Journal Reviews
October 1, 1998 6 minutes read
Journal Reviews
Wenzel RP, Edmond MB. Vancomycin-resistant Staphylococcus aureus: Infection control considerations. Clin Infect Dis 1998; 27:245-251.
With intermediate levels of vancomycin resistance now appearing in staphylococcal strains, the authors update their 1996 assessment of infection control measures for a pathogen that was then "unthinkable": vancomycin-resistant S. aureus (VRSA).
Japanese reports of rapid dissemination of S. aureus strains with intermediate resistance to vancomycin mimic the earlier situation with the rapid spread of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE), they warn.
"Such observations support our view that one cannot be too compulsive with early isolation and case finding when infections due to strains with either intermediate or frank resistance to vancomycin arise in hospitals in the United States," they emphasize.
Outlining measures similar to those recommended by the Centers for Disease Control and Prevention, they underscore proper antibiotic use to minimize the emergence of resistant pathogens; rapid isolation of newly admitted patients who are likely to be carrying resistant strains; and institution of a program of infection control policies to prevent transmission. They cite, for example, that in the Netherlands - where control of MRSA is a priority - every patient arriving from outside the country is isolated until surveillance cultures reveal that they do not harbor MRSA.
Even if patients are isolated, however, compliance among health care workers has been shown to be erratic in observational studies. In view of such data, as well as "the gravity of failure to control the transmission of VRSA," the authors recommend assigning a nurse at the doorway to enhance compliance with isolation protocols for patients with infections suspected to be caused by VRSA.
"When rates of endemic MRSA rose above 20% in United States hospitals, some infection control physicians had forsaken efforts toward assiduous isolation, continued identification of new cases, and improved hand washing practices," they conclude. "However, noting that it is possible to reduce transmission, and thus prevalence rates, other physicians viewed such data as compelling medical reasons for renewed efforts at infection control. A common excuse offered for inaction - the ineluctable march of high infection rates due to resistant organisms - is not useful for infection control. Furthermore, favorable infection control data resulting from renewed efforts provide an ethical incentive for maintaining great efforts at infection control."t
Managan LP, Simonds DN, Pugliese G, et al. Are U.S. hospitals making progress in implementing guidelines for prevention of Mycobacterium tuberculosis transmission? Arch Intern Med 1998; 158:1,440-1,444.
Most hospitals in the United States appear to be making progress in the implementation of Centers for Disease Control and Prevention guidelines for preventing the transmission of tuberculosis, the authors report.
In particular, an increase in the number of adequate TB isolation rooms and the use of appropriate respiratory protection by health care workers may have contributed to a concomitant reduction of occupational TB skin test conversion rates recorded in other studies, they noted.
The authors found an improvement in the number of hospitals that included house staff and attending physicians in skin-testing programs from 1992 to 1996 (69% vs. 89% and 50% vs. 69%, respectively). Nonetheless, the study identified a need for continued improvement in including those physicians in programs, and in the surveillance of skin test conversions among all health care workers. In 1992 the authors surveyed 632 public hospitals and 444 private hospitals. In 1996, they resurveyed 136 samples (50%) of all 1992 respondent hospitals with six or more TB admissions in 1991.
Of the 1,076 hospitals surveyed in 1992, 763 (71%) respondents returned a completed questionnaire. Among these, 536 (71%) of 755 reported having rooms that met CDC criteria for acid-fast bacilli isolation, i.e., negative air pressure, at least six air exchanges per hour, and air directly vented to the outside. The predominant respiratory protective device for health care workers was a nonfitted surgical mask, and attending physicians were infrequently (50%) included in tuberculin skin-testing programs. In the 1996 resurvey, 103 (76%) of 136 respondents returned a completed questionnaire. Of these, 99 (96%) reported having rooms that met CDC criteria for acid-fast bacilli isolation. The currently recommended N95 respiratory protective devices were predominantly used by health care workers, and physicians were increasingly included in the hospitals' tuberculin skin-testing programs.t
Sutton PM, Nicas M, Reinisch F, et al. Evaluating the control of tuberculosis among health care workers: adherence to CDC guidelines of three urban hospitals in California. Infect Control Hosp Epidemiol 1998; 19:487-493.
In contrast to the findings reported above, the authors of this study of three hospitals found lapses in infection control and noted that important aspects of day-to-day tuberculosis control practice did not conform to the written TB control policy.
"Subsequent to the identification of TB patients, healthcare workers at all three hospitals were potentially exposed to Mycobacterium tuberculosis aerosol due to breaches in negative-pressure isolation, the limitations of dilution ventilation, and the failure to maintain engineering controls and to implement respiratory protection controls fully," they state. "These findings lend support to the Occupational Safety and Health Administration's policy presumption that, absent clear evidence to the contrary, newly acquired healthcare worker M. tuberculosis infections are work-related."
To evaluate adherence to components of the Centers for Disease Control and Prevention (CDC) guidelines for preventing the transmission of TB in health care facilities, they used direct observation in addition to a standardized questionnaire.
In all, 28% (7/25) of isolation rooms tested were under positive pressure, and in 83% (20/24) of rooms, tested supply air did not mix rapidly with room air. In virtually all (26/27) rooms tested, air potentially containing TB aerosol moved toward, rather than away from, likely worker locations, they reported.
"None of the hospitals regularly checked the performance of engineering controls," they said. "Only one hospital adhered to the CDC minimum requirements for respiratory protection. Training of health care workers generally was underutilized as a TB prevention measure. Hospitals did not provide comprehensive counseling regarding the need for health care workers to know their immune status and the risks associated with M. tuberculosis infection in an immunocompromised individual. Employee representatives did not have a voice in TB-related decision making."
The authors concede that TB infection is not a uniquely occupational event, and the fact that hospitals do not adhere to the CDC guidelines does not mean skin-test conversions are due to hospital exposures. However, hospital workers are in a setting where there may be a substantially greater risk of TB exposure as compared to the general community environment, they noted. To illustrate, a hospital can be considered a community of inpatients, and the case rate of TB in the hospital community can be expressed as the percentage of hospital inpatients having infectious TB, the authors explained. The rate of hospital inpatients having infectious TB in 1995 in the three hospitals was equivalent to 350 per 100,000, 390 per 100,000, and 410 per 100,000, respectively.
"These rates are 12 to 20 times greater than the TB incidence rate in the corresponding county where each hospital is located," they concluded.t
Souvenir D, Anderson DE Jr., Palpant L, et al. Blood cultures positive for coagulase-negative staphylococci: Antisepsis, pseudobacteremia, and therapy of patients. J Clin Microbiol 1998; 36:1,923-1,926.
The authors conducted a cohort study over 12 weeks in two tertiary-care teaching hospitals to determine the incidence of significant coagulase-negative staphylococcal bacteremia vs. that of so-called pseudobacteremia, i.e., contaminated blood cultures, and to evaluate drug therapy in patients whose blood cultures yielded coagulase-negative staphylococci.
A total of 3,276 cultures of blood from 1,433 patients were evaluated in the study. Using published criteria, significance was assigned retrospectively to the results of blood cultures by a panel of infectious disease physicians who achieved 100% agreement with the attending physicians' intuitive clinical impressions when classifying significant bacteremia. Overall, 89 (2.7%) cultures yielded skin flora, with 81 of 89 (91%) involving coagulase-negative staphylococci. Significant coagulase-negative staphylococcal bacteremia accounted for 20 of 81 (24.7%), indeterminate bacteremia for 10 of 81 (12.3%), and contamination for 59 of 81 (72.8%).
All patients with significant coagulase-negative staphylococcal bacteremia were treated, as were five of 10 with indeterminate bacteremia and 24 of 59 patients with contaminated blood cultures. Vancomycin was used to treat 18 (90%) of those with significant bacteremia and 20 (83%) of those with contaminated blood cultures, almost the same proportion. Although inappropriate, there were no significant adverse events or prolongation of hospital stays. However, due to the use of vancomycin, an extra $1,000 per patient was spent. The authors noted that coagulase-negative staphylococci continue to be the most common cause of pseudobacteremia, and although recognized as such at the time, attending physicians nonetheless opted to treat empirically, usually with vancomycin, indicating that measures to limit the unnecessary use of vancomycin and other agents have yet to take effect.n
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