Pseudomonas: Microbiologic and Clinical Features T. Mazzulli, MD, FRCPC, FACP Microbiologist and Infectious Diseases Consultant Mount Sinai Hospital/UHN.

Pseudomonas: Microbiologic and Clinical Features

T. Mazzulli, MD, FRCPC, FACP

Microbiologist and Infectious DiseasesConsultant

Mount Sinai Hospital/UHN

Objectives

Review the current epidemiology of antimicrobial resistance of key bacterial pathogensDiscuss the mechanism of resistance, cross-resistance and co-resistance and laboratory detection Review recommendations for treatment and control of multi-drug resistant pathogens

Microbiology

Family Pseudomonadaceae– Aerobic, non-spore forming Gram negative straight or

slightly curved rod (1 to 3 um in length), polar flagella– Non-fermenters– Catalase and oxidase positive– Morphologic characteristics on lab media:

Production of pigments:– Soluble blue-coloured phenazine pigment called pyocyanin)– Some strains produce red or black colonies due to pigments

termed pyorubin and pyomelanin, respectively– P. aerugnosa produces pyoverdin (diffusible yellow-green to

yellow-brown pigment) which, when produced with pyocyanin gives rise to green-blue colonies on solid media

– Term ‘aeruginosa” stems from green-blue hue

Microbiology

Term Pseudo = “false”; monas = “single unit”

Term ‘aeruginosa” stems from green-blue hue

Pseudomonas are classified as strict aerobes but some exceptions:– May use nitrate– Biofilm formation

Microbiology

Pseudomonads classified into five rRNA homology groups:– Pseudomonas (sensu stricto)– Burkholderia species– Comamonas, Acidovorax, and Hydrogenophaga

genera– Brevundimonas species– Stenotrophomonas and Xanthomonas genera

Genus Pseudomonas contains over 160 species but only 12 are clinically relevant

Microbiology

P. aeruginosa is the type species and may have highly varied morphology

Typical colonies may appear to spread over the plate, lie flat with a metallic sheen and frequently produce a gelatinous or “slimy” appearance

Most strains produce characteristic ‘grapelike’ or ‘corn taco-like’ odor

P. aeruginosa on blood agar

MacConkey Agar

Non-Lactose Fermenter

Lactose Fermenter

MacConkey Agar

P. aeruginosa Mucoid P. aeruginosa

Epidemiology and Clinical Aspects of P. aeruginosa

Epidemiology and Transmission

Natural habitat:– Temperature between 4 to 36oC (can survive up to

42oC)– Found throughout nature in moist environment

(hydrophilic) (e.g. sink drains, vegetables, river water, antiseptic solutions, mineral water, etc.)

– P. aeruginosa rarely colonizes healthy humansNormal skin does not support P. aeruginosa colonization (unlike burned skin)

– Acquisition is from the environment, but occasionally can be from patient-to-patient spread

Range of clinical infections caused by P. aeruginosa

P. aeruginosa is an opportunistic infection:– Individuals with normal host defenses are not at risk

for serious infection with P. aeruginosa

Those at risk for serious infections include:– Profoundly depressed circulating neutrophil count

(e.g. cancer chemotherapy)– Thermal burns– Patients on mechanical ventilation– Cystic fibrosis patients

Range of clinical infections caused by P. aeruginosa

Immunocompetent Host:– Most common cause of osteochondritis of dorsum of foot

following puncture wounds (running shoes)– Hot tub folliculitis– Swimmer’s ear– Conjunctivitis in contact lens users (poor hygiene or if lenses are

worn for extended periods)

Other Hosts:– Malignant otitis externa in diabetics– Meningitis post trauma or surgery– Sepsis and meningitis in newborns– Endocarditis or osteomyelitis in IVDUs– Community-acquired pneumonia in pts with bronchiectasis– UTI in patients with urinary tract abnormalitis

Hospital-acquired gram negative organisms Distribution in the ICU, 2004-2007

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OtherSerratiaAcinetobacterStenotrophomonasEnterobacter/citrobacterE. coliKlebsiella spp.P. aeruginosa

Bacterial Infections in the ICU:Organism Distribution in North America

Staphylococcus aureus 24.1Pseudomonas aeruginosa 12.2Escherichia coli 10.1Klebsiella species 8.9Enterococcus species 7.2Coagulase negative staph 7.0Enterobacter species 7.0Acinetobacter species 4.0Serratia species 3.0Stenotrphomonas maltophilia 3.0

SENTRY: 200124-36 medical centers in N.A., n = 1321

Jones, Sem Resp Crit Care Med, 2003

Incidence of Pathogens from ICUs in Canada Incidence of Pathogens from ICUs in Canada (87 hospitals sites): 2000 to 2002(87 hospitals sites): 2000 to 2002

OrganismOrganism Incidence (%)Incidence (%)

S. aureusS. aureus 17.417.4

Coag. Neg StaphylococcusCoag. Neg Staphylococcus 16.116.1

Enterococcus spp.Enterococcus spp. 9.79.7

E. coliE. coli 12.612.6

P. aeruginosaP. aeruginosa 11.311.3

K. pneumoniaeK. pneumoniae 5.55.5

Enterobacter cloacaeEnterobacter cloacae 4.24.2

Enterobacteriaceae (all Enterobacteriaceae (all species combined)species combined)

33.033.0

Jones ME, et al. Ann Clin Microbiol Antmicrob 2004;3N = 54,445

ICU Bloodstream InfectionsOrganism Distribution (1989-1998, NNIS)

Coagulase negative staph 39.3%Staphylococcus aureus 10.7%Enterococcus spp 10.3%Enterobacteriaceae 10.0%Candida albicans 4.9%Pseudomonas aeruginosa 3.0%

70 ICUs, n = 50,091

Fridkin and Gaynes, Clin Chest Med, 20:303, 1999

Hospital-acquired pneumonia Pathogens Hospital-acquired pneumonia Pathogens causing infection, USA vs Canadacausing infection, USA vs Canada

OrganismOrganism USA (%)USA (%) Canada (%)Canada (%)

S. aureusS. aureus 23.023.0 22.522.5

P. aeruginosaP. aeruginosa 18.218.2 17.617.6

H. influenzaeH. influenzae 10.110.1 11.011.0

Klebsiella spp.Klebsiella spp. 8.78.7 8.78.7

S. pneumoniaeS. pneumoniae 7.67.6 8.18.1

Enterobacter spEnterobacter sp 7.87.8 6.16.1

E. coliE. coli 4.44.4 5.75.7

S. maltophiliaS. maltophilia 3.53.5 3.73.7

S. marcescensS. marcescens 2.62.6 2.42.4

Jones RN. Chest 2001;119

Potential Amp C carriers: Enterobacter clocae, Serratia marcescens, Citrobacter freundii, Enterobacter aerogenes, Enterobacter species, Proteus mirabilis, Citrobacter koseri, Acinetobacter, Proteus vulgaris

TGH ICU: Total Respiratory Tract Positive Cultures = 280

Courtesy of Beth Allan, TGH Pharmacy

When to Suspect P. aeruginosa

Retrospective analysis from 4 hospitals

151 patients and 152 controls

– P. aeruginosa caused 6.8% of 4,114 episodes of Gram-negative bacteremia

– Risk factors: severe immunodeficiency, age >90, antimicrobials within 30 days, presence of central venous catheter or a urinary device

If ≥2 had over 25% risk for P. aeruginosa

V Schechner et al, CID 48:580-6, 2009

Risk factors for P. aeruginosa in pneumonia

– Structural lung disease (bronchiectasis)– Corticosteroids (> 10 mg prednisone/day)– Broad-spectrum antibiotics for > 7 days within

the past month– Malnutrition– Late-onset HAP (>5 days)

AMJRCCM 1999:160, Semin Resp Infect 13:1998; Infect Dis Clin North Amer 12:1998

Antimicrobial Resistance in P. aeruginosa

Antimicrobial Resistance in P. aeruginosa

Intrinsic resistance to most antibiotics is attributed to:– Efflux pumps: Chromosomally-encoded genes (e.g.

mexAB-oprM, mexXY, etc) and – Low permeability of the bacterial cellular envelope

Acquired resistance with development of multi-drug resistant strains by:– Mutations in chromosomally-encoded genes, or – Horizontal gene transfer of antibiotic resistance

determinants

Rehm SJ et al. CID 2006;42(Suppl 2)

Antimicrobial Resistance in the USA

Susceptibility of Canadian Isolates of Pseudomonas aeruginosa

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Cipro

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SENTRY. CID 2001:32; *Jones ME. Ann Clin Microbiol Antimicrob 2004;3

1997 1998 1999 2000-2002*

N = 6783; Blood = 3840 (57%); Resp = 1659 (24%)

P. aeruginosa – ciprofloxacin resistance, 2004-7 MSH

one isolate per patient per visit; admit=in hosp<3 days

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Perinatal OPD ER Inpt-admit Inpt-noso ICU-admit ICU-noso

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2007

P. aeruginosa – gentamicin resistance, 2004-7MSH

one isolate per patient per visit; admit=in hosp<3 days

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101520253035404550

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Perinatal OPD ER Inpt-admit Inpt-noso ICU-admit ICU-noso

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2005

2006

2007

P. aeruginosa – tobramycin resistance, 2004-7MSH

one isolate per patient per visit; admit=in hosp<3 days

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Perinatal OPD ER Inpt-admit Inpt-noso ICU-admit ICU-noso

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2005

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2007

P. aeruginosa – ceftazidime resistance, 2004-7MSH

one isolate per patient per visit; admit=in hosp<3 days

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101520253035404550

Perc

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Perinatal OPD ER Inpt-admit Inpt-noso ICU-admit ICU-noso

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P. aeruginosa – Pip-tazo resistance, 2004-7 MSH

one isolate per patient per visit; admit=in hosp<3 days

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Perc

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Perinatal OPD ER Inpt-admit Inpt-noso ICU-admit ICU-noso

2004

2005

2006

2007

P. aeruginosa – Meropenem resistance, 2004-7 MSH

one isolate per patient per visit; admit=in hosp<3 days

05

101520253035404550

Perc

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Perinatal OPD ER Inpt-admit Inpt-noso ICU-admit ICU-noso

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2007

Antimicrobial Therapy of P. aeruginosa

Likelihood of Inadequate Therapy

Inadequate therapy more likely if antibiotic resistance is present, and certain organisms (antibiotic resistant ones) more commonly associated with inadequate therapy.

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PA Acin KE

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Kollef CID 2000; 31: S 131-138SA Other

Other = H. infl, E. coli, P. mirabilis, S. marcescens

Case #1

MQ 42 y/o mailman; stubbed left toe

Walk in clinic - Keflex

5 days later - fatigue, tired, no improvement

- d/c keflex, start Cloxacillin

3 days later - fever, fatigue, increased redness in toe

What therapy would you choose?

Case Study Continued

Assessed in E.R. - WBC = 32x109 with blasts

Transferred on I.V. Cloxacillin

4 days later - Fever and Rash

- Diagnosis?

Legs Left Arm

Case Study... continued

Bone Marrow AML

Blood cultures drawn on admission grew gram negative bacilli at 24 hours

At 48 hours culture was positive for ……?

Case #2

73 y/o male, relapsed ALL:– Fatigue, WBC = 19x109/L (1%

blasts)– Reinduction chemotherapy– Day 14 - home on Septra; WBC =

0.5

Case #2

Day 15 - 38.2oC; pain at Hickman site

Returned to ER

Swab - no bacteria/pus

Admit to ward

What therapy would you choose?

Case Study

Admitted and started on Vancomycin

6 hours post-admission - hypotensive; tachycardia; 39.6oC

Remove Hickman line; continue vancomycin; transfer to ICU

4 hours later - black, necrotic lesion at Hickman site with spreading erythema

4 hours later - died

10 hours post-admission:

Case Study

Blood cultures:

- 24 hours post-admission:

Gram negative bacilli

- 48 hours culture was positive for ….?

TGH ICU Isolates 2007 Antibiogram (% Susceptible)

Species (N) Pip/Tazo Imipenem Ceftazidime Ciprofloxacin Tobramycin

P. aeruginosa (71) 83 65 63 63 76

Kleb. species (31) 87 100 97 97 100

E. coli (27) 96 100 81 56 78

E. cloacae (18) 78 100 78 94 100

S. marcescens (13) 92 100 92 85 92

S. maltophilia (8) - - - - -

C. freundii (6) 83 100 50 83 100

E. aerogenes (4) 100 100 100 100 100

Enterobacter sp. (3) 100 100 67 100 100

Empiric Coverage of Gram Negative Organisms with Selected Agents

1: Consider Amp Cs not induced

*MDR pathogens: Pseudomonas aeruginosa, Stenotrophomonas maltophilia

Courtesy of Beth Allan, TGH Pharmacy

ICU-Specific Antibiogram

Trouillet JL, et al. Am J Respir Crit Care Med. 1998;157:531

0 20 40 60 80 100

% Susceptibility

Imipenem + amikacinImipenem + amikacin+ vancomycin+ vancomycin

Ceftazidime + amikacinCeftazidime + amikacin+ vancomycin+ vancomycin

Piperacillin/tazobactamPiperacillin/tazobactam + amikacin + vancomycin+ amikacin + vancomycin

Aztreonam + amikacinAztreonam + amikacin+ vancomycin+ vancomycin

Combination Therapy Against Pseudomonas aeruginosa

Due to increasing resistance patterns, combination therapy may be required for empirical treatmentFluoroquinolone treatment plus a cephalosporin achieves in vitro synergy in 60-80% of the P. aeruginosa strains tested.– 92% synergistic when strains were resistant to one or

both agents– Prevented resistance development

61% synergistic effect of meropenem and ciprofloxacin at 1x MIC against P. aeruginosa.

Ermertcan et al. Scand J Infect Dis. 2001;33(11):818-21 Fish et al. J Antimicrob Chemother. 2002 Dec;50(6):1045-9