Epidemiology of community-acquired respiratory tract infections in adults. Incidence, etiology, and impact.

Upper respiratory tract infections are the most common types of infectious diseases among adults. It is estimated that each adult in the United States experiences two to four respiratory infections annually. The morbidity of these infections is measured by an estimated 75 million physician visits per year, almost 150 million days lost from work, and more than $10 billion in costs for medical care. Serotypes of the rhinoviruses account for 20 to 30 percent of episodes of the common cold. However, the specific causes of most upper respiratory infections are undefined. Pneumonia remains an important cause of morbidity and mortality for nonhospitalized adults despite the widespread use of effective antimicrobial agents. There are no accurate figures on the number of episodes of pneumonia that occur each year in ambulatory patients. In younger adults, the atypical pneumonia syndrome is the most common clinical presentation; Mycoplasma pneumoniae is the most frequently identified causative agent. Other less common agents include Legionella pneumophila, influenza viruses, adenoviruses, and Chlamydia. More than half a million adults are hospitalized each year with pneumonia. Persons older than 65 years of age have the highest rate of pneumonia admissions, 11.5 per 1,000 population. Pneumonia ranks as the sixth leading cause of death in the United States. The pathogens responsible for community-acquired pneumonias are changing. Forty years ago, Streptococcus pneumoniae accounted for the majority of infections. Today, a broad array of community-acquired pathogens have been implicated as etiologic agents including Legionella species, gram-negative bacilli, Hemophilus influenzae, Staphylococcus aureus and nonbacterial pathogens. Given the diversity of pathogenic agents, it has become imperative for clinicians to establish a specific etiologic diagnosis before initiating therapy or to consider the diagnostic possibilities and treat with antimicrobial agents that are effective against the most likely pathogens.

Infections in the elderly.

Elderly patients appear to be predisposed to serious infections because of coexisting chronic or acute diseases that disrupt integumental barriers, impair clearance mechanisms, or compromise cellular responses to infection. The severely disabled elderly are particularly at high risk, because they are often unable to care for their personal hygiene and are malnourished, immobile, incontinent, or institutionalized. Senescence of the immune system per se does not appear to be a major predisposing factor for infection in this population. Infections in the elderly frequently present with non-specific signs and symptoms. Clues of focal infection are often absent or obscured by underlying chronic conditions. Once a site of infection is identified, clinicians should initiate therapy with broad-spectrum antibiotics to treat the array of most likely potential pathogens. Strategies to prevent infection include programs to help the elderly maintain active, non-institutionalized life-styles and the appropriate use of available vaccines.

Risk factors for postoperative infection.

During a 4-year period, we collected prospective epidemiologic data and intraoperative wound cultures from 1,852 surgery patients at a university-affiliated community hospital in order to identify the critical risk factors for postoperative wound infections and study the impact of perioperative antibiotics on the bacteriology of infected wounds. Stepwise logistic regression analysis revealed four risk factors that were independent of each other and highly predictive for subsequent wound infection. These were the surgical wound class, American Society of Anesthesiologists physical status grouping, duration of surgery, and results of intraoperative cultures. Addition of other variables to our model did not increase the predicted probability of infection. Even though patients with positive intraoperative cultures had an increased rate of infection, this information had limited clinical utility. The predictive value of a positive culture was low (32%), false-positive rate was high (82%), and concordance with isolates from infected wounds was low (41% when both cultures were positive). Patients who had received perioperative antibiotics and who developed infections were frequently infected with organisms that were resistant to the perioperative drug regimen, compared with patients who had not received antibiotics. A better understanding of the variables that affect the epidemiology and pathogenesis of postoperative wound infection will enable us to make more valid comparisons of rates among hospitals, help us to develop more effective infection control strategies and provide us with more effective treatments.

Risk factors for postoperative pneumonia.

Prospectively studied were 520 patients undergoing elective thoracic, upper abdominal and lower abdominal surgeries to analyze risk factors for postoperative pneumonias. Over-all, pneumonias developed in 91 of the 520 patients studied (17.5 percent). The acquisition of pneumonia was highly associated with preoperative markers of the severity of underlying diseases such as low serum albumin concentrations on admission (P less than 0.005) and high American Society of Anesthesiologists pre-anesthesia physical status classification (P less than 0.0001). History of smoking (P less than 0.001), longer preoperative stays (P less than 0.0001), longer operative procedures (P less than 0.0001) and thoracic or upper abdominal sites of surgery (P less than 0.0001) were also significant risk factors for postoperative pneumonias. Although massive obesity, old age and male sex were also associated with increased incidences of pneumonia, statistical significance was lost when these variables were controlled for site or duration of surgery. We were able to identify risk factors for pneumonia and to define a subpopulation of patients in which the risk of pneumonia was negligible. The acquisition of pneumonia by a low-risk patient should alert the physician to the possibility of a potentially preventable nosocomial infection.

Prevention of catheter-associated urinary tract infections. Efficacy of daily meatal care regimens.

To evaluate the efficacy of daily cleansing of the urethral meatus-catheter junction in preventing bacteriuria during closed urinary drainage, randomized, controlled trials of two widely recommended regimens for meatal care were completed. In 32 (16.0 percent) of 200 patients given twice daily applications of a povidone-iodine solution and ointment bacteriuria was acquired, as compared with 24 (12.4 percent) of 194 patients not given this treatment. In 28 (12.2 percent) of 229 patients given once daily meatal cleansing with a nonantiseptic solution of green soap and water bacteriuria was acquired, as compared with 18 (8.1 percent) of 23 patients not given special meatal care. There was no evidence in either trial of a beneficial effect of meatal care. Moreover, each of four different statistical methods indicated that the rates of bacteriuria were higher in the treated groups than in the untreated groups. In subsets of female patients at high risk in both studies significantly higher rates of bacteriuria were noted in the treated groups than in the untreated groups. Current methods of meatal care appear to be hazardous, as well as expensive, and cannot be recommended as measures to control infection.

Bacillus species isolates from cerebrospinal fluid in patients without shunts.

Of 849 CSF cultures done at Hartford Hospital, nine were positive for nonanthrax Bacillus species. Differentiation of true nonanthrax Bacillus species infection from contamination requires careful consideration of the clinical findings, the clinical course, and the laboratory data. In seven patients the nonanthrax Bacillus species represented contamination. In two patients the nonanthrax Bacillus species represented true infection. In one of these infected patients, nonanthrax Bacillus species complicated a cranial gun shot wound. Bacillus cereus meningitis developed in the second patient, a premature infant, following sepsis from a contaminated IV catheter. Nonanthrax Bacillus species, especially B cereus, can be resistant to penicillins and cephalosporins when nonanthrax Bacillus species infections are being treated, susceptibility testing should always be performed.

Infection control in long-term-care facilities.

Although patients in long-term-care facilities are at increased risk of infection, little is known about how to practice infection control in this setting. This article reviews risk factors for infection, the components of an infection control program, and particular infections that are important in long-term-care facilities. In addition, special characteristics of long-term-care facilities that challenge the individuals charged with conducting effective infection control programs will be discussed.

The impact of preoperative skin disinfection on preventing intraoperative wound contamination.

The efficacy of total body showering and incision site scrub with disinfectant agents was evaluated in a randomized, prospective study of 575 patients undergoing selected surgical procedures. Patients who showered twice with 4% chlorhexidine gluconate had lower mean colony counts of skin bacteria at the surgical incision site in the operating room prior to the final scrub than patients who showered twice with povidone-iodine solution or medicated bar soap. Patients in the chlorhexidine group had no growth on 43% of the incision site skin cultures compared with 16% in the povidone-iodine group and 6% in the soap and water group. Patients who showered and who were scrubbed with chlorhexidine also had lower rates of intraoperative wound contamination. Bacteria were recovered from the wounds of 4% of patients using this regimen compared with 9% for patients who used povidone-iodine and 15% for patients who showered with medicated soap and water and were scrubbed with povidone-iodine. We noted no difference in surgery-specific infection rates among patients in the three treatment groups; however, our sample sizes were too small to evaluate this outcome parameter adequately. These data suggest that preoperative showering and scrubbing with chlorhexidine is an effective regimen to reduce extrinsic intraoperative contamination of the surgical wound from skin bacteria. The efficacy of this regimen to prevent postoperative wound infection needs to be evaluated in a well-designed, carefully controlled prospective trial with adequate numbers of patients to achieve statistically valid conclusions.

Description of case-mix adjusters by the Severity of Illness Working Group of the Society of Hospital Epidemiologists of America (SHEA).

Hospitals, insurance companies, and federal and state governments are increasingly concerned about reducing patient cost expenditures while maintaining high quality patient care. One method of reducing expenditures has been to tie hospital reimbursement with a prospective payment system based on diagnosis-related groups (DRGs). However, reimbursement under the DRG system is not acceptable for all patients in all hospitals because it is neither an accurate predictor of costs nor of clinical outcome. This deficiency poses significant problems for hospitals because DRGs are used nationwide as the prospective payment system for inpatients covered by Medicare. Several case-mix adjusters have been proposed to modify DRGs to improve their accuracy in predicting costs and outcome. We reviewed five of the most widely available indices: Acute Physiologic and Chronic Health Evaluation (APACHE II), Coded Disease Staging, Computerized Severity Index (CSI), Medical Illness Severity Group System (MEDISGROUPS), and Patient Management Categories (PMC). Recommendations for the use of a single case-mix adjuster cannot be made at this time because all indices have not been compared in sufficiently diverse settings and because some are better predictors of costs while others are better predictors of clinical outcome. Hospital epidemiologists and other infection control practitioners should be informed about these indices and their potential applications as they expand their role beyond infection control problems to issues concerning cost containment, quality assurance, and reimbursement.

Requirements for infrastructure and essential activities of infection control and epidemiology in hospitals: a consensus panel report. Society for Healthcare Epidemiology of America.

The scientific basis for claims of efficacy of nosocomial infection surveillance and control programs was established by the Study on the Efficacy of Nosocomial Infection Control project. Subsequent analyses have demonstrated nosocomial infection prevention and control programs to be not only clinically effective but also cost-effective. Although governmental and professional organizations have developed a wide variety of useful recommendations and guidelines for infection control, and apart from general guidance provided by the Joint Commission on Accreditation of Healthcare Organizations, there are surprisingly few recommendations on infrastructure and essential activities for infection control and epidemiology programs. In April 1996, the Society for Healthcare Epidemiology of America established a consensus panel to develop recommendations for optimal infrastructure and essential activities of infection control and epidemiology programs in hospitals. The following report represents the consensus panel's best assessment of needs for a healthy and effective hospital-based infection control and epidemiology program. The recommendations fall into eight categories: managing critical data and information; setting and recommending policies and procedures; compliance with regulations, guidelines, and accreditation requirements; employee health; direct intervention to prevent transmission of infectious diseases; education and training of healthcare workers; personnel resources; and nonpersonnel resources. The consensus panel used an evidence-based approach and categorized recommendations according to modifications of the scheme developed by the Clinical Affairs Committee of the Infectious Diseases Society of America and the Centers for Disease Control and Prevention's Hospital Infection Control Practices Advisory Committee.

Requirements for infrastructure and essential activities of infection control and epidemiology in hospitals: A consensus panel report. Society for Healthcare Epidemiology of America.

The scientific basis for claims of efficacy of nosocomial infection surveillance and control programs was established by the Study on the Efficacy of Nosocomial Infection Control project. Subsequent analyses have demonstrated nosocomial infection prevention and control programs to be not only clinically effective but also cost-effective. Although governmental and professional organizations have developed a wide variety of useful recommendations and guidelines for infection control, and apart from general guidance provided by the Joint Commission on Accreditation of Healthcare Organizations, there are surprisingly few recommendations on infrastructure and essential activities for infection control and epidemiology programs. In April 1996, the Society for Healthcare Epidemiology of America established a consensus panel to develop recommendations for optimal infrastructure and essential activities of infection control and epidemiology programs in hospitals. The following report represents the consensus panel's best assessment of needs for a healthy and effective hospital-based infection control and epidemiology program. The recommendations fall into eight categories: managing critical data and information; setting and recommending policies and procedures; compliance with regulations, guidelines, and accreditation requirements; employee health; direct intervention to prevent transmission of infectious diseases; education and training of healthcare workers; personnel resources; and nonpersonnel resources. The consensus panel used an evidence-based approach and categorized recommendations according to modifications of the scheme developed by the Clinical Affairs Committee of the Infectious Diseases Society of America and the Centers for Disease Control and Prevention's Hospital Infection Control Practices Advisory Committee.

Stevens-Johnson syndrome associated with Mycoplasma pneumoniae infections.

The Stevens-Johnson syndrome is a multisystem inflammatory disorder associated with a widespread erythematous eruption that can result in death. Although usually considered a pediatric disease, this syndrome frequently affects adults. There are many etiologic associations including drugs and infections; however, the pathophysiology of the syndrome remains obscure. Treatment at present is symptomatic and supportive. Although frequently used, the beneficial role of corticosteroids in this syndrome remains to be proved. The case report describes a young woman who after treatment with several drugs developed the Stevens-Johnson syndrome in association with a Mycoplasma pneumoniae infection. We include a brief review of the literature with emphasis on the Stevens-Johnsons syndrome's association with M pneumoniae infections. Those caring for patients with skin disease should be aware of the association between such treatable infections and this syndrome.

Residential care and the elderly: the burden of infection.

Long term care facilities (LTCFs) include a variety of different types of healthcare settings, each with their own unique infectious disease problems. This report focuses on the epidemiological considerations, risk factors and types of infections that occur in elderly patients institutionalized in nursing home settings. In the US, the number of patients in nursing homes continues to grow as the population ages. Today, patients in nursing homes have more complicated medical conditions than they did five years ago as they become even more elderly and the trend continues towards shorter and shorter hospital stays in acute care facilities. The patient population in nursing homes is uniquely susceptible to infections because of the physiological changes that occur with ageing, the underlying chronic diseases of the patients and the institutional environment within which residents socialize and live. In addition, in nursing home settings, problems with infections may be more difficult to diagnose because of their subtle presentations, the presence of co-morbid illnesses which obscure the symptoms of infection and the lack of on site diagnostic facilities. Delays in diagnosing and treating infections allow transmission to occur within the facility. Both endemic and epidemic infections occur relatively commonly in nursing homes. The incidence of endemic infections, such as catheter-associated urinary tract infections, lower respiratory infections and skin infections, is influenced by the debility level of the patients. Calculations of infection rates are influenced by the intensity of surveillance methods at each institution. Many endemic infections are unpreventable. Epidemic infections account for 10-20% of nursing home infections. These include clusters of upper or lower respiratory infections, gastroenteritis, diarrhoea, and catheter-associated UTI's. Epidemic infections are potentially preventable with sound infection control practices. Special attention must be paid to promote universal precautions and give certain patients, such as those with known infection or colonization with Clostridium difficile, MRSA or VRE, special consideration. The potential for epidemic infections with antibiotic-resistant organisms is real. In the nursing home setting, attention must be given to develop and support strong infection control programmes that can monitor the occurrence of institutionally-acquired infections and initiate control strategies to prevent the spread of epidemic infections. Education in infection control issues and attention to employee health is essential to enable staff to care appropriately for today's nursing home population and to prepare them for the even more complicated patients who will be cared for in this type of setting in future.

Prevention of intraoperative wound contamination with chlorhexidine shower and scrub.

In a prospective, controlled, clinical trial, we found that preoperative showering and scrubbing with 4% chlorhexidine gluconate was more effective than povidone-iodine or triclocarban medicated soap in reducing skin colonization at the site of surgical incision. Mean log colony counts of the incision site were one half to one log lower for patients who showered with chlorhexidine compared to those who showered with the other regimens. No growth was observed on 43% of the post shower skin cultures from patients in the chlorhexidine group compared with 16% of the cultures from patients who had povidone-iodine showers and 5% of those from patients who used medicated soap and water. The frequency of positive intraoperative wound cultures was 4% with chlorhexidine, 9% with povidone-iodine and 14% with medicated soap and water. This study demonstrates that chlorhexidine gluconate is a more effective skin disinfectant than either povidone-iodine or triclocarban soap and water and that its use is associated with lower rates of intraoperative wound contamination.

Postoperative pneumonia and urinary-tract infection: epidemiology and prevention.

Hospital-acquired pneumonias and urinary-tract infections are important causes of morbidity and mortality in surgical patients, and a great deal of effort has been expended on infection control strategies to prevent their occurrence. Prophylactic antibiotics, used either systemically or topically, are not routinely recommended for the prevention of either of these infections. The beneficial effects of these agents are transient, and they are often in association with the acquisition of colonization or infection with resistant bacteria. New approaches for infection control, not involving antibiotic agents, are being developed to lower the infection rates of both hospital-acquired pneumonias and urinary-tract infections to an irreducible minimum.

Predictors of intraoperative-acquired surgical wound infections.

During a 4-year period, we collected prospective epidemiological data and intraoperative wound cultures from 1852 surgery patients at a university-affiliated community hospital in order to identify the critical risk factors for postoperative wound infections and study the impact of perioperative antibiotics on the bacteriology of infected wounds. Stepwise logistic regression analysis revealed four risk factors that were independent of each other and highly predictive for subsequent wound infection. These were the surgical wound class, American Society of Anesthesiology (ASA) physical status grouping, duration of surgery and results of intraoperative cultures. Addition of other variables to our model did not increase the predicted probability of infection. Even though patients with positive intraoperative cultures had an increased rate of infection, this information had limited clinical utility because of its low predictive value, high false-positive rate and poor concordance with isolates from infected wounds. Patients who had received perioperative antibiotics and who developed infections were frequently infected with organisms that were resistant to the perioperative drug regimen, compared with patients who had not received antibiotics.

Comparison of nonwoven and woven gown and drape fabric to prevent intraoperative wound contamination and postoperative infection.

In a prospective, controlled clinical trial, nonwoven, disposable gown and drape fabrics were no better barriers to intraoperative wound contamination or postoperative wound infection than reusable cotton poplin. We observed no difference between the two study groups in either the frequency or level of intraoperative wound contamination as judged by cultures of specimens collected at the time of wound closure. Of procedures in which reusable fabrics were used, 13.1 percent had positive cultures compared with 15.5 percent of those in which disposable fabrics were used (difference not statistically significant). We recovered coagulase-negative Staphylococci from more than 95 percent of contaminated wounds. Rates of postoperative wound infection were virtually identical in the two groups. Our data suggest that either both fabrics were similar in their ability to block bacteria that were shed from skin surfaces from entering the wound, or that bacteria which contaminate the wound in clean surgical procedures are derived from sources other than skin.