesn’t usually happen except for contact-lens associated keratitis

PAE makes up 3-5% of all bacteraemia

Grows easily in culture

37
Q

What is keratitis?

A

Inflammation of the cornea because of infection of the eye:
Improper contact lens care (cleaning with tap water / homemade solution)
Swimming with lenses in

Typically caused by PAE

38
Q

What is pseudomonas keratitis?

A

PAE-induced keratitis that can occur if the wrong antibiotic is used

In severe cases, corneal transplant becomes necessary / loss of eye with enucleation

39
Q

Outline the disease caused by PAE

A

Fluorescent wound!

Pneumonia, UTI, SSTI that could develop into septicaemia

Infection also occurs at the site of entry (nail-bed)

Nasty SSTIs -> Ecthyma, Malignant (not tumour, just very bad) otitis externa

40
Q

Treatment of PAE?
What drugs is it resistant to?

A

Resistance to broad spectrum antibiotics, co-amoxiclav, ceftriaxone

Give piperacillin + tazobactam! (Pip-tazo)

41
Q

Diagnosis of pseudomonas?

A

Gram stain, oxidase positive

Conduct biochemical tests and mass spectroscopy

42
Q

What bacteria develops in wards where carbap enem usage is heavy?

A

Stenotrophomonas maltophilia

43
Q

Outline Stenotrophomonas maltophilia

A

MDR-GNR that is usually HAI

Naturally resistant to carbapenems (carbapenemase) and hence develops in wards with heavy carbapenem usage

Treated with co-trimoxazole, levofloxacin

44
Q

Treatment of stenotrophomonas maltophilia?

A

Co-trimoxazole, lefofloxacin

45
Q

What bacteria is commonly linked to soil?

A

Burkholderia pseudomallei

Killed our gorillas :(

Aerosolised with rainfall

Causes melioidosis

46
Q

What demographic does Burkholderia pseudomallei target?

A

Immunocompromised! 40-70% of cases have DM

Pts whose jobs require them to be exposed to soil regularly

Also - Alcoholism, chronic renal disease, chronic lung disease, thalassaemia, non-HIV immunosuppression

47
Q

How long is the incubation period for Burkholderia pseudomallei?

A

Days to years and even decades, until immunosenescence is reached

48
Q

Disease caused by Burkholderia pseudomallei

A

Melioidosis !

Septicaemia, acute / chronic pneumonia, acute / chronic abscesses

Easy to misdiagnose melioidosis as TB !

Affects almost any organ system, thereby making it difficult to diagnose

49
Q

Diagnosis of Burkholderia pseudomallei?

A

Culture, serology

50
Q

What is the treatment for Burkholderia pseudomallei?

A

IV Ceftazidime or imipenem for minimally 2 weeks

> 6 months of oral doxycyclin, augmentin, chloramphenicol, co-trimoxazole

Drain any abscesses that come about

These measures are taken to prevent reinfection

51
Q

What is Burkholderia cepacia?

A

Rare in healthy people but very resistant. Emerges after prolonged antibiotic usage and infamously hits patients with CF! Think about cepacia when you see CF

Poor prognosis, however. Pts are usually shunned / isolated if they have it

52
Q

Give examples of bacteria that MUST NOTIFY MOH

A

Corynebacterium diphtheriae

Burkholderia pseudomallei

Vibrio cholerae

53
Q

What are the two classifications of Vibrio?

A

Cholera-causing Vibrio spp. (produces the cholera toxin)

Non-cholera vibrios (including strains of V. cholerae that don’t produce the toxin)

54
Q

How is vibrio cholerae spread?

A

Water, raw seafood
Humans are the only known host

55
Q

Outline the cholera toxin

A

“A” subunit that causes the diarrhoeal disease (prevents Na and HCO3 uptake and hyper-secretes Cl and HCO3)

“B” subunit that binds to the small intestine cell. This subunit is also immunogenic!

Toxin is spread via a bacteriophage

Type O-1 (somatic antigen 1) makes up 98% of epidemic cholera

56
Q

Give two variants of Vibrio

A

Vibrio parahaemolyticus - Gastroenteritis (nausea and vomiting within 24h), SSTI

Vibrio vulnificus - SSTI, fasciitis, septicaemia in immunocompromised, wound infection

Both obtained from raw seafood and seawater

57
Q

What are the virulence factors of vibrio cholerae?

A
  • It vibrates a lot
  • It has the cholera toxin
58
Q

How is VC diagnosed?

A

Curved Gram negative Rods that appear yellow on the special medium TCBS

Thiosulphate Citrate Bile Salts and Sucrose

59
Q

Disease caused by cholerae?

A

CT results in devastating diarrhoea and enteritis that leads to severe dehydration. At some point, the stool just appears like ricewater

ORS is very important

60
Q

Treatment of Vibrio cholerae?

A

Oral vaccine - Inactivated V. cholerae O-1 and toxin B subunit (recall that this is immunogenic!)

61
Q

What bacteria forms wrinkled colonies?

A

Burkholderia pseudomallei

62
Q

Vibrio cholerae is grown in _

A

TCBS - Thiosulphate Citrate Bile Salts Sucrose agar

63
Q

What does “fastidious” mean?

A

Bacteria that have specific nutritional requirements and can be challenging to grow

64
Q

Does Haemophilus influenzae cause influenza?

A

NO, though it may lead to other things that do

65
Q

Does Haemophilus influenzae cause influenza?

A

NO, though it may lead to other things that do

66
Q

Outline Haemophilius influenzae

A

Gram negative
Does not actually cause influenza, but causes invasive disease
Has encapsulated strains which are more virulent; Capsule types a, b, c, d, e, f (Differ by antigens. Recall that H. influenzae serotype B is the most important)
Non-encapsulated Hinf are carried in 65% of infants

67
Q

In present day, most of the disease is caused by what kind of H. influenzae?

A

Non-encapsulated because we vaccinate against Hib so much

Invasive - Neonatal infections and pneumonia

Non-invasive - Sinusitis, conjunctivitis, otitis media, exacerbation of COPD

68
Q

Treatment of Hinf?

A

Hib vaccinations are routine globally

HAI -> Ceftriaxone and co-amoxiclav because of BLase Inhibitors

CAI -> Amoxicillin is ok and good to give anyway because the symptoms resemble Streptococcus pneumoniae

69
Q

What do you think when you see the HACEK group?

A

ENDOCARDITIS! Slow-growing, fastidious GNR

H parainfluenzae, H aphrophilus
Aggregatibacter
Cardiobacterium hominis
Eikenella corrodens
Kingella kingae

70
Q

Whooping cough is caused by what bacteria?

A

Bordetella pertussis

90% household contact infection,
50-80% school contact

71
Q

Outline Bordetella pertussis diagnosis

A

PCR!!!!

Culture using NP sample (go deep, difficult to get) => Gives mercury droplet-like colonies

72
Q

Treatment of B. pertussis?

A

Vaccines:
Whole cell vaccines, very reactogenic

Acellular ‘aP’ vaccines (TdaP, DTaP)

Cocoon strategy! Vaccinate pregnant mom and family

73
Q

Brucella spp. outline

A

Can be used to explain PUO
Osteomyelitis and joint infection
Maltese fever also assoc (Brucella melitensis)

Diagnose with a blood culture adn serology

B. suis from pigs
B. abortus from cattle

Untreated milk, i.e. camels milk

74
Q

Outline bartonella spp.

A

Causes what we know as cat scratch disease

Sandflies, lice, fleas, etc. directly trasnmit or can infect cats.

Bacillary angiomatosis, Bacillary peliosis can occur

Painful, persistent regional lymphadenopathy

LEADS TO TRENCH FEVER - JRR TOLKIEN

75
Q

Outline Yersinia spp.

A

Y. pestis is a cause of the bubonic plague because it is spread by fleas via rats and other small mammals

“Bubo” = Local lymph node infection.

Sub-group of enterobacterales!

Other species like Y. enterocolitica and Y. pseudotuberculosis can cause GE, ileitis, mesenteric lymphadenitis, septicaemia

Antibiotics are enough for treatment

76
Q

What bacteria is associated with cat / dog bites?
Treatment ?

A

Pasteurella multicoda

Infecitons tend to be polymicrobial and include anaerobes + other bacteria too

Co-amoxiclav

77
Q

Outline Legionella spp.

A

Most promnient is Legionella pneumophila. Infects typically water distribution equipment - Taps, shower heasd, water fountains. Medical equipment too

Immunofluorescent under the microscope

78
Q

Disease caused by legionella pneumophila

A

Legionnaire’s disease - Pneumonia, high mortality

Pontiac fever that is less severe than above

79
Q

Diagnosis for legionella spp.?

A

Urine antigen test (specifically for L pneumophila serogroup 1)

Bronchoalveolar Lavage (BAL) culture

Immunofluorescent stain

Nucleic Acid Test

80
Q

Outline the acinetobacter spp.

A

Commonest species is acinetobacter baumannii

BIG problem if it arises in the ICU. It tends to do that for burn victims as well as cause pneumonia

RESISTANT TO ALMOST ALL ANTIBIOTICS

Not fastidious, HAI, IMmunocompromised

81
Q

What are the criteria for diagnosing bacillary vaginosis?

A

It is a case of vaginal dysbiosis, usually with unknown aetiology.
Lactobacillus spp. that produced lactic acid in healthy vagina are now replaced by gardnerella vaginalis, prevotella spp., mobiluncus spp., etc.

May decrease fertility, increase risk of other STIs

Actual crtieria:
Amsel criteria - Thin vaginal discharge of pH > 4.5, Amine smell // Fish smell because of KOH (“Whiff test”)

Nugent criteria - CLUE CELLS IN A MICROSCOPY OF THE VAGINAL SWAB

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