Mechanisms of pneumococcal antibiotic resistance and treatment of pneumococcal infections in 2002

Pneumococcal Vaccines

Streptococcus pneumoniae is a Gram-Positive pathogen that is a major causative agent of pneumonia, otitis media, sepsis and meningitis across the world. The World Health Organization estimates that globally over 500,000 children are killed each year by this pathogen. Vaccines offer the best protection against S. pneumoniae infections. The current polysaccharide conjugate vaccines have been very effective in reducing rates of invasive pneumococcal disease caused by vaccine type strains. However, the effectiveness of these vaccines have been somewhat diminished by the increasing numbers of cases of invasive disease caused by non-vaccine type strains, a phenomenon known as serotype replacement. Since, there are currently at least 98 known serotypes of S. pneumoniae, it may become cumbersome and expensive to add many additional serotypes to the current 13-valent vaccine, to circumvent the effect of serotype replacement. Hence, alternative serotype independent strategies, such as vaccination with highly cross-reactive pneumococcal protein antigens, should continue to be investigated to address this problem. This chapter provides a comprehensive discussion of pneumococcal vaccines past and present, protein antigens that are currently under investigation as vaccine candidates, and other alternatives, such as the pneumococcal whole cell vaccine, that may be successful in reducing current rates of disease caused by S. pneumoniae.

Penicillin resistance is not extrapolable to amoxicillin resistance in Streptococcus pneumoniae isolated from middle ear fluid in children with acute otitis media

OBJECTIVES

We evaluated the in vitro antibacterial activity of amoxicillin against penicillin-susceptible and -nonsusceptible Streptococcus pneumoniae strains isolated from children with acute otitis media (AOM).

METHODS

Children more than 3 months of age with AOM who were seen in the Dr Sótero del Rio and Luis Calvo Mackenna Hospitals in Santiago, Chile, between July 1998 and December 2002 were subjected to tympanic puncture for middle ear fluid culture. The penicillin and amoxicillin susceptibilities of the S pneumoniae isolates were determined by epsilometer test (E test).

RESULTS

A bacterial pathogen was isolated in 432 of 543 children (80%) as follows: S pneumoniae, 40%; Haemophilus influenzae, 29%; Moraxella catarrhalis, 7%; and Streptococcus pyogenes, 4%. Penicillin-susceptible S pneumoniae strains were less common than amoxicillin-susceptible strains (60% versus 95%; odds ratio [OR], 0.08; 95% confidence interval [CI], 0.04 to 0.18). Both intermediate- and high-resistance strains were more common for penicillin (22% versus 4.5%; OR, 5.6; 95% CI, 2.5 to 12.7) than for amoxicillin (18% versus 0.5%; OR, 41.3; 95% CI, 6.0 to 821).

CONCLUSIONS

Penicillin resistance is not extrapolable to amoxicillin among S pneumoniae strains isolated from middle ear fluid of children with AOM. Our results support the recommendation to evaluate the minimal inhibitory concentrations of penicillin-nonsusceptible S pneumoniae for amoxicillin and to continue use of this antimicrobial as a first-line antimicrobial choice for children with AOM.

Airway infectious disease emergencies

Upper and lower respiratory infections are encountered commonly in the emergency department. Visits resulting from occurrences of respiratory disease account for 10% of all pediatric emergency department visits and 20% of all pediatric hospital admissions. Causes of upper airway infections include croup, epiglottitis, retropharyngeal abscess, cellulitis, pharyngitis, and peritonsillar abscesses. Lower airway viral and bacterial infections cause illnesses such as pneumonia and bronchiolitis. Signs and symptoms of upper and lower airway infections overlap, but the differentiation is important for appropriate treatment of these conditions. This article reviews the varied clinical characteristics of upper and lower airway infections.

Effectiveness of Centers for Disease Control and Prevention recommendations for outcomes of acute otitis media

OBJECTIVES

To determine whether we could increase adherence to the Centers for Disease Control and Prevention (CDC) recommendations with well-accepted approaches to improving quality of care and adherence to the CDC recommendations resulted in improved outcomes for acute otitis media (AOM).

METHODS

A cluster randomization study was conducted in 12 pediatric practices (6 intervention and 6 control sites). The main outcome measures were adherence to the CDC recommendations (modified to include 2 additional antimicrobial agents) and a subsequent antibiotic prescription for AOM within 30 days after diagnosis.

RESULTS

Of 3152 patients referred to research assistants, 2584 (82%) were eligible. Of those eligible, 1368 (99%) of 1382 at the intervention sites and 1138 (99%) of 1146 at the control sites consented to participate. Rates of adherence to the CDC recommendations were not significantly higher at the intervention sites than at the control sites, for initial enrollment episodes (78.2% vs 70.6%) or second episodes (62.6% vs 59.9%). After controlling for clustering according to site and covariates, children who were not treated in adherence to the CDC recommendations for both episodes had 1.60 times the odds of a subsequent prescription within 12 days, compared with those treated in adherence at both episodes.

CONCLUSIONS

Despite using evidence-based approaches that are known to influence physician behavior, we were unable to increase adherence to the CDC recommendations for treatment of AOM. However, we did establish that prescription of antimicrobial therapy consistent with the CDC recommendations for a second episode of AOM was associated with improved outcomes, measured as the need for subsequent antibiotic prescription. Because of the selection of resistant otopathogens, adherence to the CDC recommendations is likely more important in subsequent episodes of AOM than in the initial episode.

Efficacy of telavancin against penicillin-resistant pneumococci and Staphylococcus aureus in a rabbit meningitis model and determination of kinetic parameters

The penetration of telavancin was 2% into inflamed meninges and ca. 1 per thousand into noninflamed meninges after two intravenous injections (30 mg/kg of body weight). In experimental meningitis, telavancin was significantly superior to vancomycin combined with ceftriaxone against a penicillin-resistant pneumococcal strain. Against a methicillin-sensitive staphylococcal strain, telavancin was slightly but not significantly superior to vancomycin.

Azithromycin compared with beta-lactam antibiotic treatment failures in pneumococcal infections of children

OBJECTIVE

To determine whether treatment failures occurred more commonly with azithromycin than with beta-lactam antibiotics in children who developed invasive pneumococcal disease within 30 days of receiving prior antimicrobial therapy.

METHODS

Retrospective review of medical records of children evaluated at Texas Children's Hospital between 1996 and 2002 who had received antimicrobials (azithromycin or a beta-lactam antibiotic) and developed invasive pneumococcal disease within 30 days. Treatment failure was defined as invasive pneumococcal infection that occurred while taking antimicrobials or within 3 days of stopping azithromycin treatment or 1 day of stopping beta-lactam treatment. Penicillin and azithromycin susceptibilities were determined and categorized according to National Committee for Clinical Laboratory Standards guidelines.

RESULTS

We identified 21 and 33 children with similar demographic features who had developed invasive pneumococcal disease within 1 month of receiving azithromycin or a beta-lactam antibiotic, respectively. Eleven (52%) children in the azithromycin group and 11 (33%) in the beta-lactam group met the definition for treatment failures (P = 0.34). Eight treatment failures while receiving azithromycin were caused by pneumococci with the macrolide-resistant (M) phenotype, 2 with the macrolide-, lincosamide- and streptogramin B-resistant (MLSB) phenotype and 1 by a macrolide-susceptible organism. In the beta-lactam group 7 had a penicillin-resistant isolate, 3 had an intermediately susceptible isolate and 1 had a susceptible isolate.

CONCLUSIONS

Our study suggests that treatment failures among patients who developed invasive disease within 30 days of receiving an antimicrobial occur as frequently in patients who receive beta-lactam antibiotics as in those who receive azithromycin. Furthermore macrolide resistant organisms are not more likely to be recovered after a macrolide treatment failure than a penicillin-nonsusceptible isolate being recovered after a beta-lactam treatment failure (P = 1.0).

Current concepts in antibiotic resistance

PURPOSE OF REVIEW

Although antibiotic resistance is not often considered an exciting topic for pediatric surgical subspecialists, we face the consequences of increasing antibiotic resistance daily in our clinical practice. By the very nature that our patients are often referred to us after extended periods of medical therapy, antibiotic resistance becomes a significant factor in management of patients both medically and surgically. Antibiotic resistance is increasing, and a number of organisms demonstrate multiple-drug resistance. The purpose of this review is to outline the scope of antibiotic resistance as it relates to pediatric otolaryngology. Specifically, the mechanisms of resistance, the pharmacodynamics involved, and selected infections are discussed.

RECENT FINDINGS

The children particularly at risk for infections with resistant organisms are those 2 years of age or younger with exposure to daycare and treatment with antimicrobials within the last 30 days. Although there is increasing resistance to antibiotics commonly used for outpatient infections such as otitis media, sinusitis, and tonsillitis, many of the first-line therapies still show significant therapeutic advantage. Vaccines to pneumococcal bacteria have been shown to decrease severe infections. However, there has been only a slight decline in the number of outpatient otolaryngologic infections after vaccination.

SUMMARY

Therefore, children who have received multiple courses of antibiotics, are 2 years of age or younger, attend daycare, or have received antimicrobial therapy within the last 30 days may need high-dose therapy or antimicrobial therapy with an increased spectrum of coverage. Those children with infections that do not respond clinically to appropriate therapy should be treated with the suspicion of multiple-drug resistant strains being present. Continued surveillance of resistance patterns within individual communities, especially areas served by children's hospitals, are important, as there are distinct local and regional differences in antimicrobial resistance.

Pediatric pneumonia

Respiratory disease is common in pediatrics and diagnosing pneumonia may be clinically challenging. Changes in pneumococcal resistance and immunization practices continue to change the incidence and etiologies of pneumonia. Careful attention to epidemiologic, seasonal, and specific pediatric clinical factors and using adjunct radiographs and laboratory tests should guide the emergency physician in his or her management strategy, including selection of antibiotics and inpatient or outpatient disposition.