Colonization is the presence of a microorganism in or on a host, with growth and multiplication but without any overt clinical expression or detected immune response in the host at the time it is isolated. Normal colonization in humans begins during the birth process and through subsequent contacts with the inanimate or animate environments until a delicately balanced “normal” flora is established; subsequently, the precise components of this flora evolve. This normal flora, such as coagulase-negative Staphylococcus or Staphylococcus aureus on the skin or Candida albicansin the gastrointestinal tract, vagina, or perineal area, can result in infection when normal body defenses are impaired through underlying disease, immunomodulating therapy, or the use of invasive devices, or when the delicate balance of the normal flora is altered through antimicrobial therapy. Many, if not most, hospital-acquired infections result directly or indirectly from patient colonization; studies have shown that hospitalized patients are colonized rapidly with hospital flora. Recognizing this reservoir of patients colonized with epidemiologically important pathogens in our hospitals and improving barrier precaution measures or altering host susceptibility will be necessary if we are to reduce the incidence of infections with these organisms.

Transmissible spongiform encephalopathies are rare lethal diseases induced in humans and animals by unconventional agents called transmissible spongiform encephalopathy agents (TSEAs), virions, or prions. Several cases of iatrogenic Creutzfeldt-Jakob disease (CJD) have been reported in the literature after neuro-surgery, treatment with pituitary-derived hormones, corneal grafting, and use of dura mater lyophilisates. In a given infected individual, TSEA-associated infectiousness depends on the nature of the organ: the central nervous system has the highest infectiousness, spleen and lymph nodes a medium infectiousness, and organs such as bone, skin, or skeletal muscles do not harbor any detectable infectiousness in experimental models. Transmissible spongiform encephalopathy/prions have unconventional properties; in particular, they resist almost all the chemical and physical processes that inactivate conventional viruses. Therefore, prevention of CJD agent transmission must be taken into account in daily hospital practice. Efficient sterilization procedures should be determined. In tissue and blood donation, donors with a neurologic history must be excluded, and patients treated with pituitary-derived hormones should be considered potentially infected with TSEA and excluded.

A case-control (46 cases, 23 controls) study was done to determine risk factors for an outbreak of a multiresistant Acinetobacter baumanii (only susceptible to colistin) in a university hospital. The use of antecedent antibacterials and intubation were independent risk factors. No common source was found. With control measures, the outbreak resolved gradually.

Patients frequently develop nosocomial infections that are caused by normal flora colonizing the patient at the time of admission, or by exogenous pathogens that are acquired and subsequently colonize the patient after admission to the hospital. To prevent nosocomial infections, a variety of strategies have been used either to prevent colonization from occurring, to eradicate colonizing organisms, or to prevent the progression from colonization to infection. These strategies include implementation of infection control measures designed to prevent acquisition of exogenous pathogens, eradication of exogenous pathogens from patients or personnel who have become colonized, suppression of normal flora, prevention of colonizing flora from entering sterile body sites during invasive procedures, microbial interference therapy, immunization of high-risk patients, and modification of antibiotic utilization practices. Because strategies that require widespread use of antimicrobial agents to suppress or eradicate colonizing organisms tend to promote emergence of multidrug-resistant pathogens, greater emphasis should be given to those strategies that prevent colonization from occurring or employ techniques other than administration of prophylactic antibiotics to eradicate colonization. Restricting inappropriate use of antibiotics should reduce the frequency with which patients become colonized and infected with multidrug-resistant organisms.

Conventional wisdom suggests that those who assess healthcare processes and outcomes always should stratify cases by severity of illness; however, infection control personnel should analyze each quality assessment tool with and without severity adjustment and determine whether such adjustment is necessary. This article briefly reviews severity adjustments for diseases or procedures involving specific organ systems, as well as those applicable to all diseases, including the commercially available systems. Also discussed is whether and how these various systems for severity adjustment can be compared. Finally, the article will provide selected references for individuals who will use these scoring systems and need more information.

We performed tuberculin and anergy testing in 91 healthy volunteer employees from the patient transport and housekeeping units at an urban tertiary-care hospital, stratifying results by the risk factor of patient contact. Tuberculin positivity was highly prevalent in this group; patient contact was not a predictor of tuberculosis infection risk, and anergy was rare.

Controversy has surrounded the use of liquid chemical germicides to reprocess medical instruments that are damaged by heat sterilization. A review of the literature was performed to assess and compare the efficacy of disinfection and sterilization processes. The results of this review demonstrate that high-level disinfection of thoroughly cleaned endoscopes is not associated with a higher infection rate than is “sterilization.” While there may be a theoretical distinction between the highest level of disinfection and sterilization, thorough cleaning eliminates clinical differences between the two. High-level disinfection is quick, effective, inexpensive, and recommended whenever heat sterilization is not feasible. A low-temperature sterilization process should be considered only if it is comparable in cost to disinfection or if it offers demonstrated advantages without damaging the instrument. Neither disinfection nor sterilization is likely to be effective if the instrument is not cleaned thoroughly after use.