Measurement of Klebsiella Intestinal Colonization Density To Assess Infection Risk

Colonization by bacterial pathogens often precedes infection and offers a window of opportunity to prevent these infections in the first place. Klebsiella colonization is significantly and reproducibly associated with subsequent infection; however, factors that enhance or mitigate this risk in individual patients are unclear. This study developed an assay to measure the density of Klebsiella colonization, relative to total fecal bacteria, in rectal swabs from hospitalized patients.

Affinity of Staphylococcus aureus for prostheses colonization compared to other bacteria. An in vitro study

Staphylococcus aureus biofilms have been recognized as a leading cause of multiple infections, including implant-associated infections and chronic wounds. We evaluated the colonization capacity of two distinct textured prostheses by different bacterial strains. Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Proteus mirabilis and Enterococcus faecalis were evaluated. Initially, the hydrophobicity and biofilm formation capacity were determined. Subsequently, 20 fragments of vascular prosthesis and 20 silicone prostheses were embedded in suspensions with the microorganisms and incubated. The prostheses were then sown in culture medium and incubated for 48 hours. Petri dishes were photographed and analyzed by fractal dimension. The Kruskal-Wallis test and the Dunn test were applied for the analysis of biofilm formation. To compare the mean intensity for the type of bacteria and the type of prosthesis, a general linear model was applied. Staphylococcus aureus was the bacterium with the highest colonization density in both prostheses (p = 0.0001). E. coli showed strong adherence in the biofilm formation capacity test (p = 0.0001), however, it did not colonize either prosthesis. We demonstrated that Staphylococcus aureus has a greater affinity for vascular and silicone prostheses than other bacteria.

Measurement of Klebsiella Intestinal Colonization Density to Assess Infection Risk

BackgroundKlebsiella pneumoniae and closely related species K. variicola and K. quasipneumoniae are common causes of healthcare-associated infections, and patients frequently become infected with their intestinal colonizing strain. To assess the association between Klebsiella colonization density and subsequent infections, a case-control study was performed.MethodsA multiplex qPCR assay was developed and validated to quantify Klebsiella (K. pneumoniae, K. variicola, and K. quasipneumoniae combined) relative to total bacterial DNA copies in rectal swabs. Cases of Klebsiella infection were identified based on clinical definitions and having a clinical culture isolate and preceding or co-incident colonization isolate with the same wzi capsular sequence type. Controls were colonized patients without subsequent infection and were matched 2:1 to cases based on age, sex, and rectal swab collection date. Quantitative PCR (qPCR) from rectal swab samples was used to measure the association between relative abundance (RA) of Klebsiella and subsequent infections.ResultsKlebsiella RA by qPCR highly correlated with 16S sequencing (ρ=0.79; P <.001). The median Klebsiella RA in the study group was 2.6% (interquartile range (IQR) 0.1-22.5, n=238), and was higher in cases (15.7%, IQR 0.93-52.6%, n=83) than controls (1.01%, IQR 0.02-12.8%; n=155; P <0.0001). After adjusting for multiple clinical covariates using inverse probability of treatment weighting, subjects with a Klebsiella RA > 22% had a 2.87-fold (1.64-5.03, P =0.0003) increased odds of infection compared to those with lower colonization density levels.ConclusionsMeasurement of colonization density by qPCR could represent a novel approach to identify hospitalized patients at risk for Klebsiella infection.ImportanceColonization by bacterial pathogens often precedes infection, and offers a window of opportunity to prevent these infections. Klebsiella colonization is significantly and reproducibly associated with subsequent infection, however factors that enhance or mitigate this risk in individual patients are unclear. This study developed an assay to measure the density of Klebsiella colonization, relative to total fecal bacteria, in rectal swabs from hospitalized patients. Applying this assay to 238 colonized patients, high Klebsiella density defined as >22% of total bacteria, was significantly associated with subsequent infection. Based on widely available polymerase chain reaction (PCR) technology, this type of assay could be deployed in clinical laboratories to identify patients at increased risk of Klebsiella infections. As novel therapeutics are developed to eliminate pathogens from the gut microbiome, a rapid Klebsiella colonization density assay could identify patients who would benefit from this type of infection prevention interventions.

2617. Increased Nasopharyngeal Pneumococcal Density During Asymptomatic Respiratory Virus Infection Is Associated with Subsequent Development of Acute Respiratory Illness

Background Increased density of nasopharyngeal (NP) pneumococcal colonization has been associated with invasive pneumococcal disease in children. However, factors that lead to increased pneumococcal density are poorly understood. We sought to determine whether viral detection during asymptomatic periods in young children was associated with increased NP pneumococcal density and the subsequent development of acute respiratory illness (ARI). Methods Using NP samples obtained during asymptomatic periods from children less than 3 years of age in the rural Peruvian Andes, we determined NP pneumococcal colonization density by quantitative polymerase chain reaction (qPCR) and identified respiratory viruses by RT–PCR. We examined the association between viral detection and pneumococcal density adjusting for relevant covariates using a multivariable quantile mixed effects regression model. We also assessed the association of pneumococcal density during asymptomatic periods in these children on the time to the next ARI using survival analysis. Results During asymptomatic periods, the presence of NP pneumococcal colonization was more common when respiratory viruses were detected. In addition, in the multivariable model, log10-transformed pneumococcal densities were significantly higher during asymptomatic periods when viruses were detected [median 4.52 (4.14, 5.01) P < 0.001], specifically human rhinovirus (HRV) [median 4.58 (4.27, 5.12), P < 0.001] and adenovirus (AdV) [median 4.21 (3.79, 4.91), P = 0.014], compared with when no virus was detected [median 3.16 (2.92, 3.73), Figure 1]. Increased pneumococcal density was also significantly associated with a higher rate of subsequent ARI (p = 0.008, Figure 2). Conclusion Among young children, detection of respiratory viruses during asymptomatic periods was associated with increased pneumococcal colonization density, which, in turn, was associated with higher rate of subsequent ARI. Disclosures All authors: No reported disclosures.

Association of Laboratory Methods, Colonization Density, and Age With Detection of Streptococcus pneumoniae in the Nasopharynx

Culture-based methods for detecting Streptococcus pneumoniae in the nasopharynx lack sensitivity. In this study, we aimed to compare the performance of culture and molecular methods in detecting pneumococcus in the nasopharynx of healthy individuals and to evaluate the associations of age and colonization density with detection. Between 2010 and 2012, nasopharyngeal specimens were collected from healthy individuals living on Navajo Nation and White Mountain Apache Tribal lands in the United States. Pneumococci were detected by means of broth-enrichment culture and autolysin-encoding gene (lytA) quantitative polymerase chain reaction (qPCR). Among 982 persons evaluated (median age, 18.7 years; 47% male), 35% were culture-positive and an additional 27% were qPCR-positive. Agreement between culture and qPCR was 70.9% but was higher among children (age &lt;18 years) (75.9%–84.4%) than among adults (age ≥18 years) (61.0%–74.6%). The mean density of colonization was lower for culture-negative samples (3.14 log10 copies/mL) than for culture-positive samples (5.02 log10 copies/mL), overall and for all age groups. The percent culture-positive increased with increasing density, exceeding 80% at densities of ≥10,000 copies/mL. Mean colonization density decreased with age. Use of qPCR improved detection of pneumococcus in the nasopharynx of healthy individuals. This finding was most notable among adults, probably because of improved detection of low-density colonization.

Rational antibiotic therapy in treatment of bacterial tonsillitis in children

On the part of tonsillitis every second child suffers, and chronization of the infectious process leads to a number of complications from the organs and systems. Peritonsillar abscesses, tonsillitis sepsis, arthritis, vasculitis, rheumatism and heart disease all of these are the consequence of defective tonsillitis. There fore, the approach to the treatment of inflammations of palatine tonsils should be comprehensive and based on the results of continuous monitoring of microbial flora with a clear definition of the spectrum of its sensitivity to antibacterial agents. Purpose — improvement of antibiotic therapy of acute bacterial tonsillitis in children, based on the results of antibioticograms. The bacteriological method was used for the study, the seeds were culled quantitatively on 5% blood meat peptone agar and dense Saburo agar. Determination of the sensitivity of isolated microorganisms' cultures to antibacterial preparations was carried out by disc diffusion method. The examined contingent was made up of 75 children aged 1 to 17 years old who were on treatment with a diagnosis of acute tonsillitis in VRCCIH. Gr. (+) bacterial microflora was represented by coca flora with a high density of colonization: S.pyogenes (in 100% of children) — (4.16±0.07) Ig CFU/ml, S.salivarius (at 24.0%) — (2.96±0.12) Ig CFU / ml, S.epidermidis (62.6%) — (2.27±0.09) Ig CFU / ml, S.aureus (91.0%) — (3.38±0.11) Ig CFU / ml and Enterococcus spp. (42.6%) — (4.17±0.32) Ig CFU / ml. Among the microbial flora of Gr. (–), K.pneumoniae (in 65.3% of patients) with colonization ability (4.61±0.43) Ig CFU /ml, P.aeruginosa (in 20.0%) — (5,53±0.13) Ig CFU/ml, Alcaligenes spp. (24.0%) — (4.71±0.25) Ig CFU/ml, E.coli (at 65.3%) — (5,13±0.22) Ig CFU/ml, E.coli (69.3%) — (4.35±0.15) Ig CFU/ml. The isolated microflora was characterized by a low spectrum of sensitivity to antibacterial agents. So, S.pyogenes and Enterococcus spp. were sensitive to ceftriaxone (83.5% and 89.9% respectively), and S.aureus to oxacillin (84.0%), whereas S.pyogenes was resistant to 92.3%. Resistant S.aureus and Enterococcus spp. to the reserve cefepime (96.2% and 58.6% respectively) to which P.aeruginosa and Alcaligenes spp. were sensitive (79.3% and 78.2% respectively). Resistant to the latter were up to azithromycin in 95.1% and 91.3% of cases. E.coli, E.coli and K.pneumoniae were almost equally resistant to clarithromycin, showing high susceptibility to reserve vancomycin. Thus, in a microbiological study all children in the smears showed β-hemolytic streptococcus represented by S.pyogenes with high colonization density (4.16±0.07) Ig CFC / ml and in 91.0% of children S.aureus was isolated from colonization capacity (3.38 ± 0.11) Ig CFU / ml. Bacteria of the genus Alkaligenes were sown in 18 diseased children (24.0%), and 15 children (20.0%) isolated Pseudomonas aeruginosa. Conditionally pathogenic E.coli, E.cloacae and K.pneumoniae cultivated in more than 60.0% of cases and were characterized by high pathogenic activity. According to the results of the antibioticograms S.pyogenes and Enterococcus spp. were sensitive to ceftriaxone and resistant to cefepime. Gr.( –) flora, on the contrary, reacted to the reserve cefepimum, while exhibiting high resistance to the macrolide.

Nasopharyngeal Pneumococcal Density Is Associated With Viral Activity but Not With Use of Improved Stoves Among Young Andean Children

Background Indoor smoke exposure is common in developing countries and may influence nasopharyngeal (NP) pneumococcal colonization density and risk of acute respiratory illness. We compared colonization density among Andean children living in households previously enrolled in a randomized controlled trial of a home intervention package including improved stoves to reduce smoke, kitchen sinks, and water disinfection. Methods We enrolled 260 children aged &lt;3 years and made weekly household visits to assess for acute respiratory illness (ARI) and collect nasal swabs for respiratory virus polymerase chain reaction (PCR) testing during ARI. At monthly intervals, NP swabs were collected to determine pneumococcal colonization density through quantitative lytA PCR. We used linear quantile mixed-effects models to compare median log-transformed colonization densities among children in households randomized to the control (n = 129) versus intervention (n = 131) in sequential time points, accounting for random effects of multiple samples from individual children. Other covariates included age, sex, month, antibiotic exposure, and timing of sample collection relative to ARI with and without viral detection. Results Age and sociodemographic characteristics were similar between groups. Although no differences were observed in densities between groups, colonization density varied significantly over time in both groups, with highest densities coinciding with spring months. Time during and after virus-associated ARI was also associated with higher pneumococcal colonization density than time remote from ARIs. Conclusions A home intervention package, including improved stoves, was not associated with changes in pneumococcal densities in young Andean children. However, increasing pneumococcal density was observed with spring season and viral-associated ARIs.

Reproduction of Walnut Twig Beetle in Black Walnut and Butternut

The walnut twig beetle [WTB (Pityophthorus juglandis Blackman)] is the primary insect vector for a pathogen that causes thousand cankers disease (TCD), a disease complex that leads to mortality in species of walnut (Juglans L.). We performed field and laboratory trials to determine if reproduction by WTB varies between two black walnut (Juglans nigra L.) parent trees of a full-sib mapping population of 323 offspring, and between black walnut and butternut (Juglans cinerea L.). These two tree species are native to eastern North America. In field trials, we found no significant differences in colonization density or mean number of adult offspring per female among branch sections from black walnut parent trees or among branch sections from black walnut and butternut, respectively. In laboratory trials with controlled colonization densities of WTB, we found that significantly fewer adult offspring developed in branch sections of the black walnut maternal ‘Sparrow’ parent than the paternal ‘Schessler’ parent over three summer months and one winter month. In the field, high colonization densities likely limited reproduction due to increased intraspecific competition beneath the bark. In the laboratory, where we established a lower colonization density, reproduction was likely influenced by differences in host quality. In laboratory trials, no differences were detected in the number of adult offspring emerging from black walnut and butternut accessions. This finding suggests that butternut is a suitable host for WTB. Future screening of the full-sib mapping population of 323 offspring of black walnut parent trees for WTB resistance is a warranted next step in developing alternative management strategies for TCD in black walnut.