Diagnostic microbiology and therapeutic drug monitoring in pediatric infectious diseases

Retrospective evaluation of blood culture isolates and sepsis survival rate in foals in the Czech Republic: 50 cases (2011-2013)

OBJECTIVE

To identify the specific pathogens causing sepsis in hospitalized foals in the Czech Republic and identify important factors associated with their survival.

DESIGN

A retrospective study from 2011 to 2013.

SETTING

University veterinary teaching hospital.

ANIMALS

Fifty compromised foals.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Blood was aseptically collected for bacterial culture from compromised foals. The foals were classified as septic according to a positive blood culture result or sepsis score ≥11. Blood cultures were positive in 44% of the foals. In these positive cultures, 27.3% had only Gram-positive (G+) bacteria and 54.5% had only Gram-negative (G-) bacteria. A mixed bacterial population was presented in 18.2% of the positive cultures. Thirty-six foals were classified as septic on the basis of positive blood culture or a sepsis score ≥11. In the group of foals that did not survive, there were significantly more foals with low levels of immunoglobulin G (IgG) than foals with normal levels of IgG (P < 0.0001). We also found a significant difference in the proportion of foals with low levels of IgG and positive blood cultures when compared to negative blood cultures. Twenty-six of the 50 foals were discharged from the hospital. Survival was significantly lower in foals with a diagnosis of sepsis than in foals without sepsis. There was no statistically significant difference between foals that died as a result of infection caused by G- or G+ pathogens. There was no difference in the proportion of survivors that did or did not receive antimicrobials prior to admission.

CONCLUSIONS

In our study, we confirmed the increasing trend for G+ bacteria in blood cultures but G- still predominate. The percentage of nonsurviving septic foals was high.

Tests for bactericidal effects of antimicrobial agents: technical performance and clinical relevance

Bactericidal testing has been used for several decades as a guide for antimicrobial therapy of serious infections. Such testing is most frequently performed when bactericidal antimicrobial agent therapy is considered necessary (such as when treating infectious endocarditis or infection in an immunocompromised host). It has also been used to ensure that the infecting organism is killed by (not tolerant to) usually bactericidal compounds. However, few data are available to support the role of such tests in direct patient care. Several important variables affect the reproducibility of the test results; however, proposed reference methods are now available for performing the MBC test. With minor modifications, these can provide a standardized approach for laboratories that need to perform them. Currently, little evidence is available to support the routine use of such testing for the care of individual patients. However, testing of new (investigational) antimicrobial agents can be beneficial in determining their potential to provide bactericidal antimicrobial activity during clinical use. New methods to assess bactericidal activity are being developed, but as yet none have been rigorously tested in patient care settings; further, for most of these methods, little information is available as to which technical parameters affect their results. In clinical laboratories, all bactericidal tests must be performed with rigorously standardized techniques and adequate controls, bearing in mind the limitations of the currently available test procedures.

C-reactive protein in early detection of bacteremic versus viral infections in immunocompetent and compromised children

The value of quantitatively determined C-reactive protein (CRP), measured from a finger prick sample for rapid detection of septicemia, was examined in 76 blood culture-positive infections in 54 immunocompetent and 18 compromised children; 73 patients with systemic viral infections served as controls. Development of a positive CRP reaction was also studied in 40 cases of acute epiglottitis. Beyond the neonatal age, an increased CRP value (greater than or equal to 20 mg/L) was found in 60 of 64 (94%) children with a positive blood culture for bacteria or fungus. By contrast, CRP remained below this value in 56 of 73 (77%) with viral infections. The immunologic status did not influence the CRP response. However, time had a highly significant (p less than 0.001) effect on CRP; a history of 6 to 12 hours of illness was required before CRP increased above normal. We conclude that CRP is a sensitive and rapidly reacting index in bacteremic infections. However, because other factors than septicemia also increase CRP, we deem a negative CRP value most informative; if two determinations taken several hours apart are less than 20 mg/L, the patient is very unlikely to have invasive bacterial infection.

Aspects of pharmacology in the neonatal foal

Other therapeutic agents used in foals for specific diseases are discussed elsewhere. The marked effect of species, age, and degree of maturity on drug metabolism in the neonate reinforces the danger of interspecies extrapolation of pharmacology, the need for information specific for the foal, and the necessity for monitoring drug levels in the individual. Suggested antimicrobial doses are listed in Tables 3, 4, and 6. Recommended doses of anticonvulsants and sedatives are listed in Table 8 and in the article "Intensive Care of the Neonatal Foal." The following are recommendations for drug therapy in the neonate: Avoid unnecessary administration of drug to the dam at parturition because of possible placental transfer of the drug with subsequent effects on the neonate. If possible, avoid unnecessary drug therapy in foals under 30 days of age. Select a drug that undergoes minimal biotransformation (hepatic metabolism) and is not highly protein bound. Owing to probable immunodeficiency in the neonate, broad-spectrum, bactericidal drugs are preferred for treatment of life-threatening infections. Every attempt should be made to identify the etiologic agent so that drug therapy can be based on cultures and sensitivity test results to maximize the benefit-risk ratio. Parenteral (intramuscular or intravenous) drug administration is preferable to oral. Avoid drugs that are known oxidants, which may produce hemolysis or methemoglobinemia. In general, the same or a slightly higher initial dose should be employed in the neonate, but it should be given less frequently than in the adult if it has a high potential to cause toxicity. When possible, individual monitoring of serum levels of potentially toxic drugs should be employed in premature and newborn foals unless specific drug pharmacokinetics are known for that age group.