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This review of Acinetobacter outbreaks summarizes factors related to the presence and recognition of organism transmission and describes the implementation of control and prevention measures directed at limiting spread. Exogenous transmission of Acinetobacter should be considered when infections are endemic and when case rates increase. Increasing or new antimicrobial resistances in a collection of isolates also suggest transmission, and transmission can be definitively confirmed when isolates are found to be indistinguishable from or related to one another by a discriminatory genotyping test. An investigation for a common source should be conducted. When a common source cannot be found and eliminated, or once an endemically transmitted organism is established, containment or prevention efforts may require aggressive interventions, complex interventions, or both. Colonization at multiple sites, the relative ease of induction of antibiotic resistance in the organism following patient exposure to multiple drugs, and long-term environmental survival provide enhanced opportunities for the transmission of Acinetobacter between and among patients. New approaches and interventional trials are needed to define effective measures for the prevention and control of Acinetobacter infections.
To determine if an apparent increase in bloodstream infections (BSIs) in patients with central venous catheters (CVCs) was associated with the implementation of a needleless access device.
Retrospective cohort study using a derived CVC-days factor for estimating appropriate denominator data.
A 350-bed urban, acute, tertiary-care hospital.
BSI surveillance data were obtained, and high-risk areas for BSIs were determined. A random 5% sample of medical records was used to estimate CVC days, and a cohort study was conducted to compare BSI rates before and during needleless device use. A survey was conducted of nursing needleless-device practices.
The surgical intensive-care unit (SICU), the medical intensive-care unit, and the solid organ transplant unit (OTU) were identified as high-risk units. Using existing surveillance BSI data and the estimated CVC days, the catheter-related BSI rates in the high-risk surgical patients were significantly higher during the needleless-device period compared with the preneedleless-device period (SICU, 9.4 vs 5.0/1,000 CVC days; OTU, 13.6 vs 2.2/1,000 CVC days). A survey of the nurses revealed that 60% to 70% were maintaining the needleless devices correctly.
We observed a significant increase in the BSI rate in two surgical units, SICU and OTU, associated with introduction of a needleless device. This increase occurred shortly after the needleless device was implemented and was associated with nurses' unfamiliarity with the device, and needless-device use and care practices different from the manufacturer's recommendations.
An outbreak investigation was conducted to determine if an increase in bloodstream infections (BSIs) in patients with central venous catheters (CVC) had occurred. Because other methods of obtaining CVC days were not feasible, we used an estimation method based on a random 5% sample of medical records to determine the proportion of days that a CVC was present for each of three patient units. This calculated ratio was used to estimate the total CVC days for each unit. A cohort study was conducted in which the BSI rates before and during needleless device use were compared. This article describes the methods used to calculate this estimated denominator and discusses the need for such a denominator to be used by infection control practitioners when prospective collection of CVC days is not possible.
To describe control of endemic and outbreak-related methicillin-resistant Staphylococcus aureus (MRSA) at two affiliated hospitals.
Prospective surveillance of patients with MRSA. Disposable gloves were used by all staff having direct contact with the affected patient or his immediate environment, and patient isolates were typed by pulsedfield gel electrophoresis (PFGE) of genomic DNA. Surveillance and PFGE typing were used concurrently to identify possible nosocomial outbreaks, confirm or refute cross-infection, and support a need for additional outbreak control interventions.
A university hospital (Hospital A) and a university-affiliated public hospital (Hospital B).
Patients with MRSA colonization or infection over an 18-month interval (June 1993-November 1994).
Proper handwashing and gloving practices were reemphasized with staff following confirmation of outbreaks.
Hospital A had 60 community-acquired and 48 nosocomial cases of MRSA. Two small outbreaks (affecting a total of seven patients) and two pseudo-outbreaks were identified. Hospital B had 36 community-acquired and 22 nosocomial cases of MRSA. Only one outbreak affecting five patients occurred. All outbreaks ended shortly after staff meetings that emphasized ongoing and extremely careful handwashing and gloving when caring for identified patients. The majority of nosocomial cases at both hospitals were not related epidemiologically or had isolates with unique PFGE types. Pseudo-outbreaks were confirmed by demonstrating that isolates from epidemiologically related cases (by time and clinical service or hospital unit) had different PFGE types. Hospital A cases had 39 different PFGE types, and Hospital B cases had 31 different PFGE types.
MRSA in hospitals, including outbreaks identified by prospective surveillance and confirmed by PFGE typing, can be controlled by minimal special precautions and interventions. This is possible despite the continuous admission of patients with MRSA from the community. PFGE typing is useful to confirm outbreaks and pseudo-outbreaks, demonstrate differences among epidemiologically unrelated isolates, and substantiate the efficacy of MRSA control programs within hospitals.
To describe methicillin-resistant Staphylococcus aureus (MRSA) control in a hospital, including a surgical intensive care unit (SICU) outbreak.
Prospective surveillance of newly identified patients with MRSA. Barrier isolation (disposable gloves for direct contact with patient or immediate environment) was used for the routine care of hospitalized MRSA patients as of October 1991. Begirming in 1992, MRSA isolates were typed by restriction endonuclease enzyme analysis of plasmid DNA (REAP) and/or pulsed-field gel electrophoresis of genomic DNA (PFGE). Surveillance information and MRSA typing were used concurrently to identify nosocomial case clustering, confirm cross-infection, and support a need for additional outbreak control interventions.
University-affiliated public hospital.
Patients with newly identified MRSA colonization or infection from 1991 through 1993 and epidemiologically associated staff providing care to eight SICU patients in an outbreak.
Barrier isolation for affected and unaffected patients in and admitted to the SICU institution when the outbreak was identified and cross-infection confirmed. Anterior nares cultures of staff in contact with outbreak cases for detection of MRSA colonization.
Fifty-six hospitalized patients with community-acquired MRSA and 80 patients with nosocomial MRSA colonization or infection were identified during the 3 years. After the introduction of barrier isolation, the annual frequency of new nosocomial MRSA cases decreased and only one outbreak (eight cases in the SICU) caused by type-related isolates occurred, The other 35 nosocomial cases of MRSA during 1992 and 1993 were not epidemiologically related or were caused by isolates with different types. The SICU outbreak ended after instituting barrier isolation for all patients (with and without MRSA) in and admitted to the unit. Six colonized SICU staff were identified. All outbreak cases had identical or related MRSA types by PFGE and REAP. Staff isolates were different from case isolates by typing, and staff were not restricted and not given treatment for colonization. After more than 6 months of follow up, no further outbreaks of MRSA in the SICU or elsewhere in the hospital occurred despite returning to barrier isolation for affected patients only.
MRSA in hospitals and outbreaks of MRSA in ICUs can be controlled by surveillance and minimal barrier interventions. REAP or PFGE typing of MRSA can be used to support or refute the presence of cross-transmission. Typing also may be helpful when planning and assessing the effectiveness of interventions directed at endemic, as well as outbreak, MRSA control.
The incidence of methicillin-resistant Staphylococcus aureus (MRSA) has increased in communities and in healthcare facilities in the United States since the mid-1970s. Although MRSA often is thought of as a nosocomial infection problem because it is encountered in facilities of all types and sizes, it also causes many community-acquired infections. Approaches to control of MRSA vary widely, and there is lack of agreement on the most appropriate measures to control MRSA in healthcare facilities. The wide variation in approaches is due, in part, to the lack of data establishing the efficacy of specific control measures. As a result, the approaches that have been advocated have resulted in confusing and often conflicting recommendations and control measures. In some settings, there also have been unreasonable barriers and administrative hurdles that delay or prevent the transfer of patients between acute care and nursing (extended care) facilities.
Forty-three intubated and mechanically ventilated patients in five intensive care units (ICUs) of one hospital developed respiratory colonization or infection with Acinetobacter calcoaceticus subspecies anitratus over a 16-month interval. Neither the frequency nor rate of A anitratus isolation exceeded the hospital endemic norms. Single isolates from 34 of the patients were subtyped by plasmid DNA analysis, two biotyping systems and antimicrobial susceptibility to 24 drugs. Plasmid DNA fingerprints were distinct in 18 isolates (they differed from each other and all others), similar in two and identical or similar in ten. The latter group of isolates were recovered from patients in four ICUs. Reproducibility of biotyping was poor. Neither biotyping nor antimicrobial susceptibility were successful in identifying sameness among the group isolates nor differences among other isolates. We conclude that plasmid DNA fingerprinting should be used to assess the possibility of multiple patient transmissions of the same A anitratus strain in the absence of an obvious outbreak.
Clinical, bacteriologie, epidemiologic and hospital infection-control observations related to an inter-hospital outbreak of methicillin-resistant Staphylococcus aureus are described. The outbreak involved 66 patients at the University of Oregon Health Sciences Center (UOHSC) and its closely affiliated VA hospital, the Portland VA Medical Center (PVAMC). No environmental source of infection was identified; person-to-person transmission was most likely responsible for its spread. Surveillance cultures demonstrated nasal colonization in house staff and nursing personnel at both hospitals. Inter-hospital transfer of infection was, in all likelihood, achieved via nasal carriage by a single physician. Case-control analysis indicated a significantly increased risk (p < 0.05) of acquisition of infection related to age, number of days hospitalized, severity of underlying disease and number of invasive procedures. Prior antibiotic receipt was a significant risk factor when analyzed by univariate analysis (p < 0.01), but, in contrast to previous studies, this was not a significant risk factor (p > 0.05) when related variables were controlled by multivariate analysis. Prevention of spread of infection by routine infection control measures was less effective at PVAMC than at UOHSC. Patients at PVAMC were significantly older and had longer durations of hospitalization (p < 0.05). Antimicrobial therapy of colonized patients and personnel appeared to assist in the control of the outbreak at PVAMC. Antimicrobial therapy with topical bacitracin and oral rifampin, alone or in combination with oral trimethoprim-sulfamethoxazole, was effective in eliminating colonization with methicillin-resistant S. aureus. [Infect Control 1981; 2(6):453-459.]
This study describes the evaluation of 108 patients who had indwelling urethral catheters for acute medical and surgical indications. Patients were evaluated daily, and cultures from bladders and drainage bags were obtained. Appropriateness for continuing catheterization was assessed using preset criteria. Twenty-five patients developed urinary tract infections. Exposure to antibiotics and a shorter duration of catheterization were the only factors that correlated significantly with a delayed onset or decreased prevalence of infection. Factors found to have insignificant effects included age, sex, maintenance of the closed system, underlying host disease status, catheter type, and reason for catheterization. No collection systems with one way valves were used, but significant colony counts in drainage bag urine preceded urinary tract infection in only two patients. Thirty-six percent of the total 562 catheter days were judged unnecessary. A major emphasis must be placed on prompt catheter removal if the prevalence of nosocomial urinary tract infections is to be reduced substantially in a cost-effective manner [Infect Control 1981; 2(5):380-386.]
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