Effects of methylprednisolone on intracellular bacterial growth.

Clinical studies have shown positive associations among sustained and intense inflammatory responses and the incidence of bacterial infections. Patients presenting with acute respiratory distress syndrome (ARDS) and high levels of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta), and IL-6, have increased risk for developing nosocomial infections attributable to organisms such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter spp., compared to those patients with lower levels. Our previous in vitro studies have demonstrated that these bacterial strains exhibit enhanced growth extracellularly when supplemented with high concentrations of pure recombinant TNF-alpha, IL-1 beta, or IL-6. In addition, we have shown that the intracellular milieu of phagocytic cells that are exposed to supraoptimal concentrations of TNF-alpha, IL-1 beta, and IL-6 or lipopolysaccharide (LPS) favors survival and replication of ingested bacteria. Therefore, we hypothesized that under conditions of intense inflammation the host's micromilieu favors bacterial infections by exposing phagocytic cells to protracted high levels of inflammatory cytokines. Our clinical studies have shown that methylprednisolone is capable of reducing the levels of TNF-alpha, IL-1 beta, and IL-6 in ARDS patients. Hence, we designed a series of in vitro experiments to test whether human monocytic cells (U937 cells) that are activated with high concentrations of LPS, which upregulate the release of proinflammatory cytokines from these phagocytic cells, would effectively kill or restrict bacterial survival and replication after exposure to methylprednisolone. Fresh isolates of S. aureus, P. aeruginosa, and Acinetobacter were used in our studies. Our results indicate that, compared with the control, stimulation of U937 cells with 100-ng/ml, 1.0-microg/ml, 5.0-microg/ml, or 10.0-microg/ml concentrations of LPS enhanced the intracellular survival and replication of all three species of bacteria significantly (for all, P = 0.0001). Stimulation with < or =10.0 ng of LPS generally resulted in efficient killing of the ingested bacteria. Interestingly, when exposed to graded concentrations of methylprednisolone, U937 cells that had been stimulated with 10.0 microg of LPS were able to suppress bacterial replication efficiently in a concentration-dependent manner. Significant reduction in numbers of CFU was observed at > or =150 microg of methylprednisolone per ml (P values were 0.032, 0.008, and 0.009 for S. aureus, P. aeruginosa, and Acinetobacter, respectively). We have also shown that steady-state mRNA levels of TNF-alpha, IL-1 beta, and IL-6 in LPS-activated cells were reduced by treatment of such cells with methylprednisolone, in a concentration-dependent manner. The effective dose of methylprednisolone was 175 mg, a value that appeared to be independent of priming level of LPS and type of mRNA. We therefore postulate that a U-shaped relationship exists between the level of expression of TNF-alpha, IL-1 beta, and IL-6 within the phagocytic cells and their abilities to suppress active survival and replication of phagocytized bacteria.

Academic managed care organizations and adverse selection under Medicaid managed care in Tennessee.

CONTEXT: Health plans competing in a managed care system may face serious financial consequences if they are disproportionately selected by enrollees with expensive health conditions. Academic medical centers (AMCs) have traditionally provided medical care for the sickest patients and may be at particularly high risk for adverse selection, but whether this occurs is not known. OBJECTIVE: To determine whether managed care organizations (MCOs) representing AMCs are adversely selected by Medicaid managed care (MMC) enrollees with expensive chronic health conditions. DESIGN AND SETTING: Observational study using state Medicaid claims data from all of 1994 and January to August 1995 for Tennessee's statewide MMC program (TennCare). PARTICIPANTS: All 12 capitated MCOs in Tennessee, which collectively provided services for 1.2 million Medicaid enrollees from January 1994 through August 1995 following the initiation of TennCare. MAIN OUTCOME MEASURES: Prevalence of 6 state-specified high-cost chronic conditions-acquired immunodeficiency syndrome (AIDS), coagulation defects, cystic fibrosis, pregnancy, prematurity, and organ transplantation-and 27 additional high-cost conditions compared by academic, statewide, and regional MCOs. RESULTS: The prevalence of state-specified high-cost chronic conditions was generally higher for academic MCOs compared with other MCOs. Specifically, prevalence of AIDS was 14.1 times higher in academic MCOs than in statewide MCOs; coagulation defects, 6.4 times higher; transplantations, 4.4; pregnancy, 3.3; cystic fibrosis, 2.4; and prevalence of prematurity was equivalent. Prevalence was higher for academic than for statewide MCOs for 22 of the additional 27 high-cost conditions considered and similar for the remaining 5 conditions. CONCLUSIONS: Our results suggest that academic MCOs in an MMC system are selected by a large percentage of the sickest patients. Adverse selection may present serious financial risks for AMCs participating in managed care.

Effects of cytokines and endotoxin on the intracellular growth of bacteria.

Patients with unresolving acute respiratory distress syndrome (ARDS) have persistently elevated levels of proinflammatory cytokines in the lungs and circulation and increased rates of bacterial infections. Phagocytic cells hyperactivated with lipopolysaccharide (LPS), which induces high levels of proinflammatory cytokines in monocytic cells, are inefficient in killing ingested bacteria despite having intact phagocytic activity. On the other hand, phagocytic cells that are activated with an analogue of LPS that does not induce the expression of proinflammatory cytokines effectively ingest and kill bacteria. We hypothesized that in the presence of high concentrations of proinflammatory cytokines, bacteria may adapt and utilize cytokines to their growth advantage. To test our hypothesis, we primed a human monocytic cell line (U937) with escalating concentrations of the proinflammatory cytokines tumor necrosis factor alpha, interleukin-1beta (IL-1beta), and IL-6 and with LPS. These cells were then exposed to fresh isolates of three common nosocomial pathogens: Staphylococcus aureus, Pseudomonas aeruginosa, and an Acinetobacter sp. In human monocytes primed with lower concentrations of proinflammatory cytokines (10 to 250 pg) or LPS (1 and 10 ng), intracellular bacterial growth decreased. However, when human monocytes were primed with higher concentrations of proinflammatory cytokines (1 to 10 ng) or LPS (1 to 10 micrograms), intracellular growth of the tested bacteria increased significantly (P <0.0001). These results were reproduced with peripheral blood monocytes obtained from normal healthy volunteers. The specificity of the cytokine activity was demonstrated by neutralizing the cytokines with specific antibodies. Our findings provide a possible mechanism to explain the frequent development of bacterial infections in patients with an intense and protracted inflammatory response.

Nosocomial pneumococcal infection: an outbreak.

When an outbreak of pneumococcal disease occurs an institution--be it a hospital, nursing home, day care center, or other facility--management includes treatment of affected cases and prevention of new cases. Patients and staff should be tested for nasopharyngeal carriage and their vaccination status ascertained. Antibiotic use should be reviewed, especially if the causative strain is resistant.

Group G streptococcal arthritis: case report and review of the literature.

Nongonococcal septic arthritis in adults is usually caused by infections with staphylococcal or streptococcal species. In patients with underlying diseases, especially those with chronic joint disease or malignancy, bacterial isolates from infected joint spaces may include group G streptococci. Occasionally, group G streptococcal arthritis may occur in otherwise healthy individuals. We report a case of pyogenic sacroiliitis in a healthy young adult and review the pertinent literature concerning group G streptococcal arthritis.

Colonization and transmission of high-level gentamicin-resistant enterococci in a long-term care facility.

OBJECTIVES: To assess the prevalence of high-level gentamicin-resistant enterococcus (HGRE) colonization, transmission patterns, and spectrum of illness among residents of a long-term care facility. DESIGN: Monthly surveillance for HGRE colonization of wounds, rectum, and perineum over a 1-year period. SETTING: A Veterans Affairs long-term care facility attached to an acute-care facility. PATIENTS: All 341 patients in the facility during the observation period. RESULTS: Over the 1-year period, 120 patients (35.2%) were colonized with HGRE at least once, with an overall monthly colonization rate of 20 +/- 1.5%. HGRE were isolated from rectum (12.8%), wounds (11.7%), and perineum (9.3%). Patients with the poorest functional status had the highest rate of colonization (P < 0.0005). HGRE-colonized patients were more likely to be colonized with methicillin-resistant Staphylococcus aureus (51% versus 25%; P < 0.0005). Seventy-four patients (21.7%) were colonized at admission or at the start of the study. Another 46 patients (13.5%) acquired HGRE during the study, including 36 who acquired HGRE while in the long-term care facility and 10 who were positive when transferred back from the acute-care hospital. Based on plasmid profiles, only two patients appeared to have isolates similar to those of current or previous roommates. Carriage of HGRE was transient in most cases. Only 20 patients were colonized for 4 or more months, and those patients usually carried different strains intermittently. Infections were infrequent, occurring in only 4.1% of total patients. CONCLUSIONS: In our long-term care facility, HGRE were endemic, and new acquisition of HGRE occurred frequently. However, only two patients had evidence of acquisition from a roommate, suggesting that cross-infection from a roommate was not a major route of spread of HGRE.

Resistant gram-positive organisms.

Antimicrobial resistance in Gram-positive bacteria has reemerged in the last decade as a major clinical problem. Methicillin-resistant staphylococci, penicillin-resistant pneumococci, and enterococci resistant to penicillin, vancomycin, and/or gentamicin have become new considerations in the selection of therapy. Both mutation and acquisition of new DNA on either the chromosome or plasmids can be responsible for resistance in Gram-positive species. Because therapies are often limited, renewed efforts are needed to understand the epidemiology in order to effect control.

Detection and characterization of mupirocin resistance in Staphylococcus aureus.

Fourteen mupirocin-resistant Staphylococcus aureus strains were isolated over 18 months; 12 exhibited low-level resistance, while two showed high-level resistance. Highly mupirocin-resistant strains contained a large plasmid which transferred mupirocin resistance to other S. aureus strains and to Staphylococcus epidermidis. This plasmid and pAM899-1, a self-transferable gentamicin resistance plasmid, have molecular and biologic similarities.

Development of a rapid and efficient restriction endonuclease analysis typing system for Clostridium difficile and correlation with other typing systems.

A HindIII restriction endonuclease analysis (REA) typing system for total genomic Clostridium difficile DNA including a rapid and efficient method of DNA extraction and a scheme for organizing unique electrophoretic DNA band patterns was developed. REA typing was performed by two extraction methods for 1,965 C. difficile isolates obtained from patients with symptomatic C. difficile disease, asymptomatic patients who were C. difficile culture positive, and environmental surfaces. This isolate collection yielded 206 unique REA types, which were organized into 75 groups. A reference strain representing each unique REA type was chosen for DNA band pattern comparisons, cytotoxin testing, and plasmid analysis. The DNA band patterns utilizing a guanidine thiocyanate-EDTA-Sarkosyl DNA extraction method were 94% reproducible, while the original and sporadically problematic diethyl pyrocarbonate-sodium dodecyl sulfate DNA extraction method was 98% reproducible when readable patterns were obtained. Reference strains from 43 of the 75 groups were cytotoxin positive, 28 groups were cytotoxin negative, and 4 groups included both toxigenic and nontoxigenic strains. Cytotoxicity of isolates with a particular REA type was always consistent with the toxicity of the reference strain for that type. REA typing was able to discriminate strain differences within types identified by the immunoblot (89 isolates), bacteriophage-bacteriocin (44 isolates), and ribotyping (23 isolates) methods. REA typing is a sensitive, discriminating, reproducible, and rapid method for differentiating C. difficile strains and is suitable for large-scale epidemiologic studies.

Increasing resistance of enterococci to ciprofloxacin.

We determined that resistance to ciprofloxacin has emerged in enterococci over the last 5 years in our hospital, mainly in strains demonstrating the phenotype of high-level gentamicin resistance. All high-level-gentamicin-resistant isolates from 1985 and 1986 were susceptible, whereas 24% of isolates from 1989 and 1990 were resistant to ciprofloxacin. Plasmid and genomic DNA typing showed at least six unique strains exhibiting resistance, but one type accounted for 80% of recent resistant isolates, suggesting a role for cross infection in the emergence of resistance.

Endoscopic detection and therapy of colonic actinomycosis.

Abdominal actinomycosis is a disease that is difficult to diagnose nonoperatively. Usual manifestations are abscesses and draining sinus tracts. Treatment is typically surgical and requires prolonged intravenous antibiotics. Presented is a patient who underwent surveillance colonoscopy after resection for colon carcinoma. Diagnosis of colonic actinomycosis and subsequent resolution was demonstrated endoscopically after lengthy oral penicillin therapy (2 g/day for 1 yr). This case documents that resection may not be necessary to effect cure of abdominal actinomycosis.

Major trends in the microbial etiology of nosocomial infection.

To determine trends in the microbial etiology of nosocomial infections in the 1980s, surveillance data on the microbiology of documented nosocomial infection reported to the National Nosocomial Infections Surveillance System and from the University of Michigan Hospital were analyzed. Antimicrobial susceptibility data on selected pathogens from both sources were also reviewed. Overall, Escherichia coli decreased from 23% of infections in 1980 to 16% in 1986-1989, Klebsiella pneumoniae dropped from 7% to 5%, whereas coagulase negative staphylococci increased from 4% to 9% and Candida albicans increased from 2% to 5%. Staphylococcus aureus, Pseudomonas aeruginosa, Enterobacter species and enterococci had minor increases, but antimicrobial resistant strains for these pathogens as well as coagulase-negative staphylococci were seen more frequently. In contrast to the 1970s, major shifts in the etiology of nosocomial infection have occurred in the decade of the 1980s. Taken as a whole, the shifts are away from more easily treated pathogens toward more resistant pathogens with fewer options for therapy. These shifts underscore the continued need for prevention and control to accompany new developments in therapy.

Effect of controlled hemorrhage on tissue and serum cefazolin clearance.

Effects of blood loss on tissue and serum antibiotic levels were investigated in 30 New Zealand white rabbits. Studies were conducted over a 3.5-hr period after intravenous administration of cefazolin, 30 mg/kg, in control animals (Groups I and IV, n = 5 each) and animals having 50% (Groups II and V, n = 5 each) or 100% (Groups III and VI, n = 5 each) of their blood volume removed and replaced with either Ringer's solution (Groups I, II, and III) or rabbit whole blood (Groups IV, V, and VI) sufficient to maintain central venous pressures at baseline levels. Periodic samples of retroperitoneal fat, iliac artery, and serum were assayed for cefazolin concentration by disc diffusion. Decreased tissue antibiotic levels were observed in animals undergoing 100% blood replacement (Groups III and VI) compared to controls (Groups I and IV) in both fat (P less than or equal to 0.01) and artery (P less than or equal to 0.01) at 90 min. Decreased antibiotic serum half-life accompanying hemorrhage existed when comparing Group II to I (P less than or equal to 0.05), Group III to I (P less than or equal to 0.01), and Group IV to V (P less than or equal to 0.01). The increased antibiotic clearance related to blood loss in this study justifies reassessment of intraoperative dosing intervals. More frequent dosing may be required to maintain stable tissue and serum antibiotic levels during substantial operative hemorrhage.

Methicillin-resistant Staphylococcus aureus: colonization and infection in a long-term care facility.

OBJECTIVE: To assess methicillin-resistant Staphylococcus aureus (MRSA) colonization, transmission, and infection over a 1-year period in a long-term care facility with endemic MRSA. DESIGN: Monthly surveillance for MRSA colonization of nares, perineum, rectum, and wounds. SETTING: Long-term care facility attached to an acute care Veterans Affairs medical center. PATIENTS: All 341 patients in the facility had monthly surveillance cultures for 1 year. OUTCOME MEASUREMENTS: Colonization and infection with MRSA. MAIN RESULTS: The monthly MRSA colonization rate was 23% +/- 1.0%; colonization occurred most commonly in the nares and wounds. Poor functional status was associated with MRSA colonization. Most patients (65%) never acquired MRSA; 25% of patients were already colonized at admission to the facility or at the start of the study, and only 10% of newly admitted patients acquired MRSA while in the facility. These latter patients acquired several different strains in a pattern of acquisition similar to that generally seen within the facility. In the course of 1 year, only nine patients who acquired MRSA had a roommate with the same phage type; no clustering was evident, and none of these patients developed infection. Nine other patients (3%) developed MRSA infection; five of these patients required hospitalization, but none died as a result of infection. CONCLUSIONS: In the long-term care facility in which our study took place, MRSA was endemic, and the infection rate was low. In such settings, the cost effectiveness of aggressive management of MRSA (widespread screening for MRSA and eradication with antimicrobial agents) needs to be assessed.

Neisseria mucosa endocarditis.

A case of Neisseria mucosa tricuspid valve endocarditis in an intravenous drug abuser is described. The patient was treated initially with intravenous penicillin G followed by oral penicillin VK but relapsed. He was cured after 4 weeks of combined therapy with penicillin G and gentamicin. In vitro synergy studies performed on the patient's and two other isolates revealed synergy in all three. Thus, combination therapy is recommended for treatment of recalcitrant cases of bacterial endocarditis caused by N. mucosa.