Progressive resistance in a single strain of Acinetobacter calcoaceticus recovered during a nosocomial outbreak

A study was undertaken to investigate a nosocomial outbreak of acinetobacter calcoaceticus. The outbreak occurred in a shock-trauma intensive care unit (ICU) during a 6-month period and involved a total of 37 cases. Although no deaths were attributable to Acinetobacter, 60% of patients from whom Acinetobacter was isolated were determined to have a lower respiratory tract infection. A significant difference (p less than 0.05) was noted between the length to stay in the unit of patients who acquired Acinetobacter (mean 23.9 days) and of those who remained free of the organism (mean 2.58 days). The average day on which cultures first became positive was 14.85. During the last 3 months of the outbreak, the ICU Acinetobacter isolates developed an unusual pattern of aminoglycoside resistance that differed significantly (p less than 0.001) from the sensitivities of non-ICU Acinetobacter isolates. No plasmids could be detected in selected aminoglycoside-resistance Acinetobacter. Pseudomonas aeruginosa isolated concurrently from patients with Acinetobacter showed no abnormal variation in antimicrobial sensitivities. These findings were interpreted to mean that the outbreak was the result of the persistence of a single strain of A. calcoaceticus within the ICU. Termination of the outbreak was attributed to initiation of control measures.     

Molecular typing of coagulase-negative staphylococci from blood cultures does not correlate with clinical criteria for true bacteremia

PURPOSE: Determining whether a blood culture that contains coagulase-negative staphylococci represents bacteremia or contamination is a clinical dilemma. We compared molecular-typing results of coagulase-negative staphylococcal blood culture isolates with clinical criteria for true bacteremia. SUBJECTS AND METHODS: Pulsed-field gel electrophoresis and arbitrary primed polymerase chain reaction (PCR) were used to determine whether patients with two or more blood cultures with coagulase-negative staphylococcal isolates had the same strain of organism in each culture (same strain bacteremia). We evaluated three different clinical criteria for bacteremia: whether the patient received more than 4 days of antibiotics, whether there was an explicit note in the medical chart in which the physician diagnosed a true bacteremia, and the Centers for Disease Control surveillance criteria for primary bloodstream infection. Agreement between same-strain bacteremia and each definition was examined, based on the assumption that most true infections should be the result of a single strain. RESULTS: The study sample consisted of 42 patients and 106 isolates. Nineteen of the 42 bacteremias (45%) were the same strain. Classification of bacteremias as same-strain correlated poorly with all three clinical assessments (range of percent agreement, 50% to 57%; range of kappa statistic, 0.01 to 0.15). There were both false-positive and false-negative errors. Patients with three or more positive blood cultures were more likely to have same-strain bacteremia than those with only two positive cultures [11 of 15 (73%) vs 8 of 27 (30%), P = 0.006]. Pulsed-field gel electrophoresis was more discriminating than arbitrary primed PCR (percent agreement, 83%; kappa, 0.67). CONCLUSION: Molecular typing correlated poorly with clinical criteria for true bacteremia, suggesting either that true bacteremias are frequently the result of multiple strains or that the commonly used clinical criteria are not accurate for distinguishing contamination from true bacteremia. Vancomycin treatment of clinically defined coagulase-negative staphylococcal bacteremia may frequently be unnecessary.     

Anaerobic bacteremia: incidence, patient characteristics, and clinical significance.

PURPOSE: In the 1970s, blood culture for obligate anaerobic bacteria became routine in most United States hospitals. Since then, various authorities have reported isolation of obligate anaerobes in 5% to 25% of blood cultures. Our experience suggests a much lower frequency; therefore, we retrospectively assessed the occurrence and significance of these cultures at our institutions. PATIENTS AND METHODS: Sixty-six patients at the University of Michigan Hospitals (UMH) and nine patients at the Ann Arbor Veteran's Administration Medical Center (AAVAMC) had one or more blood cultures positive for an obligate anaerobe between July 1, 1987, and December 31, 1988. Their medical records were reviewed retrospectively. RESULTS: The proportion of positive blood cultures yielding obligate anaerobes was 3.2% at the UMH and 1.8% at the AAVAMC. The incidences of clinically significant anaerobic bacteremia at the two hospitals were 0.68 and 0.54 cases per 1,000 patient admissions. Among the 40 patients from whom significant isolates were obtained, 15 (38%) had a fatal outcome. Bacteroides and Clostridium species accounted for 90% of the isolates and all of the fatal cases. The source for anaerobic bacteremia was usually obvious; 30 of the 40 patients were given empiric antibiotic therapy for anaerobes. The gastrointestinal tract was the source in two thirds of the cases and was clearly implicated as the source of 80% of the fatal bacteremias. CONCLUSIONS: The frequency of anaerobic bacteremia in our hospitals is much lower than was suggested in several large studies during the 1970s, probably reflecting a real decline in the incidence. The clinical features of our cases are similar to those of previous studies, and the mortality is still high despite the use of antibiotics effective against anaerobes. Since most patients were thought to have anaerobic infections at the time that cultures were obtained, they were usually treated empirically. Subsequent blood cultures positive for anaerobes infrequently influenced clinical management.     

Incidence of bacteremia in transesophageal echocardiography: a prospective study of 140 consecutive patients

The incidence of bacteremia related to transesophageal echocardiography was studied in 140 consecutive patients (71 women and 69 men with a mean age of 53.7 +/- 15 years). Thirty-four patients had one or more prosthetic heart valves. Blood cultures were obtained from each patient through separate venipuncture sites immediately before and after transesophageal echocardiography. An additional late blood culture was obtained in 114 patients 1 h later. The skin was cleaned with povidone-iodine and venipunctures were performed with separate butterfly needles with use of sterile gloves and drapes. Blood samples were drawn into separate syringes, transferred to aerobic and anaerobic culture bottles and processed with use of a semiautomated system. The overall incidence of blood cultures positive for bacteremia was 2% (8 of 394 bottles) and all positive cultures grew in a single blood culture bottle. Positive cultures occurred in 4 (1.4%) of 280 bottles before the procedure, in 2 (0.7%) of 280 bottles immediately after the procedure and in 2 (0.9%) of 228 late (1-h) blood culture bottles. Bacterial isolates were coagulase-negative staphylococci (n = 5), Propionibacterium (n = 2) and Moraxella (n = 1). All were considered contaminants. Mean endoscopic time in these patients was not significantly different from that in the other patients. Follow-up of patients with a blood culture positive for bacteremia revealed no clinical evidence of systemic infection. It is concluded that 1) the incidence of bacteremia related to transesophageal echocardiography is very low, and 2) the incidence of blood cultures positive for bacteremia after transesophageal echocardiography is indistinguishable from the anticipated contamination rate.     

Routine use of anaerobic blood cultures: are they still indicated?

PURPOSE: To determine the number of patients with bacteremia and fungemia and to evaluate the utility of routine anaerobic blood cultures as part of the work-up for suspected bacteremia. SUBJECTS AND METHODS: Retrospective review of microbiology data followed by selective chart review at a university-affiliated Veterans Affairs Medical Center. We determined the number of bacterial blood cultures drawn from January 1, 1994, to December 31, 1996, and the number of anaerobic, aerobic, and fungal isolates. Chart reviews were then performed on all patients with a positive anaerobic result.RESULTS: There were 6,891 sets of blood cultures processed through the laboratory, yielding 1,626 patients with positive results. Anaerobic isolates were recovered from 36 patients (2.2%) in 48 bottles. Aerobic isolates were recovered from 1550 patients (95.3%), and fungal isolates were recovered from 40 patients (2.5%). Seven patients (0.4%) had true anaerobic bacteremia. All seven patients had an obvious source of anaerobic infection that was known or suspected before the cultures were drawn. Antibiotic changes were made in four of these patients after the positive anaerobic results were known. Antibiotic changes led to clinical improvement in one patient. CONCLUSIONS: Routine use of anaerobic blood cultures rarely results in clinically important diagnostic or therapeutic benefits, based on the low incidence of anaerobic bacteremia in patients who are not at increased risk. Anaerobic blood cultures should be selectively ordered in patients at risk for anaerobic infections.     

Mycobacterium tuberculosis bacteremia in a university hospital.

SETTING: Patients with blood cultures positive for Mycobacterium tuberculosis between 1988 and 1999. OBJECTIVE: To study the clinical and microbiological characteristics of patients with tuberculous bacteremia, including data about evolution and management. DESIGN: Retrospective review of the clinical charts and microbiological records of patients with culture-proven tuberculous bacteremia between 1988-1999. RESULTS: During the study period, 19 patients with culture-proven M. tuberculosis bacteremia were detected (1.42 isolates/patient, 4.7% of all patients with blood cultures for mycobacteria). Four patients were non-infected with the human immunodeficiency virus and 15 were HIV-infected. In four patients blood was the only positive sample. Five patients were diagnosed simultaneously with tuberculosis and HIV infection. Only 13 had a temperature higher than 37.5 degrees C. Most patients had symptoms or signs of respiratory tract involvement, and 11 patients died (10 from tuberculosis). The average time for detection of positive blood cultures was 33.25 days for lysis-centrifugation cultures and 26.46 days for BACTEC cultures. The incidence of M. tuberculosis bacteremia remained stable during the study period. CONCLUSIONS: Although blood cultures are useful for definitive diagnosis of disseminated tuberculosis, the long incubation times made them of limited usefulness in the clinical management of patients. Mortality remains high in these patients.     

Bacteriological studies of blood, tissue fluid, lymph and lymph nodes in patients with acute dermatolymphangioadenitis (DLA) in course of 'filarial' lymphedema.

Filarial lymphedema is complicated by frequent episodes of dermatolymphangioadenitis (DLA). Severe systemic symptoms during attacks of DLA resemble those of septicemia. The question we asked was whether bacterial isolates can be found in the peripheral blood of patients during the episodes of DLA. Out of 100 patients referred to us with 'filarial' lymphedema 14 displayed acute and five subacute symptoms of DLA. All were on admission blood microfilariae negative but had a positive test in the past. Blood bacterial isolates were found in nine cases, four acute (21%) and five subacute (26%). In 10 acute cases blood cultures were found negative. Six blood isolates belonged to Bacilli, four to Cocci and one was Sarcina. To identify the sites of origin of bacterial dissemination, swabs taken from the calf skin biopsy wounds and tissue fluid, lymph and lymph node specimens were cultured. Swabs from the calf skin biopsy wound contained isolates in nine (47%) cases. They were Bacilli in nine, Cocci in three, Acinetobacter and Erwinia in two cases. Tissue fluid was collected from 10 patients and contained Bacilli in four (40%) and Staphylococci in three (30%). Lymph was drained in four patients and contained isolates in all samples (100%). They were Staphylococcus epidermis, xylosus and aureus, Acinetobacter, Bacillus subtilis and Sarcina. Three lymph nodes were biopsied and contained Staphylococcus chromogenes, xylosus, Enterococcus and Bacillus cereus. In six cases the same phenotypically defined species of bacteria were found in blood and limb tissues or fluids. In the 'control' group of patients with lymphedema without acute or subacute changes all blood cultures were negative. Interestingly, swabs from biopsy wound of these patients contained isolates in 80%, tissue fluid in 68%, lymph in 70% and lymph nodes in 58% of cases. In healthy controls, tissue fluid did not contain bacteria, and lymph isolates were found only in 12% of cases. This study demonstrates that patients with acute episodes of DLA reveal bacteremia in a high percentage of cases. Diversity of blood and tissue bacterial isolates in these patients points to a breakdown of the skin immune barrier in lymphedema and subsequently indiscriminate bacterial colonization of deep tissues and spread to an blood circulation.     

Identification of acinetobacter species isolated from human infections based on a new classification by Bouvet and Grimont

The genus Acinetobacter was recently re-classified by Bouvet and Grimont who described four new species, A. baumannii, A. haemolyticus, A. johnsonii and A. junii, and five unnamed genospecies, with a re-definition of A. calcoaceticus and A. lwoffii which appeared in the Approved Lists of Bacterial Names, 1980. One hundred and twenty-eight clinical isolates previously identified as Acinetobacter were retrieved from storage and re-characterized by using a system based on the grouping reactions described by Bouvet and Grimont. Of these 86.7%, 2.3%, and 1.6% were identified as A. baumannii, A. junii and Acinetobacter genospecies 11, respectively, and the remaining 9.4% of the cultures were unidentified. None of the cultures identified as A. calcoaceticus and A. lwoffii was included in the 128 cultures.     

Clinical and epidemiologic significance of coagulase-negative staphylococci bacteremia in a tertiary care university Israeli hospital

OBJECTIVES: To characterize the clinical significance of coagulase-negative staphylococci (CNS) bacteremia. DESIGN: Prospective cohort study. SETTING: A 900-bed hospital in Haifa, Israel, from November 1996 to March 1997. RESULTS: Of 137 episodes of positive blood cultures for CNS, 41 (30%) were considered as true infection. Twenty-seven of 119 episodes associated with only 1 blood culture positive for CNS (23%) met the definition of infection as compared with 14 of 18 episodes (78%) associated with 2 or more blood cultures positive for CNS (P <.001). Methicillin resistance was significantly more frequent among Staphylococcus epidermidis isolates of episodes of true bacteremia than of episodes of contamination (15 of 22 [68%] vs. 11 of 33 [33%], respectively; P =.02). S hominis was isolated only in episodes considered as contamination (P =.01). It was estimated that CNS represents 24% of all nosocomial bloodstream pathogens. When CNS were isolated in the first 48 hours of hospitalization, an intravascular device was more frequently associated with episodes of true bacteremia than in those considered as contamination (7 of 7 [100%] vs. 10 of 57 [18%], respectively; P <.001). The mortality rate among patients with true CNS bacteremia was 16%. CONCLUSION: Some laboratory parameters may help identify episodes of true CNS bacteremia, which appears to be more common than previously considered.     

Blood cultures in ambulatory patients who are discharged from emergency with community-acquired pneumonia.

OBJECTIVES: To determine the factors that predict whether or not ambulatory patients with community-acquired pneumonia (CAP) treated in an emergency room (ER) setting will have blood cultures drawn and the factors that predict a positive blood culture. METHODS: Prospective observational study of all patients with a diagnosis of CAP, as made by an ER physician, who presented to any of seven Edmonton-area ERs over a two-year period. RESULTS: Seven hundred ninety-three (19.2%) of 4124 patients with CAP had blood cultures drawn. The site-specific blood culture rates ranged from 7.8% to 25% (P<0.001); 41 of 793 (5.1%) were positive. Streptococcus pneumoniae accounted for 58.5% of the isolates while Staphylococcus aureus and Escherichia coli each accounted for 14.6%, or six patients each. Only two of the 24 patients with S pneumoniae bacteremia were subsequently admitted to hospital while all six of the patients with S aureus were admitted. Only one of the six patients with E coli bacteremia was treated at home. No factors were predictive of positive blood cultures on multivariate analysis. CONCLUSIONS: Physicians are selective in ordering blood cultures on patients with ambulatory pneumonia who present to an ER, and the positivity rate of 5.1% is quite high. No factors are predictive of positive blood cultures on multivariate analysis, thus clinical judgment has to prevail in the decision to perform blood cultures. Breakthrough bacteremia can occur with microorganisms susceptible to the antibiotics that the patient is receiving.     

Bacteremia associated with percutaneous transluminal coronary angioplasty

Bacteremia after diagnostic cardiac catheterization is uncommon, but bacteremia after percutaneous transluminal coronary angioplasty (PTCA) has not been studied prospectively. Unlike diagnostic cardiac catheterization, PTCA involves the use of an indwelling arterial sheath after completion of the procedure, which is connected to a pressurized heparin solution, both of which increase the risk of local infection and/or bacteremia. During a 16-week period, we prospectively evaluated patients undergoing 164 PTCA procedures in order to determine the frequency of bacteremia and the significance of fever in this patient population. Blood cultures were obtained from the femoral catheter at the conclusion of the procedure and again 30 min later from the indwelling arterial sheath. Temperature was recorded every 30 min for 2 h following PTCA, then every 4 h over the subsequent 36-hr period. Bacterial isolates were recovered from 23/286 blood cultures (8.0%), with Staphylococcus epidermidis the most common organism present (74%). Only one isolate of Staphylococcus aureus was considered to represent true bacteremia and corresponded with the only documented infectious complication. Fever, defined as ?101°F developed in four (2.4%) patients but was procedure related in only one case. The use of the ipsilateral femoral artery for repeat procedures was not associated with either positive blood cultures or difference in maximum temperature elevation. We conclude the overall risk of bacteremia after PTCA is low; therefore, antimicrobial prophylaxis is not warranted. © 1995 Wiley-Liss, Inc.     

Incidence of trimethoprim-sulfamethoxazole-resistant enterobacteriaceae among transplant recipients

Of 114 recipients of pancreatic, renal, and bone marrow transplants who were given trimethoprim-sulfamethoxazole (TMP-SMZ) for antimicrobial prophylaxis, 44 (39%) had a total of 52 fecal isolates of TMP-SMZ-resistant gram-negative bacilli. In most of these 44 patients, the resistant isolate was found at a concentration of greater than or equal to 10(6) organisms/ml of feces. Escherichia coli was the most frequent of the isolates, and Citrobacter freundii was the next most frequent. Eight of the 114 transplant recipients had gram-negative bacteremia; in six of these eight patients, a TMP-SMZ-resistant gram-negative bacillus was the etiologic agent of bacteremia. Four of the latter six patients had stool cultures analyzed prior to the detection of bacteremia; all four had high concentrations (greater than or equal to 10(8)/ml) of fecal TMP-SMZ-resistant E. coli one to 20 days before they were found to have E. coli bacteremia. In each of these instances, the E. coli isolates from the stool and the blood had similar antibiograms. These findings indicated that resistance to TMP-SMZ is becoming more prevalent and that the screening of patients for the presence of fecal TMP-SMZ-resistant Enterobacteriaceae prior to initiation of long-term therapy with this antimicrobial agent may be worthwhile.     

Molecular analysis of coagulase-negative Staphylococcus isolates from blood cultures: prevalence of genotypic variation and polyclonal bacteremia.

Fifty-seven coagulase-negative Staphylococcus isolates from 22 inpatients who had > or =2 blood cultures that were positive for Staphylococcus within 24 hours were analyzed to determine the frequency of polyclonal bacteremia. Patients were considered to have bacteremia (14 patients) or contamination of sample (8 patients) on the basis of clinical criteria. Nine colonies were randomly selected from each blood culture and genotyped by means of SmaI digestion/pulsed-field gel electrophoresis. Relatedness was determined by calculation of the Dice coefficient of banding-pattern similarity (S(AB)). Analysis of bacteremic isolates demonstrated the presence of a single species in 35 of 41 blood cultures, 1 related variant in 5 blood cultures (87%-92% S(AB)), and an unrelated strain in 1 blood culture (79% S(AB)). Analysis of contaminated samples demonstrated the presence of a single strain in 10 of 16 blood cultures and 1-3 variants (28%-97% S(AB)) in the remainder. Genotype diversity was significantly more common in the contaminated samples (P=.036). Almost all coagulase-negative Staphylococcus bacteremias were monoclonal.     

Blood stream infections throught the entire course of acute lymphoblastic leukemia treatment

The incidence, type and mortality of bacteremias were evaluated in a pediatric patient cohort, during the entire course of treatment for acute lymphoblastic leukemia (ALL). Eighty-six patients with newly diagnosed ALL were studied. A bacteremic episode was defined as blood isolation of a pathogen in the presence of clinical symptomatology of septicaemia. Bacteremias were analyzed according to the treatment element being delivered and the degree of neutropenia. A central venous catheter (CVC) was inserted at diagnosis in all patients. Fifty-two episodes of bacteremias were encountered in 38/86 (44%) patients, while 48/86 patients had no positive blood culture. Three out of the 38 patients had bacteremia and CVC area infection, simultaneously. Most blood stream infections (29/52, 56%) were documented during the induction phase. Isolated Gram-positive organisms were 48%, Gram-negative 50% and 2% of the positive blood cultures represented fungaemias. The most common Gram-positive isolates were Staphylococcus species (N=22) and the commonest Gram-negative isolated pathogens were Escherichia coli and Pseudomonas aeruginosa. The majority of bacteremias (75%) occurred during neutropenia. The initial antibiotic treatment was ceftazidime or piperacillin/tazobactam and amikacin or tobramycin. CVC was not removed in the majority of bacteremias (94%). No infection related fatality was recorded. Bacteremias constituted a severe and common complication in our patient cohort. However, infection-related fatality rate was negligible, most probably due to the prompt initiation of broad coverage antimicrobial therapy.     

Nontypable Haemophilus influenzae (biotype 4) as a neonatal, maternal, and genital pathogen

Between 1976 and 1981 Haemophilus influenzae was identified in 16 women with postpartum bacteremia and 36 neonates with bacteremia or meningitis. H. influenzae was also recovered from neonatal or genital cultures of 50 additional patients. By counter-immunoelectrophoresis 17% of neonatal isolates from blood or cerebrospinal fluid (CSF) were type b. All remaining strains (94% overall) were nontypable (NT). Of the NT blood or CSF isolates, 38% belonged to biotype 4. Of all the NT biotype 4 isolates referred to the Centers for Disease Control during the study, 82% were of genital, neonatal, or maternal origin, a finding that suggests that this isolate is a genital biotype. Clinical disease was similar to that observed in patients infected with group B Streptococcus except for the infrequent (11%) occurrence of meningitis. Maternal bacteremia resulted in mild febrile illness, while neonatal bacteremia was associated with a high incidence of shock, respiratory distress (50%), and death (30%). H. influenzae bacteremia in these two patient groups was rare in Houston before 1976, but since then it has been responsible for 2.5% of cases of significant bacteremia. NT H. influenzae should be recognized as a definite neonatal, maternal, and genital pathogen.     

Analysis of 1,186 episodes of gram-negative bacteremia in non-university hospitals: the effects of antimicrobial therapy

Over the five-year period 1977-1981, we studied 1,186 episodes of bacteremia due to Enterobacteriaceae and Pseudomonadaceae in the four non-university hospitals of a single metropolitan area. Overall patient mortality was 36.3%, and mortality attributed specifically to infection was 19.0%. The importance of severity of underlying disease, site of infection, microorganism, and age--previously determined to be prognostic factors in studies conducted at tertiary-care centers--was confirmed. Appropriate initial antimicrobial therapy (defined as the administration of an effective agent in adequate dose and by a suitable route of administration on the first calendar day on which blood cultures were positive) did not improve survival compared with the use of an ineffective antimicrobial agent or no therapy at all. However, appropriate antimicrobial therapy subsequent to the first calendar day on which blood cultures were positive clearly affected survival. These findings confirm previous conclusions regarding the frequency and severity of gram-negative bacteremia and the overall impact of antimicrobial therapy on this condition. These studies also suggest the possibility that the definition of optimal initial therapy in some groups of patients should be reconsidered.     

Risk factors and outcomes of bloodstream infections with metallo-beta-lactamase-producing Acinetobacter

The spread of Gram-negative bacilli with acquired metallo-beta-lactamase (MBL) threatens the successful treatment of major nosocomial infections. The objective of this study was to evaluate the differences in the clinical characteristics of bacteremia caused by MBL-producing Acinetobacter species and MBL non-producing isolates. Two retrospective case-control studies were conducted using data on patients with Acinetobacter bacteremia, who were admitted between January 2001 and December 2005 at a 1500-bed, tertiary-care teaching hospital. Case group 1 (n=27) included patients from whom imipenem-resistant Acinetobacter was isolated in blood culture, and case group 2 (n=7) consisted of those patients from group 1 who yielded MBL-producing isolates. The control group (n=41) included patients from whom carbapenem-susceptible Acinetobacter isolates were isolated in blood culture. Multivariate analysis revealed that the independent risk factors for imipenem-resistant Acinetobacter bacteremia were neutropenia and prolonged use of carbapenem. The independent risk factors for MBL-producing Acinetobacter bacteremia were neutropenia and prolonged use of cephalosporins. The results of this study suggest that a prolonged use of cephalosporins may be associated with MBL-producing Acinetobacter bacteremia.     

The relevance of cultures of catheter-drawn blood and heparin-lock fluid to diagnose infection in hematologic patients

Summary The results of bacteriologic cultures of blood and heparin-lock fluid, both drawn from the central venous catheters of 54 consecutive oncohematologic patients, have been used to determine their value for the diagnosis of systemic and catheter-associated infection. In 30 patients with clinical signs of infection (bacteremia or septicemia), 74 of 1000 (7.4%) heparin-lock fluid cultures, 114 of 542 (21%) catheter-drawn blood cultures, and 36 of 134 (26%) venipuncture blood cultures became positive, whereas in 24 patients without clinical signs of infection the respective values were 5 of 700 (0.7%), one of 220 (0.4%), and none of ten cultures. Comparison of the results of cultures sampled on the same day reveals that the positive and negative predictive values for catheter-drawn blood cultures, with the venipuncture blood cultures taken as the standard for bacteremia, are 82% and 95% respectively. The results of heparin-lock fluid are indicative for clinically relevant colonization of the catheter. Three or more positive heparin-lock fluid cultures, sampled on subsequent days, were correlated with the occurrence of bacteremia or septicemia with a positive predictive value of 100%. The conclusions are supported by the results of scanning electron microscopy.     

Bacteremic disease due to Haemophilus influenzae capsular type f in adults: report of five cases and review

Five cases of bacteremic infections due to Haemophilus influenzae type f in adults are described, and previous reports of type f disease in nonpediatric patients are reviewed. Respiratory tract infections were most common in our series (two cases of pneumonia, one of epiglottitis, and one of nosocomial septicemia probably resulting from aspiration pneumonitis). All of these patients had factors predisposing them to respiratory tract infections, e.g., neurologic disease, congestive heart failure, or cigarette smoking. A fifth patient, who was bacteremic without an apparent primary focus, had dysgammaglobulinemia. Six episodes of bacteremia occurred in five patients; 11 of 13 cultures of blood obtained before parenteral antibiotic therapy were positive. All isolates were biotype I and susceptible to ampicillin. Antibiotic therapy was curative in cases of proved respiratory tract infection but failed in the setting of nosocomial septicemia, perhaps because of delayed initiation. The brevity of antibiotic treatment of the cryptogenic bacteremia permitted infection of a prosthetic vascular graft and recurrent bacteremia. Graft removal and repeated antibiotic therapy were curative.     

Outcome of bacteremia and fungemia in paediatric oncology patients.

OBJECTIVE: To determine the outcome of paediatric oncology patients with positive blood cultures. DESIGN: Retrospective chart review. SETTING: Tertiary care hospital. POPULATION STUDIED: Oncology patients up to 17 years of age with positive blood cultures from January 1, 1994 to March 31, 1999. MAIN RESULTS: There were 121 episodes of positive blood cultures in 76 patients. Seventeen episodes were excluded because blood cultures were contaminated. Of the organisms grown from the remaining episodes, 63% were Gram-positive organisms, 23% were Gram-negative organisms, 3% were fungal and 11% were mixed. There were 13 episodes with pure or mixed isolates of Staphylococcus aureus, of which nine occurred within 14 days of the placement of a new central venous tunnelled catheter. Central venous tunnelled catheters were retained in 76 of the 102 episodes when they were present. There were two relapses, and four children were admitted to the intensive care unit with septic shock, but all survived. CONCLUSIONS: The outcome was excellent with the current management of possible bacteremia in paediatric oncology patients, but the high incidence of S aureus bacteremia suggests that empirical antibiotics should be altered if sepsis is suspected within 14 days of the placement of a central venous catheter.