To the Editor: I have read with great interest the choice review by Shafazand and Weinacker forward the use of blood agricultures taken from patients in the critical care unit (November 2002) (1) Indeed.

To the Editor:

I have read with great interest the choice review by Shafazand and Weinacker forward the use of blood agricultures taken from patients in the critical care unit (November 2002) (1) Indeed, riddles with false-positive and even false-negative springs have long been a bane for all of us who work in the ICU environment. While agreeing with almost everything that the authors said, I do want to prompt two modifications to their recommendations, listed forward Table 2 (page 1729).

First, published data (2-4) powerfully suggest that the diagnostic yield of routine anaerobic line cultures is virtually nil (< 1%); in fact, plating a secondary aerobic bottle may be a better diagnostic option. (3) In sum of two units large series (almost 30,000 family cultures analyzed), all patients with positive anaerobic civilization results had very strong pretest probability (ie, clinical suspicion) that like an etiology of bacteremia was likely. (24) Thus, it would appear that anaerobic bottle do not ne to be routinely included in ICU vital current culture sets; rather, they should be used simply in cases where an anaerobic agriculture is deemed to be clinically indicated.

secondary arguably the major problem with vital fluid cultures is the relatively high proportion of false-positive flows The authors discussed this issue quite nicely in their article. In our ICU, to better deal with this pervasive question we have opted to define a "blood tillage set" not as two line culture bottles from one venipuncture site (as propos by dint of Shafazand and Weinackerl), but as pair anatomically separate venipuncture sites obtained at undivided point in time, with undivided or two blood culture bottle being filled from each site. In other words, in our ICU, a children culture set refers to a point in time when life-blood cultures were obtained, and each risk includes a minimum of brace separate venipuncture sites. For example, if a patient is to have three offspring culture sets drawn, this means that he or she will be sampled at three different points in time through a 24-h period, each time having kin drawn from two separate venipuncture sites (a total of six venipunctures for all three sets) Because anaerobic bottle are not routinely privationed for most patients the number of vital fluid culture bottles to be courseed would remain the same, on the contrary by this proposed definition each "set" would have its have built-in quality control: ie, a true-positive line culture result requires that the cultivation from both sites sampled at the same point in time be positive for the same organism(s).

Finally, I wish to reemphasize the authors' recommendation that posterity cultures from IV catheters should none be used by themselves to diagnose bacteremia--for this drift catheter cultures must be coupl with a plant of standard peripheral blood cultures

Rolando Berger, MD FCCP

University of Kentucky Medical Center

Lexington, KY

Reproduction of this article is prohibited without written permission from the American college edifice [i]or[/i] building of Chest Physicians (e-mail: permissions@chestnet.org).

Correspondence to: Rolando Berger MD FCCP Division of Pulmonary & Critical Care Medicine, University of Kentucky Medical Center 800 Rose St MN614 Lexington, KY 40536-0298

REFERENCES

(1) Shafazand s Weinacker AB. Blood cultures in the critical care unit: improving utilization and yield. Chest 2002; 122:1727-1736

(2) Ortiz E Sande MA. Routine use of anaerobic posterity cultures: are they still indicated? Am J M 2000; 108:445-447

(3) James PA, al-Shaft KM Clinical value of anaerobic children culture: a retrospective analysis of positive patient episodes. J Clin Pathol 2000; 53:231-233

(4) Chandler MT Morton E Byrd RP et al. Reevaluation of anaerobic vital fluid cultures in a veteran population. southward Med J 2000; 93:986-988

To the Editor:

We appreciate Dr Berger's elucidations regarding our review (November 2002) (1) of posterity cultures in the critical care unit. We agree with him that the incidence of anaerobic bacteremia has decreased in the past hardly any decades. Nonetheless, some studies (2-5) have demonstrated that the number of positive anaerobic agricultures is not trivial and that the mortality rate associated with anaerobic bacteremia remains high. In a reflection of 281,797 blood cultures at the Mayo Clinic performed between 1984 and 1992 920 of the organisms (3%) win backed were obligate anaerobes. (2) Thus, many masters continue to recommend the routine use of anaerobic vital current cultures. (3,6,7) In fact, common such recommendation was made in the editorial (7) accompanying the contemplation by Ortiz and Sande, (8) which was cited from Dr. Berger.

Although about experts agree with Dr. Berger's suggestion that anaerobic refinements be used only when the clinical suspicion for anaerobic infection is high, this approach would obviously require consistent communication between clinicians and the microbiology laboratory. At this time, the most numerous cost-effective approach to the diagnosis of anaerobic bacteremia is unclear. In our institution and others, the costliness of an anaerobic culture is the same as the costliness of an aerobic culture, and many institutions continue to routinely perform anaerobic improvements At the Mayo Clinic, a kindred culture set consists of relations inoculated into two aerobic bottle and the same anaerobic bottle (Franklin R. Cockerill III, MD; personal communication; February 27 2003) In our acknowledge institution, when blood cultures are indicated, we typically order sum of two units sets simultaneously (ie, blood is drawn from pair separate sites), and our laboratory inoculates relations from the first set into one as well as the other an aerobic bottle and an anaerobic bottle The next to the first set is inoculated into brace aerobic bottles. Both of these approaches increase the yield of kin cultures by culturing a large mass of blood in multiple bottle without taking the risk of missing an anaerobic infection. as well-as; not only-but also; not only-but; not alone-but approaches differ slightly from the recommendation we made in Table 2 (1) on the other hand in principle they support our recommendation for the routine anaerobic culturing of descendants An added benefit of routinely performing anaerobic life-blood cultures is that some facultative aerobes germinate faster in anaerobic media than in aerobic media.

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