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.     

Assessment of anaerobic blood cultures in pediatric oncology patients

Introduction

The routine use of a single aerobic bottle for blood culture in pediatric patients has become commonplace, as anaerobic bacteria are not frequently involved in clinically significant infections. The aim of this study was to assess the usefulness of routinely performing anaerobic blood cultures in pediatric oncology patients.

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.     

Osteomyelitis due to Veillonella parvula: case report and review.

Anaerobic gram-negative cocci of the genus Veillonella are generally normal flora of the oropharynx and upper respiratory tract. When isolated in clinical specimens, these bacteria are usually regarded as commensal organisms rather than as pathogens. We report a case of spinal osteomyelitis in which Veillonella parvula was isolated in pure culture from bone as well as blood. Osteomyelitis of the spine due to anaerobic bacteria may occur more frequently than has been recognized, and anaerobic cultures of biopsy specimens should be routinely performed.     

Is anaerobic blood culture necessary? If so, who needs it?

BACKGROUND: The role of anaerobic blood cultures is not validated, although they are drawn routinely. METHODS: We performed a retrospective chart review at a private hospital in Japan for patients admitted between July 1, 2004 to June 30, 2005 to determine patient characteristics resulting in anaerobic blood culture. RESULTS: During the study period, 17,775 blood culture bottles were sent for the analysis, and 2132 bottles (12.0%) were positive for microbial growth. Bacteria were grown from 958 anaerobic bottles (44.7%), and 719 (33.7%) of those were judged to represent real infections, which accounted for 410 cases of bacteremia. Only 47 cases (11.5%) were detected by anaerobic cultures alone. Among those 47, obligate anaerobes represented 12 cases. Clinical evaluation could have predicted 7 of 12 cases of obligate anaerobic bacteremia. In the remaining 5 cases, the source of bacteremia was unclear. There were 2.7 cases of anaerobic bacteremia per 1000 blood cultures. The mortality attributable to anaerobic bacteremia was 50%. Among bacteremic cases not caused by obligate anaerobes yet diagnosed solely by anaerobic bottles, either the standard 2 sets of blood were not taken or their clinical outcomes were favorable. CONCLUSION: Anaerobic blood culture can be avoided in most cases. Anaerobic blood culture may be most helpful when (1) bacteremia because of obligate anaerobes is clinically suspected, (2) patients are severely immunocompromised, and (3) source of bacteremia is not identified by clinical evaluation.     

Seven-pathogen tricuspid endocarditis in an intravenous drug abuser. Pitfalls in laboratory diagnosis

Polymicrobial endocarditis is being reported with increasing frequency in drug abusers. However, the full extent of infection may be unrecognized with routine blood culture techniques because of the overgrowth of more fastidious organisms by other pathogens. This report documents an intravenous drug abuser with the first reported case of tricuspid valve endocarditis involving seven pathogens, discusses pitfalls of routine blood cultures and examines the role of the laboratory in microbiologic diagnosis.     

Histologic documentation of gonococcal infection in the absence of a culturable organism

Summary The high incidence of negative routine cultures, in the presence of suppurative involvement of a joint suggested a possible role for alternative diagnostic techniques. Bedside cultures with hypertonic and anaerobic media were utilized to evaluate synovium and synovial membrane in gonococcal arthritis. This is the first histologic documentation of the diagnosis of gonococcal arthritis in the absence of a culturable organism.     

Polymicrobial anaerobic septicemia due to lateral sinus thrombophlebitis

Continuous polymicrobial anaerobic septicemia was the main manifestation of a lateral sinus thrombophlebitis (LST) in a patient who had a history of chronic otitis media. Five different anaerobic microorganisms were isolated in blood cultures. Three of them were also present in ear cultures. The diagnosis was confirmed at surgery and the patient was successfully treated with moxalactam disodium therapy. This case emphasizes that LST should be considered before polymicrobial anaerobic septicemia, especially if there is a history of chronic otitis media.     

Median sternotomy wound infection and anterior mediastinitis caused by bacteroides fragilis.

The first reported case of median sternotomy infection and mediastinitis caused by Bacteroides fragilis is described. Several positive blood cultures led to diagnostic anaerobic cultures of the wound and administration of clindamycin therapy. This anaerobic infection should be suspected whenever Gram smears of exudates show gram-negative bacilli and aerobic cultures are sterile.     

Anaerobic bacteremia: decreasing rate over a 15-year period

At the Mayo Clinic, the number of cases of anaerobic bacteremia decreased 45% between 1974 and 1988. In addition, the percentage of blood cultures positive for anaerobes decreased significantly even though the total number of blood cultures performed increased. The number of anaerobic bacteremias per 100,000 patient-days also declined over the 15-year period. Organisms of the Bacteroides fragilis group ranked third in frequency with respect to other organisms that caused aerobic and anaerobic bacteremia in 1974 but ranked only seventh in 1988 and caused slightly less than one-half of the anaerobic bacteremias. The mechanisms responsible for these changes are unclear but might relate to earlier recognition and treatment of localized anaerobic infection, widespread preoperative use of agents prior to bowel surgery, and use of broad-spectrum antimicrobial regimens that include agents with activity against anaerobes.     

Bacteremia associated with lower gastrointestinal endoscopy: Fact or fiction?

In an effort to elucidate whether bacteremia occurs during endoscopic examination of the lower gastrointestinal tract, two prospective spective studies were undertaken involving patients undergoing colonoscopy and proctosigmoidoscopy. The former group has been presented earlier, and the second study, which includes the proctosigmoidoscopy group, is the basis for this study. Fiftyseven patients undergoing proctosigmoidoscopy were studied. Excluded from the study were patients with fever, diarrhea, inflammatory bowel disease, valvular heart disease, vascular prosthesis, chemotherapy, and immunosuppression. Aerobic and anaerobic blood cultures were taken before, during, and after proctosigmoidoscopy. Additional cultures were taken after a biopsy or polypectomy. Skin cultures were taken from the venipuncture site prior to venipuncture. No bacteremia was demonstrated. Three blood cultures were positive, but all were considered contaminants on the basis of the nature of organisms. No correlates could be drawn as to the depth of insertion, length of time, or position of patient during the procedure. It is concluded that no significant bacteremia occurs during proctosigmoidoscopy. Further studies are warranted in the excluded high-risk group.     

Decreasing the use of anaerobic culture bottles in selected febrile patients — is it reasonable?

BACKGROUND: Two sets of blood cultures are routinely obtained from febrile patients in the medical wards. The purpose of the present study was to evaluate the distribution of the aerobic versus anaerobic isolates in such patients and to examine the rationale of reducing the number of anaerobic culture bottles in selected patients. METHODS: A retrospective analysis was performed of all febrile patients admitted to medical wards during 1998. Febrile patients from whom at least two sets of blood cultures were drawn and who had a bacterial isolation in at least one bottle were included. RESULTS: A total of 317 patients were included in the analysis. Some 98.5% of all isolates were aerobic pathogens. Only 1.5% of all isolates (5/317) included obligatory anaerobes. The rate of isolation in a single anaerobic bottle was 8.5%. Analysis of the available files of patients with a single anaerobic positive bottle demonstrated that an adequate antibacterial agent was administered empirically in most of the cases (93%). CONCLUSIONS: We conclude that in carefully selected medical patients suspected of having an infectious disease, it is reasonable to obtain one anaerobic and two aerobic bottles rather than two full sets. Such an approach is clinically safe and will cut expenses on culture bottles and laboratory staff work. This approach should be examined in a prospective, randomized study.     

Leptotrichia buccalis: a rare cause of bacteraemia in non-neutropenic patients

The anaerobic bacterium, Leptotrichia buccalis (Lb), belongs to the normal oral flora of humans and is seldom found in clinically significant specimens. However, on rare occasions, Lb has been isolated from blood cultures from patients with lesions of the oral mucosa, in particular from patients with neutropenia. Over a period of 6 months, Lb was isolated from blood cultures in our laboratory from 2 immunocompetent patients. The identification characteristics of Lb are described including the typical morphology at microscopy. Furthermore, we review the bacteraemic cases reported so far together with present knowledge of the pathogenicity and epidemiology of Lb.     

Case report: prosthetic valve endocarditis due to a nutritionally variant streptococcus

The first report of prosthetic valve endocarditis due to a nutritionally variant streptococcus is presented. A 21-year-old woman developed persistent fever within one week of mitral valve replacement. Prosthetic valve dysfunction developed necessitating valve replacement. Cultures of blood and the excised prosthetic valve using routine media were negative; Streptococcus mitior grew as satellite colonies around Staphylococcus aureus and in beef heart infusion broth supplemented with 0.001% pyridoxine HCl. Treatment with penicillin G and streptomycin for six weeks was curative. Nutritionally variant streptococci should be considered in patients with prosthetic valve endocarditis and negative routine cultures.     

A Rare Case of Clostridium sordellii Bacteremia in an Immunocompromised Patient

Clostridium sordellii is a gram-positive, anaerobic sporeforming rod with peritrichous flagella that is rarely associated with disease in humans. In most cases, infections occur after trauma, childbirth and routine gynecological procedures or intravenous drug abuse. C. sordellii produce several exotoxins that lead to progressive edema and shock, and C. sordellii infections have high mortality rates of up to 70%. Since its first report in 1922, only a few cases of bacteremia have been reported. This report describes a case of C. sordellii bacteremia in a patient with rectum carcinoma and liver metastases.     

Paradoxical coexistence of atopic asthma and Human T-Lymphotropic Virus Type I (HTLV-I) infection: a case report.

In this case report, the authors report the presence of two supposedly antagonic immune diseases in the same patient. The patient is a 45-year-old white woman with a history of asthma and allergic rhinitis for the last 10 years. Asthmatic symptoms were present and were triggered after exposure to dust and mold. Her Human T-Lymphotropic Virus Type I (HTLV-I) seropositive status was detected by chance five years ago during a routine screening for blood donation. Skin prick tests were positive for Dermatophagoides pteronyssinus, Dermatophagoides farinae and Blomia tropicalis. Cytokine levels in unstimulated cultures were: IFNgamma= 1195 pg/ ml, TNFalpha = 460 pg/ml, IL5 = 41 pg/ml and IL10 = 265 pg/ml.     

Osteomyelitis caused by Veillonella

Veillonella parvula and alcalescens are anaerobic gram-negative cocci that, when isolated from anaerobic cultures of clinical specimens, are usually regarded as commensal organisms. Occasionally they play a pathogenic role and require antibiotic therapy. Limited clinical experience and in vitro susceptibility studies suggest that penicillin G is the drug of choice for these organisms and that cephalosporins, clindamycin, chloramphenicol, and metronidazole may be acceptable therapeutic alternatives. Presented herein is a case report of a Veillonella infection, a discussion of the importance of these organisms when they occur in a clinical infection, and a discussion of the appropriate antibiotic therapy.     

经口内镜下肌切开术术后一过性菌血症的发生率

目的研究经口内镜下肌切开术（POEM）术后一过性菌血症的发生率,为POEM的进一步发展及推广提供理论依据。方法前瞻性地连续选择2013年6月5日至2013年7月11日间行POEM患者12例。术后5min、30min、6h、16h分别抽血行血培养及血常规、C-反应蛋白检测,记录体温,同时密切监测患者术后感染相关并发症。结果除1例患者因术中出血,止血后终止手术,余11例患者成功完成手术,其中1例在术后5min血培养中培养出革兰阳性杆菌,而在随后的30min、6h、16h血培养中转为阴性;其余患者血培养均为阴性。同时,患者术后白细胞计数、中性粒细胞比例及C-反应蛋白均有不同程度的升高,且以中性粒细胞的升高最为明显（P〈0．001）,而体温变化方面的差异并不显著（P〉0．05）。结论POEM术后存在一过性菌血症,但其具体发生率及最终结论尚需大样本进一步研究。     

Low Incidence of Bacteremia Following Endoscopic Retrograde Cholangiopancreatography (ERCP)

Fifty patients (29 females) undergoing ERCP were studied prospectively for the occurrence of bacteremia associated with this endoscopic procedure. Each patient had blood samples drawn for aerobic and anaerobic cultures before endoscopy, after entering the duodenum, 5 and 15 minutes after cannulation of the papilla of Vater. Subcultures were made at 24 and 48 hours for a total of 1,200 cultures. No positive cultures were obtained in 48 patients. One patient developed a Staphylococcus epidermidis bacteremia during the procedure. The cleansing technic for the instruments consisted of alcohol and water only. Prophylactic antiobiotics were not administered. In contrast to other gastrointestinal procedures, our results suggest that bacteremia is an uncommon occurrence in ERCP despite the longer duration of the procedure and instrumentation of a sterile duct system.     

Characterization and antimicrobial susceptibility of Dysgonomonas capnocytophagoides isolated from human blood sample

Dysgonomonas capnocytophagoides belongs to a group of facultative anaerobic Gram-negative coccobacilli that was formerly designated CDC group DF-3. We evaluated the characteristics of this microbe and its susceptibility to antimicrobial agents. In this study, D. capnocytophagoides was isolated by anaerobic blood cultures from a 78-year-old male with pancreatic cancer, ischemic heart disease, and diabetes mellitus, who also showed symptoms of cholangitis. The isolated strain demonstrated resistance to various beta-lactams, erythromycin, aminoglycosides, and fluoroquinolones, but was susceptible to sulfamethoxazole-trimethoprim, clindamycin, minocycline, and chloramphenicol. The results of all biochemical tests and the homology of the 16S rRNA gene were consistent with previous reports of D. capnocytophagoides.