Controlled clinical comparison of BacT/alert FA plus and FN plus blood culture media with BacT/alert FA and FN blood culture media.

New blood culture media containing antibiotic-binding polymeric beads have been developed for the BacT/Alert (bioMérieux, Inc., Durham, NC) blood culture system. To assess the performance of these new media, we compared the new BacT/Alert aerobic medium (FA Plus) with resins to BacT/Alert FA medium with activated charcoal and the new BacT/Alert anaerobic medium (FN Plus) to BacT/Alert FN medium at 3 tertiary care medical centers. Study bottle pairs were inoculated with a target volume of 6 to 10 ml of blood from adults and incubated in the BacT/Alert 3D blood culture instrument. In the FA Plus versus FA comparison, there were 1,507 study pairs. Among 170 isolates causing true bloodstream infections (BSIs), significantly more Staphylococcus aureus (P<0.001) and total microorganisms (P<0.01) grew in the FA Plus bottle than in the FA bottle. Fewer coagulase-negative staphylococcal (CoNS) contaminants grew in the FA Plus bottle than in the FA bottle (10 versus 22; P=0.05). In addition, growth was detected earlier in the FA Plus bottle than in the FA bottle (P<0.001). In the FN Plus versus FN comparison, there were 2,386 study pairs. Among 201 isolates causing true BSIs, significantly more S. aureus (P<0.001), CoNS (P<0.005), and total microorganisms (P<0.001) grew in the FN Plus bottle than in the FN bottle. Also, significantly more CoNS contaminants grew in the FN Plus bottle than in the FN bottle (P<0.001). Overall, microorganisms were detected earlier in the FN Plus than in the FN bottle (P<0.001). Medical technologists at all 3 study sites preferred the new media for Gram stain interpretation. We conclude that the FA Plus and FN Plus media provide improved and earlier detection of microorganisms compared with the FA and FN media and are preferable for Gram stain interpretation as well.

Update on blood cultures: how to obtain, process, report, and interpret.

The detection and identification of microorganisms circulating in the bloodstream of patients is arguably one of the most important functions of the clinical microbiology laboratory. Effective implementation of this function requires careful consideration of specimen collection and processing, culture techniques, result reporting, and, perhaps most importantly, result interpretation by the physician. The purpose of this review is to provide a synopsis of the current state of the art for each of these areas, with the intention of providing adequate information to enable clinical laboratory personnel and physicians to critically evaluate and, if required, improve their current blood culture practices.

A deceptive case of cellulitis caused by a Gram-negative pathogen.

Yokenella regensburgei is a member of the family Enterobacteriaceae that has rarely been implicated in clinical disease. We report here a case of septicemia with a skin and soft tissue source caused by Y. regensburgei in an immunocompromised host.

Controlled multicenter evaluation of a bacteriophage-based method for rapid detection of Staphylococcus aureus in positive blood cultures.

Staphylococci are a frequent cause of bloodstream infections (BSIs). Appropriate antibiotic treatment for BSIs may be delayed because conventional laboratory testing methods take 48 to 72 h to identify and characterize isolates from positive blood cultures. We evaluated a novel assay based on bacteriophage amplification that identifies Staphylococcus aureus and differentiates between methicillin-susceptible and methicillin-resistant S. aureus (MSSA and MRSA, respectively) in samples taken directly from signal-positive Bactec blood culture bottles within 24 h of positive signal, with results available within 5 h. The performance of the MicroPhage KeyPath MRSA/MSSA blood culture test was compared to conventional identification and susceptibility testing methods. At four sites, we collectively tested a total of 1,165 specimens, of which 1,116 were included in our analysis. Compared to standard methods, the KeyPath MRSA/MSSA blood culture test demonstrated a sensitivity, specificity, positive predictive value, and negative predictive value of 91.8%, 98.3%, 96.3%, and 96.1%, respectively, for correctly identifying S. aureus. Of those correctly identified as S. aureus (n = 334), 99.1% were correctly categorized as either MSSA or MRSA. Analysis of a subset of the data revealed that the KeyPath MRSA/MSSA blood culture test delivered results a median of 30 h sooner than conventional methods (a median of 46.9 h versus a median of 16.9 h). Although the sensitivity of the test in detecting S. aureus-positive samples is not high, its accuracy in determining methicillin resistance and susceptibility among positives is very high. These characteristics may enable earlier implementation of appropriate antibiotic treatment for many S. aureus BSI patients.

Lipid class dynamics and storage depots in juvenile weakfish Cynoscion regalis and their application to condition assessment.

Lipid class dynamics, the pattern of change in the primary form and location of lipid stores and their relationship with standard length (L(S) ), were investigated in collections of young-of-the-year weakfish Cynoscion regalis for the purpose of determining the utility of this analysis as an indication of condition. The separation of total lipids into individual classes and the analysis of potential storage depots revealed the general patterns of lipid class dynamics and energy storage in C. regalis during their period of juvenile estuarine residency. Phospholipid and cholesterol exhibited moderate but variable (8·1-40·0 and 1·3-21·5 mg g(-1) , respectively) concentrations across the entire juvenile period and were the predominant lipid classes in juveniles <100 mm L(S) , while wax ester concentrations were low (c. 1 mg g(-1) ) and exhibited the least amount of variability among lipid classes. Triacylglycerols (TAG) and free fatty acids (FFA) exhibited similar dynamics, with relatively low concentrations (<15 mg g(-1) ) in individuals ≤100 mm L(S) . In larger juveniles both TAG and FFA concentrations generally increased rapidly, though there was considerable variability in both measures (0·0-199·7 and 0·0-49·7 mg g(-1) , respectively). Increasing levels of lipids, primarily in the form of TAG, with size indicated an accumulation of energy reserves with growth, thus providing an indication of individual condition for larger juveniles. Separate analysis of liver, viscera and the remaining carcass indicated that liver and viscera did not represent a significant depot of TAG reserves. Analysis of samples derived from whole juvenile C. regalis thus provided an accurate estimate of energy reserves.

Is global climate change influencing the overwintering distribution of weakfish Cynoscion regalis?

The pattern of stable isotope signatures in a sub-sample of 67 juvenile weakfish Cynoscion regalis, captured at the mouth of the Christina River, 113 km upstream of the mouth of Delaware Bay (U.S.A) in the autumn of 2000, suggested that they resided at the location since recruitment. The possibility that young C. regalis departed from the generally characteristic life-history pattern of marine migrants at this latitude, i.e. emigrating offshore with the adults in autumn was bolstered by the collection of 69 individuals during the winters of 2000-2006 from the travelling screens of a power plant located at river kilometre 88 including an 118 mm total length juvenile captured in mid-February 2006.

Controlled clinical comparison of the BacT/ALERT FN and the standard anaerobic SN blood culture medium.

To determine the optimal anaerobic companion bottle to pair with the BacT/ALERT (bioMerieux, Durham, N.C.) nonvented aerobic FA (FA) medium for recovery of pathogenic microorganisms from adult patients with bacteremia and fungemia, we compared the BacT/ALERT FN (FN) anaerobic bottle with the standard BacT/ALERT SN (SN) anaerobic bottle. Each bottle, FA, FN, and SN, was filled with 8 to 12 ml of blood. Of 11,498 blood culture sets received in the clinical microbiology laboratories at two university medical centers, 7,945 sets had all three bottles filled adequately and 8,569 had both anaerobic bottles filled adequately. Of 686 clinically important (based on previously published criteria) isolates detected in one or both adequately filled anaerobic bottles, more staphylococci (P < 0.001), including Staphylococcus aureus (P < 0.001); members of the family Enterobacteriaceae (P < 0.001); and all microorganisms combined (P < 0.001) were detected in FN bottles. In contrast, more Pseudomonas aeruginosa isolates (P < 0.01) and yeasts (P < 0.001) were detected in SN bottles. More Bacteroides fragilis group bacteremias were detected only in the FN (six) than in the SN (one) anaerobic bottle (P = not significant). Overall, the mean time to detection was shorter with FN (16.8 h) than with SN (18.2 h). This difference in time to detection was greatest for the B. fragilis group: FN, 28 h, versus SN, 60.0 h. Many of the facultative microorganisms recovered in either FN or SN were also found in the companion FA. When microorganisms found in the companion FA bottle were omitted from the analysis, significantly more staphylococci (P < 0.001), including S. aureus (P < 0.001), and Enterobacteriaceae (P < 0.005) still were detected in FN bottles, whereas there were no significant differences for P. aeruginosa and yeasts, which were found as expected in FA bottles. We conclude that the companion anaerobic FN bottle detects more microorganisms than does the anaerobic SN bottle when used in conjunction with the nonvented aerobic FA bottle in the BacT/ALERT blood culture system.

Detection of Pneumocystis jiroveci in respiratory specimens by four staining methods.

We examined four staining methods on replicate smears of 313 respiratory specimens submitted for Pneumocystis jiroveci examination. The sensitivity and specificity of Calcofluor white stain (CW) were 73.8 and 99.6%, respectively. The sensitivity and specificity of Grocott-Gomori methenamine silver stain (GMS) were 79.4 and 99.2%, respectively. The sensitivity and specificity of Diff-Quik stain were 49.2 and 99.6%, respectively. The sensitivity and specificity of Merifluor Pneumocystis stain were 90.8 and 81.9%, respectively. Only CW and GMS had positive and negative predictive values of >90%.

Relevance of the number of positive bottles in determining clinical significance of coagulase-negative staphylococci in blood cultures.

Coagulase-negative staphylococci (CNS) are the most commonly isolated contaminants from blood cultures, yet they frequently cause true infections. Determining the clinical significance of CNS is difficult, and clinicians often consider the number of positive bottles within a set of blood culture bottles in their assessment. Therefore, in three separate studies, we counted the number of positive bottles within blood culture sets comprising two, three, or four bottles in order to predict whether or not CNS were clinically significant isolates (CSI) in adult patients with suspected sepsis. Each culture was evaluated by independent, published clinical criteria to determine its clinical importance. Of 486 positive sets that included two adequately filled bottles, 127 (26%) CNS were CSI, 329 (67%) were contaminants, and 30 (6%) were indeterminate as a cause of sepsis. Among CSI, 39 and 61% were isolated from one and two bottles, respectively. The positive predictive value for sepsis was 18% when one bottle was positive and 37% when both bottles were positive. Of 235 positive sets that included three adequately filled bottles, 81 (34%) were CSI, 109 (46%) were contaminants, and 45 (19%) were indeterminate as a cause of sepsis. Of CSI, 43, 38, and 19% were found in one, two, and three bottles, respectively. The positive predictive value for sepsis was 28, 52, and 30% when one, two and three bottles were positive. Of 303 positive blood culture sets that included four adequately filled bottles, 64 (21%) were considered CSI, 197 (65%) were contaminants, and 42 (14%) were indeterminate as a cause of sepsis. Of CSI, 27, 28, 19, and 27% were found in one, two, three, and four bottles, respectively. The positive predictive value for sepsis was 11, 30, 34, and 37% when one, two, three, and four bottles were positive. We conclude that the number of culture bottles positive in a given culture set cannot reliably predict the clinical significance of the CNS isolated and, therefore, should not be used as a criterion for determining whether or not an isolate represents true infection or contamination.

Comparative evaluation of penicillin, ampicillin, and imipenem MICs and susceptibility breakpoints for vancomycin-susceptible and vancomycin-resistant Enterococcus faecalis and Enterococcus faecium.

Although imipenem has in vitro activity against Enterococcus faecalis and Food and Drug Administration-approved indications for treatment of infections caused by this microorganism, there are no NCCLS guidelines for susceptibility testing of imipenem versus enterococci. Therefore, the in vitro activities of penicillin, ampicillin, imipenem, and vancomycin against 201 blood isolates of E. faecalis and 24 blood isolates of Enterococcus faecium were compared. The susceptibility of isolates to penicillin or ampicillin accurately predicted the in vitro activity of imipenem. Since the susceptibility of enterococci to imipenem can be predicted by the results obtained by testing of penicillin or ampicillin, testing of imipenem by clinical laboratories probably is not necessary.

Controlled clinical comparison of BACTEC plus anaerobic/F to standard anaerobic/F as the anaerobic companion bottle to plus aerobic/F medium for culturing blood from adults.

To determine the optimal anaerobic companion bottle to pair with BACTEC Plus Aerobic/F medium for recovery of pathogenic microorganisms from adult patients with bacteremia and fungemia, we compared Plus Anaerobic/F bottles with Standard Anaerobic/F bottles, each of which was filled with 4 to 6 ml of blood. The two bottles were paired with a Plus Aerobic/F bottle filled with 8 to 12 ml of blood. A total of 14,011 blood culture sets were obtained. Of these, 11,583 sets were received with all three bottles filled adequately and 12,257 were received with both anaerobic bottles filled adequately. Of 818 clinically important isolates detected in one or both adequately filled anaerobic bottles, significantly more staphylococci (P < 0.001), streptococci (P < 0.005), Escherichia coli isolates (P < 0.02), Klebsiella pneumoniae isolates (P < 0.005), and all microorganisms combined (P < 0.001) were detected in Plus Anaerobic/F bottles. In contrast, significantly more anaerobic gram-negative bacilli were detected in Standard Anaerobic/F bottles (P < 0.05). Of 397 unimicrobial episodes of septicemia, 354 were detected with both pairs, 30 were detected with Plus Aerobic/F-Plus Anaerobic/F pairs only, and 13 were detected with Plus Aerobic/F-Standard Anaerobic/F pairs only (P < 0.05). Significantly more episodes of bacteremia caused by members of the family Enterobacteriaceae (P < 0.05) and aerobic and facultative gram-positive bacteria (P < 0.025) were detected with Plus Anaerobic/F bottles only. In a paired-bottle analysis, 810 of 950 isolates were recovered from both pairs, 90 were recovered from Plus Aerobic/F-Plus Anaerobic/F pairs only, and 50 were recovered from Plus Aerobic/F-Standard Anaerobic/F pairs only (P < 0.001). Paired Plus Aerobic/F-Plus Anaerobic/F bottles yielded significantly more staphylococci (P < 0.001), streptococci (P < 0.05), and members of the family Enterobacteriaceae (P <0.001). We conclude that Plus Anaerobic/F bottles detect more microorganisms and episodes of bacteremia and fungemia than Standard Anaerobic/F bottles as companion bottles to Plus Aerobic/F bottles in the BACTEC 9240 blood culture system.

Controlled comparison of BacT/ALERT FAN aerobic medium and BATEC fungal blood culture medium for detection of fungemia.

Yeasts are an increasingly common cause of nosocomial bloodstream infections. Methods for their detection are many; controlled comparisons are few. The vented FAN aerobic blood culture medium has been shown to be superior to the standard BacT/ALERT aerobic medium for the detection of fungemia as well as bacteremia. The BACTEC selective fungal medium (FM) (BD Biosciences, Sparks, Md.) allowed detection of more episodes of fungemia than did a resin-containing medium with equal volumes of blood cultured. Therefore, we compared vented FAN to FM for the ability to recover fungi from the blood of patients who were at increased risk of having fungemia. From 5,109 cultures processed for which both FAN and FM bottles were adequately filled, fungi were recovered from 87 cultures. Of these, 47 were detected with both bottles, 12 were detected with FAN only, and 28 were detected with FM only (P < 0.05). FAN was the first bottle positive for 36 of the 47 cultures for which both bottles yielded the same fungus, whereas the FM bottle was the first bottle positive for 11 cultures (P < 0.001). A total of 54 episodes of fungemia were identified, with 40 detected by both media, 4 detected only by FAN, and 10 detected only by FM (P value, not significant). We conclude that the vented FAN aerobic bottle is comparable to the FM bottle for detection of episodes of yeast infection but has the added benefit of detecting bacteria.

Laboratory diagnosis of bacteremia and fungemia.

Many of the variables that affect the laboratory diagnosis of bacteremia and fungemia have been addressed in this article. Whereas the scientific basis and principles for blood cultures are well-established, and the methodology has improved, the diagnosis of bacteremia and fungemia still depends greatly on the care that is taken in obtaining the specimens of blood and the skill of the clinician in interpreting positive results.

Comparison of iodophor and alcohol pledgets with the Medi-Flex blood culture prep kit II for preventing contamination of blood cultures.

Iodophor and alcohol pledgets were compared with the Medi-Flex Prep Kit II for skin disinfection before venipuncture. Of 12,367 blood cultures collected, 6,362 were done with conventional pledgets and 6, 005 were done with Medi-Flex kits. Contamination occurred in 351 of 6,362 blood cultures (5.5%; range, 3.7 to 8.1%) with conventional pledgets versus 328 of 6,005 (5.5%; range, 3.5 to 7.5%) with Medi-Flex kits.

Low back pain.

The communication between radiologists and their surgical colleagues is particularly important in the setting of back pain. This common disorder often does not have a definable cause, even when the imaging findings are abnormal. A shared understanding of the various causes of back pain, the appropriate terminology, and the needs of the surgeon is vital to proper patient treatment. Unfortunately, little standardization in the terminology for and management of back pain syndromes exists. This article elucidates the approaches to problems of back pain used in one clinical setting.

Multilaboratory validation of rapid spot tests for identification of Escherichia coli.

To validate the accuracy of rapid tests for identification of Escherichia coli, five laboratories sequentially collected 1,064 fresh, clinically significant strains with core criteria of indole-positive, oxidase-negative, nonspreading organisms on sheep blood agar plates (BAP), having typical gram-negative rod plate morphology, defined as good growth on gram-negative rod-selective media. An algorithm using beta-hemolysis on BAP, lactose reaction on eosin-methylene blue or MacConkey agar, L-pyrrolidonyl-beta-naphthylamide (PYR), and 4-methylumbelliferyl-beta-D-glucuronide (MUG) was evaluated. Identifications using the algorithm were compared to those obtained using commercial kit system identifications. One thousand strains were E. coli and 64 were not E. coli by kit identifications, which were supplemented with conventional biochemical testing of low probability profiles. Of the 1,064 isolates meeting the core criteria, 294 were beta-hemolytic and did not require further testing to be identified as E. coli. None of the 64 non-E. coli strains were hemolytic, although other indole-positive, lactose-negative species were found to be hemolytic when further strains were examined in a follow-up study. Of the remaining strains, 628 were identified as E. coli by a lactose-positive and PYR-negative reaction. For nonhemolytic, lactose-negative E. coli, PYR was not helpful, but a positive MUG reaction identified 65 of 78 isolates as E. coli. The remaining 13 E. coli strains required kit identifications. This scheme for E. coli identification misidentified three non-E. coli strains as E. coli, for an error rate of 0.3%. A total of 13 kit identifications, 657 PYR tests, and 113 MUG tests were needed to identify 1,000 E. coli strains with the algorithm. The use of this rapid system saves laboratory resources, provides timely identifications, and yields rare misidentifications.

Evaluation of the clinical usefulness of C. difficile toxin testing in hospitalized patients with diarrhea.

Although numerous studies have evaluated the sensitivity and specificity of different assays for Clostridium difficile toxin, none has evaluated how physicians utilize these tests or respond to test results. Therefore, we assessed patient characteristics, clinical findings, and physician responses to positive and negative assay results at two university-affiliated hospitals, one of which used a cell cytotoxicity assay to test for C. difficile toxin and the other of which used an enzyme immunoassay. Two hundred one patient samples at Hospital A and 199 samples at Hospital B were assessed. Positive toxin assays were more frequent at Hospital A than at Hospital B (p < 0.001), at least in part due to the fact that patients tested at Hospital A were more likely to have fever (p < 0.001), an abnormal abdominal exam (p < 0.001), an abnormal leukocyte count (p < 0.001), and a history of prior antibiotic use (p < 0.001). Empiric therapy for C. difficile before results of the toxin assay was more common (p < 0.001) at Hospital A (83/201, 41. 3%) than at Hospital B (25/199, 12.5%). Once empiric therapy was started, most physicians continued therapy despite negative test results (Hospital A, 76%; Hospital B, 69%). Patients who were treated empirically were more likely than patients not treated empirically to have positive toxin assay results and to have fever (p < 0.001), an abnormal abdominal exam (p = 0.003), or an abnormal leukocyte count (p < 0.05). Physicians seldom ordered repeat toxin assays (Hospital A, 14%; Hospital B, 10%) if the initial assay result was negative. In logistic regression analysis, predictors of a positive toxin assay were prior antibiotic therapy, an abnormal abdominal exam, residence at Hospital A, and age >/= 60 years. Predictors of empiric therapy were residence at Hospital A and prior antibiotic therapy. Because physicians electing to empirically treat inpatients with diarrhea rarely alter therapy based on C. difficile toxin assay results, a more cost-effective management strategy may be not to obtain a toxin assay at all in such situations. Testing should be limited to patients who have received antibiotics within the prior month and who have significant diarrhea and/or abdominal pain.

Risk of bacterial infection associated with allogeneic blood transfusion among patients undergoing hip fracture repair.

BACKGROUND: The relationship between allogeneic blood transfusion and bacterial infection remains uncertain. An increased risk of bacterial infection would represent the most important risk of allogeneic transfusion, because viral disease transmission has become so rare. STUDY DESIGN AND METHODS: A retrospective cohort study of 9598 consecutive hip fracture patients at least 60 years old who underwent surgical repair was performed. The primary outcome was serious bacterial infection, defined as bacteremia, pneumonia, deep wound infection, or septic arthritis or osteomyelitis. Secondary outcomes included two individual infections, pneumonia and urinary tract infection (UTI), and the cost of infection. Hospital cost of infection was assessed by linking the study population to Medicare data. RESULTS: Fifty-eight percent of patients received at least one transfusion. Serious bacterial infection occurred in 437 patients (4.6%); 28.8 percent of this group died during the hospital stay. Pneumonia occurred in 361 patients (3.8%) and UTI occurred in 1157 patients (12.1%). The adjusted risk of serious bacterial infection associated with transfusion was 1.35 (95% CI, 1.10-1.66). The adjusted risk for pneumonia was 1.52 (95% CI, 1.21-1.91), and that for UTI was 1.03 (95% CI, 0.91-1.17). A dose-response relationship was present for serious bacterial infection (p = 0.001) and pneumonia (p = 0.001). The cost of hospitalization was $14,000 greater for patients with serious infection than for patients without infection. CONCLUSION: Blood transfusion is associated with a 35-percent greater risk of serious bacterial infection and a 52-percent greater risk of pneumonia. Postoperative infections are costly. The risk of bacterial infection may be the most common life-threatening adverse effect of allogeneic blood transfusion.

Controlled clinical comparison of bioMérieux VITAL and BACTEC NR-660 blood culture systems for detection of bacteremia and fungemia in adults.

A total of 9,446 blood cultures were collected from adult patients at three university-affiliated hospitals. Of these, 8,943 cultures were received with both aerobic bottles filled adequately; 885 yielded 1,016 microorganisms, including 622 isolates (61%) that were the cause of sepsis, 337 isolates (33%) that were contaminants, and 57 isolates (6%) that were indeterminate as the cause of sepsis. With the exception of Staphylococcus aureus, which was recovered more often from VITAL aerobic bottles, more pathogenic microorganisms were recovered from BACTEC NR6 (aerobic) bottles than from VITAL aerobic bottles. Growth of pathogenic microorganisms was detected earlier in VITAL aerobic bottles. A total of 8,647 blood cultures were received with both anaerobic bottles filled adequately; 655 yielded 740 microorganisms, including 486 isolates (66%) that were the cause of sepsis, 215 isolates (29%) that were contaminants, and 39 isolates (6%) that were indeterminate as the cause of sepsis. More pathogenic microorganisms were recovered from VITAL anaerobic bottles than from BACTEC NR7 (anaerobic) bottles. Growth of pathogenic microorganisms was detected earlier in VITAL anaerobic bottles. In 8,500 sets all four bottles were received adequately filled. When paired aerobic and anaerobic bottle sets (systems) were compared, more pathogenic microorganisms (again with the exception of S. aureus) were recovered from the BACTEC system. For the 304 septic episodes (253 unimicrobial and 51 polymicrobial), significantly more were detected by the BACTEC system. We conclude that VITAL requires modification to improve recovery of pathogenic microorganisms to make it competitive with other commercially available blood culture systems.

Staphylococcus hominis subsp. novobiosepticus subsp. nov., a novel trehalose- and N-acetyl-D-glucosamine-negative, novobiocin- and multiple-antibiotic-resistant subspecies isolated from human blood cultures.

A new subspecies, Staphylococcus hominis subsp. novobiosepticus, isolated from human blood cultures, a wound, a breast abscess and a catheter tip, is described on the basis of a study of 26 strains isolated between 1989 and 1996. DNA-DNA reassociation reactions, conducted under stringent conditions, and macrorestriction pattern analysis demonstrated that these strains are closely related to previously characterized S. hominis strains isolated from human skin and clinical specimens, but are significantly divergent. S. hominis subsp. novobiosepticus can be distinguished from S. hominis (now named S. hominis subsp. hominis) by its combined characteristics of novobiocin resistance and failure to produce acid aerobically from D-trehalose and N-acetyl-D-glucosamine. Furthermore, all 26 strains of the new subspecies are resistant to nalidixic acid, penicillin G, oxacillin, kanamycin and streptomycin, and were either resistant or had intermediate resistance to methicillin and gentamicin. Most strains were also resistant to erythromycin, clindamycin, chloramphenicol, trimethoprim/sulfamethoxazole and ciprofloxacin. Based on a comparison of the sequences of a 1001 bp mecA amplification product from reference methicillin-resistant staphylococci, the mecA gene present in S. hominis subsp. novobiosepticus was identified as homologue A, commonly found in S. aureus and many coagulase-negative staphylococcal species. The type strain of S. hominis subsp. novobiosepticus is ATCC 700236T. Descriptions of S. hominis subsp. novobiosepticus subsp. nov and S. hominis subsp. hominis are given and the description of S. hominis is emended.