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Pathophysiology of Bacterial Infections Cheat Sheet by

Meningitis, URTI, Endocarditis, SSTI, Bone & Joint Infection, GI Infection, Intra-abdominal Infection, UTI, Sepsis
bacterial     pharmacy     pathophysiology     infection     dsm     bacteria     patho     therapeutics

MENINGITIS

Epidemiology/Facts
- 1.2 million cases every year worldwide
-30% to 50% of survivors develop neurologic disabi­lities
Risk Factors
- passive and active exposure to cigarette smoke
- children with cholera implants
- sickle cell disease
- URI, otitis media
- alcoholism
- immuno­sup­pre­ssion
Organisms
- Strep pneumoniae (available vaccine)
- Neisseria mening­itidis (vaccine available)
- Haemop­hilus influenzae (vaccine available)
- Listeria monocy­togenes (between 1 month and 60 years)
- Herpes Simplex Virus
- West Nile Virus
Infection process originates with nasoph­ary­ngeal colina­tions and transl­oca­tion
Signs/Symptoms
- fever, chills, vomiting
- headache, photophobia
- nuchal rigidity
- Brudzi­nkski sign
- Kernig sign
- altered mental status, seizure
- lethargy, drowsiness
Diagnostics
- abnormal CSF chemis­tries
a.) elevated WBC count (>100 cells/mm3)
b.) elevated protein (>50 mg/dL)
c.) decreased glucose levels (<40 mg/dL)
- CSF gram stain & cultures

LOWER RESPIR­ATORY TRACT

Etiology
- most common reason patients seek medical attention
- pneumonia most common infectious cause of death in the US
- usually follows coloni­zation of the upper respir­atory tract with potential pathogens
Pathophysiology
- inhaled aeroso­lized particles
- enter lung via bloods­tream from extra pulmonary infection
- aspiration of oropha­ryngeal contents
Organisms & Risk Factors
Acute Bronch­itis
viral, self-l­imiting
Chronic Bronch­itis
enviro­nme­ntal, bacterial
Infl­uenza
Resp­iratory Syncytial Virus (RSV): newborns (baseline health status)
CAP
S.pneumonia
H. flu
N. Menin
M. cattar
HAP/­HCAP
S. aureus
GNR
resistance
Aspiration PNA
oropharyngeal (CAP) + anaerobes
Signs & Symptoms
- cough
- coryza
- rhinitis
- sore throat
- malaise
- fatigue
- headache
- fever
- fever rhonchi
- coarse bilateral rales
- wheezing purulent sputum
- hemoptysis
- chest pain
- dense infiltrate on CXR (pneumonia only)
- increased WBC
- WBC
- decreased O2 saturation
- labored breathing
- tachycardia
- tachypnea
Diagnostics
- sputum gram stain & cultures
- rapid flu swabs
CXR

BONE AND JOINT INFECTION

Organisms
Osteom­yelitis & infectious arthritis
Staphy­loc­occus aureus (usually)
Pseudomonas aeruginosa
streptococcus
e. coli
staphylococcus epidermis
anaerobes all can be isolated
Hematogenous vs. contiguous spread
Signs & Symptoms
- significan tender­ness, pain, swelling, fever, chills, decreased motion, and malaise
- elevated erythr­ocyte sedime­ntation rate (ESR), C-reactive protein (CRP), and white blood cell (WBC) count, positive blood cultures, synovial build analysis (increased WBC, cultures)
- bone changes observed on radiog­raphs 10-14 days after the onset of infection
- contrasted CT scans positive even sooner

INTRA-­ABD­OMINAL INFECTION

Pathophysiology
- Defect in the GI tract (polymicrobic)
- Necrot­izing pancre­atitis (polymicrobic)
- Perforated ulcer (polymicrobic)
- Append­icitis (polymicrobic)
- Penetr­ating trauma (polymicrobic)
- IBD (polym­icr­obic)
- Peritoneal dialysis (eg: staphy­loc­occus auerus)
- Cirrhosis (eg: e. coli)
Signs & Symptoms
- Fever
- Hypoactive bowel sounds
- Abdominal distension/tenderness
- Nausea/vomiting
- Elevated WBC
- Hypovo­lemic shock
- Ascites fluid (eg: high WBC, high protein, gram stain)

URINARY TRACT INFECTION

Patho & Organi­sms
- E. coli (85%)
- Staph saprophyticus
- Proteus spp.
- Klebsiella spp.
- pseudo­monas aeruginosa
- entero­coccus
- Recurrent UTIs (reinf­ection more than two weeks apart)
- Relapse less than two weeks (due to unsucc­essful treatment, resistant organisms, anatomical abnorm­ali­ties)
Risk Factors
Unco­mpl­ica­ted
Often post-c­oital; healthy adult female
Comp­lic­ataed
Male, kids
Diabetes
Immunocompromised
Pregnancy
Device-related (foley catheter)
Menopause
Lower UTI Signs/­Sym­ptoms (Cystic)
- Dysuria
- Urgency
- Frequency
- Nocturia
- Suprapubic heaviness
- Hematuria
Upper UTI Signs/­Sym­ptoms (Pyelo­nep­hri­tis)
- Systemic symptoms
- Fever
- Nausea
- Vomiting
- Flank pain
Diagnostics (Urina­lys­is)
- Signif­icant bacteriuria
- > 100,000 (10^5)/mL
- > 10^2/mL + symptoms
- RBCs
- WBCs
- Nitrites
 

UPPER RESPIR­ATORY TRACT INFECTIONS

Epidemiology
- most URI's have a viral etiology and resolved spontaneously
a.) sinusitis, pharyn­gitis, otitis
b.) symptoms lasting more than 7 days = bacterial?
- antibiotic use puts recipient at increased risk of select­ion­/ca­rriage of resistant organisms and future antibiotic failure
- bacterial infection may follow viral infection
Otitis
- day-care attendance
- recent antibiotic exposure
- age younger than 2 years
- frequent bouts of otitis media
- often follows viral nasoph­ary­ngeal infection that causes eustachian tub dysfunction
- otalgia, fever, irrita­bility, tugging ears, discolored (grey), thickened, bulging eardrum
- S. pneumoniae
- H. influenzae
- M. catarrhalis
- S. aureus
- S. progenies
- P. aeruginosa
Sinusitis
- nasal discharge/congestion
- maxillary tooth pain
- facial or sinus pain that may radiate
- cough
- nasal discharge
- often follows visual URI that leads to inflamed nasal passages, trapping bacterial in sinuses
- chroni­c/r­ecu­rrent infections occur three to four times a year
- S. pneumoniae and H. influenza
Pharyngitis
- viruses, group A strep, S. pyogenes
- seasonal outbreaks occur in winter and early spring, spread via direct contact with droplets
- sore throat, odynop­hagia, fever, headache
- erythm­a/i­nfl­amm­ation of the tonsils and pharynx with or without patch exudates
- enlarged, tender lymph nodes
- red swollen uvula
- petechiae on the soft palate
- rapid antigen test for GAS

ENDOCA­RDIDTIS

Organisms & Risk Factors
- Cardia valve abnorm­ali­ties: regurg­uta­tion, prosthetic heart valves
- intrav­enous drug abuse
- viridian's streptococci
- Strept­ococcus bovis
- Staphy­loc­occus aureus
- fungal
- HACEK: haemop­hilus, aggreg­ati­bacter, cardio­bac­terium, eikenella corrodens, kingella
Diagnostics
- persistent bacteremia/fungemia
- echoca­rdi­ogr­aphy: valvular vegetation
Signs/Symptoms
- fever & murmur
- osler nodes
- infective emboli: renal, pulmonary, CNS

SKIN & SOFT TISSUE INFECTION

Organisms
Foll­icu­litis, furnucles (boils), and carbun­cle­s*
Staphy­loc­occus aureus (MRSA)
Erys­ipe­las
Strept­ococcus pyogenes
Impe­tig­o*
Staphy­loc­occus aureus
Lymp­han­gitis
S. pyogenes
Cell­uli­tis
S. pyogenes and S. aureus
Necr­otizing Faciitis
S. progenes
Diabetic Foot Infect­ions, Decubitus Ulcers
Staphy­loc­occi, strept­ococci, enteric gram negative bacilli, and anaerobes
HUma­n/A­nimal Bite Wounds
Pasteu­rella multocida, eikenella ocrrodens, S. aureus, and anaerobes
* Highly Contagious *
Notes
- use caution with "­spider bites"
- many of these infections originate as minor trauma, scratches (soap and water)
- predis­posing factors: diabetes mellitus, local trauma or infection, recent surgery
- MRSA tips: transm­ission on fomites

GASTRO­INT­ESTINAL INFECTION

Key Facts
Diarrhea is
Usually Viral
eg: E. coli
eg: Shigella
eg: campylobacter
eg: salmonella
eg: clostr­idium
Patient education & prevention strategies are key
eg: travel­ler's diarrhea
eg: food poisoning
eg: vaccin­ation
Pathophysiology: inflam­matory secretion
Signs/Symptoms
- nausea
- abdominal pain
- cramping
- bloating
- dehydration
fever
- frequent urge to evacuate
- fever blood & severe dehydr­ation
Risk Factors
- ingestion of raw or underc­ooked seafood (eg: vibrio cholera or noroviruses)
- use of antibi­otics (eg: c. diff)
- use of PPI
- travel to tropical areas(eg: parasitic infections like guard, entamoeba, strong­ylo­ides, and cryptosporidium)
- travel to endemic areas (eg: vibrio cholera)

SEPSIS

Definition: life-t­hre­atening organ dysfun­ction due to a dysreg­ulated host response to infection; it arises when the body's response to an infection injures its own tissues and organs
Infection + Quick Sepsis Organ Failure Assess­ment
Altered Mental Status
GSC < 15
Fast Respir­atory Rate
> 22 BPM
Low Blood Pressure
< 100 SBP
Increased O2 Consum­ption
Decreased O2 Delivery
Procalcitonin Levels
Healthy
0.01
Local Infection
0.1 - 0.5
Systemic Infection
0.5 - 2.0
Severe Sepsis
2.0 - 10
Septic Shock
> 10
C-Reactive Protein (mg/L)
Minor Infection
10 - 20
Moderate Infection
20- 50
Severe Infection
> 50

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