PSEUDOMONAS AERUGINOSAPSEUDOMONAS AERUGINOSA; ; AN EPITOME OF DRUG AN EPITOME OF DRUG

RESISTANCE IN BACTERIARESISTANCE IN BACTERIA

Seminar presentation by

Bamidele Tolulope Odumosu, PhD

IntroductionIntroduction

Pseudomonas aeruginosa is a well known nosocomial pathogen (hospital infection causing bacteria) responsible for a wide range of mild to severe infections.

This bacterium is naturally resistant to many antimicrobial agents used in the hospital because it has the distinctive capacity via multiple mechanism to become resistant to virtually all antibiotics available commercially

Genus PseudomonasGenus Pseudomonas

Members of the genus Pseudomonas are rod shaped, Gram-negative bacteria with one or more polar flagella, aerobic, non-spore forming and are catalase positive.

Members of this genus include Pseudomonas. aeruginosa,

P. fluorescens, P. putida, P. polycolor and P. syringae.

Pseudomonas. aeruginosaPseudomonas. aeruginosa A typical P.

aeruginosa is identified with the following biochemical characteristics

Positive oxidase reaction,

Negative for indole production,

Negative methyl red reaction,

Characteristics contdCharacteristics contd Voges-proskauer test is

negative, Negative citrate

utilization Non-Lactose fermenter beta hemolytic on blood

agar production of pyoverdin

and pyocyanin

Pseudomonas aeruginosa Pseudomonas aeruginosa as a as a pathogenpathogen

This Gram-negative bacillus exists everywhere in nature especially warm moist environment, and can be frequently isolated from soil, water, plants, sewage and occasionally from the normal human skin.

P. aeruginosa is a highly relevant opportunistic bacterium that causes disease in humans and plants

……as a pathogen contdas a pathogen contdAccording CDC ,Pseudomonas was named the

fifth most frequently isolated nosocomial pathogen,

The second leading cause of nosocomial pneumonia,

The third most common agent of urinary tract infection.

Fourth most frequently encountered pathogen in surgical site infections.

And the seventh most implicated leading cause of bloodstream infections

……as a pathogen contdas a pathogen contdAnd According to report from Pier et al.

(2004), P. aeruginosa is responsible for a number of clinical conditions, namely endocarditis, otitis, urinary tract infections, bone and joints infection, central nervous system infection, respiratory infections, gastrointestinal infections, skin and soft skin infections including wounds, bacteremia, keratitis, neonatal opthalmia, folliculitis and unmanageable forms of acne vulgaris

AdaptabilityAdaptabilityIts ability to survive harsh conditions such

as high temperature of 42oCIts minimal nutrient requirement and

oxygen usage makes it easier to persist and colonize many artificial and natural habitats

Its ubiquitousness in and around the hospitals and the community

Its efficient opportunistic abilities as a pathogen

PathogenicityPathogenicityIs largely influenced by multiple bacterial virulence

factors . They aid its colonization and invasion and its

genetic flexibility enabling it to survive in varied

environmentsColonization is due to multiple factors including

fimbriae or pili, flagella, and surface polysaccharides that enable its adherence to epithelium tissues

While its tissue invasion is by the production of elastase, alkaline proteases, hemolysins etc

Pathogenicity contd.Pathogenicity contd. Pseudomonas aeruginosa, is capable of

Biofilm formation under favourable nutrient and environmental condition which allows;

The pathogen to becomes resistant to antibiotics during an active infective stage

It also protects it from desiccationEnhances its cell-to-cell communicationIncreases its plasmid stability and genetic

exchange as well asDecreases its susceptibility to killing by host

defense mechanisms

Antibiotic resistance in Antibiotic resistance in Pseudomonas aeruginosaPseudomonas aeruginosa Inherent trait (intrinsic or

natural ability) This is related to its genetic background

Acquired trait (extrinsic). This is related to its environmental relationship

Inherent or Natural AbilitiesInherent or Natural AbilitiesThis often involves the following;Low affinity for targets cellsLow cell permeabilityActive efflux pump systemsPresence of chromosomal AmpC β-

lactamase also known as cephalosporinase

Bacteria Outer MembraneBacteria Outer Membrane

Bacteria Outer MembraneBacteria Outer Membrane

P. aeruginosa is intrinsically resistant to a number of structurally unrelated antibiotics due to low permeability of its outer membrane which is 1/100 of the permeability of E. Coli outer membrane

Mechanisms of Resistance: EffluxMechanisms of Resistance: Efflux

Active, energy dependent pumps cause efflux of drugs

Bacterial Cytosol

PG layer

Outer membrane

drug

Efflux pump

Mechanisms of Resistance: EffluxMechanisms of Resistance: Efflux Active, energy dependent pumps can also cause efflux of

drugs

Acquired resistanceAcquired resistance

Acquired resistance in bacteria is a modification of existing genetic material or acquisition of new gene that makes them to be resistant to drugs that they were previously susceptible.

Acquired resistanceAcquired resistanceThis occurs by Mutation of its own

DNA and its transfer to progeny during DNA replication also known as vertical gene transfer or

By horizontal gene transfer i.e. importation of resistance genes from other sources such as bacteria

Acquired resistanceAcquired resistanceVertical gene transfer or vertical

evolution are mutations in P. aeruginosa as well as other microorganisms which are transferred to progeny during DNA replication. They are spontaneous event hence cannot be predicted.

Acquired resistanceAcquired resistanceWhile lateral or horizontal gene

transfer is the acquisition of genetic materials such as plasmid, integrons and other mobile genetic element containing resistant genes from other bacteria in the environment. This is the most common method by which most bacteria as well as P. aeruginosa acquires resistant genes

Acquired resistanceAcquired resistanceAcquired resistance genes in P.

aeruginosa among many other functions is the presence of plasmids which allows for the production of β-lactamases and extended-spectrum β-lactamases (ESBL) enzymes that hydrolyses beta-lactam antibiotics such as the penicillins, cephalosporins and monobactams.

Enzymatic degradation of ESBLs:Enzymatic degradation of ESBLs: Mechanisms of Mechanisms of -lactamase-lactamase

N

ON

O

OH

S CH3

CH3O

RH

-lactamase

CH2

OH-lactamase

CH2

OH

N

ON

O

OH

S CH3

CH3O

RH

-lactamase

CH2

OH H2O

N

ON

O

OH

S CH3

CH3O

RH

HOH

-lactamase

CH2

OH

+Hydrolysis of Oxyimino group

Penicillin drug

Inactivated drug

Conclusion.Conclusion.Pseudomonas aeruginosa possess

arsenal of resistance genes and also has the ability to acquire more from other resistant bacteria such as Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae.

This ability and nature will continue make P. aeruginosa a very important bacteria in the hall of resistance.