Bayesian evaluation of sensitivity and specificity of blood culture media and hypoglycemia in sepsis-suspected calves

BACKGROUND

Sepsis is a life-threatening condition for which critically important antimicrobials are often indicated. The value of blood culture for sepsis is indisputable, but appropriate guidelines on sampling and interpretation are currently lacking in cattle.

OBJECTIVE

Compare the diagnostic accuracy of 2 blood culture media (pediatric plus [PP] and plus aerobic [PA]) and hypoglycemia for bacteremia detection. Estimate the contamination risk of blood cultures in critically ill calves.

ANIMALS

One hundred twenty-six critically ill calves, 0 to 114 days.

METHODS

Retrospective cross-sectional study in which the performance of PP, PA and hypoglycemia to diagnose sepsis was assessed using a Bayesian latent class model. A Cox proportional hazards model was used to compare time to positivity (TTP). Potential contamination was descriptively analyzed. Isolates were considered relevant when they were; member of the Enterobacterales, isolated from both blood cultures vials, or well-known, significant bovine pathogens.

RESULTS

The sensitivities for PP, PA, and hypoglycemia were higher when excluding assumed contaminants; 68.7% (95% credibility interval = 30.5%-93.7%), 87.5% (47.0%-99.5%), and 61.3% (49.7%-72.4%), respectively. Specificity was estimated at 95.1% (82.2%-99.7%), 94.2% (80.7%-99.7%), and 72.4% (64.6%-79.6%), respectively. Out of 121 interpretable samples, 14.9% grew a presumed contaminant in PA, PP, or both. There was no significant difference in the TTP between PA and PP.

CONCLUSIONS AND CLINICAL IMPORTANCE

PA and PP appear to outperform hypoglycemia as diagnostic tests for sepsis. PA seems most sensitive, but a larger sample size is required to verify this. Accuracy increased greatly after excluding assumed contaminants. The type of culture did not influence TTP or the contamination rate.

by Improving Conventional Diagnostic Tools

Mixed infections by different Trypanosoma species or genotypes are a common and puzzling phenomenon. Therefore, it is critical to refine the diagnostic techniques and to understand to what extent these methods detect trypanosomes. We aimed to develop an accessible strategy to enhance the sensitivity of the hemoculture, as well as to understand the limitations of the hemoculture and the blood clot as a source of parasitic DNA. We investigated trypanosomatid infections in 472 bats by molecular characterization (18S rDNA gene) of the DNA obtained from the blood clot and, innovatively, from three hemoculture sample types: the amplified flagellates ("isolate"), the pellet of the culture harvested in its very initial growth stage ("first aliquot"), and the pellet of non-grown cultures with failure of amplification ("sediment"). We compared (a) the characterization of the flagellates obtained by first aliquots and isolates; and (b) the performance of the hemoculture and blood clot for trypanosomatid detection. We observed: (i) a putative new species of Bodo in Artibeus lituratus; (ii) the potential of Trypanosoma cruzi selection in the hemoculture; (iii) that the first aliquots and sediments overcome the selective pressure of the hemoculture; and (iv) that the blood clot technique performs better than the hemoculture. However, combining these methods enhances the detection of single and mixed infections.

Bloodstream infection in hospital therapeutic patients

Bloodstream infection (BI) is the cause of high mortality. Hospital bloodstream infection (HBI) complicates hemodialysis, pneumonia, oncohematological diseases. Positive hemoculture obtaining depends on the volume of blood inoculation, the number of blood samples, the incubation time. To test the principles of microbiological culturomics in the diagnosis BI of hospital patients with a therapeutic profile. 848 hospital cardiac patients with suspected BI were included. 10 ml of blood were taken intravenously with a syringe, blood was inoculated into 200 ml of the heart-brain medium (HBM) in an anaerobic bottle. It was incubated for 7 or more days in a thermostat at +37º C. The hemocultures were obtained in 64.3% of cases with paired blood sampling with an interval of 30 minutes whereas an increase in the number of blood samples reduced the effectiveness of obtaining hemocultures to 9.1%. When incubating bottles for more than 7 days there were obtained 200 additional hemocultures containing 239 strains of microorganisms. Episodes of HBI were observed more often in the cases of the circulatory system (77.8%), including infectious endocarditis (IE) (47.0%), rheumatism (22.1%), myocarditis (14.6%). Episodes of HBI occurred more often in men with IE and coronary heart disease, in women - with rheumatism and myocarditis. Patients aged 45-75 were in the group of risk with a probability of complications of HBI up to 73.7%. When examining the blood of 848 hospital patients of cardiological profile HBI was detected in 38.3% of cases. Among clinical isolates gram-positive cocci with a great number S.epidermidis prevailed. Polymicrobial hemocultures (16.3%) were characterized by two and three associates in one blood sample. Among the hematological indicators in HBI there were: leukocytosis, increased ESR, lymphocytosis, decreased hemoglobin; increased values of fibrinogen, CRP, γ-globulin, α2-globulin, low levels of total protein and A/G coefficient. The techniques of microbiological culturomics were used. HBI was diagnosed in 38.3% of the therapeutic patients of cardiological profile. The etiology of HBI was characterized by polymicrobicity in 16.3% of cases. Hematological markers of HBI were identified.

Defining System Requirements for Simplified Blood Culture to Enable Widespread Use in Resource-Limited Settings

Bacterial blood stream infections (BSI) are a common cause of mortality and morbidity globally. As the causative agents and the resulting treatment decisions vary, near-patient testing and surveillance tools are necessary to monitor bacterial causes and resistance to antimicrobial agents. The gold standard to identify BSIs is blood culture (BC), a methodology not widely available in resource-limited settings. The aim of the study was to map out a target product profile of a simplified BC system (SBCS) to inform product development efforts. To identify the desired characteristics of a SBCS, we enlisted a small group of specialists working in Africa and Asia. Questions were used to understand challenges and how these constraints inform system requirements. The specialists were infectious disease physicians, public health/clinical microbiologists, clinical researchers, and technology experts with different geographical backgrounds. All suggested that BC should ideally be available at the district hospital level. Many of the same operational challenges, such as limited availability of culture bottles, electricity and internet connectivity, profuse dust, the lack of ambient temperature control, and human capacity constraints were identified across the different regions. BCs, although the accepted gold standard for diagnosis of BSIs, are not widely available outside of reference/research centers in Africa and Asia. To extend the reach of this important tool, it is crucial to engage product developers and academic research partners to develop accessible alternatives.

Infective endocarditis caused by Lactococcus lactis subsp. lactis and Pediococcus pentosaceus: A case report and literature review

RATIONALE

Lactococcus lactis and Pediococcus pentosaceus are rare pathogens which rarely caused infections in humans. Several cases with L. lactis endocarditis have been reported in the literature, among them few were caused by L. lactis subsp. Lactis. Opportunistic P. pentosaceus infections were rarely reported.

PATIENT CONCERNS

A 66-year-old man presented to our hospital due to persistent fever for 15 days. A physical checking revealed a grade II holosystolic murmur at the heart apex. A chest computed tomography (CT) scan suggested bronchitis. L. lactis subsp. lactis was identified in blood cultures. Transthoracic and transesophageal echocardiography revealed the presence of a large hyperechogenic mass in the left atrium, and a large floating vegetation on the mitral valve with a severe mitral regurgitation.

DIAGNOSIS

Infectious endocarditis caused by L. lactis subsp. Lactis was diagnosed.

INTERVENTIONS

Levofloxacin (0.5 g/day) was used for 20 days; however, L. lactis subsp. lactis remained to be isolated from blood culture. Therefore, vancomycin (2 g/day) was used to replace levofloxacin. Six days after the treatment with vancomycin, the blood culture revealed no L. lactis subspecies lactis, but yielded a growth of gram-positive and non-spore forming cocci; and P. pentosaceus was identified. Antimicrobial susceptibility test revealed P. pentosaceus was sensitive to penicillin and levofloxacin. Vancomycin was discontinued, and levofloxacin (0.5 g/day) was restarted and treated for another 7 days. The patient recovered with negative blood culture results, and discharged from the hospital.

OUTCOMES

The patient recovered with negative blood culture results, and discharged from the hospital.

LESSONS

Our patient had a long-period of antibiotic treatment with strategy alterations. Standard interpretation criteria of Clinical and Laboratory Standards Institute (CLSI) for L. lactis should be established, and molecular tests will increase the identification rate of L. lactis infections.

Coagulase-Negative Staphylococci Isolated from Human Bloodstream Infections Showed Multidrug Resistance Profile

Coagulase-negative staphylococci (CNS) are important pathogens causing nosocomial infections worldwide with increasing resistance to antimicrobials. The aim of this study was to characterize resistance aspects of CNS isolated from patients with bloodstream infections acquired in hospitals in Belo Horizonte, MG, Brazil. Staphylococcus strains were characterized using repetitive sequence-based polymerase chain reaction (rep-PCR) fingerprinting with (GTG)₅ primer. Phenotypic resistance was analyzed using AST-P5085 card (bioMérieuxVitek^®). PCR was used to detect mecA, vanA, blaZ, ermA/B/C, aac-aphD, and SCC-mec. For statistical analyses, we used hierarchical cluster, chi-square test (χ²), and correspondence. Several clusters were formed within the same species using (GTG)₅ primer, and strains showed resistance to the following antimicrobials: benzylpenicillin (100%); oxacillin (93.1%); gentamicin (36.3%); ciprofloxacin (63.7%); moxifloxacin (32.7%); norfloxacin (81.0%); erythromycin (86.2%); clindamycin (75.8%); linezolid, teicoplanin and vancomycin (1.7%); tigecycline (0%); fusidic acid (10.35%); rifampicin (13.7%); and trimethoprim/sulfamethoxazole (46.5%). Regarding genotypic analyses, 40%, 0%, 78%, 42%, 100%, 24%, and 30% were positive for mecA, vanA, blaZ, ermA, ermB, ermC, and aac-aphD, respectively. Regarding staphylococcal cassette mec (SCCmec) type, 3.4% presented type I; 5.0% type II; 27.1% type III; 20.3% type IIIA; and 32.2% type IIIB. Six clusters were formed and frequency distributions of resistant strains to oxacillin, gentamicin, ciprofloxacin, moxifloxacin, norfloxacin, erythromycin, clindamycin, linezolid, teicoplanin, vancomycin, fusidic acid, rifampicin, and trimethoprim/sulfamethoxazole, and mecA, blaZ, ermC, aac-aphD, and SCCmec type differed (p < 0.001). In conclusion, the strains investigated in this study were multidrug resistant and carried multiple antibiotic resistance genes.

Survival and Growth of Orientia tsutsugamushi in Conventional Hemocultures

Orientia tsutsugamushi, which requires specialized facilities for culture, is a substantial cause of disease in Asia. We demonstrate that O. tsutsugamushi numbers increased for up to 5 days in conventional hemocultures. Performing such a culture step before molecular testing could increase the sensitivity of O. tsutsugamushi molecular diagnosis.

Evolution of infection in mice inoculated by the oral route with different developmental forms of Trypanosoma cruzi I and II

Oral infection has become the most important transmission mechanism of Chagas disease in Brazil. For this study, the development of Trypanosoma cruzi infection in mice, induced by the oral and intraperitoneal (IP) routes, was compared. Four groups of Swiss mice were used to evaluate the influence of parasite genetics, number of parasites, inoculation volume and developmental stages on the development of the orally induced infection: 1 - blood trypomastigotes (BT) via oral; 2 - BT via IP; 3 - culture metacyclic trypomastigotes (MT) via oral; and 4 - culture MT via IP. Animals inoculated orally showed levels of parasitemia, as well as infectivity and mortality rates, lower than animals inoculated via IP, regardless of DTU (discrete typing unit) and inoculum. Animals infected with TcII showed higher levels of these parameters than did animals infected with TcI. The larger volume of inoculum showed a greater capacity to cause an infection when administered via the oral route. BT infection was more virulent than culture MT infection for both routes (oral and IP). However, mice inoculated orally with BT showed lower levels than via IP, while mice inoculated orally with culture MT showed similar levels of infection to those inoculated via IP. Mice inoculated with culture MT showed more histopathological changes than those inoculated with BT, regardless of the inoculation route. These results indicate that this alternative experimental model is useful for evaluating infection by T. cruzi isolates with subpatent parasitemia and low virulence, such as those belonging to the TcI and TcIV DTUs, which are prevalent in outbreaks of orally transmitted Chagas disease.