Definition of low-value care in a low-risk preoperative population: A scoping review

RATIONALE

Preoperative care is one of the main areas in which to address low-value care. A detailed definition of what low-value care is in this period of the surgical care journey paves the way for new scientific research, clinical improvements, and reduction of unnecessary costs in this field.

AIMS AND OBJECTIVE

To identify how low-value care in low-risk preoperative population has been defined in the scientific literature and propose a low-value care framework with potential consequences in this setting.

METHODS

Scoping review of theoretical studies and peer-reviewed papers, including reviews, commentaries, or expert opinions, were considered eligible for inclusion. The following databases were consulted: MEDLINE (via PubMed), EMBASE, and SCOPUS (from inception to July 24, 2021), using a structured search with the keywords "low value care", "clinical waste", "preoperative", and "elective procedures." Two independent reviewers performed study selection and data extraction. The definition of low-value care in the preoperative period and their consequences were described after extracting previous low-value care concepts and summarising the contents. Also, a visual framework was built with this information.

RESULTS

From 1519 publications identified in the initial searches, 22 underwent full-text assessment, and 11 conceptual studies were included in the review. A total of four studies (36%) presented a general low-value care definition, and all studies report some situations considered low-value care in the preoperative field of low-risk surgeries. The most common example of preoperative low-value care, listed in nine studies (81%), was having asymptomatic patients undergo screening tests before surgery. The main clinical and nonclinical consequences of low-value care in the preoperative phase included false-positive results from exams as well as psychological distress, increased costs, and delay in surgery.

CONCLUSIONS

Revisiting and integrating previous definitions of low-value care in low-risk surgery into a scoping review is a starting point for de-implementing unnecessary care and promoting improvements in surgical pathways.

Early antiretroviral therapy for HIV-infected patients admitted to an intensive care unit (EARTH-ICU): A randomized clinical trial

Background

Highly active antiretroviral therapy (HAART) has reduced HIV-related morbidity and mortality at all stages of infection and reduced transmission of HIV. Currently, the immediate start of HAART is recommended for all HIV patients, regardless of the CD4 count. There are several concerns, however, about starting treatment in critically ill patients. Unpredictable absorption of medication by the gastrointestinal tract, drug toxicity, drug interactions, limited reserve to tolerate the dysfunction of other organs resulting from hypersensitivity to drugs or immune reconstitution syndrome, and the possibility that subtherapeutic levels of drug may lead to viral resistance are the main concerns. The objective of our study was to compare the early onset (up to 5 days) with late onset (after discharge from the ICU) of HAART in HIV-infected patients admitted to the ICU.

Methods

This was a randomized, open-label clinical trial enrolling HIV-infected patients admitted to the ICU of a public hospital in southern Brazil. Patients randomized to the intervention group had to start treatment with HAART within 5 days of ICU admission. For patients in the control group, treatment should begin after discharge from the ICU. The patients were followed up to determine mortality in the ICU, in the hospital and at 6 months. The primary outcome was hospital mortality. The secondary outcome was mortality at 6 months.

Results

The calculated sample size was 344 patients. Unfortunately, we decided to discontinue the study due to a progressively slower recruitment rate. A total of 115 patients were randomized. The majority of admissions were for AIDS-defining illnesses and low CD4. The main cause of admission was respiratory failure. Regarding the early and late study groups, there was no difference in hospital (66.7% and 63.8%, p = 0.75) or 6-month (68.4% and 79.2%, p = 0.20) mortality. After multivariate analysis, the only independent predictors of in-hospital mortality were shock and dialysis during the ICU stay. For the mortality outcome at 6 months, the independent variables were shock and dialysis during the ICU stay and tuberculosis at ICU admission.

Conclusions

Although the early termination of the study precludes definitive conclusions being made, early HAART administration for HIV-infected patients admitted to the ICU compared to late administration did not show benefit in hospital mortality or 6-month mortality.

ClinicalTrials.gov, NCT01455688. Registered 20 October 2011, https://clinicaltrials.gov/show/NCT01455688

The Quality of End-of-Life Care after Limitations of Medical Treatment as Defined by a Rapid Response Team: A Retrospective Cohort Study

BACKGROUND

Despite the increase in the identification of patients at the end of life after the introduction of rapid response team (RRT), there is doubt as to whether there has been an improvement in the quality of care offered to these patients. Proper end-of-life care is the next expected step after identifying patients who are dying.

OBJECTIVE

To evaluate the end-of-life care after limitations of medical treatment (LOMTs) as defined by an RRT.

DESIGN

This is a single-center retrospective cohort study at a tertiary teaching hospital in Porto Alegre, Brazil, from July 2014 to July 2016.

SETTING/SUBJECTS

We included 242 patients with an LOMT as defined by the RRT.

MEASUREMENTS

Outcomes of interest included symptoms and palliative measures after RRT review.

RESULTS

During the study period, there were 5396 calls to 2937 patients, representing 126 calls per 1000 hospital discharges. Of these calls, 4.9% (n = 242) resulted in an LOMT. The primary care team agreed with the LOMT decision proposed by the RRT in 91.7% of cases. Regarding end-of-life symptoms, 7.4% and 5.8% of patients presented with intense or moderate pain, respectively, and 62.4% of patients presented dyspnea in the last 48 hours of hospitalization. Less than 15% of patients received attention for their spiritual needs and/or received psychological support.

CONCLUSIONS

Our data reinforce the important role of RRTs in the identification of end-of-life patients with clinical deterioration. Despite the increase in the identification of these patients, the quality of end-of-life care needs to be improved.

HIV-1 reverse transcriptase mutations found in a drug-experienced patient confer reduced susceptibility to multiple nucleoside reverse transcriptase inhibitors

HIV-1 reverse transcriptase (RT) genotypes were obtained from 13 patients treated with stavudine. No previously-reported mutations indicative of stavudine resistance were found in these patients and no novel mutations occurred in more than two patients. One patient, treated with stavudine for 1 month and treated previously with zidovudine, zalcitabine and lamivudine, carried a mutation at codon 75 of the RT (V75M). A chimeric virus, including the patient's RT sequence from codon 25 to codon 220, which carried the resistance mutations M41 L, D67N, T69D, K70R, L210W and T215Y in addition to V75M, displayed reduced susceptibility to multiple nucleoside RT inhibitors (NRTIs). Removal of V75M from this RT background resulted in a return of susceptibility to didanosine and lamivudine. Our data are in agreement with previous studies demonstrating the rarity of stavudine resistance mutations in stavudine-treated patients. However, we describe a new set of mutations, found in the RT of a heavily-treated patient, that can confer reduced susceptibility to multiple NRTIs. These results underscore the importance of increased vigilance for possible multiple-drug resistance in patients who have been heavily treated with NRTIs.

A sequence variant of Staphylococcus hominis with a high prevalence of oxacillin and fluoroquinolone resistance

A newly identified subspecies of Staphylococcus hominis, S. hominis subsp. novobiosepticus, was found to be the cause of several invasive infections at a hospital in New Jersey. This subspecies differs from classical S. hominis, now S. hominis subsp. hominis, by the phenotypic characteristics of novobiocin resistance and the inability to ferment trehalose. DNA sequences of segments of 16S rRNA, DNA gyrase (gyrA), and DNA topoisomerase IV (grlA) genes were determined for the type strains of the 2 subspecies, and for 34 S. hominis clinical isolates. The 16S rRNA sequences of the type strains differed at 3 positions over 410 bp; the grlA sequences differed at 6 positions over 119 bp. These sequence differences define S. hominis subsp. novobiosepticus and S. hominis subsp. hominis "sequevars." Of 34 S. hominis clinical isolates, 31 were S. hominis subsp. novobiosepticus sequevars, 28 of which were resistant to both oxacillin and ciprofloxacin. The clinical microbiology laboratory, using a MicroScan system, identified 7 of the 31S. hominis subsp. novobiosepticus sequevars as S. hominis subsp. hominis on the basis of phenotypic characteristics. Three S. hominis subsp. hominis sequevars were all identified phenotypically as S. hominis subsp. hominis and were oxacillin- and ciprofloxacin-susceptible. Although the precise relationship between the S. hominis sequevars and their phenotypic subspecies remains to be determined, our results indicate that antibiotic-resistant clinical isolates of S. hominis belong almost exclusively to the S. hominis subsp. novobiosepticus sequevar.

Emergence of drug resistance mutations in a group of HIV-infected children taking nelfinavir-containing regimens

HIV-1-infected children are often treated with therapy regimens including protease inhibitors (PIs). We monitored the virologic response in a small group of pediatric patients undergoing therapy with regimens including the PI nelfinavir and determined whether new drug resistance mutations were present immediately after virologic failure. Seventeen reverse transcriptase inhibitor (RTI)-experienced children starting nelfinavir-containing therapy regimens were studied. After virologic failure, HIV-1 protease (PR) and RT sequences were examined for drug resistance mutations. Viral load levels decreased to <400 HIV RNA copies/ml in six patients and remained at <400 HIV RNA copies/ml in four patients. Three patients did not respond virologically; all three had mutations specific for one or more of their regimen drugs either before or soon after nelfinavir initiation. The virologic response was transient in eight patients whose viral loads did not decrease to <400 HIV RNA copies/ml. Genotypic data from seven of the eight patients revealed mutations specific for one or more of their regimen drugs after virologic rebound. PI resistance mutations occurred in eight patients: D30N in six, and L90M in three. In three patients, the only new mutation after failure was the RT mutation M184V. Despite virologic failure, sustained increases in CD4+ lymphocyte counts were noted in eight patients. We conclude that in this small group of pediatric patients, virologic failure occurred in all patients whose viral loads did not become undetectable after the switch to a nelfinavir-containing regimen. After failure, new drug resistance mutations were found in either PR or RT. Studies of larger cohorts are warranted to determine whether HIV-1 genotypic data can help in the formulation of effective salvage therapies in children.

Sequence analysis of dru regions from methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococcal isolates

Methicillin-resistance in staphylococci results from expression of mecA, which occurs in a larger region of DNA (the mec region) lacking counterpart in susceptible cells. The mec region harbors in addition a highly polymorphic element, the dru (direct repeat unit) segment, which in an early S. aureus strain, BB270, was found to contain 10 imperfect 40 base-pair repeats. We have explored the utility of direct sequencing of dru segments for discriminating among strains of methicillin-resistant S. aureus (MRSA) and coagulase-negative staphylococci (MRCNS). We sequenced dru segments of 24 clinical isolates of MRSA, and 15 of MRCNS, and reexamined strain BB270. Six S. aureus and 2 S. epidermidis isolates were found to have deletions which removed all drus. The other strains were found to have multiple contiguous dru repeats of precisely 40 bp. Analysis of these strains plus dru segment sequence from 4 recent reports yielded 18 unique dru segment sequences (designated "dru types") differing in numbers of repeats and/or sequences of particular repeats. Dru typing was more discriminating than sequencing of non-mec region genes, including a repeat-containing segment (spa Xr) of the S. aureus protein A gene. Yet dru type was sufficiently stable to register epidemiological clusters. Dru sequencing is a useful tool for tracking methicillin-resistant lineages of S. aureus and CNS.

Distribution of methicillin-resistant Staphylococcus aureus clones among health care facilities in Connecticut, New Jersey, and Pennsylvania

A previous surveillance study conducted in 12 hospitals in New York City in 1996 identified a unique multidrug-resistant genetic lineage of methicillin-resistant Staphylococcus aureus (MRSA) that was widespread and accounted for as much as 42% of all the MRSA isolates. The purpose of the study described here was to determine possible geographic spread of this New York clone of MRSA to neighboring states. Single-patient MRSA isolates (258) from 29 health care facilities in Connecticut (CT), New Jersey (NJ), and Pennsylvania (PA) were collected during the calendar year 1998. DNA typing, consisting of fingerprinting of chromosomal macrorestriction patterns generated by SmaI digestion followed by pulsed-field gel electrophoresis (PFGE), identified 22 patterns. PFGE type A, closely related to the PFGE type of the previously identified New York clone, accounted for 154 (60%) of 258 isolates. The clone was detected in all facilities, was predominant in 19 of the 29 health care centers, and accounted for 92% of the MRSA isolates collected in PA. The overwhelming majority of MRSA with PFGE type A was also resistant to erythromycin, ciprofloxacin, and clindamycin. One of the two most common PFGE subtypes detected in the three states sampled (PFGE subtype A1) had an identical PFGE pattern to that of the previously described vancomycin-resistant strain of S. aureus (VISA) recently detected in a hospital in Westchester, NY. The second most frequent MRSA clone with PFGE type E and accounting for 26% (68/258 isolates), also described earlier in the 12 New York City hospitals, was resistant not only to erythromycin, ciprofloxacin, and clindamycin, but also to gentamicin and sulfamethoxazole-trimethoprim as well. The unique multidrug resistance pattern of this second clone and its geographic distribution accounted for the differences observed in the frequency of multidrug resistance among MRSA isolates recovered in the three states. The pandemic Iberian clone recently detected in New York City was not detected among the 258 MRSA isolates recovered in CT, NJ, and PA.

The microbial genetics of antibiotic cycling

Cycling of currently available antibiotics to reduce resistance is an attractive concept. For cycling strategies to be successful, their implementation must have a demonstrable impact on the prevalence of resistance determinants already dispersed throughout the hospital and associated healthcare facilities. While antibiotic use in hospitals clearly constitutes a stimulus for the emergence of resistance, it is by no means the only important factor. The incorporation of resistance determinants into potentially stable genetic structures, including bacteriophages, plasmids, transposons, and the more newly discovered movable elements termed integrons and gene cassettes, forces some degree of skepticism about the potential for such strategies in institutions where resistance determinants are already prevalent. In particular, the expanding role of integrons may pose an ultimate threat to formulary manipulations such as cycling. Despite these concerns, the crisis posed by antimicrobial resistance warrants investigation of any strategy with the potential for reducing the prevalence of resistance. Over the next decade, new studies with carefully designed outcomes should determine the utility of antibiotic cycling as one control measure for nosocomial resistance.

Topoisomerase sequences of coagulase-negative staphylococcal isolates resistant to ciprofloxacin or trovafloxacin

Coagulase-negative staphylococcal isolates (n = 188) were screened for susceptibility to oxacillin, ciprofloxacin, and trovafloxacin, a new fluoroquinolone. At an oxacillin concentration of >/=4 microg/ml, 43% were methicillin resistant; of these, 70% were ciprofloxacin resistant (MIC, >/=4 microg/ml). Of the methicillin-resistant, ciprofloxacin-resistant isolates, 46% were susceptible to </=2 microg of trovafloxacin per ml and 32% were susceptible to </=1 microg of trovafloxacin per ml. Sixteen isolates, including twelve that expressed fluoroquinolone resistance, were chosen for detailed analysis. Identification of species by rRNA sequencing revealed a preponderance of Staphylococcus haemolyticus and S. hominis among fluoroquinolone-resistant strains. Segments of genes (gyrA and grlA) encoding DNA gyrase and DNA topoisomerase IV were sequenced. Considerable interspecies variation was noted, mainly involving noncoding nucleotide changes. Intraspecies variation consisted of coding changes associated with fluoroquinolone resistance. As for S. aureus, ciprofloxacin resistance (MIC, >/=8 microg/ml) and increased trovafloxacin MICs (0.25 to 2 microg/ml) could be conferred by the combined presence of single mutations in each gyrA and grlA gene. Trovafloxacin MICs of >/=8 microg/ml also occurred, but these required an additional mutation in grlA.

Topoisomerase mutations in trovafloxacin-resistant Staphylococcus aureus

A total of 201 Staphylococcus aureus isolates were surveyed for susceptibility to ciprofloxacin and trovafloxacin. Of 66 methicillin-resistant isolates, 89% were ciprofloxacin resistant and 6% were also trovafloxacin resistant. Trovafloxacin-resistant strains had unusual patterns of quinoline resistance mutations in DNA topoisomerase genes, including two mutations in the A subunit (encoded by grlA) of topoisomerase IV.

Effect of the HIV-1 syncytium-inducing phenotype on disease stage in vertically-infected children

The syncytium-inducing (SI) capability of HIV-1 isolates from 48 HIV-infected children was determined in order to examine the association of the SI phenotype with an AIDS diagnosis and/or with other clinical parameters in HIV-infected children. In a retrospective cross-sectional analysis, phenotypic data were linked to clinical and immunologic data from each patient. Multiple longitudinal samples were analyzed from 14 patients. Children with SI viruses were older than children with nonsyncytium-inducing (NSI) strains. Twelve of 13 children less than 2 years old carried NSI viruses, seven of the 12 already had a diagnosis of AIDS. Two children under 2 years of age died within 1 month of NSI virus isolation. Although plasma p24 antigen levels tended to be higher in the NSI group, the difference appeared to reflect high p24 levels in children under 2 years old with AIDS. When children under 2 were omitted, differences in age, CD4+ cell counts, p24 antigenemia, and clinical parameters were not significant. The SI phenotype of HIV-1 did not occur more frequently in children with an AIDS diagnosis. Four children remained stable with SI isolates overtime periods of 16 to 31 months. Three children's isolates converted from NSI to SI and 2 converted from SI to NSI. These data indicate that SI viruses do not play a significant role in progression to AIDS during the first 2 years of life. Furthermore, for children above the age of 2, the association between advanced disease stage and the SI phenotype in adults may not apply.

Risk factors associated with the acquisition of amikacin-resistant gram-negative bacilli in central New Jersey hospitals

A case-control study was performed in central New Jersey hospitals to evaluate the potential patient factors associated with the acquisition of amikacin-resistant gram-negative bacilli (ARGNB). Univariate analysis revealed an association between numerous patient factors, and multivariate analysis revealed four factors to be associated independently with ARGNB: the number of hospital admissions during the prior year, previous aminoglycoside exposure, intubation, and intensive-care-unit admission.

Society for Healthcare Epidemiology of America and Infectious Diseases Society of America Joint Committee on the Prevention of Antimicrobial Resistance: guidelines for the prevention of antimicrobial resistance in hospitals

Antimicrobial resistance results in increased morbidity, mortality, and costs of health care. Prevention of the emergence of resistance and the dissemination of resistant microorganisms will reduce these adverse effects and their attendant costs. Appropriate antimicrobial stewardship that includes optimal selection, dose, and duration of treatment, as well as control of antibiotic use, will prevent or slow the emergence of resistance among microorganisms. A comprehensively applied infection control program will interdict the dissemination of resistant strains.

Society for Healthcare Epidemiology of America and Infectious Diseases Society of America Joint Committee on the Prevention of Antimicrobial Resistance: guidelines for the prevention of antimicrobial resistance in hospitals

Antimicrobial resistance results in increased morbidity, mortality, and costs of health care. Prevention of the emergence of resistance and the dissemination of resistant microorganisms will reduce these adverse effects and their attendant costs. Appropriate antimicrobial stewardship that includes optimal selection, dose, and duration of treatment, as well as control of antibiotic use, will prevent or slow the emergence of resistance among microorganisms. A comprehensively applied infection control program will interdict the dissemination of resistant strains.

Programmatic role of the infectious diseases physician in controlling antimicrobial costs in the hospital

Controlling antimicrobial costs has preoccupied infectious diseases physicians (IDPs). IDPs have controlled antimicrobial costs by the use of eight strategies: education, formulary restriction, pharmacy justification, formulary substitution, computer surveillance, laboratory item cost listing, purchase plans, and multidisciplinary approaches. Most strategies had input from IDPs and resulted in cost savings (up to $500,000 annually), particularly during the initiation periods. Educational efforts were successful in reducing costs but needed continual intervention. Formulary restriction was the most straightforward cost-control mechanism. Restriction of "target antimicrobials" has given way to "switch" therapy between expensive and less costly agents or between parenteral and oral regimens. Switch therapy is facilitated through the use of innovative order forms and on-line computer interaction. Computer surveillance has a capacity for interactive controls. Purchase plans may give way to centralized pharmacy monitoring, a strategy that is attractive to managed care organizations. Multidisciplinary antimicrobial management programs (AMPs) offer the best potential for sustaining savings in antimicrobial costs. Ten recommendations lay a groundwork for IDPs to translate their expertise into leadership of AMPs.

Immunoprophylaxis against klebsiella and pseudomonas aeruginosa infections. The Federal Hyperimmune Immunoglobulin Trial Study Group

To determine if passive immunization could decrease the incidence or severity of Klebsiella and Pseudomonas aeruginosa infections, patients admitted to intensive care units of 16 Department of Veterans Affairs and Department of Defense hospitals were randomized to receive either 100 mg/kg intravenous hyperimmune globulin (IVIG), derived from donors immunized with a 24-valent Klebsiella capsular polysaccharide plus an 8-valent P. aeruginosa O-polysaccharide-toxin A conjugate vaccine, or an albumin placebo. The overall incidence and severity of vaccine-specific Klebsiella plus Pseudomonas infections were not significantly different between the groups receiving albumin and IVIG. There was some evidence that IVIG may decrease the incidence (2.7% albumin vs. 1.2% IVIG) and severity (1.0% vs. 0.3%) of vaccine-specific Klebsiella infections, but these reductions were not statistically significant. The trial was stopped because it was statistically unlikely that IVIG would be protective against Pseudomonas infections at the dosage being used. Patients receiving IVIG had more adverse reactions (14.4% vs. 9.2%).

Use of acetabular models in planning complex acetabular reconstructions

The number of patients requiring revision total hip arthroplasty continues to increase each year. Accurate preoperative planning is a key factor in obtaining a good result. Radiographs provide little information concerning the actual extent of the acetabular defects. Computed tomography-generated models of the acetabulum can provide the surgeon with accurate information concerning the size and location of the defects. Evaluation of radiographs and models in 24 cases showed that radiographs alone failed to detect all 13 anterior wall defects (P < .001), 8 of 18 posterior wall defects (44.4%, P < .001), and 8 of 19 segmental central defects (42%, P < .001), all of which were easily identified with the models. This study showed that preoperative planning based on the foam models accurately predicted the actual implant used in 22 of 24 cases (92%).

Radiographic determination of the anatomic hip joint center. A cadaver study

We studied 31 human pelvic cadaver specimens with 57 intact hip joints. The teardrop, which represents the inferior portion of the acetabular notch, was identified as also was the center of rotation in the articulating femoral head. The pelvic height and the horizontal and vertical distances between the acetabular notch and the hip joint center were measured. We found the center of rotation of the hip joint to be 13 percent of the pelvic height lateral and 7 percent of the pelvic height superior to the teardrop. No sex difference was found.

In vivo R-plasmid transfer in a patient with a mixed infection of shigella dysentery

Transfer of shigella R-plasmids in vivo has seldom been demonstrated. Strains of Shigella dysenteriae type 1 and Shigella flexneri type 5b were isolated from a Bulgarian traveller who visited Vietnam and developed dysentery, which was treated with trimethoprim/sulfamethoxazole (TMP/SMZ) for a short time. Both species of shigellae are unusual in Bulgaria where strains of S. sonnei predominate. Both shigella strains were multiresistant to the same antimicrobial agents. Each strain contained a 48-kilobase plasmid that conferred the entire resistance phenotype to a susceptible Escherichia coli. Restriction endonuclease patterns of plasmid DNA from the respective strains were identical. Transmissible plasmids of the same resistance phenotypes and restriction patterns were isolated from the patient's colonic E. coli. Transconjugants hybridized to a dihydrofolate reductase type I-DNA probe. These studies support the hypothesis that R-plasmid transfer may occur between non-pathogenic, faecal strains and pathogenic shigellae, a process that may have been facilitated by inadequate treatment with TMP/SMZ at the onset of the illness.

Widespread colonization of personnel at a Veterans Affairs medical center by methicillin-resistant, coagulase-negative Staphylococcus

A serial prospective survey of nasal colonization of hospital personnel by methicillin-resistant coagulase-negative staphylococci (MRCNS) was conducted at a Veterans Affairs medical center on three occasions over a 16-month period. The epidemiological typing systems used to assess relatedness included antimicrobial susceptibility profiles; biotyping; phage typing; plasmid profiles; restriction fragment length polymorphism (RFLP) analysis with ribosomal RNA; and plasmid hybridization with a 1.68-MD plasmid as the DNA probe. Forty-three percent of all personnel and 62% of all nurses were colonized with MRCNS. Nurses on the wards (72%) and in the intensive care unit (73%) were significantly more likely to be colonized with MRCNS than nurses who had less contact with patients or those who worked in the operating room. The molecular epidemiological typing systems indicated some degree of relatedness among the strains. Specifically, riboprobe analysis revealed a Dice coefficient of > 90%. However, each typing system detected dissimilarity among strains. Further studies are needed to determine the role that such human reservoirs of MRCNS serve in horizontal transmission to and subsequent infection of hospitalized patients.

Randomized double-blinded trial of rifampin with either novobiocin or trimethoprim-sulfamethoxazole against methicillin-resistant Staphylococcus aureus colonization: prevention of antimicrobial resistance and effect of host factors on outcome

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen in hospitals. Current antimicrobial regimens for eradicating colonizing strains are not well defined and are often complicated by the emergence of resistance. The combination of novobiocin plus rifampin in vitro and in vivo was found to prevent the emergence of resistant populations of initially susceptible strains of MRSA, particularly resistance to rifampin. We therefore studied, in a randomized, double-blind, multicenter comparative trial, the combination of novobiocin plus rifampin versus trimethoprim-sulfamethoxazole (T/S) plus rifampin in order to determine the efficacy of each regimen in eradicating MRSA colonization and to further characterize the host factors involved in the response to this antimicrobial therapy. Among the 126 individuals enrolled in the study, 94 (80 patients; 14 hospital personnel) were evaluable. Among the 94 evaluable subjects, no significant demographic or medical differences existed between the two treatment groups. Successful clearance of the colonizing MRSA strains was achieved in 30 of 45 (67%) subjects receiving novobiocin plus rifampin, whereas successful clearance was achieved in 26 of 49 (53%) subjects treated with T/S plus rifampin (P = 0.18). The emergence of resistance to rifampin developed more frequently in 14% (7 of 49) of subjects treated with T/S plus rifampin than in 2% (1 of 45) of subjects treated with novobiocin plus rifampin (P = 0.04). Restriction endonuclease studies of large plasmid DNA demonstrated that the same strain was present at pretherapy and posttherapy in most refractory cases (24 of 29 [83%] subjects). Among the 56 successfully treated subjects, clearance of MRSA was age dependent: 29 of 36 (80%) subjects in the 18- to 49-year-old age group, 19 of 35 (54%) subjects in the 50- to 69-year-old age group, and 8 of 23 (35%) in the 70- to 94-year-old age group (P < 0.01). Clearance was also site dependent; culture-positive samples from wounds were related to a successful outcome in only 22 (48%) of 46 subjects, whereas culture-positive samples from sites other than wounds (e.g., nares, rectum, and sputum) were associated with a success rate of 34 of 48 (71%) subjects (P = 0.02). Foreign bodies in wounds did not prevent the eradication of MRSA by either regimen. T/S plus rifampin was less effective in clearing both pressure and other wounds, whereas novobiocin plus rifampin was equally effective in clearing both pressure and other wounds. There were no significant differences in toxicity between the two regimens. Thus, the combination of novobiocin plus rifampin, in comparison with T/S plus rifampin, was more effective in preventing the emergence of resistance to rifampin and demonstrated a trend toward greater activity in clearing the MRSA carrier state. The response to either combination depended on host factors, particularly age and the site of MRSA colonization.

Methicillin-resistant Staphylococcus aureus: a consensus review of the microbiology, pathogenesis, and epidemiology with implications for prevention and management

Methicillin-resistant Staphylococcus aureus (MRSA) has become a major nosocomial pathogen in community hospitals, long-term-care facilities, and tertiary care hospitals. The basic mechanism of resistance is alteration in penicillin-binding proteins of the organism. Methods for isolation by culture and typing of the organism are reviewed. MRSA colonization precedes infection. A major reservoir is the anterior nares. MRSA is usually introduced into an institution by a colonized or infected patient or health care worker. The principal mode of transmission is via the transiently colonized hands of hospital personnel. Indications for antibiotic therapy for eradication of colonization and treatment of infection are reviewed. Infection control guidelines and discharge policy are presented in detail for acute-care hospitals, intensive care and burn units, outpatient settings, and long-term-care facilities. Recommendations for handling an outbreak, surveillance, and culturing of patients are presented based on the known epidemiology.

Increased frequency of large R-plasmids in Klebsiella pneumoniae colonizing patients with spinal cord injury

From 1978 to 1988 strains of gentamicin-susceptible (Gms) and gentamicin-resistant (Gmr) Klebsiella pneumoniae were saved from annual surveillance cultures of the perineal region of patients with spinal cord injury (SCI). Of 38 strains selected for further study (24 Gms and 14 Gmr), there were 23 different serotypes (two nontypable). Fourteen Gms as well as 14 Gmr strains displayed no common plasmid patterns, but all contained a large plasmid of 168-208 kb. Among the 14 Gmr strains, nine had large conjugative plasmids of approximately the same size (166-193 kb), which conferred to a susceptible Escherichia coli host an identical resistance pattern: ampicillin, chloramphenicol, gentamicin, piperacillin, trimethoprim-sulfamethoxazole, tetracycline, and tobramycin. Of the nine transconjugants, eight contained a single plasmid. One transconjugant contained a 168- and 80-kb plasmid. Restriction endonuclease digestion patterns of the R-plasmids revealed minimal similarity. We conclude that, during a 10-year period, different large R-plasmids have spread among multiple serotypes of K. pneumoniae in spinal cord injury (SCI) patients in one rehabilitation hospital. We hypothesize that other genes located on large, R-, and non-R-plasmids may confer an additional advantage for colonization by K. pneumoniae in SCI patients.

Relatedness of strains of methicillin-resistant coagulase-negative Staphylococcus colonizing hospital personnel and producing bacteremias in a neonatal intensive care unit

The emergence of methicillin-resistant coagulase-negative Staphylococcus as a major bacterial pathogen in neonatal intensive care units has stimulated interest in the epidemiology of spread of the organism. During a 12-month "epidemic" of bacteremias with methicillin-resistant coagulase-negative Staphylococcus we compared the characteristics of bacteremic and personnel nasally-carried strains by traditional and biomolecular methods. Sixty-two percent of neonatal intensive care unit nurses were colonized with methicillin-resistant coagulase-negative Staphylococcus with similar speciation to bacteremic strains. Inspection of plasmid profiles revealed a moderate degree of similarity between bacteremic and colonizing strains although genomic DNA restriction patterns showed diversity. Ribotype patterns were highly conserved (90%) in personnel strains. A 2.6-kilobase plasmid DNA probe hybridized to similarly sized plasmids and larger plasmids in one-half of the strains. We hypothesize that related methicillin-resistant strains may be transferred among personnel and neonates in the neonatal intensive care unit. Epidemiologic studies of coagulase-negative staphylococci should consider multiple molecular techniques to relate strains.

Activities of newer fluoroquinolones against Shigella sonnei

The activities of six fluoroquinolones were determined for 117 separate strains of Shigella sonnei. The order of increasing activity (MICs for 90% of strains tested) was enoxacin (0.25 micrograms/ml), temafloxacin (0.032 micrograms/ml), sparfloxacin (0.016 micrograms/ml), CI-960 (0.008 micrograms/ml), ciprofloxacin (0.008 micrograms/ml), and PD-131628-2 (0.008 micrograms/ml). These data, along with results of killing and mutational rate studies, showed that all six fluoroquinolones were highly inhibitory against S. sonnei and five fluoroquinolones were rapidly and persistently bactericidal.

Molecular epidemiology of trimethoprim-resistant Shigella boydii serotype 2 strains from Bulgaria

In 1990 an increased number of strains of Shigella boydii serotype 2 were isolated from different regions of Bulgaria. Strains were reported as sporadic, although they showed identical phenotypic characteristics, including resistance to ampicillin, carbenicillin, streptomycin, sulfonamide, tetracycline, ticarcillin, and trimethoprim. The objective of this study was to determine the genetic relatedness of the strains and the mechanism of their antimicrobial resistance. Plasmid fingerprinting showed an identical pattern for 23 of 25 of the selected strains. All 25 strains tested transferred their resistances en bloc to an Escherichia coli recipient. Transconjugants contained a 112-kb R plasmid which carried all the resistance genes, including that conferring type I dihydrofolate reductase-mediated trimethoprim resistance (MIC greater than 2,000 micrograms/ml). Riboprobe analysis showed identical restriction length fragment polymorphisms, suggesting a highly conserved genome. All findings indicate that strains of S. boydii serotype 2 isolated in 1990 from different regions of Bulgaria were highly related genetically and can be considered representatives of a single bacterial clone. The presence of an R plasmid and selection pressure because of the usage of antimicrobial agents, particularly trimethoprim, have likely facilitated the spread of the clone throughout the country.

Isomeric DNA ladder formation of a plasmid encoding tobramycin resistance from Escherichia coli

During a 20-month survey of resistance to three aminoglycosides (gentamicin, tobramycin, and amikacin) in Escherichia coli at a university hospital, six tobramycin-, kanamycin-resistant isolates containing a 50 kilobase conjugative R-plasmid which encoded an aminoglycoside phosphotransferase (APH-(3')) were isolated. The APH-(3') conferred resistance to kanamycin (MIC = 100 mg/L) but not to tobramycin (MIC = 20 mg/L). In both the original isolates and transconjugants the six R-plasmids demonstrated an isomeric ladder in the range of 50-112 kb, which was enhanced by exposure of the bacterial cultures to tobramycin. pJFJ2522 is the prototype for this group of plasmids. Bacterial DNA gyrase reversed the isomeric DNA ladder in pJFJ25222 by increasing the supercoiling of the plasmid DNA. Regardless of the level of supercoiling, the plasmids produced indistinguishable restriction endonuclease fragment patterns. The clinical isolates containing these plasmids demonstrated different restriction fragment length polymorphism (RFLP) of their EcoRI digested genomic DNA using E. coli rRNA as a probe. Ladder formation was plasmid specific since other tobramycin R-plasmids did not form a ladder, but it was not host specific. pJFJ25222 formed a ladder in a recA- host and displayed the same restriction pattern in a recA- as in a recA+ environment. In conclusion, pJFJ2522 contains a new tobramycin resistance gene whose mechanism of resistance is not known and whose product probably influences the isomerization of the plasmid.

Bactericidal action of modulated ultraviolet light on six groups of Salmonella

Previous studies on the bactericidal effects of ultraviolet (UV) lamps have focused on the effects of specific wavelengths and the time and intensity of exposure. Virtually all of these studies have used continuous wave UV. Exposure to UV can induce abnormal ion flow or increased membrane permeability, or it can depolarize the membrane, induce DNA, RNA, and protein alterations, and inhibit oxidative phosphorylation. Any periodic alteration in the modulation of the intensity alters the biological effectiveness. If the waveform and pulse repetition rate are chosen carefully, the bactericidal effects of the UV light may be greatly enhanced.

We tested a prototype UV-C lamp modulated by a series of complex waveforms designed to enhance bactericidal activity. These experiments evaluated the effectiveness of the modulated WC in a series of in vitro experiments on six serogroups of Salmonella.

Antibiotic resistance in long-term care facilities

Long-term care facilities are comprised of a heterogeneous group of institutions caring for residential patients over prolonged periods of time. Included as long-term care facilities in this review are private and Veterans' Affairs (VA) nursing homes, rehabilitation centers, institutions for the developmentally disabled, and hospital wards for both long-term and intermediate care. Patients in long-term care facilities incur bacterial infections at a prevalence of 10% to 16%. These infections usually are caused by common bacterial pathogens that invade the compromised host residing within a complex physical environment. The high prevalence of institutional infections leads, in turn, to the need for multiple courses of antimicrobials or for hospitalization. This process selects strains more resistant to antibiotics, which are then available for repeated dispersal in the long-term care facility.

Methicillin-resistant Staphylococcus aureus outbreak at a Veterans' Affairs Medical Center: importance of carriage of the organism by hospital personnel

The reported prevalence of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) by hospital personnel averages 2.5%. From August 1985 to September 1987, 155 patients at our Veterans' Affairs Medical Center (VAMC) were colonized or infected with MRSA. In December 1986, only two (2.1%) of 94 healthcare workers were identified as nasal carriers. Prompted by a sharp increase in the number of patients with MRSA in early 1987, contact tracing identified 450 employees, of whom 36 (8%) were nasal carriers. Thirty-five percent of surgical residents (7 of 20) were nasal carriers. Prior to being identified as a nasal carrier, one surgical resident was associated with the inter-hospital spread of the VAMC MRSA strain to the burn unit of the affiliated university hospital. Three family members of two employee carriers were also found to harbor the epidemic strain. All 36 carriers were decolonized with various antimicrobial combinations. Vigorous infection control measures were effective in controlling the epidemic. The frequency of MRSA carriage by hospital personnel at our medical center during the epidemic proved higher than previously appreciated. Thus, healthcare workers may comprise a sizable MRSA reservoir. During an MRSA epidemic, infection control should attempt to identify and decolonize this hospital reservoir, as these individuals can disseminate MRSA both within the hospital as well as into the community.

Molecular analysis of nosocomial epidemics

Newer developments in molecular biology offer the hospital epidemiologist and clinical microbiologist powerful tools for analysis of nosocomial epidemics. Plasmid fingerprinting and genomic REA are rapid and often more definitive alternatives to serotyping and biotyping. Isolation of specific plasmids for special study involves more complicated manipulations. Polypeptide patterns, though at times diffuse in appearance, can be easily produced with SDS-PAGE of whole cells or outer membranes. Specific monoclonal antibodies as probes for individual proteins can generate more definitive answers about the exact type of protein(s) present. Multilocus enzyme electrophoresis (MLE) has become an ingenious tool for characterizing closely related nosocomial bacterial strains. The newest molecular methods using ribotyping, DNA probes, and the PCR will open many doors into the microbial genomes that were previously closed to the hospital microbial detective. These advances will compel hospitals to plan for their funding and implementation. Yet, like other scientific progress, the new biology in the nosocomial setting will raise as many questions as it will answer.

Dissemination of trimethoprim-resistant clones of Shigella sonnei in Bulgaria

Bacterial dysentery due to Shigella sonnei remains a serious public health problem in developed countries, including Bulgaria. At the National Shigella Reference Laboratory in Sofia, 17,126 strains of S. sonnei from epidemics and sporadic cases collected from 1973 to 1987 were studied. Antibiotic susceptibility testing, phage typing, colicin typing, and biotyping were performed for all strains to allow intraspecies differentiation and to track any clonal distribution. Of all strains, 84.3% were resistant to one or more antimicrobials, the most frequent being tetracycline (Tet), streptomycin (Str), sulfonamide (Sul), chloramphenicol (Chl), ampicillin (Amp), and trimethoprim (Tmp). Resistance patterns most prevalent for successive 5-y periods included Tet, StrSulTet, and AmpChlStrSulTet, respectively. For the final 5 y, a new pattern (AmpKanStrSulTetTm [Kan = kanamycin]) was spread throughout the country by two trimethoprim-resistant clones. High-level resistance to trimethoprim (MIC greater than 1500 micrograms/mL) in both clones was determined by dihydrofolate reductase type I. The genes for trimethoprim resistance were located on a conjugative R-plasmid of approximately 145 kilobases which cotransferred all other antimicrobial resistances. A similar-sized R-plasmid had been found in earlier isolates of Bulgarian S. sonnei, suggesting that new antimicrobial resistance genes had been sequentially added to an ancestral R-plasmid. Controlling the expression of these new as well as older antimicrobial resistances, particularly for enteric pathogens, must involve reduction in usage of generic antimicrobial agents.

Epidemic methicillin-gentamicin-resistant Staphylococcus aureus in a neonatal intensive care unit

Between October 1985 and August 1986, 49 isolates of methicillin-resistant Staphylococcus aureus (MRSA) were obtained from 26 neonates in the neonatal intensive care unit (NICU) at the Medical University Hospital, Charleston, SC. Sites of MRSA isolation were the respiratory tract (33%); nasopharynx (12%); gastrointestinal tract (12%); eye (8%); blood (6%); and catheter tips, wounds, or umbilicus (29%). Very low birth weight was a significant risk factor for MRSA acquisition. All isolates had the same phage type (47/54/75/83A), antibiogram, and whole-cell protein profile. Agarose gel electrophoresis of all 49 isolates disclosed a plasmid level of approximately 45 X 106 daltons (45 megadaltons) in ten different isolates and no plasmid DNA in 39 isolates. Cultures of NICU personnel failed to disclose MRSA carriers and environmental cultures for MRSA were negative. Ten selected isolates showed lower minimal bactericidal concentrations for hexachlorophene than for chlorhexidine. Standard infection-control measures such as contact isolation, hand washing with chlorhexidine, and cohorting (when possible) failed to contain the epidemic. Ultimately, eradication of MRSA from the NICU was associated with the institution of hexachlorophene hand washing.

An outbreak of Pseudomonas cepacia bacteremia associated with a contaminated intra-aortic balloon pump

In January 1983, symptomatic Pseudomonas cepacia bacteremia developed in two patients in the cardiothoracic intensive care unit within 3 days after cardiac operation and insertion of an intra-aortic balloon pump. An epidemiologic and microbiologic investigation revealed that both patients required intra-aortic balloon pumping for circulatory support and that the water reservoir of the intra-aortic balloon pump (SMEC, Inc., Cookeville, Tenn.) contained more than 10(5) Pseudomonas cepacia per milliliter. This organism was also recovered from the purge button and on-off switch of the pump and from the hands of a health care worker who manipulated the water reservoir of the intra-aortic balloon pump. Agarose gel electrophoresis of lysates of Pseudomonas cepacia with rapid methods of deoxyribonucleic acid preparation revealed three identical plasmids of the Pseudomonas cepacia from the water reservoir of the intra-aortic balloon pump and from the infected patients. Transmission from the worker's hands to patients presumably occurred by inoculation of the intravascular lines during management. No additional cases of Pseudomonas cepacia bacteremia were observed after the unit was replaced with a nonwater reservior intra-aortic balloon pump. This report substantiates the ability of Pseudomonas cepacia to multiply in water and to cause epidemic bacteremia, identifies the water reservoir of the SMEC intra-aortic balloon pump as a previously unrecognized hazard for the patient requiring intra-aortic balloon pumping, and documents the value of plasmid analysis in elucidating the mode of transmission of nosocomial Pseudomonas cepacia infections.

Protected transbronchial needle aspiration and protected specimen brush in the diagnosis of pneumonia

Protected transbronchial needle aspiration (PTBNA) of pneumonic lung theoretically could bypass dislodged upper respiratory tract flora, a potential source of contamination of protected specimen brush (PSB) cultures. To evaluate the usefulness of PSB and PTBNA in establishing the etiology of pneumonia, we prospectively studied 20 patients with acute bacterial pneumonia not receiving antibiotics. After informed consent, patients had fiberoptic bronchoscopy under fluoroscopy to localize the pneumonia, and specimens were obtained by the PSB. The protective plug of a specially devised needle for PTBNA was pneumatically dislodged and aspiration was performed within the infiltrate under fluoroscopy. Quantitative cultures were plated immediately for aerobes, anaerobes, and Legionella. Greater than 4 X 10(3) organisms/brush or 1 X 10(4) organisms/ml needle aspirate were considered to be consistent with infection. The results using PSB and PTBNA were compared in 15 of 20 patients in whom a definitive diagnosis (positive blood or pleural fluid culture) or presumptive diagnosis (expectorated sputum culture, clinical characteristics, and response to specific therapy) was established. The PSB and PTBNA cultures on uninfected control subjects (n = 5) being bronchoscoped for other reasons were negative. The PSB and PTBNA were each diagnostic in 2 of the 5 patients with definitive diagnoses. In the group with a presumptive diagnosis (n = 10), PSB was diagnostic in 7 of 10 and PTBNA in 9 of 10. The overall (definitive plus presumptive) diagnostic yield was 60% for PSB and 73% for PTBNA. Multiple organisms were isolated in high concentrations in 53% of the patients. The most common organisms recovered in addition to the primary pathogen was alpha hemolytic streptococci.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasmids as epidemiologic markers in nosocomial gram-negative bacilli: experience at a university and review of the literature

Bacterial plasmids have become valuable markers for the comparison of strains of nosocomial gram-negative bacilli. The importance of plasmids in nosocomial infections is primarily due to their transferable antibiotic resistance genes (R plasmids), but other plasmid-mediated traits may eventually serve as potential markers. Stable cryptic plasmids have also served to relate outbreak strains, particularly nonfermenting strains of gram-negative bacteria. Klebsiella pneumoniae and Serratia marcescens have been the major plasmid-containing species in outbreaks involving single or multiple species. Outbreaks of single species with common plasmid patterns have included the Enterobacteriaceae, Pseudomonas aeruginosa, Pseudomonas cepacia, Ewingella americana, and Legionella pneumophila. Intrageneric spread of the same or similar R plasmids has nearly always occurred within the Enterobacteriaceae in large medical centers or Veterans Administration hospitals. High-risk nurseries and burn units have been conspicuous foci for R plasmid evolution. Hospital epidemiologists and clinical microbiologists will likely have an ever-increasing need to determine the plasmid content of gram-negative bacilli producing endemic and epidemic nosocomial infections.

Gentamicin vs cefotaxime for therapy of neonatal sepsis. Relationship to drug resistance

An outbreak of serious infections due to gentamicin-resistant Klebsiella pneumoniae occurred in a neonatal intensive care unit in which the combination of gentamicin sulfate and ampicillin sodium had been used for standard initial therapy for suspected sepsis for nearly 11 years. After institution of control measures that included the substitution of cefotaxime sodium for gentamicin in the standard regimen, the outbreak promptly subsided. Nevertheless, a second outbreak of serious infections due to cefotaxime-resistant Enterobacter cloacae began ten weeks later. Sequential stool cultures from patients in the unit confirmed the disappearance of gentamicin-resistant K pneumoniae and the emergence of cefotaxime-resistant E cloacae after the change in antibiotic policy. These observations suggest that routine use of newer cephalosporins for therapy of suspected sepsis may lead to the emergence of drug-resistant microorganisms more rapidly than has occurred with the aminoglycosides.

Endemic Serratia marcescens infection in a neonatal intensive care nursery associated with gastrointestinal colonization

Serratia marcescens (SM) produced a prolonged outbreak in a neonatal intensive care unit of high level gastrointestinal colonization (10(9) SM/g feces) which in the early part of the outbreak predisposed to respiratory infection. The early outbreak featured a strain of SM carrying a 54 X 10(6) dalton conjugative plasmid which mediated resistance to gentamicin, tobramycin and beta-lactam agents. The second part of the outbreak involved primarily gastrointestinal colonization with SM strains that were plasmid-free. Acquisition of SM was related to very low birth weight (less than 1500 g). Among very low birth weight neonates, SM colonization was associated with pneumonia, patent ductus arteriosus, congestive heart failure and septicemia. Among neonates greater than 1500 g, SM colonization was associated with bronchopulmonary dysplasia, use of a respirator, patent ductus arteriosus and congestive heart failure. Respirator contamination, respiratory tract colonization and consequent pneumonia were reduced by more frequent changing of respirator tubing. Colonized sinks remained chronically colonized with multiresistant SM.

Amifloxacin activity against well-defined gentamicin-resistant, gram-negative bacteria

Amifloxacin (WIN 49375) activity against a well-defined group of gentamicin-resistant gram-negative bacilli was compared with the activity of 11 other antimicrobial agents. For all strains, amifloxacin and norfloxacin were the most active agents, followed by cefotaxime and moxalactam. For Acinetobacter sp. only amifloxacin had an achievable MIC for 90% of the strains. Amifloxacin joins other newly developed DNA gyrase inhibitors as potentially useful agents for infections due to aminoglycoside-resistant gram-negative bacilli.