Author - Dr. Manoj Luthra, Dr. Suryasnata Das
Hospital-acquired infections (HAIs), also termed healthcare-associated infections (HCAIs) or nosocomial infections. HAIs represent one of the most significant and preventable causes of patient morbidity, mortality, and prolonged hospitalisation worldwide.[27]

The spectrum of HAIs includes ventilator-associated pneumonia (VAP)[24] and hospital-acquired pneumonia (HAP), catheter-associated urinary tract infections (CAUTI), central line-associated bloodstream infections (CLABSI), surgical site infections (SSI), and Clostridioides difficile infections (CDI). 

Cardiac surgery patients carry a uniquely high risk of HAIs due to prolonged operative times, extensive use of invasive devices (central lines, urinary catheters, endotracheal tubes), immunosuppression, and cardiopulmonary bypass-induced immune dysregulation. HAIs after cardiac surgery are associated with significantly higher mortality, prolonged intensive care unit (ICU) stays, and increased healthcare costs.[26]

The object of this chapter is to provide a broad framework for common hospital acquired infections in the post operative cardiothoracic patient and outline a reasonable empiric antibiotic regimen based on the likely causative organisms.

Hospital acquired pneumonia and Ventilator acquired pneumonia

HAP is defined as pneumonia occurring more than 48 hours after hospital admission. VAP is defined as pneumonia occurring more than 48 hours after endotracheal intubation. Both are particularly common in the cardiac surgery ICU given prolonged ventilatory support and suppressed mucociliary clearance following cardiopulmonary bypass.[1]

Common Pathogens

Most Common organisms are [1,5]Pseudomonas aeruginosa (25-48%), Staphylococcus aureus (including MRSA) (20-28%), and Klebsiella pneumoniae.

However, locally prevalent organisms can be the cause also and include Acinetobacter species (often multidrug-resistant), Escherichia coli, S. pneumoniae or H. influenzae.

Early-onset (<4 days) is often caused by antibiotic-sensitive organisms while late-onset (>4 days) is more likely to more likely to involve multi drug resistant (MDR) pathogens.

Diagnosis

• Clinical criteria: new fever, purulent sputum, leucocytosis or leukopenia, and declining oxygen saturation.
• Radiographic evidence: new or progressive pulmonary opacities on chest X-ray or CT.
• Microbiology: blood cultures and sputum cultures should ideally be obtained before initiating antibiotics. Bronchoalveolar lavage (BAL) is reserved for specific indications.

CT chest: not routine, but useful for detailed evaluation, pleural collections, and to guide invasive sampling

Treatment

Empiric therapy is usually initiated with intravenous antibiotics targeting [1,2]MRSA (e.g., Vancomycin, Teicoplanin or Linezolid) and Gram-negative organisms, especially anti-pseudomonal agents (e.g., Ceftazidime,Piperacillin-tazobactam, Cefepime, Meropenem).

Appropriate targeted antibiotic therapy is initiated once culture results are available with identification of the organism and antibiotic susceptibility. The choice of regimen should be guided by the onset timing, local antibiogram, and risk factors for MDR organisms. De-escalation is mandatory upon culture results

Duration: the duration of treatment is individualised based on clinical, radiological and biochemical (e.g. procalcitonin) improvement. A 7-day course is adequate for most HAP/VAP; extended courses (10–14 days) may be required when clinical improvement is slow. Daily reassessment is essential.[1]

Aspiration pneumonia 

Aspiration contributes to a significant proportion of both HAP and VAP, particularly in post-operative, sedated, and neurologically impaired patients But surprisingly, current recommendations and guidelines suggest that the causative organism in aspiration pneumonia is unlikely to be anaerobic bacteria. Current IDSA/ATS 2016 guidelines do not recommend routine empirical anaerobic coverage for aspiration pneumonia unless lung abscess, pleural empyema, or putrid sputum (strongly suggestive of anaerobes) is present.[1]

Preventive Management (VAP Bundle)

Bundle-based approaches have demonstrated up to 45–70% reduction in VAP rates in high-income countries. Implementation in Indian ICUs has shown significant reductions in VAP rates across participating ICMR network hospitals.[3,4]

Urinary Tract Infections (UTI)

1. Uncomplicated Urinary Tract Infection

E. coli accounts for 75-95% of all cases of uncomplicated cystitis . Other organisms include other Enterobacteriaceae ([9]Proteus pp.s, Klebsiella spp.) and Gram-positive cocci (e.g.Enterococcus spp.).

Treatment

 Empiric oral treatment options include:

•  Nitrofurantoin 100 mg twice daily for 5 days
• Fosfomycin 3 g as a single dose
• Fluoroquinolones (ciprofloxacin or levofloxacin) for 3 days — note high fluoroquinolone resistance in Indian E. coli strains
• Amoxicillin-clavulanate, cefdinir, or cefpodoxime for 3-7 days

Note: Fosfomycin and nitrofurantoin should not be used for suspected pyelonephritis. Amoxicillin monotherapy is not recommended due to high resistance prevalence.[9]

1. Complicated UTI 

UTIs associated with systemic symptoms (fever, chills, rigors) or extension beyond the bladder to the kideney or prostrate (signs suggestive of pyelonephritis or prostatitis) have been referred to as complicated UTI. 

E. coli is still the most common organism, but MDR Enterobacteriaceae group bacteria, Pseudomonas or a Gram positive bacteria become more likely in hospitalised patients.. [9]

Treatment

• IV ceftriaxone or amikacin for non-MDR organisms
• Fluoroquinolones: bear in mind high resistance rates in India before prescribing
• Piperacillin-tazobactam or meropenem when MDR is suspected
• Vancomycin, linezolid, or daptomycin if Gram stain suggests a Gram-positive organism (e.g., MRSA, VRE)

1. Catheter associated urinary tract infection (CAUTI)

CAUTI is defined as a positive urinary culture associated with symptoms or signs consistent with UTI, in a patient with an indwelling or suprapubic catheter for more than 2 days. Patients who have had a catheter within the past 48 h are also considered as CAUTI.Common symptoms of UTI include fever [7](>38°C),suprapubic tenderness, costovertebral angle pain or acute mental status changes. 

Bacteriology 

• Short-term (<2 weeks): E. coli accounts for approximately 1/3 of isolates; the remainder include other Enterobacteriaceae, Pseudomonas spp. and  Gram-positive cocci (Enterococcus spp.).
• Long-term (>2 weeks): infections tend to be polymicrobial; Proteus mirabilis is particularly common

Preventive Management

• Insert urinary catheters only when clinically necessary and remove as soon as possible — daily review of catheter necessity is mandatory.
• Use aseptic technique for insertion.
• Maintain a closed drainage system continuously.
• Consider external urinary collection devices where feasible — the CDC recommends external devices as an alternative to indwelling catheters where possible.
• In patients where catheter removal is not possible (e.g., obstructive uropathy), set clear clinical parameters and protocols for early removal.[8,10]

Treatment

In patients with short term catheterization, urine samples can be collected through the sample collection  port. However, in patients with long term indwelling catheters, a urine specimen after a freshly placed catheter is preferred.

Antibiotic choice mirrors acute complicated UTI (see above). Duration is typically 7-14 days.Emperic antimicrobials should be used according to the local or institutional antibiogram. Usually, when ESBL or MDR organisms are suspected carbapenems (meropenem, imipenem) or piperacillin-tazobactam for Gram-negatives; vancomycin or linezolid for Gram-positives are recommended. 

Central Line-Associated Bloodstream Infections (CLABSI)

CLABSI is defined as a primary bloodstream infection in a patient who has a central venous catheter (CVC) in place within the 48-hour period before the onset of the infection, with no infection identifiable at another source. [11]

Central Line-Associated Bloodstream Infections (CLABSI) are primarily caused by skin flora and gram-negative bacteria, most commonly coagulase-negative staphylococci (31%), S. aureus (20%), and Candida species (9%). [14]

• Common Pathogens Gram-Positive Bacteria (most common): coagulase-negative staphylococci (S. epidermidis), Staphylococcus aureus including MRSA , and Enterococcus species.
• Gram-Negative Bacteria: Pseudomonas aeruginosa, Klebsiella pneumoniae, E. coli, and Acinetobacter baumannii.

Fungi: Candida species (C. albicans and non-albicans Candida. In recent times a rise infection due to non albican Candida like Candida tropicalis, Candida auris has been seen. 

Diagnosis

Blood cultures must be drawn simultaneously from both a peripheral vein and the central line lumen.

• Preferably paired cultures ( 2 sets of aerobic and anaerobic blood culture bottles) should be collected
• Differential time-to-positivity (DTP): if the central line culture turns positive more than 2 hours before the peripheral culture, catheter-related bloodstream infection (CRBSI) is likely.[11]
• Clinical signs: fever, chills, rigors, hypotension without an alternative source of infection.

Management

Management involves a combination of removing the source of infection and antimicrobial therapy.[11]

Antimicrobial Therapy

• Empiric coverage: Vancomycin or Teicoplanin for MRSA and coagulase-negative staphylococci; add Gram-negative coverage (third-generation cephalosporin or antipseudomonal agent such as piperacillin-tazobactam) based on local susceptibility patterns and risk factors.
• Empiric antifungal coverage: echinocandins (e.g., micafungin or caspofungin) should be started early if Candida is suspected — particularly in patients with prolonged ICU stay, TPN, or prior broad-spectrum antibiotics.[15]
• Step-down to targeted therapy once culture sensitivities are available.

Catheter Management:

• Bathe ICU patients aged >2 months with a chlorhexidine preparation on a daily basis before insertion
• Subclavian vein is considered the preferable site for central venous catheter (CVC) [12]
• Use ultrasound guidance for catheter insertion
• Use chlorhexidine-containing dressings (> 2 years of age)
• For non-tunneled CVCs in adults and children, change transparent dressings and perform site care with a chlorhexidine-based antiseptic at least every 7 days or immediately if the dressing is soiled, loose, or damp. Change gauze dressings every 2 days or earlier if the dressing is soiled, loose, or damp
• Remove nonessential catheters
• Routine replacement of administration sets not used for blood, blood products, or lipid formulations can be performed at intervals of up to 7 days
• Disinfect catheter hubs, needleless connectors, and injection ports before accessing the catheter
• Additional Precautions
  • Use antiseptic- or antimicrobial-impregnated CVCs
  • Use antimicrobial lock therapy for long-term CVCs
  • Use an antiseptic-containing hub/connector cap/port protector to cover connectors
• Points to remember
  • Do not use antimicrobial prophylaxis for short-term or tunneled catheter insertion or while catheters are in situ
  • Do not routinely replace CVCs or arterial catheters

Duration of Therapy: 

• Uncomplicated CLABSI (e.g., S. epidermidis): typically 7-14 days after catheter removal.[11]
• Complicated CLABSI (endocarditis, osteomyelitis, septic thrombosis): 4-6 weeks of targeted intravenous therapy.[11]

Surgical Site Infections (SSI)

Surgical site infections are among the most serious complications following cardiac surgery, given the proximity of the sternal wound to the heart and mediastinum. Sternal wound infections range from superficial wound infections to the life-threatening deep sternal wound infection (DSWI) or mediastinitis.[21]

Definitions

The CDC defines SSI as an infection occurring within 30 days of a surgical procedure (or within 90 days if a prosthetic implant is placed). In cardiac surgery, SSIs are classified as:[16]

• Superficial Incisional SSI: involving only skin and subcutaneous tissue . Usually diagnosed within 30 days of surgery.
• Deep Incisional SSI: involving deep soft tissues such as fascia and muscle and is diagnosed within 30-90 days of surgery.
• Organ/Space SSI (Mediastinitis): the most serious category, involving structures within the operative field such as the mediastinum and pericardium.

Risk Factors Specific to Cardiac Surgery

• Diabetes mellitus — especially poorly controlled perioperative hyperglycaemia (blood glucose >180 mg/dL)[17,18]
  • Obesity (BMI >30) — infection risk is higher in obese patients and 6 times higher in morbidly obese patients[17]
    • Use of bilateral internal mammary artery (BIMA) — compromises sternal blood supply[18]
    • Prolonged cardiopulmonary bypass time
    • Renal failure, immunosuppression, and prior MRSA carriage
    • Female sex and unplanned reoperation

Prevention Bundles

• Surgical antibiotic prophylaxis (SAP) should be administered within 60 minutes before incision; use cefazolin/ cefuroxime as first-line agent. In MRSA carriers, add vancomycin prophylaxis.[23] SAP should continue no longer than 24 hours postoperatively. For cardiac surgery, where data is conflicting, some centres extend up to 48 hours — but routine prolonged prophylaxis increases antimicrobial resistance without additional benefit.
• Redosing is required during prolonged procedures (over 4 hours) or in cases of significant blood loss (>1500 mL)[23]
• Hair removal: use an electric clipper only if hair removal is absolutely necessary. Shaving with a razor is strongly discouraged as it creates micro-abrasions that increase infection risk.[6]
• MRSA decolonisation: cardiac and orthopaedic surgery patients who are known nasal carriers of [6]S. aureus should receive perioperative intranasal mupirocin 2% ointment, with or without chlorhexidine body wash.
• Skin preparation: Preferably use 2 % chlorhexidine gluconate (CHG) in alcohol-based solution for surgical site preparation.[6]
• Blood glucose control: maintain perioperative blood glucose below 180 mg/dL; compromised glucose levels are independently associated with SSI risk.[17]
• Normothermia: maintain body temperature throughout the perioperative period.
• Surgical Safety Checklist: routine use of the WHO Surgical Safety Checklist is recommended.[28]
• Training of patient and attendant on wound care should be done to avoid SSI post discharge 

Management of SSI

Risk factors include diabetes, obesity, bilateral IMA harvesting, prolonged bypass time, and re-exploration for bleeding. [19,22]Early recognition is paramount — fever, leukocytosis, sternal instability, wound erythema/discharge beyond post-op day 5, and elevated CRP/procalcitonin should prompt urgent evaluation. CT chest is the investigation of choice to assess sternal dehiscence, fluid collections, and mediastinal involvement.

Superficial SSIs are managed with wound opening, debridement, culture-directed antibiotics (cover S. aureus, S. epidermidis, and gram-negatives including Pseudomonas in high-risk units), and negative pressure wound therapy(NPWT).

Deep SSIs and mediastinitis require aggressive surgical debridement, sternal rewiring if bone is viable, and primary closure with pectoralis major or rectus abdominis muscle flap coverage — the latter being the cornerstone of modern management, dramatically reducing mortality compared to open packing. NPWT as a bridge to flap reconstruction has become standard practice.[20] Omentoplasty is also a highly effective, often salvage, surgical technique for treating deep sternal wounds infections and mediastinitis when other methods fail like muscle flap.

Microbiology Sample Collection

Empirical IV antibiotics (vancomycin + piperacillin-tazobactam) should be started immediately and narrowed per culture sensitivity. Duration is typically 4–6 weeks for mediastinitis. Sternal plating systems (titanium) are increasingly used for rigid fixation in complex reconstructions.

  Duration of Antimicrobial Therapy

References

Hospital-Acquired Pneumonia / Ventilator-Associated Pneumonia

1. Kalil AC, Metersky ML, Klompas M, et al. Management of Adults with Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016;63(5):e61-e111. doi:10.1093/cid/ciw353

2. Torres A, Niederman MS, Chastre J, et al. International ERS/ESICM/ESCMID/ALAT guidelines for the management of hospital-acquired pneumonia and ventilator-associated pneumonia. Eur Respir J. 2017;50(3):1700582. doi:10.1183/13993003.00582-2017

3. Klompas M, Branson R, Cawcutt K, et al. Strategies to Prevent Ventilator-Associated Pneumonia, Ventilator-Associated Events, and Nonventilator Hospital-Acquired Pneumonia in Acute-Care Hospitals: 2022 Update. Infect Control Hosp Epidemiol. 2022;43(6):687-713. doi:10.1017/ice.2022.88

4. Indian Council of Medical Research (ICMR). Annual Report on Antimicrobial Resistance Surveillance Network (AMRSN). New Delhi: ICMR; 2023. Available at: https://main.icmr.nic.in/amr

5. Rello J, Ollendorf DA, Oster G, et al. Epidemiology and outcomes of ventilator-associated pneumonia in a large US database. Chest. 2002;122(6):2115-2121. doi:10.1378/chest.122.6.2115

6. World Health Organization. Global guidelines for the prevention of surgical site infection. 2nd ed. Geneva: WHO; 2018. ISBN 978-92-4-155047-5

Urinary Tract Infections / CAUTI

7. Hooton TM, Bradley SF, Cardenas DD, et al. Diagnosis, Prevention, and Treatment of Catheter-Associated Urinary Tract Infection in Adults: 2009 International Clinical Practice Guidelines from the Infectious Diseases Society of America. Clin Infect Dis. 2010;50(5):625-663. doi:10.1086/650482

8. Gould CV, Umscheid CA, Agarwal RK, Kuntz G, Pegues DA; Healthcare Infection Control Practices Advisory Committee. Guideline for Prevention of Catheter-Associated Urinary Tract Infections 2009. Infect Control Hosp Epidemiol. 2010;31(4):319-326. doi:10.1086/651091

9. Gupta K, Hooton TM, Naber KG, et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis. 2011;52(5):e103-e120. doi:10.1093/cid/ciq257

10. Lo E, Nicolle LE, Coffin SE, et al. Strategies to Prevent Catheter-Associated Urinary Tract Infections in Acute Care Hospitals: 2014 Update. Infect Control Hosp Epidemiol. 2014;35(5):464-479. doi:10.1086/675718

Central Line-Associated Bloodstream Infections (CLABSI)

11. Mermel LA, Allon M, Bouza E, et al. Clinical Practice Guidelines for the Diagnosis and Management of Intravascular Catheter-Related Infection: 2009 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2009;49(1):1-45. doi:10.1086/599376

12. O’Grady NP, Alexander M, Burns LA, et al. Guidelines for the prevention of intravascular catheter-related infections, 2011. Clin Infect Dis. 2011;52(9):e162-e193. doi:10.1093/cid/cir257

13. Marschall J, Mermel LA, Fakih M, et al. Strategies to Prevent Central Line-Associated Bloodstream Infections in Acute Care Hospitals: 2014 Update. Infect Control Hosp Epidemiol. 2014;35(7):753-771. doi:10.1086/676533

14. Wisplinghoff H, Bischoff T, Tallent SM, Seifert H, Wenzel RP, Edmond MB. Nosocomial bloodstream infections in US hospitals: analysis of 24,179 cases from a prospective nationwide surveillance study. Clin Infect Dis. 2004;39(3):309-317. doi:10.1086/421946

15. Pappas PG, Kauffman CA, Andes DR, et al. Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2016;62(4):e1-e50. doi:10.1093/cid/civ933

Surgical Site Infections in Cardiac Surgery

16. Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR. Guideline for Prevention of Surgical Site Infection, 1999. Centers for Disease Control and Prevention (CDC) Hospital Infection Control Practices Advisory Committee. Am J Infect Control. 1999;27(2):97-132. doi:10.1016/s0196-6553(99)70088-x

17. Lola I, Levidiotou S, Petrou A, et al. Are there independent predisposing factors for postoperative infections following open heart surgery? J Cardiothorac Surg. 2011;6:151. doi:10.1186/1749-8090-6-151

18. Diez C, Koch D, Kuss O, et al. Risk factors for mediastinitis after cardiac surgery – a retrospective analysis of 1700 patients. J Cardiothorac Surg. 2007;2:23. doi:10.1186/1749-8090-2-23

19. Braxton JH, Marrin CA, McGrath PD, et al. Mediastinitis and long-term survival after coronary artery bypass graft surgery. Ann Thorac Surg. 2000;70(6):2004-2007. doi:10.1016/s0003-4975(00)01963-4

20. Petzina R, Hoffmann J, Navasardyan A, et al. Negative pressure wound therapy for post-sternotomy mediastinitis reduces mortality rate and sternal re-infection rate compared to conventional treatment. Eur J Cardiothorac Surg. 2010;38(1):110-113. doi:10.1016/j.ejcts.2010.01.033

21. Fowler VG Jr, O’Brien SM, Muhlbaier LH, Corey GR, Ferguson TB, Peterson ED. Clinical predictors of major infections after cardiac surgery. Circulation. 2005;112(9 Suppl):I358-365. doi:10.1161/CIRCULATIONAHA.104.525790

22. Ridderstolpe L, Gill H, Granfeldt H, Ahlfeldt H, Rutberg H. Superficial and deep sternal wound complications: incidence, risk factors and mortality. Eur J Cardiothorac Surg. 2001;20(6):1168-1175. doi:10.1016/s1010-7940(01)00991-5

23. Bratzler DW, Dellinger EP, Olsen KM, et al. Clinical practice guidelines for antimicrobial prophylaxis in surgery. Am J Health Syst Pharm. 2013;70(3):195-283. doi:10.2146/ajhp120568

General Hospital-Acquired Infections / Guidelines

24. Centers for Disease Control and Prevention (CDC). National Healthcare Safety Network (NHSN). Healthcare-Associated Infection (HAI) Surveillance Definitions. Atlanta: CDC; 2024. Available at: https://www.cdc.gov/nhsn

25. World Health Organization. Report on the Burden of Endemic Health Care-Associated Infection Worldwide. Geneva: WHO; 2011. ISBN 978 92 4 150150 7

26. Allegranzi B, Bagheri Nejad S, Combescure C, et al. Burden of endemic health-care-associated infection in developing countries: systematic review and meta-analysis. Lancet. 2011;377(9761):228-241. doi:10.1016/S0140-6736(10)61458-4

27. Magill SS, Edwards JR, Bamberg W, et al. Multistate point-prevalence survey of health care-associated infections. N Engl J Med. 2014;370(13):1198-1208. doi:10.1056/NEJMoa1306801

28. van Klei WA, Moons KG, Leyssius AT, Knape JT, Rutten CL, Grobbee DE. A reduction in anesthesia-related major complications after implementation of 2010 WHO Surgical Safety Checklist at a university medical center. Br J Anaesth. 2012;108(2):222-231. doi:10.1093/bja/aer390