Potential of in-plant intramuscular fat predictions to enable sheep breeders to incorporate consumer preferences in breeding programmes

The inclusion of eating quality traits in sheep genetic improvement programmes is desirable. Intramuscular fat (IMF) plays a key role in ensuring consumer satisfaction when eating lamb, but genetic progress for IMF is constrained by a lack of routine data collection. This study investigated the potential for IMF predictor traits to substitute for measured IMF in genetic improvement programmes. Carcass and predicted IMF (near-infrared estimated IMF and marbling score) data were available on 10,113 New Zealand lambs, 1678 of which also had measured chemical IMF on a slice of M. longissimus lumborum on which the predictions of IMF had been made. Genetic antagonisms were observed between carcass lean traits and IMF. The genetic correlation between the predictors and measured IMF approached one, indicating that predictors of IMF can be used in genetic improvement programmes. Through using selection indexes, simultaneous increases in IMF and the existing terminal selection index are possible, provided all traits are measured. This study highlights the importance and potential of predicted IMF to achieve genetic improvement in traits of importance to consumers.

Quantitative trait loci for organ weights and adipose fat composition in Jersey and Limousin back-cross cattle finished on pasture or feedlot

A QTL study of live animal and carcass traits in beef cattle was carried out in New Zealand and Australia. Back-cross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. This paper reports on weights of eight organs (heart, liver, lungs, kidneys, spleen, gastro-intestinal tract, fat, and rumen contents) and 12 fat composition traits (fatty acid (FA) percentages, saturated and monounsaturated FA subtotals, and fat melting point). The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. For organ weights and fat composition traits, 10 and 12 significant QTL locations (P<0.05), respectively, were detected on a genome-wide basis, in combined-sire or within-sire analyses. Seven QTL significant for organ weights were found at the proximal end of chromosome 2. This chromosome carries a variant myostatin allele (F94L), segregating from the Limousin ancestry, and this is a positional candidate for the QTL. Ten significant QTL for fat composition were found on chromosomes 19 and 26. Fatty acid synthase and stearoyl-CoA desaturase (SCD1), respectively, are positional candidate genes for these QTL. Two FA QTL found to be common to sire groups in both populations were for percentages of C14:0 and C14:1 (relative to all FAs) on chromosome 26, near the SCD1 candidate gene.

Genetic mapping of quantitative trait loci for meat quality and muscle metabolic traits in cattle

A whole-genome scan was carried out in New Zealand and Australia to detect quantitative trait loci (QTL) for live animal and carcass composition traits and meat quality attributes in cattle. Backcross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. This paper reports on meat quality traits (tenderness measured as shear force at 4-5 ages on two muscles as well as associated traits of meat colour, pH and cooking loss) and a number of metabolic traits. For meat quality traits, 18 significant QTL (P < 0.05), located in nine linkage groups, were detected on a genome-wise basis, in combined-sire (seven QTL) or within-sire analyses (11 QTL). For metabolic traits, 11 significant QTL (P < 0.05), located in eight linkage groups, were detected on a genome-wise basis, in combined-sire (five QTL) or within-sire analyses (six QTL). BTA2 and BTA3 had QTL for both metabolic traits and meat quality traits. Six significant QTL for meat quality and metabolic traits were found at the proximal end of chromosome 2. BTA2 and BTA29 were the most common chromosomes harbouring QTL for meat quality traits; QTL for improved tenderness were associated with Limousin-derived and Jersey-derived alleles on these two chromosomes, respectively.

Relationship between sporidesmin-induced liver injury and serum activity of gamma-glutamyltransferase in Romney lambs sired by facial eczema-resistant or control rams

AIM

To test whether long-term selection for resistance to facial eczema (FE) influences the relationship between liver injury score (LIS) and serum activity of gamma-glutamyltransferase (GGT) in sporidesmin-dosed sheep.

METHODS

Two groups of Romney lambs were generated for this study in 1999, out of an unselected group of ewes and sired by either selected FE-resistant (R) line (n=74 lambs) or unselected Control (C) line (n=119 lambs) rams from the Ruakura Research Centre long-term FE-selection experiment. The lambs were given a single oral dose of sporidesmin, sampled for determination of serum GGT activity 3 weeks later, and lambs that had serum GGT activity >55 IU/l (reactors) were humanely killed and assessed for LIS post mortem, 6 weeks after dosing. A second round of dosing was applied to the nonreactors, followed as above by analysis of serum GGT activity and assessment of LIS post mortem (both reactors and nonreactors).

RESULTS

There was a significant linear relationship between LIS and logeGGT, which did not differ between the 2 sire lines (LIS= -2.96 (SE 0.38) + 0.89 (SE 0.07) x loge GGT, R2=0.54, p<0.001).

CONCLUSIONS

Serum GGT is a valid indicator of LIS in lambs by sires selected for different levels of susceptibility to FE. The logeGGT-LIS relationship has not changed as a result of genetic selection for resistance to FE.

The effect of Johne's disease on production traits in Romney, Merino and Merino x Romney-cross ewes

AIM

To quantify the effects of clinical Johne's disease on the performance of Romney, Merino and Merino x Romney-cross ewes.

METHODS

The performance of ewes was compared using eight birth cohorts (1971-1978). Merino and Merino-cross genotypes included New Zealand Merino and Australian Superfine Merino sources. Intensive monitoring of Johne's disease was undertaken over the production years 1975-1982. Positive diagnostic evidence of Johne's disease was established post mortem from lesions of granulomatous enteritis associated with high numbers of acid-fast bacilli. Over years, data on a total of 2,341 Romney ewes and 1,292 Merino and Merino x Romney-cross ewes were recorded, consisting of annual records of liveweight (LWT), greasy fleece weight (FWT), number of lambs born per ewe per year (NLB), and lifetime productivity of ewes.

RESULTS

A total of 82 (3.5%) Romney ewes and 62 (4.8%) Merino and Merino x Romney-cross ewes were diagnosed with clinical Johne's disease over the 8-year monitoring period, equivalent to 0.9% and 1.2% annual cases for these breeds, respectively, of the ewes present at mating. The percentage of clinical cases (p<0.04) and the age at death from Johne's disease (p<0.02) were lower for Romneys than for Superfine Merinos. The mean age of death from Johne's disease was 3.41 (standard error (SE) 0.06) years, lower than the mean disposal age from the flock of 5.03 (SE 0.02) years for clinically normal ewes (p<0.001). In their final year of production, ewes with clinical Johne's disease had lower LWT by 5.3 kg (10.5% of the mean; p<0.001), lower annual FWT by 0.54 (SE 0.10) kg (14.2%; p<0.001), fewer NLB by 0.15 (SE 0.07) lambs (13%; p<0.05), and lower litter weaning weights by 3.6 (SE 1.3) kg (15%; p<0.01) compared with clinically normal ewes. The size of the production losses associated with Johne's disease depended on the age to which ewes survived. Considering all production years of ewes (up to 8 years), the total weight of lambs weaned by ewes with clinical Johne's disease was 30.9 (SE 3.4) kg lower (46%; p<0.001) than the total from clinically normal ewes.

CONCLUSIONS

Clinical Johne's disease led to significant losses in LWT, FWT, NLB, and in the lifetime production of ewes, amounting overall to a 46% reduction in productivity (p<0.001).

CLINICAL RELEVANCE

Productivity losses from clinical cases of Johne's disease would be of considerable economic importance in flocks with a high incidence of the disease. The lack of good diagnostic tests for Johne's disease in the live animal, and the lack of active surveillance programmes, has made it difficult to establish the true prevalence of Johne's disease in sheep flocks in New Zealand, and its economic consequences.

Genotypic effects of calpain 1 and calpastatin on the tenderness of cooked M. longissimus dorsi steaks from Jersey x Limousin, Angus and Hereford-cross cattle

Single nucleotide polymorphisms (SNPs) in the calpain 1 (CAPN1) and calpastatin (CAST) genes were studied to determine their effects on meat tenderness in Bos taurus cattle. Strip loins (M. longissimus dorsi) were removed from cattle in four resource populations after slaughter (n = 1042), aged under controlled conditions until fixed times after rigor mortis, cooked and measured using a tenderometer. Animals were genotyped for the CAPN1 SNP c.947C>G (p.Ala316Gly; AF252504) and for the CAST SNP c.2959A>G (AF159246). Frequencies of CAPN1 C alleles ranged from 23% to 68%, and CAST A alleles from 84% to 99.5%. From all data combined, the CAPN1 CC genotype (compared with the GG genotype) was associated with a 20.1 +/- 1.7% reduced average shear force at intermediate stages of ageing (P < 0.001) and with a 9.5 +/- 1.3% reduction near ultimate tenderness (P < 0.001). The heterozygote was intermediate. For CAST, corresponding values for AA compared with AG genotypes were reductions of 8.6 +/- 2.0% and 5.1 +/- 1.6% respectively (both P < 0.001), but there were too few GG genotypes for comparison. There were small interactions between the CAPN1 and CAST genotypes. For the CAPN1 and CAST genotypes combined, the maximal genotype effect in average shear force was 25.7 +/- 5.5% (P < 0.001) at intermediate stages and 15.2 +/- 4.8% near ultimate tenderness (P < 0.01).

What every pediatrician should know about infectious mononucleosis in adolescents

Infectious mononucleosis (IM) is one of the most common diseases occurring during adolescence. Appreciation of IM's varied clinical presentations, its differential diagnosis, and the difficulties involved in making the laboratory diagnosis will enable clinicians to treat teenagers more effectively in their office practices.

The effect of interleukin-10 on meningeal inflammation in experimental bacterial meningitis

Interleukin-10 (IL-10) is a cytokine with antiinflammatory effects. In a rabbit model of meningitis, IL-10 was given intracisternally or intravenously to evaluate the impact on inflammation induced by lipooligosaccharide (LOS), Haemophilus influenzae type b (Hib), or Listeria monocytogenes. Intracisternal IL-10 in concentrations >1 microg significantly reduced tumor necrosis factor-alpha (TNF-alpha) and lactate values in cerebrospinal fluid (CSF). Intravenous IL-10 (1 mg/kg) in two doses after intracisternal LOS significantly reduced CSF TNF-alpha and lactate. When Hib was used, animals were treated with ceftriaxone and dexamethasone with or without IL-10 (1 mg/kg). TNF-alpha was significantly reduced in animals treated with IL-10, dexamethasone, or both compared with levels in rabbits receiving ceftriaxone alone. Comparable results were obtained when L. monocytogenes was inoculated and animals were treated with ampicillin with or without IL-10, dexamethasone, or nothing. In conclusion, IL-10 modulates CSF TNF-alpha concentrations in experimental LOS, Hib, or L. monocytogenes meningitis. The maximal inhibitory effect was seen when IL-10 and dexamethasone were combined.

Clinical utility of the polymerase chain reaction for diagnosis of enteroviral meningitis in infancy

OBJECTIVE

To determine the utility of polymerase chain reaction (PCR) assay of cerebrospinal fluid (CSF), serum, and urine for rapid diagnosis of enteroviral meningitis in infants 3 months of age and younger.

STUDY DESIGN

We identified prospectively infants 3 months of age and younger coming to the emergency department with fever whose examination included a lumbar puncture, blood culture, or both. Samples of CSF, serum, urine, throat, and stool specimens were collected for viral culture and, with the exception of stool, for PCR assay. Those infants who had not received prior antibiotic therapy and had sterile bacterial cultures of CSF, blood, and urine were selected for the present analysis.

RESULTS

A total of 259 specimens for viral culture and 203 specimens for PCR assay were collected from 64 infants. Comparison of results of PCR assay of CSF with viral culture, the gold standard for diagnosis of enteroviral meningitis, demonstrated a sensitivity of 100% and a specificity of 90%. Because enteroviruses are not always detectable by culture, the following modified standard was established to define enteroviral meningitis: either CSF pleocytosis, sterile bacterial cultures and detection of an enterovirus in stool culture or positive viral culture of CSF, or both. With this modified definition, the sensitivity and specificity of the PCR assay of CSF were 92% and 94%, respectively. PCR assay of serum and urine offered no benefit over PCR assay of CSF alone for diagnosis of meningitis.

CONCLUSION

PCR assay of CSF is useful for the rapid and reliable diagnosis of enteroviral meningitis. Application of this technique in the clinical setting can potentially diminish unnecessary hospitalization and use of antibiotics.

Once-daily gentamicin therapy for experimental Escherichia coli meningitis

In vitro and in vivo studies have demonstrated that the bacteriologic efficacy of once-daily aminoglycoside therapy is equivalent to that achieved with conventional multiple daily dosing. The impact of once-daily dosing for meningitis has not been studied. Using the well-characterized rabbit meningitis model, we compared two regimens of the same daily dosage of gentamicin given either once or in three divided doses for 24 or 72 h. The initial 1 h mean cerebrospinal fluid (CSF) gentamicin concentration for animals receiving a single dose (2.9 +/- 1.7 micrograms/ml) was threefold higher than that for the animals receiving multiple doses. The rate of bacterial killing in the first 8 h of treatment was significantly greater for the animals with higher concentrations in their CSF (-0.21 +/- 0.19 versus -0.03 +/- 0.22 log10 CFU/ml/h), suggesting concentration-dependent killing. By 24h, the mean reduction in bacterial titers was similar for the two regimens. In animals treated for 72 h, no differences in bactericidal activity was noted for 24, 48, or 72 h. Gentamicin at two different dosages was administered intracisternally to a separate set of animals to achieve considerably higher CSF gentamicin concentrations. In these animals, the rate of bacterial clearance in the first 8 h (0.52 +/- 0.15 and 0.58 +/- 0.15 log10 CFU/ml/h for the lower and higher dosages, respectively) was significantly greater than that in animals treated intravenously. In conclusion, there is evidence of concentration-dependent killing with gentamicin early in treatment for experimental E. coli meningitis, and once-daily dosing therapy appears to be at least as effective as multiple-dose therapy in reducing bacterial counts in CSF.

Cerebrospinal fluid values in the term neonate

BACKGROUND

Cerebrospinal fluid (CSF) values in the noninfected neonate are not well-delineated. Studies analyzing these values are inconsistent in the criteria used to define the noninfected population. The purpose of our study was to examine CSF values in neonates in the first 30 days of life in whom infection was more thoroughly excluded than in previous reports. Stringent inclusion criteria defined the noninfected population, and the recently available polymerase chain reaction (PCR) for enteroviruses was used in addition to cultures to help exclude viral disease. Results were also stratified by age in weeks to evaluate for any variability that occurs in CSF values during the first month of life.

METHODS

Neonates were selected from subjects enrolled in two studies on aseptic meningitis. Noninfected infants were identified by the following criteria: (1) atraumatic lumbar puncture (< or = 1000 red blood cells/mm3); (2) no antibiotic therapy before lumbar puncture; (3) sterile blood, CSF and urine bacterial cultures; (4) negative CSF viral culture; and (5) negative CSF PCR for enteroviruses.

RESULTS

The mean +/- SD total CSF white blood cell count for 108 noninfected neonates was 7.3 +/- 14/mm3 (95% confidence interval 6.6 to 8.0/mm3) with a median of 4/mm3 and a range of 0 to 130/mm3. There were no significant differences in the mean CSF white blood cell counts among age categories.

CONCLUSIONS

The application of stringent inclusion criteria and the use of the PCR yielded a population of infants that better represents the noninfected neonate than earlier reports. These values can be used for reference in evaluating the febrile or ill neonate.

Clindamycin therapy of experimental meningitis caused by penicillin- and cephalosporin-resistant Streptococcus pneumoniae

Although penicillin resistance among Streptococcus pneumoniae strains is increasing in many areas, resistance to clindamycin remains low. In our well-characterized rabbit meningitis model, we conducted experiments to evaluate the bacteriologic efficacy of clindamycin after a penicillin- and cephalosporin-resistant S. pneumoniae strain was intracisternally inoculated. Animals received a loading intravenous dose of 30 mg of clindamycin per kg of body weight and then two doses of 20 mg/kg given 5 h apart. In addition to clindamycin, some animals received dexamethasone (DXM) with or without ceftriaxone. The concentrations of clindamycin in cerebrospinal fluid were from 8.9 to 12.8% of the concomitant concentrations in serum and were unaffected by DXM administration. Mean changes in CFU (log10 per milliliter) at 10 and 24 h were -3.7 and -6.1, respectively, for clindamycin-treated rabbits, -3.6 and -6.3 for clindamycin-DXM-treated rabbits, -3.9 and -5.8, respectively, for clindamycin-ceftriaxone-treated rabbits, and -5.0 and -6.7, respectively, for clindamycin-ceftriaxone-DXM-treated rabbits. By 24 h all but one of the cultures of cerebrospinal fluid (that from a clindamycin-DXM-treated rabbit) were sterile. Because of the potential risk for clindamycin-treated rabbits to develop macrolide-lincosamide resistance, we attempted, unsuccessfully, to induce clindamycin resistance in vitro in two S. pneumoniae strains. Although clindamycin therapy might be effective in selected patients with multiple-drug-resistant pneumococcal meningitis who have failed conventional treatments, clinical experience is necessary before it can be recommended.

Modulation of expression of genes involved in the inflammatory response by lipopolysaccharide and temperature in cultured human astroglial cells

In bacterial sepsis and meningitis, large concentrations of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) correlate directly with morbidity and mortality. This laboratory has reported previously that elevated temperature in the physiologic range is associated with down regulation of IL-1 beta and TNF alpha expression in cultured astroglia after lipopolysaccharide (LPS) stimulation. To further investigate the role of elevated temperature in the CNS inflammatory response, the effects of LPS and elevated temperature on the expression of genes that participate in the inflammatory response were determined in cultured transformed human fetal astrocytes and in an astrocytoma cell line. The effect of physiologic temperature elevation on cytokine concentrations in cerebrospinal fluid (CSF) was also investigated in a rabbit meningitis model. The findings indicate that astrocytes express a wide variety of cytokines, growth factors, growth factor receptors, and other genes that could play important roles in CNS inflammation. Furthermore, temperature elevation in the febrile range can lead to alterations in the patterns of expression of many genes involved in the inflammatory response of these cells.

Genetic factors affecting antibody responses to four species of nematode parasite in Romney ewe lambs

Serum levels of antibodies (Ab) and immunoglobulin G1 (IgG1) to the larval (L3) stage of the internal parasites Cooperia curticei and Trichostrongylus colubriformis and levels of Ab to the L3 stages of Haemonchus contortus and Ostertagia circumcincta were determined in 1432 Romney ewe lambs which were born on one farm in 1990 and 1991 and were the progeny of 63 rams. The objectives were to estimate heritabilities of, and genetic correlations among, the serum concentrations in newly weaned lambs under commercial conditions and to estimate genetic correlations of Ab and IgG1 with production traits. Lambs were exposed to a natural parasite challenge on pasture, following an anthelmintic drench at weaning. Blood and faecal samples from 4- to 6-month-old lambs were then taken when the mean faecal nematode egg count of a monitor group reached 800-1500 eggs g-1. Heritabilities for the serum levels of the four Abs ranged from 0.25 +/- 0.05 to 0.37 +/- 0.06. Heritabilities for the level of IgG1 developed against C. curticei was 0.19 +/- 0.04 and against T. colubriformis, 0.18 +/- 0.05. Genetic correlations between Abs for the 4 species were high, averaging 0.84, and between the two IgG1s it was 0.82. The genetic correlations between Ab or IgG1 levels and weight or gain traits were negative (for the 6 significant values out of 18), with yearling fleece weight positive (for the 2 significant values out of 6), whilst those with loge faecal egg count were all negative (average -0.15).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of CP-99,219, a new fluoroquinolone, for treatment of experimental penicillin- and cephalosporin-resistant pneumococcal meningitis

CP-99,219 is a new fluoroquinolone that has excellent activity against gram-positive organisms including penicillin- and cephalosporin-resistant Streptococcus pneumoniae strains. In our well-established rabbit model of meningitis, we conducted experiments to determine the concentrations of CP-99,219 in cerebrospinal fluid (CSF) after intravenous administration and its ability to eradicate two penicillin-resistant pneumococcal isolates. The peak and trough concentrations of CP-99,219 in the CSF were from 19 to 25% of the concentrations simultaneously obtained in serum and were unaffected by concomitant dexamethasone administration. Compared with untreated (control) animals, three doses of CP-99,219 given 5 h apart significantly reduced the bacterial count in CSF by 5 to 6 log10 CFU at 10 h. Although 47% of the dexamethasone-treated animals and 18% of those not given the steroid had positive cultures at 24 h (14 h after administration of the last antibiotic dose), the mean bacterial counts did not change from those observed at 10 h. Additionally, only results for animals infected with one of the two pneumococcal strains appeared to be affected by concomitant dexamethasone therapy.

Effect of interleukin-1 receptor antagonist and soluble tumor necrosis factor receptor in animal models of infection

Intracisternal or intraarticular inoculation of rabbit recombinant interleukin (IL)-1 beta and rabbit tumor necrosis factor-alpha combined with IL-1 receptor antagonist (IL-1RA) and soluble tumor necrosis factor receptor (sTNFR), respectively, produced significantly less inflammation in rabbits than after inoculation of these cytokines alone. In contrast, when Haemophilus influenzae type b (Hib) or Hib lipooligosaccharide (LOS) was given intraarticularly with IL-1RA, sTNFR, or the combination, there was no significant or consistent modulation of synovial inflammation and cartilage proteoglycan degradation. In the experimental meningitis model, IL-1RA and sTNFR did not significantly reduce the meningeal inflammatory response associated with intracisternal inoculation of Hib LOS. These data indicate that specific cytokine inhibitors (sTNFR and IL-1RA) may not be effective in modulating inflammation induced by a broad inflammatory stimulus such as gram-negative bacteria or their products and suggest caution in using them to treat these infectious conditions in humans.

Escherichia coli septicemia in nonperforated appendicitis

OBJECTIVE

To determine the association between nonperforated appendicitis and Escherichia coli septicemia, and the frequency with which blood cultures are obtained in the clinical setting of appendicitis.

DESIGN

Three case reports of E coli septicemia and nonperforated appendicitis and a retrospective survey.

SETTING

Children's Medical Center, Dallas, Tex, a primary care and tertiary referral center.

PATIENTS

All children admitted in a 2-year period with a diagnosis of appendicitis.

INTERVENTIONS

None.

RESULTS

Preoperative blood cultures were obtained in 20 (21%) of 96 patients with histologic evidence of appendicitis. Fifty percent of the patients had gross or microscopic evidence of appendiceal perforation. Twelve (25%) of the 48 patients with perforated appendicitis had blood cultures obtained before the initiation of antimicrobial therapy, and in two of these patients (17%) the results were positive. Blood cultures were drawn before antibiotic therapy in four (8%) of the 48 patients with nonperforated appendicitis, and in two of these the results were positive. The blood culture isolates (coagulase-negative Staphylococcus and E coli) were the same in both groups.

CONCLUSIONS

Nonperforated appendicitis and septicemia may be more common than formerly appreciated. Only a prospective study can determine the true incidence of septicemia in children with perforated or nonperforated appendicitis.

Effect of dexamethasone on therapy of experimental penicillin- and cephalosporin-resistant pneumococcal meningitis

Treatment of pneumococcal meningitis has become problematic because of the emergence of penicillin- and cephalosporin-resistant strains and because of the concern that dexamethasone therapy might reduce penetration of antibiotics into the cerebrospinal fluid (CSF). We addressed these issues with our rabbit meningitis model by studying two pneumococcal isolates that were resistant to penicillin and ceftriaxone and susceptible to vancomycin and rifampin. Ceftriaxone, vancomycin, and rifampin were given alone or in combination, with or without coadministration of dexamethasone. Treatment was started 12 to 14 h after intracisternal inoculation of approximately 10(4) CFU of one of the organisms. Rifampin concentrations in serum and CSF were similar, regardless of whether dexamethasone was given, whereas those of ceftriaxone were somewhat lower at each time point in animals given dexamethasone. The penetration of vancomycin into CSF was consistently and substantially reduced with dexamethasone treatment, which resulted in a delay in CSF sterilization not observed in non-dexamethasone-treated animals. When rifampin was used with ceftriaxone for treatment of meningitis caused by the more resistant strain, bacteriologic cure occurred promptly, with or without dexamethasone therapy. In areas with high rates of occurrence of resistant pneumococcal strains, we believe initial empiric therapy of bacterial meningitis should include two antibiotics: ceftriaxone and either rifampin or vancomycin. When dexamethasone is used, the combination of ceftriaxone and rifampin is preferred for therapy.