In health care, a cross infection, also called a hospital infection or a nosocomial infection, is "any infection which a patient contracts in a health-care institution." Important microbes are methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Clostridium difficile.
Examples include ventilator-associated pneumonia, surgical site infections, infections associated with indwelling catheters, such as after urinary catheterization. Legionella pneumophila outbreaks have been associated with contaminated ventilation systems, and devices assumed to be safe, such as bedside steam humidifiers.
- Recommendations for Appropriate urinary catheterization
- Prevention of Intravascular Catheter-Associated Infections
- Prevention of Surgical Site Infections
- Prevention of Ventilator-Associated Pneumonia
Prevention of cross infections is a priority of the Institute for Healthcare Improvement (IHI).
- From the IHI 100,000 Lives Campaign
- "Prevent Central Line Infections…by implementing a series of interdependent, scientifically grounded steps called the "Central Line Bundle"."
- "Prevent Surgical Site Infections…by reliably delivering the correct perioperative antibiotics at the proper time." Significant reduction may be achieved by procedures as simple as proper hand washing, use of clippers rather than razors to shave the site of surgery, or prompt administration of antibiotics following surgery.
- "Prevent Ventilator-AssociatedPneumonia…by implementing a series of interdependent, scientifically grounded steps including the 'Ventilator Bundle'."
- From the IHI 5 Million Lives Campaign: 
- "Reduce Methicillin-Resistant Staphylococcus aureus (MRSA) infection…by reliably implementing scientifically proven infection control practices."
Some sources may be obscure Legionella spp., known to colonize building heating, ventilation and air conditioning (HVAC) systems, has caused infection from hospital equipment that traditionally has been considered resistant to bacterial growth, such as heated bedside humidifiers.  The replacement of heated with ultrasonic humidifiers reduced a risk of burns but increased the risk of infection; current practices include sterilizing humidifiers between patients, changing water frequently, and using sterile water.
Manifestations of cross infections
|Extended-spectrum β-lactamase (ESBL) producing||Carbapenem such as meropenem|
|K. pneumoniae carbapenemase (KPC) producing||Polymyxins such as colistin|
Nosocomially-acquired infection often are resistant to multiple antibiotics.  Given the ability for antibiotic resistance to transfer among organisms, less common antibiotics may be needed to treat multidrug-resistant forms.
- Anonymous (2023), Cross infection (English). Medical Subject Headings. U.S. National Library of Medicine.
- Anonymous (2009). HHS Action Plan to Prevent Healthcare-Associated Infections: Executive Summary. U.S. Department of Health & Human Services. Retrieved on 2009-01-07.
- Anonymous (2009). HHS Action Plan to Prevent Healthcare-Associated Infections: Prevention – Prioritized Recommendations. U.S. Department of Health & Human Services. Retrieved on 2009-01-07.
- Berwick DM, Calkins DR, McCannon CJ, Hackbarth AD (2006). "The 100,000 lives campaign: setting a goal and a deadline for improving health care quality". JAMA 295 (3): 324–7. DOI:10.1001/jama.295.3.324. PMID 16418469. Research Blogging.
- Institute for Healthcare Improvement: Overview of the 100,000 Lives Campaign. Retrieved on 2008-01-03.
- “Status Quon’t”, IHI’s 2007 Progress Report (PDF file)
- "Nosocomial Infection: Approach to Postoperative Symptoms of Infection", From ACS Surgery Online, Posted 06/07/2006, E. Patchen Dellinger, M.D., F.A.C.S.
- Institute for Healthcare Improvement: Campaign. Retrieved on 2008-01-03.
- "Overview of the 5 Million Lives Campaign"
- "IHI Launches National Initiative to Reduce Medical Harm in U.S. Hospitals, Builds on 100,000 Lives Campaign" Infection Control Today, December 12, 2006
- Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (March 26, 2004), "Guidelines for Preventing Health-Care--Associated Pneumonia, 2003", Morbidity and Mortality Weekly Report 53(RR03): 1-36
- Bor DH, Makadon HJ, Friedland G, Dasse P, Komaroff AL, Aronson MD (1988). "Fever in hospitalized medical patients: characteristics and significance". J Gen Intern Med 3 (2): 119–25. PMID 3357068.
- McGowan JE, Rose RC, Jacobs NF, Schaberg DR, Haley RW (March 1987). "Fever in hospitalized patients. With special reference to the medical service". Am. J. Med. 82 (3 Spec No): 580–6. PMID 3826121.
- Wanahita A, Goldsmith EA, Musher DM (June 2002). "Conditions associated with leukocytosis in a tertiary care hospital, with particular attention to the role of infection caused by clostridium difficile". Clin. Infect. Dis. 34 (12): 1585–92. DOI:10.1086/340536. PMID 12032893. Research Blogging.
- Peleg AY, Hooper DC (2010). "Hospital-acquired infections due to gram-negative bacteria.". N Engl J Med 362 (19): 1804-13. DOI:10.1056/NEJMra0904124. PMID 20463340. Research Blogging.
- Jane D. Siegel, Emily Rhinehart, Marguerite Jackson, Linda Chiarello, the Healthcare Infection Control Practices Advisory Committee (2006), Management of Multidrug-Resistant Organisms In Healthcare Settings,, Centers for Disease Control
- Chastre J, Wolff M, Fagon JY, Chevret S, Thomas F, Wermert D et al. (2003). "Comparison of 8 vs 15 days of antibiotic therapy for ventilator-associated pneumonia in adults: a randomized trial.". JAMA 290 (19): 2588-98. DOI:10.1001/jama.290.19.2588. PMID 14625336. Research Blogging. Review in: ACP J Club. 2004 Sep-Oct;141(2):30
- Gorwitz RJ, Jernigan DB, Powers JH, Jernigan JA, and Participants in the CDC Convened Experts’ Meeting on Management of MRSA in the Community (2006), Strategies for clinical management of MRSA in the community: Summary of an experts’ meeting convened by the Centers for Disease Control and Prevention, Gorwitz