The importance of prevalence and pre-test probability on the microbiological diagnosis of SARS-CoV-2: the case of Spain in 2020.

OBJECTIVE: The aim of this work was to estimate the conditioned probability for the diagnosis of SARS-CoV-2 infection with reverse transcription polymerase chain reaction (RT-PCR), viral antigen rapid diagnostic tests (Ag-RDT), and antibody detection tests depending on the prevalence in the specific healthcare settings in Spain in 2020, and on the pre-test probability (PTP) according to the clinical situation, age and unknown or close contacts of the patient. METHODS: Performance parameters of tests were obtained from literature. Prevalence data and PTP were obtained from Spanish sources and a survey, respectively. The post-test probability is the positive predictive value (PPV) when test is positive. For negative result, we also calculated the probability of having the infection (false negatives). RESULTS: For both RT-PCR and viral Ag-RDT, the lowest PPV values were for the population screenings. This strategy proved to be useful in ruling out infection but generates a high number of false positives. At individual level, both tools provided high PPV (≥ 97%) when the PTP values are over 35%. In seroprevalence studies, though the specificity of IgG alone tests is high, under low seroprevalence, false positives cannot be avoided. Total antibodies tests are useful for diagnosis of COVID-19 in those doubtful cases with RT-PCR or Ag-RDT tests being repeatedly negative. CONCLUSIONS: The interpretating of results depends not only on the accuracy of the test, but also on the prevalence of the infection in different settings, and the PTP associated to the patient before performing the test.

Antimicrobial resistance in Gram-negative bacilli in Spain: an experts' view.

BACKGROUND: Antibiotic resistance in Gram-negative bacilli poses a serious problem for public health. In hospitals, in addition to high mortality rates, the emergence and spread of resistance to practically all antibiotics restricts therapeutic options against serious and frequent infections. OBJECTIVE: The aim of this work is to present the views of a group of experts on the following aspects regarding resistance to antimicrobial agents in Gram-negative bacilli: 1) the current epidemiology in Spain, 2) how it is related to local clinical practice and 3) new therapies in this area, based on currently available evidence. METHODS: After reviewing the most noteworthy evidence, the most relevant data on these three aspects were presented at a national meeting to 99 experts in infectious diseases, clinical microbiology, internal medicine, intensive care medicine, anaesthesiology and hospital pharmacy. RESULTS AND CONCLUSIONS: Subsequent local debates among these experts led to conclusions in this matter, including the opinion that the approval of new antibiotics makes it necessary to train the specialists involved in order to optimise how they use them and improve health outcomes; microbiology laboratories in hospitals must be available throughout a continuous timetable; all antibiotics must be available when needed and it is necessary to learn to use them correctly; and the Antimicrobial Stewardship Programs (ASP) play a key role in quickly allocating the new antibiotics within the guidelines and ensure appropriate use of them.

Value of syndromic panels in the management of severe community-acquired pneumonia.

Community-acquired pneumonia requiring hospital admission is a prevalent and potentially serious infection, especially in high-risk patients (e.g., those requiring ICU admission or immunocompromised). International guidelines recommend early aetiological diagnosis to improve prognosis and reduce mortality. Syndromic panels that detect causative pathogens by molecular methods are here to stay. They are highly sensitive and specific for detecting the targets included in the test. A growing number of studies measuring their clinical impact have observed increased treatment appropriateness and decreased turnaround time to aetiological diagnosis, need for admission, length of hospital stay, days of isolation, adverse effects of medication and hospital costs. Its use is recommended a) per a pre-established protocol on making the diagnosis and managing the patient, b) together with an antimicrobial stewardship programme involving both the Microbiology Service and the clinicians responsible for the patient, and c) the final evaluation of the whole process. However, we recall that microbiological diagnosis with traditional methods remains mandatory due to the possibility that the aetiological agent is not included among the molecular targets and to determine the antimicrobial susceptibility of the pathogens detected.

Deciphering pharmacokinetics and pharmacodynamics of fosfomycin.

Fosfomycin, a low molecular weight and hydrophilic drug with negligible protein binding, is eliminated almost exclusively by glomerular filtration, whose clearance is subject to patient renal function. The volume of distribution approximates to the extracellular body water (about 0.3 L/Kg) in healthy volunteers, but it is increased in critically ill patients with bacterial infections. Fosfomycin presents a high ability to distribute into many tissues, including inflamed tissues and abscess fluids. Based on PK/PD analysis and Monte Carlo simulations, we have evaluated different fosfomycin dosing regimen to optimize the treatment of septic patients due to Enterobacterales and Pseudomonas aeruginosa. As PK/PD targets, we selected %T>MIC > 70% for all pathogens, and AUC24/MIC > 24 and AUC24/MIC > 15 for net stasis of Enterobacterales and P. aeruginosa, respectively. Pharmacokinetic parameters in critically ill patients were obtained from the literature. Several dosing regimens were studied in patients with normal renal function: fosfomycin 2-8 g given every 6-12 hours, infused over 30 minutes- 24 hours. At the susceptibility EUCAST breakpoint for Enterobacterales and Staphylococcus spp. (MIC ≤ 32 mg/L), fosfomycin 4 g/8h or higher infused over 30 minutes achieved a probability of target attainment (PTA) > 90%, based in both %T>MIC and AUC24/MIC. For MIC of 64 mg/L, fosfomycin 6 g/6h in 30-minute infusion and 8 g/ 8h in 30-minute and 6 hours infusions also achieved PTA values higher than 90%. No fosfomycin monotherapy regimen was able to achieve PK/PD targets related to antimicrobial efficacy for P. aeruginosa with MICs of 256-512 mg/L.

Application of pharmacokinetic/pharmacodynamic analysis to evaluate the adequacy of antimicrobial therapy for pediatric acute otitis media in Spain before and after the introduction of the PCV7 vaccine.

OBJECTIVE: To evaluate, by applying pharmacokinetic/pharmacodynamic (PK/PD) analysis, if the change in antibiotic susceptibility after the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in Spain had any influence on the usefulness of the antimicrobials more frequently used as empirical treatment of pediatric acute otitis media (AOM). METHODS: PK parameters and susceptibility of Streptococcus pneumoniae and Haemophilus influenzae were obtained from bibliography. Monte Carlo simulation was used to estimate the cumulative fraction of response (CFR), understood as the expected probability of therapy success. For amoxicillin and amoxicillin/clavulanate, the target was free antibiotic concentration remaining above the minimum inhibitory concentration (MIC) for ≥50% of the dosing interval (fT>MIC≥50%), whereas for cefuroxime axetil and cefotaxime, the target was fT>MIC≥60%. CFR values ≥90% were considered successful. RESULTS: When all serotypes of S. pneumoniae are considered, amoxicillin and cefotaxime turned out to reach a high probability of success, and difference before and after vaccination was scarce. For H. influenzae, CFR values were higher with amoxicillin/clavulanate than with amoxicillin. For both microorganisms, cefuroxime axetil resulted in low probability of success in the two periods of study. CONCLUSIONS: We have shown that the introduction of the PCV7 vaccination did not lead to changes in the probability of success of the current empiric treatments of the AOM. Integrated PK/PD analysis has demonstrated to be a useful tool to identify changes in antimicrobial activity after the implantation of a vaccination program, providing complementary information to the simple assessment of MIC values.

Accuracy of the BD MAX™ vaginal panel in the diagnosis of infectious vaginitis.

The aim of this study was to evaluate the BD MAX™ vaginal panel in the diagnosis of bacterial vaginosis (BV), vulvovaginal candidiasis (VVC), and trichomoniasis by comparing it with conventional methods: (i) combination of Hay criteria and presence of clue cells with predominant growth of Gardnerella vaginalis, (ii) yeast culture, and (iii) combination of culture, wet mount microscopic examination, and an alternative molecular assay. One thousand vaginal samples of women ≥ 14 years were analyzed; 5% of the samples belonged to pregnant women. 19.3% were classified as BV, in 33.6% yeasts were recovered and in 1.5% TV was detected. For BV, sensitivity and specificity were of 89.8% and 96.5%, respectively; for VVC, sensitivity and specificity were of 97.4% and 96.8%, respectively, and for T. vaginalis, the sensitivity and specificity were of 100%. The BD MAX™ vaginal panel is highly sensitive and specific and simplifies the identification of infectious vaginitis.

[Evolution of antimicrobial use during the years 1996-2000 in a general hospital. A detailed ICU study]. / Evolución de la utilización de antimicrobianos durante los años 1996-2000 en un hospital general. Estudio pormenorizado de la UCI.

PURPOSE: Antimicrobials are a mayor part of hospital pharmacy budgets and must be considered in resource planning and spending projections. This study describes the profile of antibiotic use at a medium-sized hospital (by examining the ICU separately) and analyses its evolution over the period 1996-2000. METHODS: Descriptive and retrospective study. Pharmacy records were reviewed to identify oral and parenteral antimicrobial agents administered to inpatients. Results were expressed in Daily Defined Doses (DDD) per 100 stays and day. RESULTS: During the five-year study period 176.162 DDD / 100 s-d of antibiotics were consumed in the ICU, whereas in the rest of the hospital usage was much lower (54.540 DDD / 100 s-d). Aminoglycosides, cephalosporins, penicillins, glycopeptides and carbapenems were the most commonly used groups of antimicrobials in the ICU, and penicillins, cephalosporins, trimethoprim/sulfonamide combinations, aminoglycosides and quinolones in the rest of the hospital. CONCLUSIONS: ICUs have some special features which make them different to the rest of inpatient areas. Because of that fact we consider important to study this specific patient-care area separately.

[Familial outbreaks of fascioliasis: usefulness of serologic investigation by enzyme immunoassay]. / Brotes familiares de fascioliasis: utilidad del estudio serológico por enzimoinmunoanálisis.

BACKGROUND: To assess the usefulness of an enzyme immuno-assay test for the diagnosis of two familial outbreaks of Fasciola hepatica parasitosis in the Zamora area, where watercress are a normal part of the diet. PATIENTS AND METHODS: The microbiological diagnosis of two familial outbreaks of fascioliasis was analyzed, which included the search for eggs in feces by the Kato technique and two serologic tests, one screening test by indirect hemagglutination, and a confirmatory test by enzyme-immunoassay in 12 patients. RESULTS: Five out of the six seropositive patients had eggs detected in their feces. To note that two of the patients with eosinophilia that excreted eggs--one asymptomatic and the other with abdominal pain--had a positive result in the EIA test only and with high titers. CONCLUSIONS: The EIA test is useful for the diagnosis and study of fascioliasis outbreaks to interpret the significance of low titers in the screening test in patients with eosinophilia.

Seasonal prevalences of Cryptosporidium and Giardia infections in children attending day care centres in Salamanca (Spain) studied for a period of 15 months.

Five studies were carried out in children younger than 4 years old attending regularly day care centres in order to determine the intestinal parasitization by Cryptosporidium and Giardia. The percent of children parasitized by Cryptosporidium was 10% (17 children out of 170 studied). Cryptosporidiosis was more frequent in winter than in other seasons (difference statistically significant). Giardia intestinalis, which was the most frequent parasite, was identified in 25.3% (43 children out of 170 studied). Giardiasis was more frequent in autumn and in the low SEL (difference statistically significant in both cases). The frequency of giardiasis increased from 8% in children studied during 1-2 seasons, to 34% in children studied for 3-5 seasons (difference statistically significant), whereas the frequency of cryptosporidiosis did not show variation with increased number of specimens studied per child. The 35% of children parasitized by Cryptosporidium sp. showed gastrointestinal symptoms but only 14% of children with Giardia intestinalis.

[Epidemiology and diagnosis of Cryptosporidium spp. parasitosis in children: usefulness of the serologic study]. / Epidemiología y diagnóstico de la parasitación por Cryptosporidium spp. en niños: utilidad del estudio serológico.

BACKGROUND: Evaluate the contribution of the serological study of Cryptosporidium spp. for more precise knowledge of the epidemiology of this parasitation within a child population and its usefulness in laboratory diagnosis of cryptosporidiasis. METHODS: Using a prospective study design, the presence of antibodies for Cryptosporidium spp. was determined by indirect immunofluorescence in sera of 106 children, aged 0-13 years in the province of Salamanca. RESULTS: The seroprevalence of IgG against Cryptosporidium spp. n the child population was 22.6% (24/106). 20.8% of the children seropositive for IgG (5/24) also presented with specific IgM. In a newborn, IgG (12.5%; 1 out of 8 newborns) was detected but IgM not found. The seroprevalence of IgG in rural areas was 18.2% (10/55) and the average in urban areas was 27.4% (14/51). In both instances, the age group with the highest seroprevalence corresponded to that of 2-3 year olds. CONCLUSIONS: The rate of seroprevalence of Cryptosporidium spp. in the child population of Salamanca is appreciably higher than the prevalence detected in feces. Recent infection can manifest itself with simultaneous seropositivity of IgG and IgM. This serological pattern, in the presence of a clinical framework compatible with the detection of oocysts in feces, can complement the diagnosis of cryptosporidiasis.

Cryptosporidium oocysts in water for human consumption. Comparison of staining methods.

A study was carried out on the presence of oocysts of Cryptosporidium spp. in water for human consumption in the Province of Salamanca, Spain, using four different staining techniques: Ziehl-Neelsen, auramine, indirect immunofluorescence with monoclonal antibodies (Meridian, USA) and direct immunofluorescence with monoclonal antibodies (Pasteur, France). The presence of oocysts was detected in the water used for the washing of sand filters in the four water purifying plants and in the drinking water of two of the six geographical areas studied. The Ziehl-Neelsen and auramine staining techniques were found to have excellent diagnostic correlation. Immunofluorescence stainings with monoclonal antibodies proved to be less sensitive.