Pseudomonas aeruginosa bacteremia associated with hematologic disorders [II]. Blood culture isolates and surveillance cultures

We experienced 57 episodes of Pseudomonas aeruginosa bacteremia in 55 patients with hematologic disorders such as acute leukemia over a 16-year period. All the patients were treated on the same hospital ward. A total of 57 blood culture isolates of P. aeruginosa were divided into nine serogroups. Seventy-four percent of the isolates belonged to four serogroups, which became preponderant one after the other. Surveillance throat and/or stool cultures grew the organisms identical to the isolates from the blood at or prior to the onset of bacteremia in 75% of the episodes. Only 11% of the patients had had P. aeruginosa cultured at admission. The acquisition of the organism was closely associated with antibiotic therapy for other presumed or proved infection. On the other hand, 60% of the episodes occurred during the administration of at least one in vitro effective antibiotic. In five episodes, the patients had received an antipseudomonal penicillin and an aminoglycoside in combination, both of which proved effective in vitro against the infecting organism, when bacteremia occurred. In managing P. aeruginosa bacteremia complicating hematologic disorders, it was thus suggested that surveillance cultures should be regularly carried out, and that attention should be drawn to the occurrence of "breakthrough" bacteremia.     

Nosocomial bacteremia in a large Spanish teaching hospital: analysis of factors influencing prognosis

Five hundred forty-three episodes of nosocomial bacteremia were prospectively followed in a large Spanish university hospital. The commonest isolates were Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida species. The most frequent sources of infection were intravenous lines, urinary tract, and lower respiratory tract. Overall mortality was 18%. A step-forward logistic regression analysis defined eight variables independently influencing the outcome: shock, underlying rapidly fatal disease, high-risk source of bacteremia (intraabdominal, lower respiratory tract, or not identified), age more than 70 years, hospitalization in intensive care or medical units, inappropriate antibiotic treatment, infection due to a high-risk microorganism (P. aeruginosa, Serratia marcescens, Klebsiella, Bacteroides, or Candida), and development of septic metastasis. The identification of those factors independently influencing the outcome and their possible modification may represent a further step in the control of nosocomial bacteremia by improving its prognosis.     

Dissemination of Pseudomonas aeruginosa during lung infection in hamsters. Role of oxygen-induced lung injury

Pseudomonas aeruginosa was inoculated into the lungs of normal and oxygen-exposed hamsters. Air-breathing animals developed focal bronchopneumonias but viable organisms were not recovered from the lungs after 3 days; bacteremia was not detected but P. aeruginosa was isolated from the livers of 3 of 12 animals with positive lung cultures. Pseudomonas aeruginosa infection shortened the survival time of oxygen-breathing hamsters, and organisms persisted in the lungs during oxygen exposure. Focal bronchopneumonias were uncommon in animals inoculated after 4 days of oxygen exposure; the predominant histopathologic finding was accentuation of diffuse alveolar damage and increased numbers of scattered neutrophils. Pseudomonas aeruginosa was recovered from the livers of 15 of 18 oxygen-exposed animals in which lung colony counts exceeded 10(3)/lung; only 8 of these animals had demonstrable bacteremia. The concentration of elongation factor-2 in the livers and lungs of oxygen-exposed animals was reduced as colony counts of P. aeruginosa increased in the lungs of infected animals, suggesting exotoxin A activity in these organisms. These findings suggest that bacterial superinfection of injured lungs may account for both worsening lung function and impaired function of other organs.     

Comparison of antibiotic regimens for treatment of experimental pneumonia due to Pseudomonas.

The high mortality associated with pneumonia due to Pseudomonas aeruginosa prompted a comparative trial of several currently available antibiotic regimens for this infection in a guinea pig model. Normal guinea pigs receiving an intratracheal challenge of 10(8) colony-forming units of Pseudomonas routinely died within 3-48 hr when treated with saline injections. Treatment with carbenicillin or ticarcillin did not affect this uniformly fatal outcome. Groups of animals treated with gentamicin or tobramycin had survival rates of 39% and 67%, respectively. The addition of either carbenicillin or ticarcillin to an aminoglycoside failed to enhance further the survival rates or durations of survival after infection. These survival data were supported by studies showing superior clearance of viable Pseudomonas from lung tissues in aminoglycoside-treated animals chosen at random for sacrifice 3 hr after infection. Thus, in animals experimentally challenged with P. aeruginosa to cause pneumonia and in which only a single isolate of Pseudomonas was evaluated, protection from pulmonary infection was best provided by an aminoglycoside rather than by a beta-lactam antibiotic.     

Bacteremia due to Stenotrophomonas maltophilia in patients with hematologic malignancies.

Predisposing factors, clinical characteristics, and antimicrobial treatment of 37 hematology patients with Stenotrophomonas maltophilia bacteremia who were seen at the department of hematology of the University La Sapienza (Rome) from 1987 to 1996 were evaluated. The results were compared with a control group of patients with Pseudomonas aeruginosa bacteremia. Profound neutropenia was more prolonged in the S. maltophilia group (P=.025), severe cellulitis occurred only in S. maltophilia-infected patients (11 [30%]; P=.0002), and the bacteremia presented as breakthrough infection in 56% of the cases due to S. maltophilia (vs. only 24% of those due to P. aeruginosa; P=.002). Acute mortality rates associated with S. maltophilia and P. aeruginosa bacteremia were 24% and 21%, respectively. In both groups, profound neutropenia and hypotension at the onset of bacteremia, duration of profound neutropenia during bacteremia, severity-of-illness score > or =4, and inappropriate antibacterial treatment were factors significantly associated with death. Most S. maltophilia isolates were resistant to aminoglycosides, beta-lactams, and ciprofloxacin. Cotrimoxazole and ticarcillin-clavulanic acid showed borderline activity. Prompt administration of in vitro-active antibiotics may improve the prognosis of S. maltophilia bacteremia, especially for immunocompromised patients, and novel drug combinations are needed for the treatment of severe infections.     

Epidemiology of bacteremia and factors associated with multi-drug-resistant gram-negative bacteremia in hematopoietic stem cell transplant recipients

The incidence of Gram-negative bacteremia has increased in hematopoietic stem cell transplant (HSCT) recipients. We prospectively collected data from 13 Brazilian HSCT centers to characterize the epidemiology of bacteremia occurring early post transplant, and to identify factors associated with infection due to multi-drug-resistant (MDR) Gram-negative isolates. MDR was defined as an isolate with resistance to at least two of the following: third- or fourth-generation cephalosporins, carbapenems or piperacillin-tazobactam. Among 411 HSCT, fever occurred in 333, and 91 developed bacteremia (118 isolates): 47% owing to Gram-positive, 37% owing to Gram-negative, and 16% caused by Gram-positive and Gram-negative bacteria. Pseudomonas aeruginosa (22%), Klebsiella pneumoniae (19%) and Escherichia coli (17%) accounted for the majority of Gram-negative isolates, and 37% were MDR. These isolates were recovered from 20 patients, representing 5% of all 411 HSCT and 22% of the episodes with bacteremia. By multivariate analysis, treatment with third-generation cephalosporins (odds ratio (OR) 10.65, 95% confidence interval (CI) 3.75-30.27) and being at one of the hospitals (OR 9.47, 95% CI 2.60-34.40) were associated with infection due to MDR Gram-negative isolates. These findings may have important clinical implications in the decision of giving prophylaxis and selecting the empiric antibiotic regimen.     

Recent experience with Pseudomonas aeruginosa bacteremia in patients with cancer: Retrospective analysis of 245 episodes

BACKGROUND: Pseudomonas aeruginosa bacteremia is a serious and possibly fatal condition in patients with cancer. OBJECTIVES: To ascertain the frequency, demographics, and predisposing factors for P. aeruginosa bacteremia in patients with cancer and to determine the efficacy of various therapeutic regimens. SUBJECTS AND METHODS: Patient records of the Clinical Microbiology Laboratory, The University of Texas, M. D. Anderson Cancer Center, Houston, were reviewed. From January 1, 1991, through December 31, 1995, 245 eligible cases of P. aeruginosa bacteremia were identified. We examined the patient records for the underlying malignant neoplasm and its management, symptoms and signs of infection, culture results of appropriate specimens, antibiotic therapy, and outcome. We also compared our present experience with a previous analysis from this institution covering the period from January 1, 1972, to December 31, 1981. RESULTS: The incidence of P. aeruginosa bacteremia has decreased compared with the previous study (2.8 vs 4.7 cases per 1000 admissions). It was most common in patients with acute leukemia (55 of 1000 registrations), and the frequency in this disease has not changed. Half of the patients were not in the hospital when they developed their infection. The overall cure rate was 80%, which was a significant (P<.001) increase compared with the 62% cure rate in the previous study. In this study, no significant difference in the cure rates was observed between monotherapy with a beta-lactam and combination therapy overall (P = .72), and in patients with shock (P = 1.0) and those with pneumonia (P = .60). The patients' initial neutrophil counts were not of prognostic value; however, the cure rate depended on subsequent changes in neutrophil count during therapy. CONCLUSIONS: The frequency rate of P. aeruginosa bacteremia has decreased in patients with solid tumors but has remained unchanged in patients with acute leukemia. Antibiotic regimens for empirical therapy of neutropenic patients and especially patients with acute leukemia should still provide coverage against P. aeruginosa.     

Outcomes of bacteremia due to Pseudomonas aeruginosa with reduced susceptibility to piperacillin-tazobactam: implications on the appropriateness of the resistance breakpoint.

BACKGROUND: Bacteremia due to Pseudomonas aeruginosa is associated with grave clinical outcomes. Recent studies have emphasized the importance of appropriate empirical therapy, but controversy arises when piperacillin-tazobactam is used against isolates with reduced susceptibility. METHODS: We performed a retrospective cohort study of pseudomonal bacteremia from 2002 to 2006. Patients were identified by the microbiology laboratory database, and pertinent clinical data (demographic characteristics, baseline Acute Physiology and Chronic Health Evaluation [APACHE] II scores, source of bacteremia, and therapy) were retrieved from the electronic medical records. All patients received appropriate empirical therapy within 24 h of positive culture results. Patients receiving piperacillin-tazobactam were compared with those receiving other agents (control subjects). The primary outcome was 30-day mortality from the first day of bacteremia. RESULTS: A total of 34 bacteremia episodes were identified involving isolates with reduced susceptibility to piperacillin-tazobactam (minimum inhibitory concentration, 32 or 64 mg/L, reported as susceptible); piperacillin-tazobactam was empirically given in 7 episodes. There was no significant difference in baseline characteristics between the 2 groups. Thirty-day mortality was found to be 85.7% in the piperacillin-tazobactam group and 22.2% in the control group (P = .004). Time to hospital mortality was also found to be shorter in the piperacillin-tazobactam group (P < .001). In the multivariate analysis, 30-day mortality was found to be associated with empirical piperacillin-tazobactam therapy (odds ratio, 220.5; 95% confidence interval, 3.8-12707.4; P = .009), after adjustment for differences in age and APACHE II score. CONCLUSIONS: In P. aeruginosa bacteremia due to isolates with reduced piperacillin-tazobactam susceptibility, empirical piperacillin-tazobactam therapy was associated with increased mortality. Additional studies are warranted to examine the appropriateness of the current Clinical Laboratory Standards Institute resistance breakpoint of piperacillin-tazobactam.     

Outbreak caused by tobramycin-resistant Pseudomonas aeruginosa in a bone marrow transplantation unit.

Between May and August 1995, 5 patients in a bone marrow transplantation (BMT) ward developed bacteremia caused by Pseudomonas aeruginosa resistant to tobramycin (TRPA). Previously, isolates of TRPA had been limited to patients who were treated in 1 intensive care unit (ICU) of this tertiary care teaching hospital in Helsinki, Finland. To study whether the outbreak was caused by a single or multiple strains of P. aeruginosa, 102 isolates of TRPA from clinical samples obtained from different hospital units and 22 isolates obtained from the hospital environment were characterized by pulsed-field gel electrophoresis. All isolates from hematological patients produced 1 unique fragment pattern, which was also isolated from 3 ICU patients before the BMT ward outbreak began as well as from 5 shower heads in the BMT ward. The outbreak in the BMT ward was successfully controlled by eradicating the probable environmental source--contaminated hand showers--but the endemic infections continued in the ICU.     

Serum sensitivity of Pseudomonas aeruginosa isolated from sputum as a virulence factor in the lower respiratory tract

To elucidate the clinical significance of serum-sensitivity of respiratory pathogenic Pseudomonas aeruginosa (P. aeruginosa) strains, we examined serum-sensitivity of P. aeruginosa isolated from 16 patients with lower respiratory tract infections and clinical backgrounds of these patients. We also evaluated the virulence of four serum-resistant and four serum-sensitive P. aeruginosa strains in murine pneumonia model induced by intratracheal challenge, and the silver-stained profiles of purified lipopolysaccharide (LPS) from these strains. Serum-sensitive strains were isolated only from patients with chronic bronchitis, bronchiectasis, and diffuse panbronchiolitis colonized with P. aeruginosa, and rarely caused pneumonias, while serum-resistant strains caused pneumonias in some cases. Intratracheal challenge of mice with 5 x 10(7) cfu per mouse of a serum resistant strain caused fatal hemorrhagic pneumonia with bacteremia. In contrast, the same dose of a serum-sensitive strain provided non-fatal pneumonia without bacteremia. LD50 of serum-sensitive strains in a murine model of P. aeruginosa pneumonia were at least 2-10 times higher than those of serum-resistant strain. The LPS profiles of two serum-resistant strains and one serum-sensitive strain showed ladder-like patterns. The similar analysis demonstrated that one serum-sensitive strain was lack of ladder-like patterns. These data support that serum-sensitive P. aeruginosa strains are less virulent than serum-resistant P. aeruginosa strains in the lower respiratory tract, and serum sensitivity of P. aeruginosa strains is determined by the structure of the O-side chain of LPS; either lack of the O-side chain or the presence of sparse O-side chain.     

Changing patterns of blood culture isolates from patients with acute leukemia: a review of twenty years' experience.

During the 20-year period, 1972-1991, 286 episodes of bacteremia occurred in 200 (45%) of 445 patients with acute leukemia in a hematology ward, giving an incidence of 482 episodes per 1,000 hospital admissions. The frequency of bacteremia was almost unchanged throughout the study period. The frequency of gram-negative bacilli decreased significantly, however, from 81% of all the isolates for the first half of the study period to 50% for the latter half. Despite the common use of ceftazidime and imipenem during the last 5-year period, Pseudomonas aeruginosa increased in frequency to be the most frequent organism. This was opposite to the decreased frequencies of Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae. The isolates of P. aeruginosa obtained during this period, all of which proved sensitive to ceftazidime and/or imipenem, were almost equally distributed among five serogroups, although a temporal preponderance of a limited number of serogroups was observed during the preceding 15-year period. On the other hand, the frequency of gram-positive cocci increased from 9% in the first decade to 35% in the latter decade. Staphylococcus epidermidis, Enterococcus species and, to a lesser extent, Staphylococcus aureus were ranked as major pathogens. Among the recent isolates of S. aureus, methicillin-resistant strains virtually replaced methicillin-sensitive ones. Therefore, until more effective means for control of P. aeruginosa bacteremia in particular become available, the occurrence of this infection will continue to limit the successful treatment of acute leukemia.     

Pseudomonas aeruginosa infection after living-donor liver transplantation in adults

Objectives. Pseudomonas aeruginosa infection is a major cause of bacterial infection after deceased-donor liver transplantation. The incidence and risk factors of P. aeruginosa infection after living-donor liver transplantation (LDLT), however, are not known.
Methods. We retrospectively reviewed the data from 170 adult patients who underwent LDLT at the University of Tokyo Hospital. The microbiologic and medical records of the patients from admission to 3 months after LDLT were reviewed. Uni- and multivariate analyses were performed to identify the independent risk factors for postoperative P. aeruginosa infection.
Result. Preoperative P. aeruginosa carriage was identified in 15 (9%) patients. Only 2 of the 15 patients later presented with postoperative P. aeruginosa infection. Postoperative P. aeruginosa infection occurred in 27 (16%) of 170 patients by median postoperative day 38. Among those 27 patients, surgical site infections were recorded in 8 (30%) and intra-abdominal infections in 14 (52%). In 5 of the 27 (19%) patients, P. aeruginosa isolates were multiple antimicrobial resistant. Postoperative bile leakage independently predicted postoperative P. aeruginosa infection.
Conclusion. P. aeruginosa infections were frequently detected after LDLT, including those by multiple antimicrobial-resistant isolates. Postoperative bile leakage predisposed patients to P. aeruginosa infection. Surveillance culture should be checked periodically after LDLT to ensure that appropriate antimicrobials can be administered for postoperative infection.     

Infectious complications during remission induction therapy in 577 patients with acute myeloid leukemia in the Japan Adult Leukemia Study Group studies between 1987 and 1991

The Japan Adult Leukemia Study Group analyzed infectious episodes in 577 patients with acute myeloid leukemia during remission induction therapy between 1987 and 1991. 542 patients (93.9%) experienced at least one infectious episode, 121 (21.0%) had microbiologically documented infection; there was clinically documented infection in 184 (31.9%) and unexplained fever in 237 (41.1%). Among 121 microbiologically documented infections, bacteremia/fungemia was observed in 68, pneumonia in 33, and other types of infections in 20. Among the bacteremia/fungemia, gram-negative bacteria accounted for 41.2% (Pseudomonas aeruginosa was the most common), gram-positive bacteria for 39.7%, fungi for 16.2% (Candida spp. being most frequent), and polymicrobial for 2.9%. The most frequent isolates among pneumonia were Pseudomonas aeruginosa and Aspergillus. A total of 70 patients (12.1%) died during remission induction. Mortality of 68 patients with bacteremia/fungemia was 26.5%; in these patients, mortality with concomitant pneumonia increased to 41.4%; without pneumonia, mortality was 15.4% (P < 0.05). Mortality according to the isolated microbes was 17.2% for gram-negative bacteria, 25% for gram-positive bacteria, and 54.5% for fungi. Mortality of 113 patients with pneumonia (33 microbiologically documented and 80 clinically documented), 20 with other microbiologically documented infections, 104 with other clinically documented infections, and 237 with unexplained fever was 25.7%, 5.0%, 5.8%, and 5.1%, respectively.     

Bacteremia in narcotic addicts at the Detroit Medical Center. I. Microbiology, epidemiology, risk factors, and empiric therapy

The changing microbiology of bacteremia among narcotic addicts in Detroit raised concerns about current presumptive antimicrobial therapy. In a one-year study of incidence, microbiology, sites, and risk factors, 180 bacteremic addicts (15% of addict-related admissions) were followed prospectively. Cases of bacteremia were caused by methicillin-sensitive Staphylococcus aureus (33%), methicillin-resistant S. aureus (MRSA, 24%), streptococci (20%), mixed organisms (11%), Pseudomonas aeruginosa (9%), and miscellaneous other single organisms (3%). Endocarditis (41%) and abscess or cellulitis (34%) were usually found. Multivariate analysis of host factors and addiction habits yielded results predictive of bacterial species but not of infection sites. Previous hospitalization, long-term addiction, and nonprescribed antibiotic use were associated with MRSA acquisition (odds ratio, 8.6:1). All addicts with polymicrobial or P. aeruginosa bacteremia abused pentazocine and tripelennamine (P = .05). Many of the addicts with streptococcal bacteremia were women who did not abuse antibiotics (odds ratio, 20.7:1). Physicians inappropriately prescribed empiric antibiotics for 67 of 72 addicts with MRSA, P. aeruginosa, or polymicrobial infection. The results of regression analysis suggest that, guided by the patient's history, the physician can prescribe appropriate empiric antimicrobial therapy for bacteremia in the febrile addict in Detroit.     

Longitudinal assessment of Pseudomonas aeruginosa in young children with cystic fibrosis

Pseudomonas aeruginosa lung infection is an important cause of morbidity and mortality in cystic fibrosis (CF). Longitudinal assessment of the phenotypic changes in P. aeruginosa isolated from young children with CF is lacking. This study investigated genotypic and phenotypic changes in P. aeruginosa from oropharynx (OP) and bronchoalveolar lavage fluid (BALF) in a cohort of 40 CF patients during the first 3 years of life; antibody response was also examined. A high degree of genotypic variability was identified, and each patient had unique genotypes. Early isolates had a phenotype distinct from those of usual CF isolates: generally nonmucoid and antibiotic susceptible. Genotype and phenotype correlated between OP and BALF isolates. As determined by culture, 72.5% of patients demonstrated P. aeruginosa during their first 3 years. On the basis of combined culture and serologic results, 97.5% of patients had evidence of infection by age 3 years, which suggests that P. aeruginosa infection occurs early in CF and may be intermittent or undetectable by culture.     

Pathogenesis of Pseudomonas aeruginosa pneumonia during immunosuppression.

A guinea pig model of immunosuppression was utilized to study the effects of immunosuppressive chemotherapy on lung response to challenge with Pseudomonas aeruginosa. Study groups included normal guinea pigs, as well as guinea pigs that received a one-week course of cortisone acetate (CA, 100 mg/kg per day) plus 15 mg of cyclophosphamide (CTX)/kg per day (CA + LoCTX group) or 30 mg of cyclophosphamide/kg per day (CA + HiCTX group). Separate groups received CA or HiCTX alone. Intratracheal instillation of P. aeruginosa resulted in bilateral hemorrhagic pneumonia in both normal and immunosuppressed animals. Survival was 100% for normal animals and for those given CA alone, 67% in the CA + LoCTX and the HiCTX groups, and 0 in the CA + HiCTX group. Increased mortality correlated with a diminished polymorphonuclear leukocyte inflammatory response in infected lung tissues and also with the addition of CA to CTX. Clearance of viable P. aeruginosa from lung tissue was significantly reduced in animals receiving the combination CA + HiCTX. Thus, decreased lung inflammation and the addition of CA appeared to be important determinants for fatal pseudomonas pneumonia.     

Significance of Pseudomonas aeruginosa colonization of the gastrointestinal tract

OBJECTIVE: This study was conducted to determine the association between gastrointestinal (GI) colonization and the development of invasive Pseudomonas aeruginosa infections and risk factors for acquisition of P. aeruginosa colonization in gut. METHODS: All stool specimens sent for microbiological examination were cultured for P. aeruginosa search for three years. PATIENTS AND MATERIALS: P. aeruginosa had been isolated from stool of 207 patients for three years. Of the 207 patients, 87 patients were identified P. aeruginosa-colonized patients. RESULTS: Forty-five (52%) were exposed to previous invasive procedures and eighty-three (95%) were prescribed antibiotics before the isolation of P. aeruginosa. Fourteen distinctive P. aeruginosa infections were developed in 13 patients (15%). Infections associated with GI colonization included 4 pneumonia, 4 urinary tract infection, 3 skin infection, and 3 bacteremia. The age, gender, underlying diseases, previous invasive procedures, and the duration of hospitalization were not significant. Twelve (34%) patients were diagnosed with ileus and three (9%) were undergoing gastrostomy during the acquisition of P. aeruginosa colonization in gut. CONCLUSION: Gastrointestinal disorders, especially obstruction and surgical interventions, are also important for the acquisition of by P. aeruginosa, in the GI tract.     

Pseudomonas aeruginosa infection in human immunodeficiency virus infected patients.

OBJECTIVES: (1) To determine the incidence and outcome of Pseudomonas aeruginosa infection in HIV-infected patients. (2) To study the antimicrobial susceptibility of P. aeruginosa isolates in this particular population. (3) To identify risk factors for these infections. PATIENTS AND METHODS: A retrospective case-control study performed in a 28-bed infectious-diseases unit in a 940-bed university hospital. All cases were defined as HIV-infected patients with severe infections due to P. aeruginosa, including bacteremia, lower or upper respiratory tract infections, infections related to a central venous catheter, and cutaneous/muscular infection. Each case was matched with an HIV-seropositive control not infected by P. aeruginosa and hospitalized on the same dates as the cases. RESULTS: One thousand and thirty-five HIV-infected patients were hospitalized during the study period. A first severe P. aeruginosa infection was documented in 41 patients, giving an overall annual incidence note of 2.51 episodes per 100 admissions. Forty of the 41 case notes were available for analysis. They consisted of 17 cases of bacteraemia, four upper respiratory tract infections, 10 lower respiratory tract infections, three catheter-related infections, and six cutaneous/muscular infections. Of these 40 cases, 60% were nosocomial and the remainder were community-acquired. The overall mortality rate was 22% (47% in bacteraemic forms). Twenty five percent of patients relapsed after an average of 37 days. The case-control comparison showed that AIDS was more frequent among the cases (92% vs. 74%, P = 0.04), who also had a lower PN count (P = 0.005), and a lower CD4 cell count (15.7 +/- 18.8/mm3 vs. 118 +/- 211/mm3; P = 0.0007). The number of days spent in hospital in the previous 3 months (29.3 +/- 20.7 vs. 19.7 +/- 14, P = 0.04) was significantly higher among the cases. In a multivariate analysis, examining treatments received in the previous month, only co-trimoxazole [OR = 5.5 (1.1-26.9)], penicillins [OR = 5.2 (1.1-25.3)], steroids [OR = 5.5, (1.2-25.5)] and a CD4 cell count below 50/mm3 [OR = 13.2 (1.4-129.4)] were identified as risk factors. CONCLUSION: P. aeruginosa infection is a not frequent bacterial disease in highly immunodeficient HIV-infected patients. It is frequently fatal and must be borne in mind in the advanced stages of HIV disease, especially when patients have received co-trimoxazole (trianthoprim-sulphamethoxazole), penicillins or steroids.     

Bacterial translocation and gram-negative bacteremia in patients with hematological malignancies

Between 1976 and 1982, Enterobacteriaceae and Pseudomonas aeruginosa were prospectively counted in fecal specimens from leukemic patients with gram-negative bacteremia. The strains isolated from the blood and feces of 55 patients were compared. Translocation of the dominant fecal strain of Enterobacteriaceae or P. aeruginosa was observed in 45 cases (82%) and was strongly associated with granulocytopenia of less than 10(2) cells/microliter (P less than .0001). Thirteen (81%) of 16 patients with bacteremia caused by P. aeruginosa were intestinal carriers of the same strain, whereas only 2 (5%) of 39 patients with bacteremia caused by Enterobacteriaceae were carriers of P. aeruginosa. Bacterial translocation of Enterobacteriaceae was not associated with an abnormally high fecal population of the translocating strain. Prospective quantitative and qualitative analyses of fecal flora were useful in forecasting the most probable translocating gram-negative organism in neutropenic leukemic patients with clinical signs of bacteremia.     

Gram-negative bacillary bacteremia in the elderly: incidence, ecology, etiology, and mortality

The incidence, ecology, and mortality of gram-negative bacillary bacteremia in elderly patients were studied in an analysis of 334 episodes over a four-year-period in a 489-bed North Carolina community teaching hospital, 135 (40.4%) of which occurred in patients 70 years of age or older. The bacteremia rate per 1000 hospital admissions increased sharply with increasing age. The ecology and in vitro antimicrobial susceptibilities of the bacterial isolates were strongly influenced by community v hospital acquisition, but not by age. Urosepsis was significantly more likely to be the underlying source of hospital-acquired bacteremia in patients 70 years or older (P less than 0.01). Total bacteremia-related mortality did not increase with increasing age; in the group of patients aged 70 years or older with nonfatal/ultimately fatal underlying diseases (NF/UFUD), however, mortality was 9.1% compared to 2.9% in the younger age group (P less than 0.001). Significantly increased bacteremia-related mortality was also noted in the older patients with NF/UFUD admitted from nursing homes (P less than 0.05) and those not treated with an appropriate antimicrobial agent within 24 hours (P less than 0.01). Overall, the older patients with hospital-acquired bacteremia, neutropenia-associated infection, those bacteremic from a nonurinary source of infection, and those treated with multiple-drug regimens had higher mortality (P less than 0.05). Gram-negative bacteremia is much more common in patients 70 years of age or older and compared with younger patients mortality appears to be significantly increased for the important subgroup of older patients with nonfatal or ultimately fatal underlying diseases.