Comparison of LightCycler PCR, rapid antigen immunoassay, and culture for detection of group A streptococci from throat swabs.

We compared the performance characteristics of a real-time PCR method, the LightCycler Strep-A assay (Roche Applied Science, Indianapolis, Ind.), to those of a rapid antigen immunoassay, the Directigen 1-2-3 Group A Strep Test kit (BD Diagnostic Systems, Sparks, Md.), and a standard culture method for detection of group A streptococci (GAS) from 384 throat swabs. The LightCycler PCR produced more positive results (n = 58) than either culture (n = 55) or the Directigen immunoassay (n = 31). The results of the LightCycler PCR and the Directigen method were independently compared to the results of the accepted "gold standard," bacterial culture. The sensitivities, specificities, and positive and negative predictive values for this comparison were as follows: for the Directigen method, 55, 99, 97, and 93%, respectively; for the LightCycler PCR, 93, 98, 88, and 99%, respectively. In no case was a throat swab positive by both the LightCycler PCR and the Directigen method but negative by culture. The medical histories of patients whose throat swabs were negative by culture but positive by either the LightCycler PCR (n = 7) or the Directigen method (n = 1) were reviewed. All of these patients had signs or symptoms compatible with GAS disease, and therefore, all of these discordant positive results (along with positive results by either the Directigen method or the LightCycler PCR that agreed with the culture results) were counted as true positives for statistical analysis. For this analysis, the LightCycler PCR detected more true-positive results than the culture method (58 versus 55 swabs); however, this difference was not statistically significant (P = 0.5465). In contrast, statistically significantly more true-positive results occurred by culture than by the Directigen method (55 versus 31 swabs; P < 0.0001) and by the LightCycler PCR than by the Directigen method (58 versus 31 swabs; P < 0.0001). The LightCycler PCR is a suitable stand-alone method for the detection of GAS from throat swabs. Additionally, this method requires less than half the personnel time and the procedure can be completed in considerably less time ( approximately 1 h) than our standard approach (up to 2 days) for detection of GAS in throat swabs (i.e., testing by the Directigen method with negative results verified by culture).

Antimicrobial therapy for infants and children: guidelines for the inpatient and outpatient practice of pediatriac infectious diseases.

In this article, we discuss antimicrobial regimens for both outpatient and inpatient use in infants and children. A substantial number of pediatric patient visits annually result in the prescribing of antimicrobial drugs. The emergence of bacteria resistant to commonly used antimicrobial agents is a growing concern. Information on newer drugs such as meropenem, which is active against penicillin-resistant Streptococcus pneumoniae and gram-negative bacilli, and cefepime, which has activity against gram-negative bacilli including Pseudomonas aeruginosa and against gram-positive cocci is also presented. Management of patients with congenital or acquired immunodeficiencies continues to be challenging in regard to the use of antimicrobial drugs to treat various fungal and viral infections. New formulations of older drugs such as aerosolized tobramycin and amphotericin B lipid complex are available. New antiviral agents have been approved, most of which are antiretroviral agents. Childhood tuberculosis is an ongoing concern, and regimens to treat Mycobacterium tuberculosis in children are discussed.

Clinical evaluation of the Gen-Probe Amplified Direct Test for detection of Mycobacterium tuberculosis complex organisms in cerebrospinal fluid.

Eighty-four cerebrospinal fluid (CSF) samples from different children who presented with signs and symptoms of meningitis were evaluated for the presence of Mycobacterium tuberculosis complex organisms by the Gen-Probe Amplified Mycobacterium tuberculosis Direct Test (MTD; Gen-Probe, San Diego, Calif.). All CSF samples had negative acid-fast smears by the Ziehl-Neelsen staining method. M. tuberculosis was recovered from five samples. M. tuberculosis did not grow from 19 additional samples, but the samples were from patients who fulfilled specific clinical and laboratory criteria for probable tuberculous meningitis (TBM). The remaining samples (n = 60) were from patients with other infections or noninfectious causes of meningitis. The results of the MTD were interpreted as positive or negative on the basis of recommended cutoff values for respiratory specimens. These results were interpreted as true or false positives or true or false negatives on the basis of the results of M. tuberculosis culture or whether the patient fulfilled criteria for probable TBM. The Gen-Probe MTD was 33% sensitive and 100% specific for detecting M. tuberculosis complex organisms in these 84 CSF samples. If the cutoff values for positive results were decreased for the MTD (> or = 11,000 versus > or = 30,000 relative light units), the sensitivity increased to 83% and the specificity remained 100%. These results for the MTD are encouraging considering that TBM is a highly fatal disease and difficult to diagnose by conventional laboratory techniques.

Clinical comparison of BACTEC 9240 plus aerobic/F resin bottles and the isolator aerobic culture system for detection of bloodstream infections.

The Plus Aerobic/F resin bottle of the BACTEC 9240 automated blood culture system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) was compared with aerobic culture of the Isolator system (Wampole Laboratories, Cranbury, N.J.) for the detection of bloodstream microorganisms from 6,145 blood cultures collected from adult patients with suspected septicemia. The BACTEC resin bottles were incubated for 7 days, and the sediment from the Isolator tube was inoculated to sheep blood and chocolate agars which were incubated for 72 h and to inhibitory mold, brain heart infusion, and Sabouraud agars which were incubated for 21 days. A total of 622 microorganisms were recovered from 583 blood cultures. The BACTEC resin bottle recovered statistically significantly more pathogens overall than the Isolator system (P = 0.0006). When individual pathogens isolated from either system for a 7-day study period were assessed, it was determined that the BACTEC resin bottle detected statistically significantly more isolates of Staphylococcus aureus (P = 0.0113) and coagulase-negative Staphylococcus spp. (P = 0.0029) than the Isolator system. The BACTEC resin bottle also detected statistically significantly more bloodstream infections (septic episodes) caused by coagulase-negative Staphylococcus spp. (P = 0.0146). The Isolator system recovered statistically significantly more contaminants overall (P < 0.0001), and among this group of microorganisms, recovered statistically significantly more Bacillus spp. (P < 0.0001), coagulase-negative Staphylococcus spp. (P < 0.0001), and viridans group Streptococcus spp. (P = 0.0156). The Isolator system detected statistically significantly more isolates of Histoplasma capsulatum (P = 0.004), but all of these isolates were detected at > or = 7 days of incubation of fungal plates, i.e., after the system to system comparison study period (7 days). In blood culture sets which produced growth of the same pathogen in both systems, there was a statistically significant difference in median time to detection for all pathogens combined favoring the BACTEC resin bottle over the Isolator tube (P < 0.05). When assessing individual microorganisms, the median times for detection of S. aureus, Enterococcus spp., and Pseudomonas spp. were all statistically significantly less for the BACTEC system (P < 0.05). The BACTEC instrument had 79 (1.3%) false positive signals. The BACTEC system required less processing time than the Isolator system and eliminates the hands-on time for detection of positive cultures required with the Isolator system.

Leuconostoc bacteremia in an infant with short-gut syndrome: case report and literature review.

In this article, we report a case of Leuconostoc bacteremia in a 7-month-old infant who had short-gut syndrome after a gastroschisis repair and who was dependent on total parenteral nutrition through a central venous catheter. The organism was initially misidentified as viridans group streptococcus. Detection of vancomycin resistance led to the correct diagnosis of Leuconostoc species. The patient was successfully treated with ampicillin and an aminoglycoside. A review of the literature revealed prematurity, short-gut syndrome, prior vancomycin use, and central venous catheters as important predisposing factors. Leuconostoc species is an emerging pathogen that should be considered in the differential diagnosis of vancomycin-resistant gram-positive bacteremia, particularly in these clinical settings.

Pediatric bone and joint infections. Diagnosis and antimicrobial management.

Bone and joint infections in children provide unique clinical challenges. When evaluating children with suspected bone and joint infection, the differential diagnosis is broad. Consideration must be given to possible neoplastic and traumatic causes. Appropriate imaging and diagnostic techniques should be initiated without delay. Orthopedic consultation for surgical evaluation should be made early. Prolonged use of antibiotics is often warranted. Treatment often is continued in the outpatient setting, requiring frequent follow-up with appropriate serial laboratory studies to monitor side effects of antimicrobial agents.

Yield of positive blood cultures in pediatric oncology patients by a new method of blood culture collection.

BACKGROUND: The optimal number of blood cultures and the volume of blood for pediatric blood cultures have not been defined. In 1990 such criteria were established at our institution. We retrospectively reviewed records of all pediatric oncology patients who were admitted for febrile episodes in 1989 and in 1991 and 1992 to determine whether there was an increase in the detection of bacteremia and fungemia. METHODS: Blood was drawn via venipuncture and central intravascular catheters and inoculated into the designated blood culture bottles. Each patient had a minimum of two separate blood draws, i.e. two separate cultures; the volume was determined by the patient's weight. In all cases < 1% of the patient's blood volume was drawn per culture. Patients' records were reviewed regarding type of malignancy, chemotherapy and neutropenia. RESULTS: The rate of bacteremic patients increased from 12% (13 of 113) in 1989 to 22% (27 of 123) in 1991. This increase continued through 1992 with 23% (27 of 118) of patients having positive blood cultures. Gram-positive bacteria predominated throughout the study period. CONCLUSIONS: Although factors such as more aggressive chemotherapy or a different spectrum of malignant diseases may contribute to the statistically significant increase in identification of bacteremic patients, a standardized method of blood culture collection is merited. The consistent volumes of blood per culture and the minimum of two cultures per febrile episode follow the principles of blood culture collection established for adults. The same principles should apply to pediatric patients.

Clinical comparison of difco ESP, Wampole isolator, and Becton Dickinson Septi-Chek aerobic blood culturing systems.

The ESP 80A aerobic blood culture of the ESP automated blood culture system (Difco Laboratories. Detroit, Mich.) was compared with two manual aerobic blood culture systems, the Isolator (Wampole Laboratories, Cranbury, N.J.) and the Septi-Chek (Becton Dickinson, Cockeysville, Md.) systems, for the detection of bloodstream microorganisms from 5,845 blood samples for culture collected from adult patients with suspected septicemia. The bottles were incubated for 7 days, and the sediment from the Isolator tube was inoculated onto solid medium and this medium was incubated for 72 h. A total of 609 microorganisms were recovered from 546 blood cultures. There was no statistically significant difference in the total recovery of microorganisms for the ESP 80A system when compared with that for the Septi-Chek system (P = 0.083); however, the Isolator system recovered significantly more microorganisms overall than either the ESP 80A (P < 0.001) or the Septi-Chek (P < 0.001) system. When assessing individual probable pathogens, the Isolator system detected statistically significantly more Staphylococcus aureus and Candida spp. than either the ESP 80A or the Septi-Chek system (P < 0.05). Similarly, the Isolator system detected statistically significantly more bloodstream infections (septic episodes) caused by S. aureus and Candida spp. than either the ESP 80A or the Septi-Chek system (P < 0.05). In blood culture sets which produced growth of the same probable pathogens in the ESP 80A and the Isolator systems, there was no statistically significant difference in the median times to detection for all pathogens combined (P = 0.067). However, a similar comparison showed the Isolator and the ESP 80A systems to have statistically significantly shorter median detection times for all pathogens combined (P < 0.001) when they were independently compared with the Septi-Chek system. The ESP 80A system had 29 (0.5%) false-positive signals. The ESP system required less processing time than the Isolator system and eliminates the hands-on time for the detection of positive cultures required by the manual systems.

Relative efficacies of broad-spectrum cephalosporins for treatment of methicillin-susceptible Staphylococcus aureus experimental infective endocarditis.

The effects of treatment with broad-spectrum parenterally administered cephalosporins and cefuroxime, cefazolin, or nafcillin were compared in an experimental model of Staphylococcus aureus infective endocarditis, and the results in vivo were compared with the activities of the study drugs in vitro. After 3 days of treatment, all antimicrobial agents tested were more effective than no treatment in reducing the number of surviving bacteria in cardiac valve vegetations. Nafcillin was the most effective agent studied and was significantly more active than was ceftizoxime, ceftriaxone, cefotaxime, cefoperazone, cefuroxime, or cefazolin (P < or = 0.05). Cefpirome and ceftazidime were the most effective broad-spectrum cephalosporins. The outcome of treatment with cefpirome or ceftazidime was similar to that of treatment with nafcillin and significantly better than that of treatment with ceftizoxime or cefotaxime (P < or = 0.05). Treatment outcome correlated closely with the MICs of the antimicrobial agents for the study strain with the exception of ceftazidime, which was significantly more active in vivo in comparison with other agents than predicted by its MIC (P < or = 0.0003). When ceftazidime was excluded as an outlier, treatment outcome correlated with the MICs of the remaining study drugs (Spearman's correlation coefficient, 0.95; P < or = 0.0004), as well as with the estimated percentage of time during which the concentration of total drug (correlation coefficient, -0.85; P < or = 0.007) or free drug (correlation coefficient, -0.90; P < or = 0.003) exceeded the MIC. A consideration of total or free drug concentrations in relation to MICs did not significantly improve the correlation with outcome observed with the MICs alone.

Ciprofloxacin versus trimethoprim-sulfamethoxazole: treatment of community-acquired urinary tract infections in a prospective, controlled, double-blind comparison.

In this study, we determined the safety and efficacy of the treatment of adults with urinary tract infection with ciprofloxacin hydrochloride (250 mg twice daily for 10 days) in comparison with trimethoprim-sulfamethoxazole (160 mg of trimethoprim and 800 mg of sulfamethoxazole twice daily for 10 days). Patients with signs and symptoms of urinary tract infection were randomized to receive ciprofloxacin (98 women and 5 men) or trimethoprim-sulfamethoxazole (92 women and 8 men). The success rate of therapy was 91% for both treatment arms of the study. Among seven failures after ciprofloxacin therapy, three were due to relapse of infection and two to side effects that necessitated a change in medication; in addition, two patients had persistent symptoms and required hospitalization. Among the six failures associated with trimethoprim-sulfamethoxazole therapy, four were due to relapse, one to persistence of infection, and one to a side effect that necessitated a change in medication. Among the patients treated with trimethoprim-sulfamethoxazole, 32% had mild or moderate adverse reactions; in comparison, 17% of the ciprofloxacin-treated patients had adverse reactions (P = 0.026). For the treatment of urinary tract infection in adult patients in this study, ciprofloxacin and trimethoprim-sulfamethoxazole were equally effective, but ciprofloxacin was associated with fewer adverse reactions.

Continuous intravenous versus intermittent ampicillin therapy of experimental endocarditis caused by aminoglycoside-resistant enterococci.

We studied the efficacy of continuous intravenous infusion of ampicillin compared with that of intermittent administration of ampicillin alone or in combination with gentamicin for the therapy of highly aminoglycoside-resistant enterococcal experimental endocarditis. Rabbits were infected with a gentamicin-susceptible (MIC, 256 micrograms/ml) strain of Enterococcus faecalis or a strain of E. faecalis which was highly resistant to gentamicin in vitro (MIC, greater than 2,000 micrograms/ml). Administration of ampicillin by continuous intravenous infusion did not significantly enhance the killing of enterococci in vivo compared with that by intermittent administration of ampicillin for either the aminoglycoside-susceptible or the aminoglycoside-resistant strain. In combination with gentamicin, there were no significant differences in efficacies obtained with intermittent versus continuous intravenous infusion of ampicillin therapy for experimental endocarditis caused by either strain of E. faecalis.

Animal models as predictors of outcome of therapy with broad spectrum cephalosporins.

Broad spectrum cephalosporins have been studied extensively in animal models of experimental infections. There is generally good correlation between the results of therapy of experimental infections and clinical trials in humans. However, the results of animal model studies are better predictors of the failure than of the success of a chemotherapeutic regimen. Cefotaxime and the new 'fourth' generation agent, cefpirome, were comparable in the treatment of experimental meningitis caused by Streptococcus pneumoniae. Cefpirome was the most effective cephalosporin as therapy for methicillin-susceptible Staphylococcus aureus experimental endocarditis. The most effective broad spectrum cephalosporins for the treatment of Gram-negative experimental pneumonia were cefpirome, cefotaxime and cefodizime. Cefpirome was equivalent to ceftazidime or cefazolin as treatment for Pseudomonas aeruginosa or methicillin-susceptible S. aureus experimental osteomyelitis. Because of its potent activity in vitro and in animal models of experimental infections caused by methicillin-susceptible S. aureus and Gram-negative bacilli, cefpirome may offer a therapeutic advantage over currently available broad spectrum cephalosporins.

Antibiotic therapy for severe infections in infants and children.

In infants and children, the absorption, distribution, metabolism, and excretion of drugs may differ considerably in comparison with these factors in adults; consequently, differences exist in therapeutic efficacy and toxicity of various antibiotic agents. Because of known toxicity, certain drugs--such as chloramphenicol in high doses, the sulfonamides, and tetracycline--should not be used in neonates. Antibiotic therapy should be modified in neonates because of biologic immaturity of organs important for the termination of drug action. Because of poor conjugation, inactivation, or excretion, the serum concentrations of many antibiotics may be higher and more prolonged in neonates than in older infants; thus, lower doses and longer intervals between administration may be necessary. In this article, we suggest dosages of antimicrobial agents for severe infections in children, older infants, and neonates. Included in the discussion are the cephalosporins, especially the third-generation cephalosporins that have assumed an important role in empiric treatment of bacterial meningitis in pediatric patients because of their ability to penetrate the central nervous system and their effectiveness against beta-lactamase-positive and negative strains of Haemophilus influenzae type b, Streptococcus pneumoniae, Neisseria meningitidis, and many gram-negative bacteria in the Enterobacteriaceae group. In patients with congenital or acquired immunodeficiencies, antifungal, antiviral, or anti-Pneumocystis agents are often added to the antimicrobial regimen for severe infections. We review the agents available for such treatment in children, the drugs used for childhood tuberculosis, and certain new antibiotics (aztreonam, ticarcillin-clavulanate, ciprofloxacin, and imipenem-cilastatin) that have proved useful in select cases but whose precise role in pediatric practice will necessitate additional clinical experience.

Efficacy of cilofungin therapy administered by continuous intravenous infusion for experimental disseminated candidiasis in rabbits.

Cilofungin has potent in vitro activity against Candida albicans, but previous in vivo models using twice daily intermittent dosing regimens have not consistently demonstrated in vivo efficacy. Because of the pharmacokinetics of cilofungin in rabbits, it has been suggested that administration by continuous intravenous infusion might be more effective. We compared the in vivo efficacy of continuous intravenous infusion of cilofungin with that of amphotericin B in a rabbit model of disseminated candidiasis. Cilofungin prepared as previously described in phosphate-buffered 33% polyethylene glycol was lethal to infected rabbits in this model, as was phosphate-buffered 33% polyethylene glycol alone. In contrast, cilofungin in 26% polyethylene glycol and sterile water administered by continuous intravenous infusion was tolerated by rabbits, was significantly more effective than amphotericin therapy in reducing candida colony counts in kidney tissue, and was as effective as amphotericin therapy in lung and spleen tissue and in cardiac valvular vegetations. The dosage regimen and diluent used in some previous studies may have adversely affected outcome of treatment with cilofungin.

Ciprofloxacin therapy of experimental endocarditis caused by methicillin-resistant Staphylococcus epidermidis.

Ciprofloxacin or rifampin was significantly (P less than 0.05) more effective than vancomycin or the combination of vancomycin plus gentamicin for the treatment of Staphylococcus epidermidis experimental endocarditis. There were no significant differences in efficacy among any of the combinations of antimicrobial agents that included ciprofloxacin or rifampin. One animal treated with rifampin alone and one treated with the combination of vancomycin, rifampin, and gentamicin were found to be infected with rifampin-resistant strains of S. epidermidis during therapy. Resistant subpopulations of S. epidermidis were not detected during therapy with any other antimicrobial agent used alone or in combination. Ciprofloxacin alone or in combination with rifampin was effective therapy against S. epidermidis experimental endocarditis.

Prospective randomized comparison of mezlocillin therapy alone with combined ampicillin and gentamicin therapy for patients with cholangitis.

Forty-six patients with cholangitis were randomized to receive therapy with mezlocillin sodium (24 patients) or a combination of ampicillin sodium--gentamicin sulfate (22 patients). The biliary concentration of mezlocillin was 112 times higher than that of ampicillin and 778 times higher than that of gentamicin. The ratio of the concentration in serum or bile over the minimum inhibitory concentration against aerobic gram-negative bacilli (therapeutic index) was higher for mezlocillin than for either ampicillin or gentamicin. Twenty (83%) of 24 patients were cured following mezlocillin therapy compared with 9 (41%) of 22 patients after ampicillin-gentamicin therapy. The 3 patients with superinfection were in the ampicillin-gentamicin arm of the study. Fewer toxic or adverse effects occurred in association with mezlocillin treatment than with ampicillin-gentamicin treatment. Mezlocillin therapy was more effective, less toxic, and less expensive than treatment with ampicillin and gentamicin for patients with cholangitis.

In vitro and in vivo studies of streptomycin-resistant, penicillin-susceptible streptococci from patients with infective endocarditis.

The combination of penicillin and streptomycin did not act synergistically in vitro against three streptomycin-resistant strains (MIC, greater than or equal to 1,000 micrograms of streptomycin/ml) of penicillin-susceptible streptococci. Using a model of experimental infective endocarditis, we infected rabbits with a control streptomycin-susceptible strain, with an intermediately streptomycin-resistant strain (MIC, 1,000 micrograms/ml), and with a highly streptomycin-resistant strain (MIC, greater than 32,000 micrograms/ml). Treating animals with a combination of procaine penicillin and streptomycin was more effective (P less than .01) than treating them with procaine penicillin alone only for those animals infected with the control streptomycin-susceptible strain. Treatment with procaine penicillin plus gentamicin was more effective (P less than .01) than treatment with procaine penicillin alone for all three treatment groups and was more effective (P less than .01) than treatment with procaine penicillin and streptomycin for those animals infected with an intermediately or highly streptomycin-resistant strain of streptococci.

Treatment of methicillin-resistant Staphylococcus aureus experimental osteomyelitis with ciprofloxacin or vancomycin alone or in combination with rifampin.

Therapy with vancomycin alone or ciprofloxacin alone did not significantly reduce the number of methicillin-resistant Staphylococcus aureus (MRSA) in bone in rats with experimental osteomyelitis, compared with the number in control rats. Treatment with rifampin significantly (p less than 0.01) decreased the number of MRSA per gram of bone compared with the number in control animals. There was no significant difference in the results of therapy with rifampin compared with the results obtained with the combination of vancomycin plus rifampin. The combination of ciprofloxacin plus rifampin was the most effective regimen for the treatment of MRSA experimental osteomyelitis and the results of therapy were significantly (p less than 0.01) superior to those following treatment with rifampin alone or the combination of vancomycin and rifampin. Following cessation of antimicrobial therapy, significant (p less than 0.01) regrowth of MRSA in bone occurred in animals treated with rifampin alone or ciprofloxacin plus rifampin. The emergence of resistance of MRSA during treatment occurred in two rats treated with rifampin alone and in one treated with rifampin plus vancomycin.

In vitro and in vivo activity of ciprofloxacin against enterococci isolated from patients with infective endocarditis.

In vitro activity of ciprofloxacin against 27 strains of enterococci was inoculum dependent. Using inocula of 10(5) to 10(6) or 10(7) to 10(8) CFU of enterococci per ml, the MICs for 50 and 90% of strains tested increased from 1 to greater than or equal to 128 micrograms of ciprofloxacin per ml with the higher inoculum compared with the lower inoculum. The MBC for 50% of strains tested increased from 2 to greater than 128 micrograms/ml and the MBC for 90% of strains tested increased from 8 to greater than 128 micrograms of ciprofloxacin per ml with the lower and higher inocula, respectively. The combination of penicillin-gentamicin was more effective in vitro than the combination of ciprofloxacin-gentamicin against the low or high inoculum of enterococci. Using two strains of enterococci, we studied the efficacy of ciprofloxacin in the treatment of enterococcal experimental endocarditis in rabbits. Ciprofloxacin used alone or combined with gentamicin was significantly less effective (P less than 0.01) than procaine penicillin alone or procaine penicillin combined with gentamicin for the treatment of enterococcal experimental endocarditis. The combination of ciprofloxacin-procaine penicillin was not a more effective therapy than procaine penicillin alone.