Microbes and Sepsis

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MICROBES & Dr H.R.V.RAJKUMAR CONSULTANT MICROBIOLOGIST KAMINENI HOSPITALS HYDERABAD

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Schottmüller (1914) Severe, systemic infection due to bacteria getting into the bloodstream from an infectious focus in the body New approach (1990) It became clear that non-infectious diseases give rise to the same clinical syndrome that is caused by bacteria (burns, pancreatitis etc.)

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1991 Consensus conference SIRS – Systemic Inflammatory Response Syndrome By definition: at least 2 criteria Temperature above 38.4 or below 35.60c Heart rate above 90/min. Respiratory rate above 24 Leukocyte count above 12000 or below 4000 or more than 10 % immature forms

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SIRS – Non-infectious systemic inflammatory response syndrome Sepsis – Infectious systemic inflammatory response syndrome Infection – Invasion of microbes that provokes a controlled, local inflammatory response Sepsis – Develops if the response to the infection becomes generalized and damages remote anatomical sites and organs

Sepsis is an extremely complex response syndrome evoked by microbial agents : 

Sepsis is an extremely complex response syndrome evoked by microbial agents Endothelium damage, micro vascular dysfunction, impaired tissue oxygen uptake with consecutive organ damage Immunosuppression, anergy The sepsis is an auto destructive process that precipitates the dysfunction of multiple organs: MODS (multiple organ dysfunction syndrome)

Mediators of sepsis : 

Mediators of sepsis Cytokines (more than 150) Proinflammatory cytokines TNF – Tumour necrosis factor Interleukins 1, 2, 6, 12 PAF – Thrombocyte activating factor Anti-inflammatory cytokines Interleukin 4, 10, 11, 13 etc.

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The sepsis syndrome is the response of the human organism to microbe invasion: the outcome depends on the interrelation ship of pro- and anti-inflammatory cytokines. If the infectious source can be controlled and the function of pro- and anti-inflammatory cytokines is balanced, the patient survives. If the function of proinflammatory cytokines – for any reason-outweighs the anti-inflammatory system, the developing organ damage becomes irreversible and the patient dies.

Pathogens in sepsis : 

Pathogens in sepsis Community acquired infections Gram-positive bacteria S. pyogenes, S. pneumoniae, S. aureus Gram-negative bacteria E. coli, N. meningitidis, L. pneumophila

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Nosocomial infections Gram-positive bacteriaS. aureus (MRSA), S. epidermidis (MRSE), Enterococcus spp Gram-negative bacteria E. coli, K. pneumoniae, P. aeruginosa, A. baumannii Fungi Candida spp, Aspergillus spp

Microbial factors in sepsis : 

Microbial factors in sepsis Gram-negative bacteria Endotoxins: Constituents of the outer membrane of Gram-negative bacteria (lipopolysaccharides – LPS) Exotoxins: Actively produced and secreted proteins (V. cholera)

Microbial factors in sepsis : 

Microbial factors in sepsis Gram-positive bacteria: Exotoxins (C. difficile) Pyrogen exotoxins (super antigens): S. aureus, S. pyogenes = Toxic shock syndrome

Mortality rate of sepsis according to the type of pathogens(attributable mortality rate) : 

Mortality rate of sepsis according to the type of pathogens(attributable mortality rate) S. epidermidis 15 % S. aureus 20-30 % Enterococcus spp 30 % Candida spp 40 % Pseudomonas aeruginosa 50-70 % Acinetobacter spp 50-70 %

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DIAGNOSIS OF SEPSIS

LABORATORY TESTS : 

LABORATORY TESTS COMPLETE BLOOD PICTURE Leukopenia or Neutrophil leukocytosis Toxic granulation of neutrophils Increased band forms Low platelet count – DIC COAGULATION SCREEN – For Evidence of DIC PT/APTT – Prolonged Fibrinogen – Low levels Markers of fibrinolysis (D-Dimer) - Elevated

LABORATORY TESTS : 

LABORATORY TESTS Electrolytes and Renal function tests Liver function tests Plasma albumin – acute fall C-Reactive Protein Procalcitonin levels Blood glucose Plasma lactate Arterial blood gases Endotoxin or Cytokine levels (TNF-alfa, IL-6)

LABORATORY TESTS : 

LABORATORY TESTS MICROBIOLOGY TESTS Blood Culture Sputum Culture Urine Culture

BLOOD CULTURES : 

BLOOD CULTURES Bacteraemias may be Transient Organisms comprising of normal flora are introduced into the blood. Eg: Brushing of teeth, straining during bowel movements, manipulative procedures. Intermittent. Bacteria from an infected site are spasmodically released into blood from extra vascular abscesses, empyemic cavities or diffuse infections. Eg: Cellulitis, Peritonitis, Septic arthritis. Continuous. Where organisms have direct access to the blood stream. Eg: SABE, Infected AV Fistulas, Intra arterial catheters, Indwelling cannulae.

BLOOD CULTURES : 

BLOOD CULTURES Source of Organism not determined in 1/3rd of cases. Patients with positive blood cultures were 12 times more likely to die during hospitalization than those with negative blood cultures (Bryan CS, 1989). Quality Control. < 3% Blood cultures should be contaminated. More the contamination – Hospital bill increases by 20% to 39%.

BLOOD CULTURE COLLECTION : 

BLOOD CULTURE COLLECTION Preparation of Venepuncture site. Wash with soap (Optional) Rinse with sterile water. Apply 1% - 2% Tincture of iodine or Povodine - iodine. Allow to dry for 1 – 2 minutes. Remove iodine with 70% Alcohol. (Omit this step if Povodine - iodine is used). Precautions. Wear Gloves. Avoid drawing blood from IV catheters. If blood has to be drawn from catheters – discard first 0.3 ml in infants and 1.0 ml in children.

BLOOD CULTURE COLLECTION : 

BLOOD CULTURE COLLECTION Timing. Preferably before Antibiotics. Half an hour before a temperature spike – Unpredictable Volume. 10 – 30 ml of blood collected from each arm and distributed into two culture bottles = One blood culture. (Add blood to third bottle for anaerobic incubation if indicated) Do not change the needle. Collection of blood < 10 ml yield is reduced by 7.2%. Yield increases by 3% for every ml of blood collected. In children 1 – 5 ml of blood is sufficient.

BLOOD CULTURE COLLECTION : 

BLOOD CULTURE COLLECTION Number. In acute febrile illnesses (Meningitis, Bacterial Pneumonia) and for patients with infectious diseases like Osteomyelitis, Suppurative arthritis 2 separate cultures from opposite arms. In PUO First culture stat Second culture after 45 – 60 min Third culture after 24 hours Fourth culture after 48 hours if necessary

BLOOD CULTURE COLLECTION : 

BLOOD CULTURE COLLECTION In Acute IE 3 cultures from 3 separate sites in first 1 – 2 hours before starting treatment. In SABE 3 cultures on first day – each 30 min apart 2 more cultures on second and third day

Components of the treatment of sepsis : 

Components of the treatment of sepsis Eradication of the focus surgical intervention antimicrobial therapy Intensive therapy for the maintenance of basic organ functions Influence of the pathophysiological process of sepsis steroids (small doses) activated protein C

Principles of antimicrobial therapy in sepsis : 

Principles of antimicrobial therapy in sepsis For the optimum treatment of sepsis one has to have some imagination about the focus and the type of pathogen Samples have to be taken for culture before the administration of antibiotics Bactericidal antibiotics should be chosen The probability of effectiveness of antimicrobial therapy should be at least 90-95 % in severe infections

Recently confirmed recognitions : 

Recently confirmed recognitions The mortality rate is about 20-30 % higher if the antimicrobial therapy is inadequate The final outcome of sepsis is decided in the first 48-72 hours. The subsequent changes in antimicrobial therapy does not reduce significantly the mortality rate The consequence of the above recognitions: the most effective antibacterial therapy should be provided in the first 2-3 days!

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Vallés et al. Chest 2003 123:1615–1624

The effectivity of antimicrobial therapy can be improved by : 

The effectivity of antimicrobial therapy can be improved by The knowledge of the local antibiotic resistance pattern of important bacteria Application of modern PK/PD principles in antimicrobial administration Proper use of antibiotic combinations

Factors to be considered for the choice of antibiotics : 

Factors to be considered for the choice of antibiotics 1. Community versus hospital-acquired infections The pathogens are different in term of spectrum and antibiotic sensitivity The pathogens of the nosocomial infections are more resistant or even multiply resistant

Factors to be considered for the choice of antibiotics : 

Factors to be considered for the choice of antibiotics The anatomical site of the focus of sepsis The anatomical site determines the types of possible pathogens, especially in community-acquired infections

Factors to be considered for the choice of antibiotics : 

Factors to be considered for the choice of antibiotics The presence of underlying diseases Diabetes mellitus Alcoholism Splenectomy Neutropenia Myeloma Immunosuppression

Factors to be considered for the choice of antibiotics : 

Factors to be considered for the choice of antibiotics Diagnostic or surgical intervention in the recent past IV lines Indwelling catheter Implantations Operation

Strategy of antibiotic treatment in severe infections De-escalation therapy : 

Strategy of antibiotic treatment in severe infections De-escalation therapy Begin with the most effective therapy Streamline the therapy later, when the patient is already getting better and/or the pathogen and its antibiotic sensitivity are known

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Increasing Antimicrobial Resistance A Global-Local Problem

Clinical Impact of Growing Resistance : 

Clinical Impact of Growing Resistance Masterton RG. Int J Antimicrob Agents. 2009 Feb;33(2):105-10 Impact of Resistance Infections with resistant organisms results in Higher morbidity Higher mortality Prolonged hospitalization Higher morbidity

Antibiotic treatment in the ICU : 

Antibiotic treatment in the ICU Appropriate initial antibiotic treatment Avoid unnecessary antibiotics A balancing act

Adequate initial therapy: 21-day mortality rates : 

Adequate initial therapy: 21-day mortality rates Tumbarello M et al. Antimicrob Agents Chemother Jun 2007;51(6):1987–94 Patients (%) Aminoglycosidesn=20 β-lactam / β-lactamase inhibitors n=33 Carbapenemsn=28 Ciprofloxacinn=16 p=0.40 p=0.24 p=0.01 p<0.001

Effect of initial antibiotic therapy on mortality : 

Effect of initial antibiotic therapy on mortality Tumbarello M et al. Antimicrob Agents Chemother Jun 2007;51(6):1987–94 Inadequate initial therapy n=89 p<0.001 Adequate initial therapy n=97 n=186 Mortality (%)

Effect of switching initial antimicrobial therapy on mortality : 

Effect of switching initial antimicrobial therapy on mortality Tumbarello M et al. Antimicrob Agents Chemother Jun 2007;51(6):1987–94 Switching after susceptibility results p<0.001 Adequate treatment within a few hours n=75 Mortality (%)

Does inadequate therapy result from antibiotic resistance? : 

Does inadequate therapy result from antibiotic resistance? Inadequate therapy is more likely if antibiotic resistance is present, and antibiotic-resistant organisms are more commonly associated with inadequate therapy Adapted from Kollef. Clin Infect Dis 2000;31(Suppl. 4):S131–S138 Inadequate treatment (%) P. aeruginosa S. aureus Acinetobacter spp. Other K. pneumoniae

Low Exposure To Antibiotics Enables Development Of Resistance : 

Low Exposure To Antibiotics Enables Development Of Resistance Critical Care Medicine August 2008;36:2433-40

MRSA : 

MRSA Methicillin-resistant Staphylococcus aureus. Methicillin resistance implies resistance to all penicillins, cephalosporins, carbapenems and beta lactam/beta lactamase inhibitor combinations.

MRSA : 

MRSA Hospital associated MRSA isolates often are multiply resistant to other commonly used antimicrobial agents, including erythromycin, clindamycin and tetracycline. Community associated MRSA isolates are often resistant only to beta lactam agents and erythromycin

Why are MRSA important? : 

Why are MRSA important? Pathogenicity Limited treatment options MRSA are transmissible Some strains of MRSA – known as epidemic strains or EMRSA – are more easily spread. 16 epidemic strains are identified and the commonest to affect hospitals are EMRSA-15 and EMRSA-16.

Systemic treatment of infections : 

Systemic treatment of infections Glycopeptides Vancomycin Highly purified and less toxic preparations are available Although used in clinical practice vancomycin/aminoglycoside combinations do not have proved synergy for both MRSA and MSSA. Poor penetration through meninges.

Systemic treatment of infections : 

Glycopeptides Teicoplanin Greater lipophilicity than vancomycin Linezolid Active against MRSA, VRE and PRSP Effective orally Blood counts should be monitored Systemic treatment of infections

Systemic treatment of infections : 

Systemic treatment of infections Rifampicin Useful in CNS infections, Bone infections and Endocarditis. Should always be used with other anti staphylococcal agents and should never be used alone. Beta lactam/BLI combinations (Augmentin, Pip+Taz) Not effective against MRSA

Systemic treatment of infections : 

Systemic treatment of infections Quinupristin/dalfopristin Derived from the streptogramins pristinamycin IA and IIB Belong to the family of macrolides-lincosamides-streptogramins The drugs are present in a fixed 30:70 ratio and are synergistic.

Emerging threats : 

Emerging threats Vancomycin-Intermediate Staphylococcus aureus (VISA) First reported from Japan 1997 and later from USA and other countries. Have reduced susceptibility to vancomycin (MIC 4-8 µg/ml) All strains of S.aureus with vancomycin MIC of ≥ 4 µg/ml should be considered candidate strains for VISA. Disc diffusion test should not be used to detect vancomycin susceptibility and instead E test should be used. Vancomycin-resistant Staphylococcus aureus (VRSA) First reported in the USA in Michigan in July 2002. MIC ≥ 32 µg/ml. Heteroresistant strains are already emerging.

ESBLs INCLUDE : 

ESBLs INCLUDE Enzymes that mediate resistance to Penicillins, 3rd generation Cephalosporins, Aztreonam. But not to Cephamycins (Cefoxitin & Cefotetan) and Carbapenems. Most of these are derived from point mutations of older TEM and SHV beta-lactamases that normally confer high level resistance to early Penicillins and 1st generation Cephalosporins. Commonly produced by E.coli and Klebsiella but may also occur in Enterobacter, Salmonella, Proteus, Citrobacter, Morganella, Serratia, Shigella etc.

NEWER ESBLs INCLUDE : 

NEWER ESBLs INCLUDE These are not mutated from TEM and SHV. CTX-M types – Evolved separately, at least some of them via the escape and mutation of chromosomal beta-lactamases of Kluyvera spp. Over 35 types are known. Spread into community. VEB-1: Acinetobacter boumanni – Vietnam/France. PER-1: Pseudomonas and Acinetobacter – Turkey OXA-2 & OXA-10 mutants: Pseudomonas – Turkey.

ESBLs ARE CLINICALLY IMPORTANT : 

ESBLs ARE CLINICALLY IMPORTANT They destroy Cephalosporins, workhorse hospital antibiotics, given as first-line agents to many severely ill patients. Delayed recognition and inappropriate treatment with Cephalosporins → Increased mortality. ESBL-mediated resistance is not always obvious in vitro to all Cephalosporins. Many ESBL producers are multi-resistant to non-beta-lactam antibiotics – Quinolones, Aminoglycosides, Co-trimoxazole.

ESBLs in the ICU : 

ESBLs in the ICU NICUs can also be a focus of infections with multiply resistant Klebsiellae ICUs in tertiary referral hospitals may acquire pts. already colonized with ESBL-producing organisms – triggering an outbreak Nursing homes and chronic care facilities: also focus of infections with ESBL-producing organisms Paterson DL & Bonomo RA. Clin Microbiol Rev 2005;18(4): 657–86 Intensive care units (ICUs) are often the epicenter of ESBL production in hospitals

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ESBL Co-resistance Aminoglycosides Fluoroquinolones Tetracyclines Sulfamethoxazole-Trimethoprim Chloramphenicol

TREATMENT OPTIONS : 

TREATMENT OPTIONS CEPHAMYCINS (Cefoxitin and Cefotetan) – Though Cephamycins are resistant to most ESBLs they should be used carefully, because they develop resistance quickly due to reduced expression of OMPs. Further Cephamycins are hydrolyzed by other type of beta-lactamases called Amp C.

TREATMENT OPTIONS : 

TREATMENT OPTIONS Beta lactamase inhibitor combinations. BLI acts as a suicide substrate that forms a stable intermediate, rendering the ESBL enzyme inactive. Clavulanic acid, Tazobactam, Sulbactam.

Problems associated with using beta-lactams with or without BLIs : 

Problems associated with using beta-lactams with or without BLIs Inoculum effect If the inoculum of the testing organism is increased by 100 fold, MIC increases very much dramatically. Inoculum CTX CTZ AZT 5 x 105 cfu 2 1 0.5 5 x 107 cfu 256 32 32

Problems associated with using beta-lactams with or without BLIs : 

Problems associated with using beta-lactams with or without BLIs Clinical importance of Inoculum effect When bacterial killing and destruction of the antibiotic occur simultaneously, liberated enzyme from the dead cells reduces the external concentration of the antibiotic. The larger the inoculum effect is - the more susceptible the drug is to hydrolysis by the organism’s beta-lactamases.

Problems associated with using beta-lactams with or without BLIs : 

Problems associated with using beta-lactams with or without BLIs Clinical importance of Inoculum effect Higher inocula occur in endocarditis, meningitis, septic arthritis, osteomyelitis, abscesses and other deep seated infections and Sepsis When treated with BLI combinations the patient initially shows improvement but later deteriorates rapidly, owing to faster destruction of the antibiotic by the enzyme released from the dead bacteria.

Problems associated with using beta-lactams with or without BLIs : 

Problems associated with using beta-lactams with or without BLIs BLI combinations are not useful when bacteria produce ESBLs along with other types of beta-lactamases like Amp C. Amp C beta-lactamases Chromosomal, Class C beta-lactamases Produced by several enterobacteriaceae and Pseudomonas Confers resistance to most beta-lactams including BLI combinations. Treatment of choice – 4th generation cephalosporins like Cefepime or Carbapenems. (Cefepime – Think about inoculum effect)

Problems associated with using beta-lactams with or without BLIs : 

Problems associated with using beta-lactams with or without BLIs Plasmid mediated Amp C Transfer of genes from chromosomes to plasmids Occurs in E.coli, Klebsiella, Citrobacter, Enterobacter, Proteus etc. MIR-1, CMY-2, BIL-1, FOX-1, MOX-1, CMY-3 Detection of plasmid mediated Amp C is difficult by routine tests because it is not inducible. So all the labs should detect both ESBLs and Amp C. We have bacteria producing 3-6 types of beta lactamases including BL of different classes.

TREATMENT OPTIONS : 

TREATMENT OPTIONS Carbapenems Meropenem, Imipenem+Cilastatin, Ertapenem Highly resistant to ESBLs – due to the trans-6 hydroxy ethyl group. They have significant PAE even against Pseudomonas Resistance mechanisms Production of Metallo carbapenamases (Class B beta-lactamases) by some-Acinetobacter and Pseudomonas strains Efflux pumps Changes in OMPs Aztreonam is the drug of choice in treating infections caused by carbapenamase producing bacteria.

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THANK YOU