Use of quantitative antibiogram analysis to determine the clonality of coagulase-negative Staphylococcus species from blood culture.

Two phenotypic methods, quantitative antibiogram analysis and colony morphology, were compared to pulsed-field gel electrophoresis (PFGE) for distinguishing the clonality of coagulase-negative Staphylococcus (CNS) species. The results of these three methods were correlated with the patients' clinical findings for 23 episodes in which CNS species were isolated from two blood culture bottles within a 24-h period. Quantitative antibiogram and colony morphology at 24 h correlated with PFGE typing in 21 (91%) and 20 (87%) episodes, respectively. All episodes associated with CNS strains with identical PFGE patterns had quantitative antibiogram similarity coefficients < 10, whereas most episodes associated with strains with different PFGE patterns had quantitative antibiogram similarity coefficients >or= 17. The CNS isolate pairs were less likely to be associated with infection if the strains had different PFGE types or a quantitative antibiogram similarity coefficient >or= 17. Clinical microbiology laboratories should consider use of the quantitative antibiogram similarity coefficient to aid clinicians in distinguishing infection-associated CNS blood isolates from contaminants.

Cluster of Mycobacterium chelonae keratitis cases following laser in-situ keratomileusis.

PURPOSE: To describe a cluster of Mycobacterium chelonae keratitis cases involving patients who underwent laser in-situ keratomileusis (LASIK) at a single refractive surgery center. DESIGN: Descriptive case series of four patients and cohort study to identify disease associations. METHODS: Examination schedules, diagnostic tests, and therapy were based on best medical judgment. Isolates from three patients were compared by pulsed-field gel electrophoresis. Epidemiologic studies were performed to identify the source of infection. RESULTS: Seven of eight eyes developed M. chelonae keratitis following bilateral simultaneous LASIK. Each patient was thought to have diffuse lamellar keratitis initially, but all seven eyes were noted to have opacities suggestive of infectious keratitis by 13 to 21 days after surgery. All eyes had undergone hyperopic LASIK over four days in April 2001 by one surgeon in a community-based refractive surgery center. A cohort study of all patients undergoing LASIK at the same center in April 2001 revealed that M. chelonae keratitis occurred only in persons undergoing correction of hyperopia (seven of 14 eyes vs. none of 217 eyes undergoing myopic LASIK, P <.001). The only difference identified between procedures was use of masks created from a soft contact lens in hyperopic LASIK. Three isolates (three patients) were indistinguishable by pulsed-field gel electrophoresis. Eyes were treated with a combination of antimicrobial agents, including topical azithromycin in three patients, with resolution of infection in all eyes over 6 to 14 weeks. The source of infection was not identified on environmental cultures. CONCLUSION: Postoperative nontuberculous mycobacterial keratitis can occur in an epidemic fashion following LASIK. Topical amikacin, azithromycin, clarithromycin, ciprofloxacin, or a combination of these agents, appears to be effective treatment for these infections.

Human cerebral cysticercosis: immunolocalization of a sodium-dependent glucose cotransporter (SGLT) in larval and adult tapeworms.

Light microscopic immunocytochemistry was used to examine human brain cysticerci resected from the fourth ventricles of patients who had not been treated with anthelminthic drugs. Tissues were examined from 3 different patients undergoing surgery for treatment of hydrocephalus. A rabbit polyclonal antiserum to the peptide corresponding to amino acids 564-575 unique to the rabbit sodium-dependent, SGLT1 glucose cotransporter labeled with immunoperoxidase, localized immunoreactive SGLT epitopes. This antibody localizes SGLT1 in the apical brush borders of human enterocytes, but is negative in cytoplasm, as well as lateral and basal enterocyte membranes. Taenia solium neurocysticerci were SGLT positive; transporter protein was highly expressed on the surface microvilli of the external cyst wall. The well-developed network of small and larger osmoregulatory ducts within racemose larval cystcerci displayed high expression of SGLT cotransporter, consistent with a resorptive function for this system of tubules. Because water is cotransported with glucose molecules by the SGLT protein, its high expression in neurocysticerci may contribute to the expansive growth of these larvae in subarachnoid and intraventricular sites. The SGLT epitopes were also immunolocalized in gravid proglottids of Taenia saginata, indicating that cotransporter expression persisted in intestinal-dwelling, adult tapeworms. Cotransporter antibody was abundantly localized at the proglottid tegumentary surface and in the lateral osmoregulatory ducts, analogous to the SGLT localization in cysticerci. Furthermore, high expression of this cotransporter was seen in the branches of the uterus, suggesting that SGLT-mediated absorption of glucose and water has an important functional role within the reproductive system of adult tapeworms.

Practical strategies for detecting and confirming vancomycin-intermediate Staphylococcus aureus: a tertiary-care hospital laboratory's experience.

The clinical microbiology laboratory plays a critical role in the detection of Staphylococcus aureus with decreased susceptibility to vancomycin. Staff education and rapid laboratory response are of utmost importance. We report on our laboratory's experience and provide recommendations for the identification and confirmation of vancomycin-intermediate S. aureus.

Laboratory-based surveillance for vancomycin-resistant enterococci: utility of screening stool specimens submitted for Clostridium difficile toxin assay.

OBJECTIVE: To study vancomycin-resistant enterococci (VRE) gastrointestinal colonization prevalence in high-risk hospitalized patients and to assess the cost and utility of this laboratory-based surveillance. SETTING: Large university teaching hospital. DESIGN: Quarterly prevalence culture survey of 50 stool specimens submitted for Clostridium difficile toxin A assay from October 1996 through June 1999 (n=526). Screening culture survey of all C difficile-positive stool specimens from July 1998 through June 1999 (n=140). PATIENTS: Specimens for analysis were collected from patients who were admitted to the hospital and who had C difficile toxin A testing ordered. Patient samples were excluded from analysis if they were obtained from patients not hospitalized at UCLA Medical Center, if the C difficile toxin assay result was indeterminate, or if the patient was known to have previous VRE colonization or infection. RESULTS: During quarterly surveillance, VRE was detected in 19.8%, C difficile toxin A in 9.5%, and both VRE and C difficile toxin A in 3.2% of stool specimens submitted for C difficile toxin assay. Patients whose stool specimens were positive for C difficile toxin A were significantly more likely than those whose specimens were negative to have VRE detected (odds ratio, 2.3; 95% confidence interval, 1.2-4.5). Based on these findings, in July 1998, we began routine screening of all C difficile-positive stool specimens for VRE. From July 1998 through June 1999, 58 (41.4%) of 140 patients with C difficile-positive specimens had VRE newly detected in the stool. The combined cost of the two laboratory-based surveillance strategies was approximately $62 per VRE-positive patient identified and $5,800 per year. CONCLUSION: Quarterly surveillance of stool submitted for C difficile assay combined with screening all C difficile-positive stools is a cost-effective and efficient strategy for detecting VRE stool colonization among high-risk hospitalized patients. Such a laboratory-based surveillance should be included as part of a comprehensive program to limit nosocomial VRE transmission.

Quinupristin/Dalfopristin therapy for infections due to vancomycin-resistant Enterococcus faecium.

The efficacy and safety of quinupristin/dalfopristin for treatment of infections due to vancomycin-resistant Enterococcus faecium were evaluated in 24 hospitalized patients with documented infections (19 bacteremias, 5 localized infections) caused by vancomycin-resistant E. faecium that was susceptible to quinupristin/dalfopristin in vitro. Patients received iv quinupristin/dalfopristin at a dosage of either 7.5 mg/kg every 8 h or 5 mg/kg every 8 h. A favorable clinical response (cure or improvement) occurred in 19 (83%) of 23 evaluable patients; bacteriologic eradication occurred in 17 (74%) of 23 evaluable patients. A favorable clinical response was observed in 12 (80%) of 15 patients who were treated with 7.5 mg/kg of quinupristin/dalfopristin every 8 h and in 7 (88%) of 8 patients treated with 5 mg/kg of quinupristin/dalfopristin every 8 h. Two of four treatment failures were associated with a decrease in the in vitro susceptibility of vancomycin-resistant E. faecium to quinupristin/dalfopristin. Superinfections developed in 6 patients (26%), but only one was caused by Enterococcus faecalis that was resistant to quinupristin/dalfopristin. Myalgias and arthralgias were the only adverse events related to quinupristin/dalfopristin. These conditions occurred in 8 (33%) of 24 patients and were dose-related (8 cases in 16 patients treated with 7.5 mg/kg of quinupristin/dalfopristin every 8 h, no cases in 8 patients treated with 5 mg/kg every 8 h). Mortality associated with vancomycin-resistant E. faecium infection was 17% (4 of 23 patients), whereas mortality from other causes was 52% (12 of 23 patients). These results suggest that quinupristin/dalfopristin is effective as treatment for vancomycin-resistant E. faecium infections in critically ill patients with serious underlying conditions. Except for myalgias and arthralgias at higher dosages, the drug is well-tolerated.

Parenteral infusions as culture media from a viewpoint of nosocomial bacteremia.

OBJECTIVE: To assess the growth patterns of selected organisms in common parenteral solutions, in order to ascertain implications for nosocomial bacteremia. DESIGN: A microbial suspension of approximately 300 CFU/mL was sequentially inoculated into common parenteral infusions from three different manufacturers and incubated at room temperature. Initially, 11 bacterial isolates and one Candida species from clinical specimens were studied. Eight gram-negative rods (GNR) were tested at varying pH's. Species variability was examined by testing an additional 39 isolates. RESULTS: The eight GNR grew in Ringer's lactate (RL) from two manufacturers and only two grew in dextrose 5% in water (D5/W) (Klebsiella pneumoniae and Serratia marcescens). No organism grew in saline or dextrose 5% in saline. The gram-positive cocci and Candida did not grow in any solution. No significant changes in growth were found after modifying the pH of solutions. Significant inter- and intra-species growth variability was noted. CONCLUSIONS: RL is a good culture media for GNR and D5/W is a poor culture media with the exception of some bacteria of the Tribe Klebsielleae. We recommend to follow high standards of nursing practice for administering intravenous infusions and to avoid nutrient-containing solutions for prolonged parenteral use, when possible.

Outbreak of Stenotrophomonas maltophilia bacteremia in allogenic bone marrow transplant patients: role of severe neutropenia and mucositis.

From March 1997 through November 1997, 8 allogenic bone marrow transplant (BMT) patients developed Stenotrophomonas maltophilia bacteremia on the hematology service at UCLA Medical Center (Los Angeles). Five of these patients had undergone transplantation during the same hospitalization that S. maltophilia bacteremia was detected (case patients). Compared with 7 concurrently hospitalized allogenic BMT patients (control patients), the 5 case patients were more likely to have been hospitalized in room A (P=.045), to have severe neutropenia on the culture date (P=.028), to have a longer duration of severe neutropenia (P=.05), to have severe mucositis (P=. 028), and to have received total parenteral nutrition (P=.028). Pulsed-field gel electrophoresis revealed that 2 of 3 isolates from case patients hospitalized in room A were identical. In allogenic BMT patients, severe neutropenia and severe mucositis may promote infection with S. maltophilia by impairing host defenses.

Helminthic food-borne infections.

The importance of food-borne helminthic infections is not well recognized and has not received the same attention as food-borne bacterial infections. Poverty, overpopulation, and cultural practices contribute to conditions that maintain food-borne helminthic infections. The development of better means of transportation and the ease of reaching otherwise inaccessible markets have increased significantly our risk of coming in contact with food containing infectious organisms. The education of industry, public health workers, governmental organizations, and consumers is the most effective means to prevent food-borne helminthic infections and safeguard the world's food supply. Prevention and intervention measures focused at the production level to disrupt the parasite's life cycle are critical for maintaining a safe food supply.

Parenteral infusions bacterial contamination in a multi-institutional survey in Mexico: considerations for nosocomial mortality.

BACKGROUND: Parenteral infusions can be contaminated during administration (extrinsic contamination). A previous survey found that extrinsic contamination was not uncommon in a hospital in Mexico with lapses in aseptic techniques. To determine whether this problem exists in other similar institutions, we undertook a multi-institutional study. METHODS: We surveyed 6 hospitals (A to F) lacking an infection control committee to determine the level of extrinsic contamination. We visited each hospital and obtained samples of all the parenteral infusions in use, drawing 0.5-1 mL from the tubing injection port. Quantitative and qualitative bacterial cultures were performed. Chlorine levels of the tap water were measured. Visits were repeated until the survey was completed. RESULTS: A total of 751 infusions were cultured, of which 16 (2.13%) were contaminated. Hospital contamination rates varied from zero to 5.56%. Klebsiella pneumoniae was the most common isolate (10 cases). During the first sampling day in hospital C, the 7 infusions from the pediatric ward were found to be contaminated with a similar K pneumoniae strain. In-service education was started in this hospital. Infusion contamination was eliminated followed by a reduction in mortality rate. Overall, a higher risk for infusion contamination was noted for pediatric patients (P =.01, odds ratio = 3.28, 95% CI, 1.10-9.91) and in wards with inadequate water chlorine levels (P =. 02, odds ratio = 3.64, 95% CI, 1.08-13.51). CONCLUSIONS: If the hospitals surveyed are representative of others in developing countries, an endemic level of parenteral infusion contamination could exist in many hospitals throughout the world.

Quantitative cytomegalovirus DNA level in the blood and its relationship to cytomegalovirus retinitis in patients with acquired immune deficiency syndrome.

OBJECTIVE: A pilot study was performed to determine whether relationships exist between changes in a quantitative solution hybridization assay for cytomegalovirus (CMV) DNA in the blood and development of CMV retinitis, development of nonocular CMV disease, or reactivation of pre-existing CMV retinitis lesions. DESIGN: Observational case series. PARTICIPANTS: Two groups of human immunodeficiency virus-infected patients: 10 CMV antibody-positive patients with CD4+ T-lymphocyte counts of less than 50 ml and no CMV disease at baseline and 11 patients with CMV retinitis but no extraocular CMV disease at baseline. INTERVENTION: Quantitative changes in leukocyte-associated CMV DNA levels were observed over time. Anti-CMV therapies were based on clinical findings only. MAIN OUTCOME MEASURES: Development of CMV end-organ disease or change in activity of pre-existing CMV retinitis lesions was measured. RESULTS: Among patients with no CMV disease at baseline, four had CMV disease develop during follow-up (three cases of CMV retinitis, one case of presumed CMV esophagitis); all had CMV DNA levels greater than 5000 genomes/ml before the onset of CMV disease. The remaining six patients had levels less than 5000 genomes/ml throughout follow-up (P = 0.05). Among patients with CMV retinitis at baseline, all whose CMV DNA blood levels rose more than tenfold had extraocular CMV disease or reactivation of CMV retinitis develop. Raised CMV DNA blood levels were not seen in every patient with clinical reactivation of CMV retinitis. CONCLUSION: Elevated or rising CMV DNA blood levels appear to be associated with the development of CMV disease in individuals with low CD4+ T-lymphocyte counts. In patients with CMV retinitis, rising levels appear to be associated with the development of extraocular CMV disease or reactivation of CMV retinitis. Conversely, reactivation of CMV retinitis also may occur in the absence of changes in CMV DNA blood levels. Further studies are warranted to determine whether changes in CMV blood levels can be used as a guide for preemptive therapy to prevent reactivation of CMV retinitis lesions or to help choose between local and systemic therapy for management of reactivations.

Critical evaluation of 4-week incubation for fungal cultures: is the fourth week useful?

To determine the benefit of a 4-week incubation for mycology cultures, we evaluated all positive cultures during the fourth week of incubation in a 1-year period. Of 3,855 positive mycology cultures (yeast, 82%; molds, 18%), 62 (1.6%) were positive during the fourth week (yeast, 42%; molds, 58%). Only 15 of the 62 cultures (24%) were considered clinically relevant (2 isolates from invasive fungal infection and 13 isolates from cutaneous mycosis). With the exception of those from skin samples, isolates recovered during the fourth week are rarely important for patient care.

Something's rotten: a nosocomial outbreak of malodorous Pseudomonas aeruginosa.

From July 1994 through November 1996, a phenotypically unique strain of Pseudomonas aeruginosa producing a pungent, "rotten-potato" odor and a positive lysine decarboxylase reaction was isolated from 39 patients at UCLA Medical Center (Los Angeles). Most cases (95%) were in intensive care units and had clinical infections (72%). Most isolates (74%) were recovered from cultures of respiratory secretions. To determine risk factors for acquisition of the organism, 23 cases were compared with 23 randomly selected controls matched by service and isolate date. Multivariate analysis revealed that isolation of malodorous P. aeruginosa was associated with mechanical ventilation of > 24 hours' duration (odds ratio [OR] = 9.4; P = .001) and transfer from an outside hospital (OR = 5.7; P = .04). DNA from outbreak strains hybridized to P. aeruginosa-specific toxin A and phospholipase C gene probes and all outbreak isolates tested were found to be identical by use of pulsed-field gel electrophoresis. An unusual phenotypic characteristic of the strain led to the recognition of a nosocomial outbreak of P. aeruginosa infection associated with mechanical ventilation.

Randomized comparison of sulbactam/cefoperazone with imipenem as empirical monotherapy for febrile granulocytopenic patients.

In a prospective, randomized, controlled trial, we compared sulbactam/cefoperazone with imipenem as empirical monotherapy for febrile, granulocytopenic patients; 101 patients received sulbactam/cefoperazone (2 g/4 g every 12 hours) and 102 patients received imipenem (500 mg every 6 hours). Documented infections were present in 40% of patients treated with sulbactam/cefoperazone (40 of 101) and in 39% of patients receiving imipenem (40 of 102). The number of pretherapy gram-positive pathogens (52 isolates) was twice the number of pretherapy gram-negative pathogens (26 isolates). The overall favorable clinical response rates for sulbactam/cefoperazone (91 of 103 patients, or 88%) and imipenem (84 of 104 patients, or 81%) were similar. Both drugs were generally well tolerated. However, diarrhea occurred more often in patients treated with sulbactam/cefoperazone (31 of 101 patients, or 31%, vs. 15 of 102 patients, or 15%; P = .007), while seizures developed only in patients receiving imipenem (0 of 101 patients vs. 3 of 102 patients, or 3%). Superinfections developed in 16% of patients in both study groups but were infrequently caused by beta-lactam-resistant gram-negative bacilli (two cases with sulbactam/cefoperazone therapy and six cases with imipenem). These results support the efficacy and safety of either sulbactam/cefoperazone or imipenem as empirical monotherapy for febrile granulocytopenic patients.

Citrobacter farmeri bacteremia in a child with short-bowel syndrome.

A case of sepsis in a pediatric patient due to the newly described Citrobacter species C. farmeri is described. Factors predisposing this child to infection included short-bowel syndrome requiring total parenteral nutrition.

Multicenter evaluation of the MicroScan Rapid Gram-Negative Identification Type 3 Panel.

The accuracy and performance of the revised MicroScan Rapid Gram-Negative Identification Type 3 Panel (Dade MicroScan Inc., West Sacramento, Calif.) were examined in a multicenter evaluation. The revised panel database includes data for 119 taxa covering a total of 150 species, with data for 12 new species added. Testing was performed in three phases: the efficacy, challenge, and reproducibility testing phases. A total of 405 fresh and stock gram-negative isolates comprising 54 species were tested in the efficacy phase; 96.8% of these species were identified correctly in comparison to the identification obtained either with the API 20E system (bioMérieux Vitek, Hazelwood, Mo.) or by the conventional tube method. The number of correctly identified isolates in the challenge phase, including new species added to the database, was 221 of 247, or 89.5%, in comparison to the number correctly identified by the conventional tube method. A total of 465 isolates were examined for intra- and interlaboratory identification reproducibility and gave an agreement of 464 of 465, or 99.8%. The overall reproducibility of each individual identification test or substrate was 14,373 of 14,384, or 99.9%. The new Rapid Gram-Negative Identification Type 3 Panel gave accurate and highly reproducible results in this multiple-laboratory evaluation.