Pseudomonas

Background

Pseudomonas is a gram negative bacteria which is a notorious cause of nosocomial or hospital acquired infections. It is a significant pathogen in several clinical settings, especially in immunocompromised patients. Psuedomonas aeruginosa is the most common disease causing Pseudomonas species.

DISEASE ASSOCIATIONS CHARACTERIZATION

Pseudomonas aeruginosa 3rd leading cause of hospital burn infections
Corenal keratitis in contact lens wearers
Endocarditis and osteomyelitis in IV drug abusers
External otitis media (Swimmer's ear)

Burkholderia cepacia Acute necrotizing pneumonia especially in cystic fibrosis patients

Gram-negative bacterial toe web infection: A survey of 123 cases from the district of Cagliari, Italy

Nicola Aste, MD
Laura Atzori, MD
Miriam Zucca, MD
Monica Pau, MD
Pietro Biggio, MD

Cagliari, Italy

J Am Acad Dermatol 2001;45:537-41 Abstract quote

Background: Foot intertrigo is mostly caused by dermatophytes and yeasts, less frequently by gram-positive and gram-negative bacteria. Nevertheless, the importance of polymicrobial infections and especially colonizations of Pseudomonas aeruginosa can cause therapy problems in relation to antibiotic resistance and the risk of potentially lethal complications.

Objective: The aim of this study was to evaluate the main epidemiologic and clinical features of intertrigo from gram-negative bacteria, the function of promoting factors, and the measures taken to treat and prevent this disorder.

Methods: Between 1989 and 1998, 123 cases of intertrigo from gram-negative bacteria were observed at the Cagliari University Dermatology Department. Routine clinical and blood examinations, repeated bacterioscopic and mycologic examinations, cultures aimed at identifying the responsible bacteria, and antibiograms were performed.

Results: P aeruginosa was found to be the prevailing pathogen, both alone and associated with other gram-negative bacteria (such as Escherichia coli, Proteus mirabilis, Morganella morganii) and gram-positive bacteria. Clinical manifestations were similar in the majority of patients: erythema, vesicopustules, erosions, and marked maceration caused by abundant, malodorous exudate. Lesions affected the interdigital spaces of both feet and frequently extended to the planta and the back of the toes. Patients complained of burning and pain. Successful therapies were achieved with combined topical and systemic treatment; to avoid the risk of antimicrobial resistance, the choice of the active antibiotic was guided by antibiograms.

Conclusion: In all symptomatic toe web infections, the presence of gram-negative germs, such as P aeruginosa, should be investigated to avoid the risk of treatment failures and more severe local or systemic complications.

PATHOGENESIS CHARACTERIZATION

Virulence Coregulated pili and adherence proteins mediating adherence to epithelial cells and lung mucin
Endotoxin secreted implicated in sepsis

Virulence factors

Alginate
Alginate secreted by bacteria forms a biofilm of mucoid exopolysaccharide protecting the organism from phagocytosis

Exotoxin A
Similar to diptheria toxin and inhibits protein synthesis by ADP-ribosylating EF-2, a ribosomal G protein

Exoenzyme S
ADP ribosylates small G proteins including p21 ras and interferes with host cell growth

Phospholipase C
Lyses red blood cells and degrades pulmonary surfactant
Elastase also degrades IgGs and extracellular matrix proteins

Iron-containing compounds
Toxic to endothelial cells

HISTOLOGICAL TYPES CHARACTERIZATION

General Most tissues exhibit a necrotizing inflammation with masses of organisms accompanied with a vasculitis

SKIN-Ecthyma gangrenosum
Well demarcated necrotic skin lesion with organisms infiltrating into the veins

VARIANTS

Pulmonary Granuloma Caused by Pseudomonas andersonii sp nov

Xiang Y. Han, MD, PhD
Audrey S. Pham, PhD
Kim U. Nguyen, MT(ASCP)
W. Roy Smythe, MD
Nelson G. Ordonez, MD
Kalen L. Jacobson, MD
Jeffrey J. Tarrand, MD

Am J Clin Pathol 2001;116:347-353 Abstract quote

Pulmonary granuloma is a common lesion for which gram-negative bacteria are rarely implicated as a cause. Hence, most physicians are unaware of this etiology.

We isolated a gram-negative bacterium from a surgically resected pulmonary granuloma in a 42-year-old, nonimmunocompromised woman. Within the necrotizing granuloma, numerous organisms also were demonstrated by Gram stain, suggesting a cause-disease relationship.

Characterization of the bacterium by sequence analysis of the 16S ribosomal gene, cellular fatty acid profiling, and microbiologic studies revealed a novel bacterium with a close relationship to Pseudomonas.

We propose a new species for the bacterium, Pseudomonas andersonii. These results suggest that the differential diagnosis of a lung granuloma also should include this gram-negative bacterium as a potential causative agent, in addition to the more common infections caused by acid-fast bacilli and fungi. This bacterium was shown to be susceptible to most antibiotics that are active against gram-negative bacteria.

Robbins Pathologic Basis of Disease. Sixth Edition. WB Saunders 1999.

Commonly Used Terms

Bacteria

Last Updated 9/19/2001

DISEASE ASSOCIATIONS	CHARACTERIZATION
Pseudomonas aeruginosa	3rd leading cause of hospital burn infections Corenal keratitis in contact lens wearers Endocarditis and osteomyelitis in IV drug abusers External otitis media (Swimmer's ear)
Burkholderia cepacia	Acute necrotizing pneumonia especially in cystic fibrosis patients
Gram-negative bacterial toe web infection: A survey of 123 cases from the district of Cagliari, Italy Nicola Aste, MD Laura Atzori, MD Miriam Zucca, MD Monica Pau, MD Pietro Biggio, MD Cagliari, Italy	J Am Acad Dermatol 2001;45:537-41 Abstract quote Background: Foot intertrigo is mostly caused by dermatophytes and yeasts, less frequently by gram-positive and gram-negative bacteria. Nevertheless, the importance of polymicrobial infections and especially colonizations of Pseudomonas aeruginosa can cause therapy problems in relation to antibiotic resistance and the risk of potentially lethal complications. Objective: The aim of this study was to evaluate the main epidemiologic and clinical features of intertrigo from gram-negative bacteria, the function of promoting factors, and the measures taken to treat and prevent this disorder. Methods: Between 1989 and 1998, 123 cases of intertrigo from gram-negative bacteria were observed at the Cagliari University Dermatology Department. Routine clinical and blood examinations, repeated bacterioscopic and mycologic examinations, cultures aimed at identifying the responsible bacteria, and antibiograms were performed. Results: P aeruginosa was found to be the prevailing pathogen, both alone and associated with other gram-negative bacteria (such as Escherichia coli, Proteus mirabilis, Morganella morganii) and gram-positive bacteria. Clinical manifestations were similar in the majority of patients: erythema, vesicopustules, erosions, and marked maceration caused by abundant, malodorous exudate. Lesions affected the interdigital spaces of both feet and frequently extended to the planta and the back of the toes. Patients complained of burning and pain. Successful therapies were achieved with combined topical and systemic treatment; to avoid the risk of antimicrobial resistance, the choice of the active antibiotic was guided by antibiograms. Conclusion: In all symptomatic toe web infections, the presence of gram-negative germs, such as P aeruginosa, should be investigated to avoid the risk of treatment failures and more severe local or systemic complications.

PATHOGENESIS	CHARACTERIZATION
Virulence	Coregulated pili and adherence proteins mediating adherence to epithelial cells and lung mucin Endotoxin secreted implicated in sepsis
Virulence factors
Alginate	Alginate secreted by bacteria forms a biofilm of mucoid exopolysaccharide protecting the organism from phagocytosis
Exotoxin A	Similar to diptheria toxin and inhibits protein synthesis by ADP-ribosylating EF-2, a ribosomal G protein
Exoenzyme S	ADP ribosylates small G proteins including p21 ras and interferes with host cell growth
Phospholipase C	Lyses red blood cells and degrades pulmonary surfactant Elastase also degrades IgGs and extracellular matrix proteins
Iron-containing compounds	Toxic to endothelial cells

HISTOLOGICAL TYPES	CHARACTERIZATION
General	Most tissues exhibit a necrotizing inflammation with masses of organisms accompanied with a vasculitis
SKIN-Ecthyma gangrenosum	Well demarcated necrotic skin lesion with organisms infiltrating into the veins
VARIANTS
Pulmonary Granuloma Caused by Pseudomonas andersonii sp nov Xiang Y. Han, MD, PhD Audrey S. Pham, PhD Kim U. Nguyen, MT(ASCP) W. Roy Smythe, MD Nelson G. Ordonez, MD Kalen L. Jacobson, MD Jeffrey J. Tarrand, MD	Am J Clin Pathol 2001;116:347-353 Abstract quote Pulmonary granuloma is a common lesion for which gram-negative bacteria are rarely implicated as a cause. Hence, most physicians are unaware of this etiology. We isolated a gram-negative bacterium from a surgically resected pulmonary granuloma in a 42-year-old, nonimmunocompromised woman. Within the necrotizing granuloma, numerous organisms also were demonstrated by Gram stain, suggesting a cause-disease relationship. Characterization of the bacterium by sequence analysis of the 16S ribosomal gene, cellular fatty acid profiling, and microbiologic studies revealed a novel bacterium with a close relationship to Pseudomonas. We propose a new species for the bacterium, Pseudomonas andersonii. These results suggest that the differential diagnosis of a lung granuloma also should include this gram-negative bacterium as a potential causative agent, in addition to the more common infections caused by acid-fast bacilli and fungi. This bacterium was shown to be susceptible to most antibiotics that are active against gram-negative bacteria.