Blood cultures (2)Endocarditis

8/5/2020A/Prof John Ferguson

John.ferguson@health.nsw.gov.au

BSI positive result liaison approach

• Daily review of every new positive Gram stain – check the microscopy yourself!

https://idmic.net/2020/05/05/positive-blood-culture-clinician-liaison-process-microbiology-part-1-2/

• Daily review of cultures and AST • Invite clinicians to attend the lab regularly – daily lab bench rounds• Document liaison process and recommendations- essential• Surveillance – classify event metadata for significant events• Evaluate potential contaminant events – check FBC if possible,

speak with doctor. If central line present and thought significant (ieisolate positive with 24 hrs), suggest repeat blood culture before antibiotics.

https://idmic.net/2016/09/26/blood-culture-liaison-process-advice-by-organism-type-gram-positives/

Pseudobacteraemia• Contamination of blood sample before inoculation to

culture bottle-– EDTA tubes – Chlorhexidine solution– betadine solution– ABG machine

• Tell-tale species: environmental GNR generally– B. cepacia– Pseudomonas– Serratia– Achromobacter– Other

Gram positives isolated from blood: commonest species

• Neonates• Streptococcus agalactiae (group B Strep.)• Staph. aureus (MSSA, MRSA)• Coagulase negative staph (prematures )

• Children • Streptococcus pneumoniae• Streptococcus pyogenes • Staph. aureus (MSSA, MRSA)

• G positives- Adults:– S. aureus– S. pneumoniae– Strep. A, B, C, G– Enterococcus species

Gram positive: principle source of infectionCommunity top 10

PneumoniaSkin/soft tissue JointEndocarditis

Healthcare associated:IV line assoc.

Principal source of infection Adult Paed TotalAbdominal sepsis (other) 67 2 69Endocard (native) 90 1 91Joint inf (other) 131 28 159No focus (e.g. febrile neutropenia) or unknown site 111 8 119Pneumonia (other) 433 22 455Sepsis (unk primary site) 732 56 788Skin structure, cellulitis, boils 82 2 84Skin(cellul/other) 281 9 290Soft tissue 181 9 190UTI (other) 90 5 95Total 2198 142 2340

Principal source of infection Adult Paed TotalAbdominal sepsis (other) 29 1 30Device-related infection without metastatic focus 64 10 74Line-assoc bstream inf 463 121 584No focus (e.g. febrile neutropenia) or unknown site 25 8 33Pneumonia (other) 34 2 36Sepsis (unk primary site) 194 65 259Skin(cellul/other) 30 1 31Soft tissue 31 31UTI (device-associated) 35 35Wound infection (surgical) 31 31Total 936 208 1144

Epidemiology of S. aureus

Gram positive pathogen- causes a wide range of infections – all ages, all body sites, community and healthcare-associated

Images : https://en.wikipedia.org/wiki/Staphylococcus_aureus

Impact of SAB- Hunter data (NSW)

A. Healthcare-associated events (2018, HNE LHD )60 healthcare-associated SAB cases occurred with 7% due to methicillin-resistant Staphylococcus aureus (MRSA) and age-adjusted 30 day mortality of 9%. SAB relapse within 15-90 days occurred in 2.1% of adult events 7% of paediatric events. Principle sites commonest:● Vascular access device (e.g. intravenous cannula, central venous catheter, arterial line,tunnelled central line, subcutaneous port) – 50%● Skin and soft tissue infection (e.g. abscess, boil, post-operative wound infection) – 10%● Primary blood stream infection with no apparent primary source or clear focus – 8%

B. Community-acquired events (2018)234 community acquired SAB events were documented with 7% due to MRSA and 30 day age-adjusted mortality of 16%. SAB relapse within 15-90 days occurred in 2% SAB adult events and 0% of paediatric events.• Primary blood stream infection with no apparent primary source or clear focus – 30%• Skin and soft tissue infection (e.g. abscess, boil, deep abscess) -26%• Joint infection or spinal osteomyelitis – 16%• Pneumonia – 6%

Strong evidence : appropriate clinical care reduces morbidity and mortality!

SAB- key steps for management: same principles everywhere – adapt as appropriate

1. Commence intravenous (IV) high dose flucloxacillin AND vancomycin (unless allergies) immediately, pending susceptibilities.2. Remove any removable foci of infection (change IV lines, drain abscesses)3. Evaluate for complicated SAB using the criteria defined below4. Repeat blood cultures between 48 and 72 hours after the start of treatment.5. Monitor full blood count (FBC), C-reactive protein (CRP), electrolytes and liver enzymes every 3 days for 2 weeks and then weekly for the duration of IV antibiotic treatment.6. Arrange trans-thoracic echocardiogram (TTE) in all adults and in selected children between days 5 and 7.7. Except in renal dialysis patients, arrange or insert a peripherally-inserted central catheter (PICC) line once blood cultures have become negative.8. Consult the Infectious Diseases on-call consultant or contact the on-call Clinical Microbiologist for ALL patients with SAB (by phone if necessary – (02) 4921 3000 for ID physician or (02) 4921 4000 for Clinical Microbiologist).9. Give adult patients 2 to 6 weeks of intravenous (IV) antibiotics10. Provide verbal & written advice to your patient and their family about the symptoms of relapse and the need for early review if problems occur. The guideline has a patient information card within.

https://aimed.net.au/2020/05/08/essential-clinical-care-of-staphylococcus-aureus-bloodstream-infection-sab-2/

SAB- “complicated”

https://aimed.net.au/2020/05/08/essential-clinical-care-of-staphylococcus-aureus-bloodstream-infection-sab-2/

Gram negatives isolated from blood: commonest species

• Neonates : Enterobacterales – E. coli, Klebsiella, Salmonella• Older patients: Healthcare associated

Organism type Adult Paed TotalGNEG (A baumannii) 22 22GNEG (A baumannii) MRAB phenotype 2 2GNEG (Acinetobacter other) 34 3 37GNEG (H influenzae) 61 11 72GNEG (N meningitidis) 26 19 45GNEG (other) 154 11 165GNEG (Salmonella) 57 7 64GNEG (Enterobacterales) 4444 109 4553GNEG (Enterobacterales) ESBL genotype 31 1 32GNEG (Enterobacterales) CRE phenotype 6 6GNEG (Enterobacterales) ESBL phenotype 47 1 48GNEG (Enterobacterales) CPE genotype 2 2GNEG (P aeruginosa) 339 14 353GNEG (environmental) 49 3 52GNEG (Stenotrophomonas) 28 6 34Total 5302 185 5487

Gram negatives: principle source of infection

Community top 10:UrinaryAbdominalGIT

Healthcare associated:UTIIntra-abdominalIV line assoc.

Principal source of infection Adult Paed TotalBiliary tract infection (including cholangitis) 613 3 616Gastroenteritis including neutropenic mucositis 105 6 111Intra-abdominal infection other than biliary tract 170 3 173No focus (e.g. febrile neutropenia) or unknown site 130 3 133Pneumonia (other) 148 4 152Sepsis (unk primary site) 793 24 817Skin(cellul/other) 43 2 45Soft tissue 41 41UTI (other) 1766 39 1805UTI (procedure or device-associated) 165 165Total 3974 84 4058

Principal source of infection Adult Paed TotalBiliary tract infection (including cholangitis) 63 1 64Device-related infection without metastatic focus 28 11 39Intra-abdominal infection other than biliary tract 81 8 89Line-assoc bstream inf 262 49 311No focus (e.g. febrile neutropenia) or unknown site 54 4 58Pneumonia (other) 35 1 36Sepsis (unk primary site) 299 19 318UTI (other) 127 1 128UTI (procedure or device-associated) 146 1 147Wound infection (surgical) 28 28Total 1123 95 1218

Key liaison questions for Gram negatives

• Gram stain morphology ? Check it yourself • Healthcare associated? ICU associated?• Assess likely source (nb mellioidosis red flags

dependent on region)– Urine (? Evidence of obstruction, catheter)– Biliary (? Evidence of obstruction, cholecystitis)– Intra-abdominal (? Evidence of perforated viscus)– GIT– Pneumonia – especially ICU ventilator-associated– IV line sepsis – esp. ICU central line-associated

• Empiric antibiotics – what has been chosen? Generally an aminoglycoside required at 5-7mg/kg single dose

• Source control? Surgical options;

https://idmicro.files.wordpress.com/2016/09/gram-stain-appearance-and-implications-ver-2-2020-ferguson.pdfhttps://idmic.net/2020/05/08/blood-culture-liaison-process-advice-by-organism-type-gram-negatives/

Risk factors for endocarditis• Prosthetic heart valves• Congenital heart defects: cumulative rate 6.1 per 1,000

children; high flow condition : lower incidence: viz. – cyanotic CHD, 31/1000– endocardial cushion defects, 11– left-sided lesions, 8; right-sided lesions, 4; – patent ductus arteriosus, 3; – ventricular septal defect, 3; atrial septal defect, 3.

• History of endocarditis• Damaged heart valves (rheumatic fever, SLE etc)• History of intravenous (IV) drug use

http://www.medscape.com/viewarticle/819866 Short paper on risk and CHD

https://www.slideshare.net/ikramdr01/infective-endocarditis-173069661?qid=9f3957a9-4895-4948-93b5-3d213078c114&v=&b=&from_search=5

Microbiology of endocarditis : largely Gram positive species responsible

Mechanisms of bloodstream invasion

• Day to day – transient bacteraemia- efficiently removed by host defences :– Tooth cleaning (influenced by state of teeth and gums)– Dental therapy– Nose blowing – Translocation from the bowel flora – cleared by portal circulation

• Invasive infections – localised skin or mucosal site entry-> localised and/or systemic infection;– E.g. Neisseria meningitidis colonises the throat -> minor pharyngitis and

thence invasion directly to blood stream– Streptococcus pneumoniae causing a lobar pneumonia with secondary spread

to the blood stream• Healthcare-associated – transgression of natural host defences

– IV lines, urinary catheters– Operative wounds– Chemotherapy or transplant induced immune suppression

Impact of foreign material• Animal wound infection models where a contaminated

sutured wound is created– High tolerance (low incidence of wound infection despite

high inoculum)– 100-1000 fold less tolerance of an organism load in the

wound• Vascular space interventions of relevance:

– Prosthetic heart valves, pacemakers– Vascular bypasses, arterial stents, AV fistulae – vein or

prosthetic material– Material becomes covered with layer of endothelium –

reduces thrombosis and infection potential

Thank you….

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