Resonant add-drop filter based on a photonic quasicrystal.

We present a numerical study of optical properties of an octagonal quasi-periodic lattice of dielectric rods. We report on a complete photonic bandgap in TM polarization up to extremely low dielectric constants of rods. The first photonic bandgap remains open down to dielectric constant as small as epsilon = 1.6 (n = 1.26). The properties of an optical microcavity and waveguides are examined for the system of rods with dielectric constant epsilon = 5.0 (n = 2.24) in order to design an add-drop filter. Proposed add-drop filter is numerically characterized and further optimized for efficient operation. The two-dimensional finite difference time domain method was exploited for numerical calculations. We provide a numerical evidence of effective add-drop filter based on low index material, thus opening further opportunities for application of low refractive index materials in photonic bandgap optics.

Tuberculous meningitis. Clinical characteristics and comparison with cryptococcal meningitis in patients with human immunodeficiency virus infection.

OBJECTIVE: To determine the prevalence and causes of meningitis in patients with human immunodeficiency virus (HIV) infection. DESIGN: A prospective study of HIV-associated neurologic complications carried out from 1988 to 1992. SETTING: A tertiary care university hospital in Madrid, Spain. PATIENTS. A total of 142 patients, 65% of whom were injecting drug users. RESULTS: Thirty-six episodes of meningitis were diagnosed in 33 patients (23%). Of these, 17 cases (47%) were tuberculous meningitis (5 definite and 12 probable) and 7 (19%) corresponded to cryptococcal meningitis. Comparative studies of the tuberculous and cryptococcal meningitis cases showed injecting drug use as the most common form of HIV transmission in the tuberculous meningitis (P = .03) and a lower mean CD4+ cell count in the cryptococcal meningitis group (P = .02). CONCLUSIONS: Tuberculous meningitis was the prime type of meningitis, which was associated with HIV transmission by injecting drug use. Cryptococcal meningitis appears in more advanced stages of HIV infection, which determines its characteristic presentation.

Temocillin. In vitro activity compared with other antibiotics.

Temocillin is a recently developed penicillin with a methoxy group in the 6-alpha position. The in vitro activity of temocillin was studied using 932 recent clinical isolates of aerobic and anaerobic Gram-negative bacilli and Gram-positive cocci, and its activity was compared with that of other beta-lactam antibiotics. Temocillin was active against the Enterobacteriaceae, with narrow ranges of MICs and MIC90 values (less than or equal to 8 mg/L) for all isolates except Serratia marcescens and Enterobacter species. Moreover, the compound was active against 46 multiresistant Enterobacteriaceae strains. The drug was also strongly active against Haemophilus influenzae, with beta-lactamase-producing strains being as susceptible as non-beta-lactamase-producing strains. Temocillin showed no useful activity against Pseudomonas aeruginosa, Acinetobacter or Gram-positive cocci, and had only discrete activity against the Bacteroides fragilis group. In general, temocillin displayed the same spectrum of activity against Enterobacteriaceae as third generation cephalosporins, but with a substantially lower intrinsic activity.

The central nervous system and infection by Candida species.

In this paper we have reviewed the main clinico-pathologic disease groups of neurocandidiasis: the microabscesses, the macroabscesses, and the meningitis. Special attention has been paid to the predisposing conditions for the appearance of neurocandidiasis, the neuroimaging techniques, and the study of the cerebrospinal fluid, needed for diagnosis. We have also discussed the differential diagnosis with other illnesses. Treatment should be given with amphotericin-B and 5-fluorocytosine. The use of other antifungal drugs for neurocandidiasis is also discussed.

Infection of the central nervous system by Mycobacterium tuberculosis in patients infected with human immunodeficiency virus (the new neurotuberculosis).

Neurologic complications of HIV infection are numerous. This review focuses on the clinical presentation, diagnostic particularities and therapeutic issues of neurotuberculosis. The pertinent literature describing this important infection is succinctly summarized with a particular emphasis on the discussion of differences in clinical presentation between HIV-infected and -uninfected patients.

Mortality associated with nosocomial bacteremia due to methicillin-resistant Staphylococcus aureus.

We prospectively studied all cases of Staphylococcus aureus bacteremia that occurred during an extensive outbreak of methicillin-resistant S. aureus (MRSA) in our hospital over a 4-year period (January 1990 through September 1993). We report the results of a comparative analysis of the clinical characteristics and mortality rates among patients with nosocomial bacteremia caused by MRSA (84 cases) or methicillin-susceptible S. aureus (MSSA; 100 cases). The patients with MRSA bacteremia were older than those with MSSA bacteremia (69 years vs. 54 years, respectively; P < .01) and were more likely than those with MSSA bacteremia to have the following predisposing factors: a prolonged hospitalization (32 days vs. 14 days, respectively; P < .01); prior antimicrobial therapy (61% vs. 34%, respectively; P < .01); urinary catheterization (58% vs. 27%, respectively; P < .01); nasogastric tube placement (31% vs. 13%, respectively; P < .01); and prior surgery (45% vs. 31%, respectively; P = .05). Multivariate analysis with use of the stepwise logistic regression method showed a relationship between mortality and the following variables: methicillin resistance (odds ratio [OR], 3), meningitis (OR, 13), and inadequate treatment (OR, 11).

[Beta-lactamase producing bacteria in the pharyngeal flora of patients with acute pharyngitis]. / Estudio de las bacterias productoras de betalactamasa en la flora faríngea en pacientes con faringitis aguda.

BACKGROUND: Production of beta-lactamase by normal pharyngeal flora could account for penicillin treatment failure in patients with acute streptococcal pharyngitis. The aim of the present investigation was to study the beta-lactamase-producing bacteria (BLPB) in 58 patients with acute pharyngitis, and to investigate the impact of two antibiotics, amoxycillin vs amoxycillin/clavulanic acid in the pharyngeal microflora. METHODS: Rapid antigen detection tests for S. pyogenes and standard microbiologic cultures were performed on simultaneously obtained throat swabs from each enrolled patient. Patients with group A streptococcal pharyngitis (GASP) were randomized in two groups: patients treated with 10 days of oral amoxycillin (group I), and patients treated with 10 days of oral amoxicyllin/clavulanic acid (group II). Patients without GASP and without antibiotic treatment were considered as controls (group III). Cultures were repeated 15 days following the first culture. All of them were processed for aerobic and anaerobic organisms. RESULTS: S. pyogenes was recovered in 25 patients (43.1%) and BLPB were isolated in 64% of the treated patients and in 78% of the non-treated control patients. We observed that the number of patients harboring BLPB did not change significantly in the untreated control group. After treatment we detected a similar increase in the number of patients harboring BLPB in groups I and II. In the present study BLPB were found in more than 70% of the patients and the failure rate was less than 10%. CONCLUSIONS: The results of this study indicate that production of beta-lactamase by pharyngeal organisms does not fully explain the failures of penicillin therapy for acute streptococcal pharyngitis.

Bacteremic pneumonia due to Staphylococcus aureus: A comparison of disease caused by methicillin-resistant and methicillin-susceptible organisms.

We performed a prospective study of all patients with bacteremic pneumonia due to Staphylococcus aureus over a period of 6 years during an outbreak of methicillin-resistant S. aureus (MRSA). Patients with bacteremic pneumonia due to MRSA (32 cases) or methicillin-susceptible S. aureus (MSSA; 54 cases) were compared. The patients with MRSA pneumonia were older and were more likely than those with MSSA pneumonia to have predisposing factors for acquisition of the infection. There were no differences in clinical findings, radiological pattern, or complications in clinical evolution among patients with MRSA and MSSA pneumonia. Mortality was significantly higher among MSSA-infected patients treated with vancomycin than among those treated with cloxacillin (47% vs. none; P<.01). Multivariate analysis (stepwise logistic regression method) showed a relationship between mortality and the following variables: septic shock (odds ratio [OR], 61), vancomycin treatment (OR, 14), and respiratory distress (OR, 8).

Epidemic outbreak of Serratia marcescens infection in a cardiac surgery unit.

Between 2 February and 16 April 1985, an outbreak of Serratia marcescens infection involving 10 male patients occurred in a cardiac surgery unit. All the patients had surgical wound infection, five also had osteomyelitis (four sternal, one costal), and another had peritonitis secondary to peritoneal dialysis. Three patients had concomitant bacteremia. All Serratia strains isolated produced a cherry-red pigment, and all had the same biochemical and antibiotic susceptibility pattern. An intensive search for the origin of the outbreak was initially unsuccessful, and it proved impossible to isolate S. marcescens from cultures of numerous samples taken from hospital personnel and from the environment. The fact that all patients were male and had been shaved for surgery by the same team of barbers led us to investigate the shaving procedures. We finally isolated a strain of pigmented S. marcescens, corresponding to that involved in the outbreak, from samples taken from the hands and equipment of the barbers. After suitable action had been taken, the epidemic terminated.

[Community-acquired respiratory infections]. / Estudio de las infecciones respiratorias extrahospitalarias.

BACKGROUND: Respiratory infections are the most frequent reason for primary health care consultation. Although generally not severe, they are responsible for a large number of days of laboral and scholar absenteeism and an excessive use of antibiotics. METHODS: The clinical and epidemiologic data of extrahospitalary infections in primary health care centers throughout Spain were collected according to the one day cut off system repeated trimestrally over one year. RESULTS: Data of 3,732 days of consultation were collected in which a total of 144,608 patients were attended. Of these, 20,614 had respiratory infections and 11,684 extrarespiratory infections. The most frequent processes were pharyngitis (33.7%), common cold (31.7%) followed by bronchitis (18.7%), otitis (11%), influenza (4.6%), laryngitis (4%), sinusitis (3.6%) and pneumonia (1.8%). Antibiotic treatment was prescribed in 13,488 patients (65%). The type of antibiotic was analyzed in the 11,977 patients treated for only one infection. Penicillins were the antibiotics most used followed by cephalosporins. The antibiotic prescribed was considered adequate in 70% of the 8,484 patients treated for potentially bacterial infection. A total of 3,493 patients had infection considered to be of viral etiology. CONCLUSIONS: Twenty-two percent of the patients attending a primary health care center presented infection and of these two out of three cases had respiratory infection. Pharyngitis and common cold were the most frequent processes observed. Two thirds of the patients consulting for respiratory infection received antibiotic treatment, with 29.2% being diagnosed with infections considered to be of viral etiology. The empiric treatment chosen for the two thirds of the potentially bacterial infections was considered as adequate.