Download MBBS General Medicine PPT 3 Gn Infections Part I Lecture Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) General Medicine 2022 PPT 3 Gn Infections Part I Lecture Notes

Infectious diseases

4/5th Semester Classes on Infectious Diseases, 8-9AM, Tuesdays (LT-1)



Approach to Infectious Diseases and their prevention


Antibiotic stewardship practices


Community-Acquired Infections


Health Care?Associated Infections


Gram-Positive Bacteria (part-1)


Gram-Positive Bacteria (part-2)


Gram-Negative Bacteria (part-1)


Gram-Negative Bacteria (part-2)


Spirochetal Diseases


Diseases Caused by Atypical/Miscellaneous Bacterial Infections


Revision-cum-exam on bacteria (Must to know type)


Infections Due to DNA Viruses



Infections Due to RNA Viruses (part 1)


Infections Due to RNA Viruses (part 2)


HIV/AIDS ? part 1


HIV/AIDS ? part 2


Fungal Infections


Parasitic Infections (part 1)


Parasitic Infections (part 2)


Revision-cum-exam on Virus, Fungal, and Parasite (Must to know type)





(E. coli, Klebsiella,

Proteus, Enterobacter)












NEISSERIA (N. meningitis & N. gonorrhoeae; IP-2-7days)

N. meningitis; diplococcus that colonizes in the nasopharynx of healthy

adolescents and adults, use glucose and maltose to produce acid

N. gonorrhoeae; grow on selective media and to use glucose but not maltose,

sucrose, or lactose

Meningococci invasive disease are usually encapsulated with polysaccharide,

and the antigenic nature of the capsule determines an organism's serogroup

Under capsule, an outer phospholipid membrane containing lipopolysaccharide

(LPS, endotoxin) and multiple outer-membrane proteins (serotype)

Gonococcus contains, on average, three genome copies per coccal unit; this

polyploidy permits a high level of antigenic variation and the survival of the

organism in its host and resistant to antibiotics

Outer-Membrane Proteins (PILLI, OPA, PORIN, etc) and lipooligosaccharide

(LOS): gonococcal structures that interact with epithelial cells, host factors seem

to be important in mediating entry of gonococci into nonphagocytic cells (e.g.

complement deficiency)

There are several patterns of disease: epidemic, outbreak, hyperendemic, and

sporadic or endemic

Clusters of cases occur where there is an opportunity for increased transmission--

i.e., in (semi-)closed communities

Smoking, crowding, and respiratory viral infection increase the risk of


Endothelial injury is central to many clinical features of meningococcemia,

including increased vascular permeability, pathologic changes in vascular tone,

loss of thromboresistance, intravascular coagulation, and myocardial dysfunction

Most common clinical syndromes are meningitis and meningococcal septicemia
MENINGITIS: While 30?50% of patients present with a meningitis syndrome alone

OR up to 40% with some features of septicemia

SEPTICEMIA: alone accounts for up to 20% of cases
CHRONIC MENINGOCOCCEMIA, presents as repeated episodes of petechial rash

associated with fever, joint pain/arthritis, and splenomegaly that may progress to

acute meningococcal septicemia if untreated

POSTMENINGOCOCCAL REACTIVE DISEASE, an immune complex disease develops

~4?10 days after the onset of meningococcal disease

Usually initially blanching in nature and indistinguishable from viral rashes, HOWEVER,

petechial or frankly purpuric over the hours after onset, THEN purpura fulminans
(fewer than <10% of children of all rashes) ? (occurs in two-thirds of Meningococcal cases)

Clinical grounds and lab confirmation (blood cultures are positive in up to 75%

of cases, (PCR) analysis of whole-blood samples, lumbar puncture

Third-generation cephalosporin, treated for 7 days
10% DEATH, most common complication 10% of cases) is scarring after necrosis

of purpuric skin lesions

Factors associated with a poorer prognosis are shock; young age (infancy),

old age, and adolescence; coma; purpura fulminans; disseminated

intravascular coagulation; thrombocytopenia; leukopenia; absence of

meningitis; metabolic acidosis; low plasma concentrations of antithrombin and

proteins S and C; high blood levels of PAI-1; and a low erythrocyte

sedimentation rate or C-reactive protein level

1. Immunization- Polysaccharide Vaccines/Conjugate Vaccines/Vaccines Based

on Subcapsular Antigens

A monovalent serogroup A vaccine, manufactured in India, was licensed in 2010

and rol ed out to countries in the sub-Saharan African meningitis belt

Chemoprophylaxis- Rifampin/Ceftriaxone as a single IM or



Gonorrhea is a sexually transmitted infection (STI) of epithelium and commonly

manifests as cervicitis, urethritis, proctitis, and conjunctivitis

Gonococcal Infections in Men

Gonococcal Infections in Women

Acute urethritis


(more acute and intense than those

of chlamydial cervicitis)



Balanitis or further deep complications


including abscesses

(occur in anestrogenic


Anorectal Gonorrhea
Pharyngeal Gonorrhea
Ocular Gonorrhea
Gonorrhea in Pregnant Women, Neonates, and Children

Gonococcal Arthritis (DGI)

Menstruation is a risk factor for dissemination, and two-thirds cases are in women
Bacteremic stage and a joint-localized stage with suppurative arthritis
D/D; reactive arthritis AND septic arthritis
Rapid diagnosis - Gram's staining of urethral exudates
Nucleic acid probe tests are being substituted for culture, BUT NOT


Single IM dose of the third-generation cephalosporin, mainstay of


OR azithromycine (1g single dose)
Because co-infection with C. trachomatis occurs frequently, initial

treatment regimens must also incorporate an agent

DGI require higher dosages and longer durations of therapy
All persons who experience more than one episode of DGI should be

evaluated for complement deficiency

Condoms, if properly used, effective protection against the transmission

and acquisition of gonorrhea

Patients should be instructed to abstain from sexual intercourse until

therapy is completed and until they and their sex partners no longer

have symptom

Grows both aerobical y (requires two factors: hemin (X factor) and nicotinamide

adenine dinucleotide (V factor) and anaerobical y as coccobacil i

Among a-f serotypes, Type b and nontypable strains are the most relevant strains


Spread by airborne droplets or by direct contact with secretions or fomites
Colonization with nontypable is a dynamic process and are primarily mucosal

pathogens (EARS, BRONCHUS)

Hib strains cause systemic disease by invasion and hematogenous spread from

the respiratory tract

DISEASES BY Hib; Meningitis, Epiglottitis (later age child), Cellulitis, Pneumonia
Nontypable H. influenzae is the most common bacterial cause of exacerbations

of COPD, Other diseases: otitis media, puerperal sepsis, sinusitis, etc

Recovery of the organism in culture is most reliable diagnostic method
Initial therapy for meningitis due to Hib should consist of a cephalosporin
Hib conjugate vaccine to all child and chemoprophylaxis with rifampin

A probable diagnosis of Chancroid

can be made when the following criteria

are met:

(1) one or more painful genital ulcers;
(2) no evidence of Treponema pallidum


(3) a typical clinical presentation for


(4) a negative test for herpes simplex virus in

the ulcer exudate

Sexually transmitted disease

characterized by genital ulceration and

inguinal adenitis

Associated with HIV infection
Treated with single dose of azithromycin or


HACEK organisms
Group of fastidious, slow-growing, gram negative bacteria

whose growth requires an atmosphere of carbon dioxide

Species belonging to this group include several

Haemophilus species, Aggregatibacter (formerly

Actinobacil us) species, Cardiobacterium hominis, Eikenel a

corrodens, and Kingel a kingae

HACEK bacteria normally reside in the oral cavity
The clinical course of HACEK endocarditis tends to be

subacute, particularly with Aggregatibacter or

Cardiobacterium, However, K. kingae endocarditis may

have a more aggressive presentation

LEGIONELLA (IC pathogen)

Legionellosis refers to the two clinical syndromes caused by bacteria of the

genus Legionella

Pontiac fever (IP- 24-48h) is an acute epidemic, febrile, self-limited il ness that has been

serological y linked to Legionel a species, whereas

Legionnaires' disease (IP- 2-10d) is the designation for pneumonia caused by these


Species L. pneumophila causes 80?90% of human infections
Natural habitats for L. pneumophila are aquatic bodies
Factors known to enhance colonization include warm temperatures (25??42?C)

and the presence of scale and sediment; The presence of symbiotic

microorganisms, including algae, ameba, ciliated protozoa, and other water-

dwelling bacteria, promotes the growth of Legionella

Multiple modes of transmission including aspiration, aerosolization, and direct

instillation into the lungs during respiratory tract manipulations

Incidence depends on the degree of contamination of the aquatic reservoir,

the immune status of the persons exposed to water from that reservoir, the

intensity of exposure, and the availability of specialized laboratory tests

Dif erential diagnosis of atypical pneumonia should be considered
Legionella cultures - best
Legionella urinary antigen test ? highly specific (for L. pneumophila serogroup 1)
Direct fluorescent antibody (DFA) staining
Antibody testing

Macrolides (especial y azithromycin) and the respiratory quinolones are now the

antibiotics of choice for 10-14 days

For critically ill patients, the authors use combination regimens of azithromycin, a

quinolone, and/or rifampin

Routine environmental culture of hospital water supplies (from cold-water taps,

hotwater taps, the hot-water recirculating line, and water-storage tanks) for

Legionella is recommended as an approach to the prevention of hospital-acquired

Legionnaires' disease

Copper-silver ionization is a reliable method for eradication

BORDETELLA (IC pathogen)

Pertussis ("whooping cough"/ "the 100-day cough")is an acute infection of the

respiratory tract caused by Bordetella pertussis

Cyclical outbreaks every 3?5 years, can affect people of all ages, However,

Severe morbidity and high mortality rates, are restricted almost entirely to


B. pertussis infects only humans, B. parapertussis causes a milder illness; and

rarely by B. holmesii, and B. bronchiseptica

Most important virulence factor is pertussis toxin, others are filamentous

hemagglutinin, pertactin, Fimbriae, tracheal cytotoxin, adenylate cyclase toxin,

dermonecrotic toxin, and LOS

Pathogenesis is unknown after attachment of the organism to the ciliated

epithelial cells of the nasopharynx

IP- 7?10 DAYS
Prolonged coughing illness with clinical manifestations that vary by age
Catarrhal phase, 1-2WKS, (indistinguishable from the common Cold)evolves into the

paroxysmal phase, 2-4WKS, (the cough becomes more frequent and spasmodic with

repetitive bursts of 5?10 coughs, often within a single expiration, episode may be terminated

by an audible whoop, which occurs upon rapid inspiration against a closed glottis at the end

of a paroxysm), Later into convalescent phase, 4-12WKS, (gradual resolution of coughing


Vomiting with cough is the best predictor of pertussis as the cause of prolonged cough in


Pneumothorax, severe weight loss, inguinal hernia, rib fracture, carotid artery aneurysm, and

cough syncope ? COMPLICATIONS

Laboratory confirmation (Culture of nasopharyngeal secretions ) should be attempted in all

cases, nowadays being replaced by PCR

Lymphocytosis (an absolute lymphocyte count of >1?10,000/cc ) is common
Pertussis should be suspected when any patient has

a cough that does not improve within 14 days,
a paroxysmal cough of any duration,
a cough followed by vomiting (adolescents and adults), or
any respiratory symptoms after contact with a laboratory-confirmed case of pertussis

Purpose of antibiotic therapy for pertussis is to eradicate the infecting bacteria from the

nasopharynx; therapy does not substantially alter the clinical course unless given early in the

catarrhal phase; Macrolide antibiotics are the drugs of choice

BRUCELLA (undulant fever, IC organism))

Brucellosis is a bacterial zoonosis transmitted directly or indirectly to humans from

infected animals, predominantly domesticated ruminants and swine

B. melitensis, B. abortus, B. suis, B. canis, B. neotomae, B. ceti, and B.


Brucellosis may be acquired by ingestion, inhalation, or mucosal or

percutaneous exposure

IP- 1 week to several months
Pathogenesis is unknown; The organism is a "stealth" pathogen who avoids

triggering innate immune responses and that permit survival within monocytic


Brucellosis almost invariably causes fever; dif ers from other fevers,

(1) Left untreated, the fever of brucel osis shows an undulating pattern that persists for

weeks before the commencement of an afebrile period that may be fol owed by


(2) The fever of brucel osis is associated with musculoskeletal symptoms and signs in

about one-half of all patients

Often fits one of three patterns:

febrile illness that resembles typhoid but is less severe;
fever and acute monoarthritis, typically of the hip or knee, in a young


long-lasting fever, misery, and low-back or hip pain in an older man

Diagnosis must be based on a history of potential exposure, a

presentation consistent with the disease, and supporting laboratory

findings (Culture, PCR, serology)

Gold standard for the treatment of brucellosis in adults is IM streptomycin

(0.75?1 g daily for 14?21 days) together with doxycycline(100 mg twice

daily for 6 weeks)

Chemoprophylaxis; the administration of rifampin plus doxycycline for 3

weeks after a low-risk exposure (e.g., an unspecified laboratory accident)

and for 6 weeks after a major exposure to aerosol or injected material

Relapse occurs in up to 30% of poorly compliant patients


Tularemia is a zoonosis caused by Francisella tularensis
Humans of any age, sex, or race are universally susceptible to this systemic


It is primarily a disease of wild animals and persists in contaminated

environments, ectoparasites, and animal carriers

Human infection is incidental and usually results from interaction with biting or

blood-sucking insects, contact with wild or domestic animals, ingestion of

contaminated water or food, or inhalation of infective aerosols

Characterized by an ulcerative lesion at the site of inoculation, with regional

lymphadenopathy and lymphadenitis

Systemic manifestations, including pneumonia, typhoidal tularemia, meningitis,

and fever without localizing findings may occur

The diagnosis of tularemia is most frequently confirmed by agglutination testing
Only aminoglycosides, tetracyclines, chloramphenicol, and rifampin are

currently approved (7?10 days)


Plague is a systemic zoonosis caused by Yersinia pestis
It predominantly affects small rodents and is usual y transmitted to humans by an

arthropod vector (the flea), Less often, contact with animal tissues or respiratory


Patients can present with the bubonic, septicemic, or pneumonic form of the


Although there is concern among the general public about epidemic spread of

plague by the respiratory route, this is not the usual route of plague transmission

Initial presumptive diagnosis followed by reference laboratory confirmation
10-day course of antimicrobial therapy is recommended
Postexposure antimicrobial prophylaxis lasting 7 days is recommended following

household, hospital, or other close contact with persons with untreated

pneumonic plague. (Close contact is defined as contact with a patient at <2 m.)

Yersiniosis is a zoonotic infection with an enteropathogenic Yersinia species,

usually Yersinia enterocolitica or Y. pseudotuberculosis


Clinical presentation generally depends on both theinfecting Bartonella

species and the immune status of the infected individual

Usually a self-limited illness, cat-scratch disease (CSD) has two general clinical


Typical CSD, the more common, is characterized by subacute regional


atypical CSD is the col ective designation for numerous extranodal manifestations

involving various organs.

B. henselae is the principal etiologic agent of CSD
A history of cat contact, a primary inoculation lesion, and regional

lymphadenopathy are highly suggestive of CSD

Azithromycin may be given, but limited role
Suppurative nodes should be drained by large-bore needle aspiration and not

by incision and drainage in order to avoid chronic draining tracts

Thank you

This post was last modified on 05 April 2022