Pseudomonas aeruginosa has very simple nutritional requirements. It is often observed &quot;growing in distilled water&quot; which is evidence of its minimal nutritional needs. In the laboratory, the simplest medium for growth of Pseudomonas aeruginosa consists of acetate for carbon and ammonium sulfate for nitrogen. It is tolerant to a wide variety of physical conditions, including temperature. It is resistant to high concentrations of salts and dyes, weak antiseptics, and many commonly used antibiotics.
Primary pneumonia occurs in patients with chronic lung disease and congestive heart failure. Lower respiratory tract colonization of cystic fibrosis patients by mucoid strains of Pseudomonas aeruginosa is common and difficult, if not impossible, to treat.
Most Pseudomonas bacteremia is acquired in hospitals and nursing homes. Pseudomonas accounts for about 25 percent of all hospital acquired Gram-negative bacteremias.
The bacterium is infrequently found in the normal ear, but often inhabits the external auditory canal in association with injury, maceration, inflammation, or simply wet and humid conditions.
Pseudomonas can colonize the ocular epithelium by means of a fimbrial attachment to sialic acid receptors. If the defenses of the environment are compromised in any way the bacterium can proliferate rapidly and, through the production of enzymes such as elastase, alkaline protease and exotoxin A, cause a rapidly destructive infection that can lead to loss of the entire eye.
Pseudomonas aeruginosa has a particular tropism for fibrocartilagenous joints of the axial skeleton.
As in the case of E. coli urinary tract infection can occur via an ascending or descending route.
As in other forms of Pseudomonas disease, those involving the GI tract occur primarily in immunocompromised individuals.
Several types of vaccines are being tested, but none is currently available for general use.
PseudomonasAcinetobacter Dr Kamran Afzal Asst Prof Microbiology
30 years old femaleAccidentally got burnt in her houseTreated with wound dressingsI/V Vancomycin + Ceftriaxone
Characteristics Gram negative rod NLF Oxidase and Catalase + Motile Obligate aerobe Non-fermentative Non-Enterobacteriaceae Optimum growth 37˚C, can grow at 42˚C Minimal nutritional requirements
Two forms Planktonic and Biofilm Some strains produce diffusible pigments Pyocyanin (blue/green) Fluorescein (yellow) Pyorubin (red) Grape-like odor Blue-green pus and colonies Broad antibiotic resistance
Colony typesThree types of colonies Small rough Large smooth colonies colonies Mucoid colonies
Transmission in hospital Ubiquitous to soil, Respiratory and other water, and vegetation hospital equipment Introduced in hospitals Contaminates soaps, on the soles of shoes, ointments, eye drops, on ornamental plants and flowers disinfectants Persist in dampness or Resistant to weak standing water antiseptics and many Sinks, taps and mops commonly used antibiotics
Pathogenicity Endocarditis Respiratory infections Bacteremia and Septicemia C N S infections Ear infections- otitis externa Eye infections Bone and joint infections Urinary tract infections Gastrointestinal infections Skin and soft tissue infections- wound infections, pyoderma and dermatitis
Bacterial Endocarditis IV drug users Prosthetic heart valves Bacteremia
Respiratory Infections Pneumonia Bacteremic pneumonia commonly occurs in neutropenic cancer and CCF patients Cystic fibrosis Lower resp tract colonization of cystic fibrosis patients by mucoid strains of Pseudomonas aeruginosa Characteristics Production of very viscid bronchial secretions Tends to lead to stasis in the lungs Predisposes to infection
Bacteremia and Septicemia Primarily in immunocompromised patients Predisposing conditions Hematologic malignancies Immunodeficiency relating to AIDS Neutropenia Diabetes mellitus Severe burns Ecthyma gangrenosum
CNS Infections Meningitis Brain abscess Portal of Entry Inner ear or paranasal sinus Inoculated directly Surgery Invasive diagnostic procedures May spread from another site of infection like the urinary tract
Bone and Joint Infections Particular tropism for fibro-cartilagenous joints of the axial skeleton Direct inoculation of the bacteria Hematogenous spread Osteo-chondritis Puncture wounds of the foot
Urinary Tract Infections Usually hospital-acquired UT catheterization, instrumentation or surgery 3rd leading cause of hospital-acquired UTIs Most adherent to the bladder uroepithelium Pseudomonas can invade the bloodstream from the urinary tract Source of nearly 40 % of Pseudomonas bacteremias
Gastrointestinal infections The GI tract is also an important portal of entry in Pseudomonas septicemia Any part of the gastrointestinal tract Perirectal infections Pediatric diarrhea Gastroenteritis Necrotizing enterocolitis
Skin and Soft tissue infections Wound infections, pyoderma and dermatitis Localized and diffuse skin infections ‘Jaccuzzi rash’ or ‘Whirlpool rash’ Common predisposing factors Breakdown of the integument Burns, trauma or dermatitis AIDS and other IC states
Treatment Pseudomonas aeruginosa is frequently resistant to many commonly used antibiotics Many strains are susceptible to 3rd and 4th gen Cephalosporins, aminoglycosides, fluoroquinolones, carbapenems and colistin, but resistant forms have developed Aminoglycoside + ceftazidime is frequently used to treat severe Pseudomonas infections 4th gen Cephalosporin or Carbapenem as monotherapy
The name, Acinetobacter, comes from the Latin word for "motionless," because they lack cilia or flagella with which to move
INTRODUCTION Gram-negative pleomorphic rods Colonize aquatic environment Associated with biofilms Survives on inanimate surfaces for weeks Infections and outbreaks Intensive care unit and healthcare settings Compromised immune systems at risk Colonized and infected patients as point sources
Mostly isolated from hospital environment Not part of normal human flora A. baumannii is often a source of nosocomial infections Can reach a very high percentage of infections in ICU settings Unfortunately it has the potential to often be multi-drug resistant
Resistance to multiple drugs - Over-expression of efflux pumps - Expression of ß-lactamases (Including ESBLs and metallo-ß-lactamases which can cause carbapenem resistance) This can necessitate use of drugs with greater toxicity (such as polymyxins)
EPIDEMIOLOGY Habitat Free living saprophyte in soil and water Human colonization 25% healthy adults - cutaneous 7% healthy adults and infants - pharyngeal Most common GNR - hospitalized patientsn Prevalence - Worldwide
TRANSMISSIONAcinetobacter can be spread from person toperson (infected or colonized patients), contactwith contaminated surfaces of exposure to theenvironment
PATHOGENICITY Virulence factors – Mostly unknown n LPS and Capsulen Opportunistic infections - Immunocompromisedn Growth at low pH and high and low temperaturesn Ability to survive for months on inanimate surfaces
Risk factors for nosocomial infections Prolonged hospitalization Catheterization - Urinary or IV Broad spectrum antimicrobials Endotracheal intubation Colonic colonization Burns
CULTURAL CHARACTERISTICSn Grows aerobically on routine culture median Grows at 44° Cn Colony morphology BA: 1-2mm round, smooth, opaque, mucoid, dome shaped, non-pigmented, hemolytic MA: NLF with purplish hue
BIOCHEMICAL REACTIONS Catalase - Positive Oxidase - Negative Nitrate reduction – Negative Indole negative Do not ferment glucose or most other sugars Saccharolytic [A. baumanii] Asaccharolytic [A. lwoffi] Urease production - Some strains Citrate utilization - Some strains
DIFFERENTIAL DIAGNOSIS n Gram stain: Neisseria species n Biochemical reactions: Enterobacteriaceae Organism Growth Oxidize Esculin L A Nit Litmus on MA Glucose D D C HStenotrophomonas + + ± + - ± +AcinetobacterSacchorylitic + + - - ± - -Asaccharolytic + - - - ± - -CDC Group NO-1 ± - - - - + ±
TREATMENTGeneral Principlesn Colonization vs. infection: Don’t treat colonization with systemic antimicrobialsn Mild infections: Removal of prosthetic devices/ foreign body, antimicrobials - not requiredn Superficial infections: Local managementn Moderately severe infections: Monotherapyn Severe/extensive deep infections: Combination therapy and debridement/drainagen Therapeutic failure to beta-lactams: 3rd or 4th generation Cephalosporins