Bacterial Diseases Flashcards
Signs/symptoms of Infection by Escherichia coli
- Tiredness, Shaking, Chills, Pain in loin, Burning sensation when peeing
- Pale, suprapubic tenderness
- Positive nitrite, pus cells and protein
Pyelonephritis
inflammation of the kidney
-commonly caused by bacterial infection spread up urinary tract or travelled through the bloodstream
Uropathogenic E. coli major cause
UTI in anatomically normal, unobstructed urinary tracts
E. coli
motile, nonsporing gram negative bacillus with a typical bacterial cell wall of LPS
What kind of flagella does E. coli have?
Peritrichous flagella
-posess fimbrias important in adhesion
Agents that cause UTI
- Enterococci
- Enterobacteriacceae
Structure of E. coli lipopolysaccharide (LPS)
-lipid containing beta-hydroxy fatty acids attached to carbohydrate, core carbohydrate component consisting of monomers of different carbohydrates
Infection by Escherichia coli
entry into body, spread within body, spread from person to person
Why is female generally more likely to have a UTI compared to male?
Length of the urethra
In adulthood, up to ______ of females will have a urinary tract infection at some time in their lives
40%
Why is lack of estrogen risk factor for UTI in post-menopausal women?
microbial flora changes from one mainly of lactobacilli (Gram +) to one with gram -
What is a significant risk factor in hospitals for both males and females for UTI?
Catheterization
UTI clinical presentation in neonates
nonspecific with vomiting and fever
UTI clinical presentation in older children and adults
Cystitis ( inflammation of urinary bladder)
Dysuria (painful or difficult urination)
Suprapubic pain and fever
Hematuria (blood in urine)
UTI clinical presentation in elderly patients
Typical picture of fever, incontinence, dementia or signs suggestive of chest infection
UTI complications
renal scarring, septicemia, papillary necrosis, parenchymal abscess and perinephric abscess
UTI diagnosis
- culturing mid-stream specimen of urine
- number of bacteria in urine greater than 10^5 CFU/ml
UTI related cystitis treated with
3 days of ATB
- Ciprofloxacin (Cipro)
- Trimethoprim-sulfamethoxazole (Bactrim)
- Amoxycillin
Mac Conkey’s agar contains
carbohydrate Lactose
-allows differentiation onf Gram-negative bacteria
Mac Conkey’s agar
organisms which ferment Lactose (E. coli) produce acid-end products
-react with pH indicator and produce pink color
Infection by Clostridium difficlile signs
Chest infection, profuse watery diarrhea, abdominal pain
toxic megacolon
abnormal dilation of the colon that develops within a few days and can be life threatening
Beta-Lactam Antibiotics
Penicillins, Aztreoman, Cephalosporins, Carbapenems
Clostridium difficile
anaerobic spore-forming motile (gram + rod bacteria)
-pathogen produce toxins that can cause severe bloody diarrhea in patients treated with antibiotics
Clostridium difficile produces
- irregular (crenated edges) white colonies in blood agar
- is saccharolytic and produces three exotoxines ( TcdA, TcdB and binary toxin)
Toxin A and B induce
glycosylation of G-proteins and ultimately affect actin polymerization leading to loss of tissue integrity
Third toxin
binary toxin that has ADP ribosylating activity
-associated with increased virulence
Clostridium difficile entry into body
following ingestion of spores from contaminated feces or environment
- bacteria colonized mainly large intestine of GI tract
- commensal, normally doesn’t cause disease
Clostridium difficile diagnosis
detection of toxins in feces by ELISA and GDH (glutamate Dehydrogenase)
Psuedomembranous colitis diagnosed by
colonoscopy
-raised yellowish plaques may be seen on mucosa
Clostridium difficile treatment
First line: Vanomycin or metronidazole
Alternatives: Cholestryamine, Bacitracin-fuscidic acid/rifaximin, probiotic/fecal enema, intravenous immunoglobulin
Fecal Microbiota Transplantation (FMT)
fecal transplant for multiple recurrence
-used primarily to treat Clostridium difficile-associated infection
Pulsed-field Gel electrophoresis (PFGE)
laboratory technique used to produce DNA fingerprint for bacterial isolate (group of same type of bacteria)
Infection by Staphylococcus aureus signs
Septic shock, acute renal and respiratory failure
- fever of 39.3 C
- Arterial blood gas pO2: 89mmHg
- WBC count: 27,000 mm3
- gram +, catalase +, coagulase + coccus resistant to methicillin
Methicillin-resistant Staphylococcus aureus (MRSA)
- gram + cocci that grow in grape like clusters
- produce enzyme catalase
S aureus
typical gram + cell wall
- thick peptidoglycan layer
- extensively cross-linked with pentaglycine bridges
- secretes coagulase (binds soluble fibrinogen)
pleural effusion
excess fluid that accumulates in the pleural cavity
- fluid-filled space that surrounds the lungs
- excess can impair breathing by limiting lung expansion
Infection by Staphylococcus aureus entry
- Requires breach in the skin or mucosa (catheter, surgical incision, burn, traumatic wound, ulceration or viral skin lesion)
- person to person spread (direct contact or contact with fomite)
fomites
an inanimate object that is capable of transmitting infectious organisms from one individual to another
Skin infection by staphylococcus aureus
superficial (impetigo), infection of hair follicles (folliculitis), boils (furuncles), deeper infections (carbuncles)
What causes carbuncles to occur?
When furuncles unite and extend deeper into the subcutaneous tissues forming sinus tracts
S. aureus is a frequent cause of:
bacteremia
-half of instances are nosocomial
Nosocomial
associated with surgical wound infection and foreign bodies such as indwelling catheters or sutures
_______ endocarditis has a _____ mortality and may throw off _____ _______ that may infer other organs
S. aureus, high, septic emboli
Pneumonia may result if
bacteria reach the lungs via the bloodstream or as a result of aspiration
What may result from hematogenous spread or from a skin infection?
Acute and chronic osteomyelitis and septic arthritis
S aureus secretes:
several toxins
-some function as superantigens
superantigens
recognized by T-cells without being processed into peptides that are captured by MHC
superantigens activate
T cells and macrophages
-leading to excessive production of pro-inflammatory cytokines and T cell proliferation
superantigens cause
fever, diffuse macular rash, desquamation (including palms, soles), hypotension and shock
Staphylococcal Scalded Skin Syndrome (SSSS)
mediated by the exfoilative toxins A and B produced by exfoliative toxins A and B produced by certain strains of S. aureus
-mainly in neonates and young children following infection of mouth, nose, throat or umbilicus
Staphylococcal Scalded Skin Syndrome syptoms
large areas of skin blister and peel away
- leaves wet, red and painful areas
- healing occurs within 1-2 weeks
Diagnosis of infection by staphylococcus aureus
microscopy: gram stain (small grape shape clusters of gram+ cocci)
culture: grow well on blood agar after 24-48 hrs at 37 C
Staphylococci are
facultative anaerobes
colonies of S. aureus are
large, smooth, glossy domes with an entire edge
-look golden yellow
almost all strains of S. aureus are
Beta-hemolytic (complete breakdown of RBCs)
- due to secretion of cytotoxins
mannitol salt agar
contains 7.5% sodium chloride and mannitol
-carbon source useful selective and differential medium to recover staphs
Phenol red reveals colonies fermenting mannitol because
acid produced by colonies changes color of agar from pink to yellow
Catalase_______ hydrogen peroxide to _____ and molecular _____
reduces, water, oxygen
s aureus is coagulase
+
coagulase will cause the plasma to
clot
resistance to penicillin is mediated by a
plasmid-encoded beta-lactamase (penicillinase) which hydrolyzes the beta-lactam ring of the molecule
MRSA
methicillin-resistant s aureus
What is reserved for staphylococcal strains that are resistant to penicillinase-resistant penicillins and clindamycin?
vancomycin
-mainly acts by prevention of cell-wall biosynthesis of bacteria
What may be used to treat superficial or localized skin infections caused by S. aureus?
mupirocin
-inhibits bacterial protein and RNA synthesis
infection by streptococcus pneumoniae
fevers, shaking chills, and productive cough
- coughing up blood-tinged sputum
- left side chest pain when breathing or coughing
- shortness of breath
- BP: 140/80, respiratory rate: 24
S. pneumoniae is one of the main causes of
respiratory tract infections
-most common cause of community-acquired bacterial pneumonia
S. pneumoniae
gram+, catalase negative diplococcus
- grows readily on blood agar
- colonies gray-green color
catalase test
used to distinguish streptococci (negative) from staphylococci (positive)
polysaccharide capsule impedes phagocytosis primarily by
inhibiting deposition of the opsonic C3b
-capsule is most importantly virulence factor
s. pneumoniae enters body through
oral-nasal route via respiratory droplets and adheres to oropharyngeal epithelium via adhesin molecule
pneumococcal pneumonia typically presents with
abrupt onset of fever and shaking chills
- majority of patients have productive cough
- blood-tinged sputum and pleurisy (pleural infection)
- sinusitis and otitis media
streptococus pneumoniae diagnosis
microsocopy: exam sputum, blood cerebrospinal fluid, bullet shaped diplococci
infection by neisseria gonorrhoae
dysuria, pus like drainage, tenderness at tip of penis, fever, shaking, chills, lower abdominal pain
What is a reportable infectious disease by law in the US to public health authorities?
gonorrhea
Gonorrhea transmission and presentation
gonococcus
- sexually transmitted pathogen
- acquired and spread horizontally by vagina, anal or oral intercourse
- can be spread vertically from mother to baby
- anorectal infection, pharyngeal infection, conjunctivitis, disseminated gonococcal infection
an increased _____ load has been found in semen of men with______
HIV, gonorrhea
gonorrhea in male
infection of genitourinary tract, urethral discomfort, pain/difficulty urinating, discharge
gonorrhea in female
endocervicitis, foul-smelling vaginal discharge, urethritis, cervicitis
neisseria gonorrhea
fastidious microorganism that grows on blood agar and chocolate agar
- usually isolated on selective media (modified thayer-martin [MTM] agar)
- gram - diplococci
- utilized glucose only (produces acid)
What is the only current recommended treatment for gonorrhea?
cephalosporins