Increased carriage of resistant non-pneumococcal alpha-hemolytic streptococci after antibiotic therapy

β-Lactam-Resistant Streptococcus pneumoniae Dynamics Following Treatment: A Dose-Response Meta-analysis

BACKGROUND

Patient exposure to antibiotics promotes the emergence of drug-resistant pathogens. The aim of this study was to identify whether the temporal dynamics of resistance emergence at the individual-patient level were predictable for specific pathogen-drug classes.

METHODS

Following a systematic review, a novel robust error meta-regression method for dose-response meta-analysis was used to estimate the odds ratio (OR) for carrying resistant bacteria during and following treatment compared to baseline. Probability density functions fitted to the resulting dose-response curves were then used to optimize the period during and/or after treatment when resistant pathogens were most likely to be identified.

RESULTS

Studies of Streptococcus pneumoniae treatment with β-lactam antibiotics demonstrated a peak in resistance prevalence among patients 4 days after completing treatment with a 3.32-fold increase in odds (95% confidence interval [CI], 1.71-6.46). Resistance waned more gradually than it emerged, returning to preexposure levels 1 month after treatment (OR, 0.98 [95% CI, .55-1.75]). Patient isolation during the peak dose-response period would be expected to reduce the risk that a transmitted pathogen is resistant equivalently to a 50% longer isolation window timed from the first day of treatment.

CONCLUSIONS

Predictable temporal dynamics of resistance levels have implications both for surveillance and control.

Resistance decay in individuals after antibiotic exposure in primary care: a systematic review and meta-analysis

BACKGROUND

Antibiotic resistance is an urgent global problem, but reversibility is poorly understood. We examined the development and decay of bacterial resistance in community patients after antibiotic use.

METHODS

This was a systematic review and meta-analysis. PubMed, EMBASE and CENTRAL (from inception to May 2017) were searched, with forward and backward citation searches of the identified studies. We contacted authors whose data were unclear, and of abstract-only reports, for further information. We considered controlled or times-series studies of patients in the community who were given antibiotics and where the subsequent prevalence of resistant bacteria was measured. Two authors extracted risk of bias and data. The meta-analysis used a fixed-effects model.

RESULTS

Of 24,492 articles screened, five controlled and 20 time-series studies (total 16,353 children and 1461 adults) were eligible. Resistance in Streptococcus pneumoniae initially increased fourfold after penicillin-class antibiotic exposure [odds ratio (OR) 4.2, 95% confidence interval (CI) 3.5-5.4], but this fell after 1 month (OR 1.7, 95% CI 1.3-2.1). After cephalosporin-class antibiotics, resistance increased (OR 2.2, 95%CI 1.7-2.9); and fell to (OR 1.6, 95% CI 1.2-2.3) at 1 month. After macrolide-class antibiotics, resistance increased (OR 3.8, 95% CI 1.9-7.6) and persisted for 1 month (OR 5.2, 95% CI 2.6-10.3) and 3 months (OR 8.1, 95% CI 4.6-14.2, from controlled studies and OR 2.3, 95% CI 0.6-9.4, from time-series studies). Resistance in Haemophilus influenzae after penicillins was not significantly increased (OR 1.3, 95% CI 0.9-1.9) initially but was at 1 month (OR 3.4, 95% CI 1.5-7.6), falling after 3 months (OR 1.0, 95% CI 0.5-2.2). Data were sparse for cephalosporins and macrolides. Resistance in Enterobacter increased post-exposure (OR 3.2, 95% CI 0.9-10.8, from controlled studies and OR 7.1, 95% CI 4.2-12, from time-series studies], but was lower after 1 month (OR 1.8, 95% CI 0.9-3.6).

CONCLUSIONS

Resistance generally increased soon after antibiotic use. For some antibiotic classes and bacteria, it partially diminished after 1 and 3 months, but longer-term data are lacking and urgently needed.

TRIAL REGISTRATION

PROSPERO CRD42015025499 .

Ten-Year Study of Acute Otitis Media in Rochester, NY

This review summarizes a prospective, longitudinal 10-year study in Rochester, NY, involving 760 children where virtually all clinically diagnosed acute otitis media (AOM) was confirmed by bacterial culture of middle ear fluid. This review describes detection of otopathogens in middle ear fluid, nasopharyngeal (NP) otopathogen colonization patterns, AOM risk factor analysis, biomarkers of AOM and antibody responses to NP colonization by otopathogens. After licensure of PCV13, there was an immediate drop in AOM caused by Streptococcus pneumoniae (Spn) vaccine serotypes and shortly thereafer an increase in nonvaccine types 16, 21 and 35B. When NP co-colonization occurred, nontypeable Haemophilus influenzae (NTHi) predominated over Spn to cause AOM, and NTHi and Spn both predominated over Moraxella catarrhalis. Transcriptome analysis of peripheral blood mononuclear cells identified unique signatures for NTHi AOM compared with Spn AOM. Elevation of 3 cytokines in serum (S100A12, intercellular adhesion molecule 1 and interleukin 10) accurately predicted the presence and recovery from AOM and the likely otopathogen. NP colonization was an immunizing event.

Commensal streptococci serve as a reservoir for β-lactam resistance genes in Streptococcus pneumoniae

Streptococcus pneumoniae is a leading cause of pneumonia, meningitis, septicemia, and middle ear infections. The incidence of S. pneumoniae isolates that are not susceptible to penicillin has risen worldwide and may be above 20% in some countries. Beta-lactam antibiotic resistance in pneumococci is associated with significant sequence polymorphism in penicillin-binding proteins (PBPs). Commensal streptococci, especially S. mitis and S. oralis, have been identified as putative donors of mutated gene fragments. However, no studies have compared sequences of the involved pbp genes in large collections of commensal streptococci with those of S. pneumoniae. We therefore investigated the sequence diversity of the transpeptidase region of the three pbp genes, pbp2x, pbp2b, and pbp1a in 107, 96, and 88 susceptible and nonsusceptible strains of commensal streptococci, respectively, at the nucleotide and amino acid levels to determine to what extent homologous recombination between commensal streptococci and S. pneumoniae plays a role in the development of beta-lactam resistance in S. pneumoniae. In contrast to pneumococci, extensive sequence variation in the transpeptidase region of pbp2x, pbp2b, and pbp1a was observed in both susceptible and nonsusceptible strains of commensal streptococci, conceivably reflecting the genetic diversity of the many evolutionary lineages of commensal streptococci combined with the recombination events occurring with intra- and interspecies homologues. Our data support the notion that resistance to beta-lactam antibiotics in pneumococci is due to sequences acquired from commensal Mitis group streptococci, especially S. mitis. However, several amino acid alterations previously linked to beta-lactam resistance in pneumococci appear to represent species signatures of the donor strain rather than being causal of resistance.

Clinical characteristics and antimicrobial susceptibilities of viridans streptococcal bacteremia during febrile neutropenia in patients with hematologic malignancies: a comparison between adults and children

Background

This study was performed to compare the clinical characteristics and antibiotic susceptibilities of viridans streptococcal bacteremia (VSB) between febrile neutropenic adults and children with hematologic malignancies.

Methods

The consecutive medical records of neutropenic patients with hematologic malignancies who were admitted to the Catholic Blood and Marrow Transplantation Center between April 2009 and July 2012, and who were subsequently diagnosed with VSB were reviewed retrospectively. A comparison was made between the clinical and laboratory characteristics of adults and pediatric patients and also between patients with cefepime susceptible or not susceptible VSB.

Results

A total of 202 episodes (141 in adults, 61 in children) of VSB were identified. Among them, 26 (12.9%) cases had severe complications including four (2.0%) cases of death attributable to VSB. For antibacterial prophylaxis, most adults received ciprofloxacin (97.1%), but children more frequently received trimethoprim/sulfamethoxazole (86.9%). Oral mucositis (p = 0.005) and abdominal pain (p = 0.001) were found more frequently in adults, and cough was found more frequently in children (p = 0.004). The occurrence rates of severe complications and death attributable to VSB were not significantly different between adults and children. Susceptibility rate to cefepime was significantly higher in adults than children (85.7% vs. 66.1%, p = 0.002). However, in multivariate analysis, cefepime susceptibility had no impact on clinical outcome.

Conclusions

There was no significant difference in clinical outcome between adults and children with VSB despite a difference in cefepime susceptibility. Hence, different antibiotic treatment strategies may not be necessary.

Impact of respiratory viral infections on α-hemolytic streptococci and otopathogens in the nasopharynx of young children

BACKGROUND

We studied nasopharyngeal (NP) colonization in a cohort of children to determine the impact of viral upper respiratory infections (URIs) on nonpneumococcal α-hemolytic streptococci (AHS) and otopathogen colonization in association with acute otitis media (AOM).

METHODS

NP samples were collected routinely when children were aged 6, 9, 12, 15, 18, 24 and 30 months and during episodes of AOM. NP samples were prospectively obtained from 248 children during a 5-year time span: 1018 during routine visits, 161 at the time of AOM and 59 at follow-up visits 3 weeks after AOM.

RESULTS

The overall NP colonization rate of AHS was 50.8% during a non-AOM visit but declined to 38.3% during a viral URI with concurrent AOM (P = 0.0006). Of 56 AOM visits with paired follow-ups, 6 (10.7%) had AHS in the NP at the time of viral URI and concurrent AOM whereas 29 (51.8%) had AHS at the follow-up (P < 0.001). Lower NP colonization rates with AHS were associated with significant increases in Streptococcus pneumoniae carriage during non-AOM visits (P < 0.001) and during viral URI and concurrent AOM visits (P = 0.003). AHS NP colonization rates were not different when children had a viral URI without AOM versus when they were URI negative, but NP colonization with nontypeable Haemophilus influenzae rates increased (P < 0.001) and Moraxella catarrhalis decreased (P < 0.001) during viral URI.

CONCLUSION

Respiratory viral infections alter NP carriage rates of commensal AHS and otopathogens, including before AOM.

Antimicrobial agent exposure and the emergence and spread of resistant microorganisms: issues associated with study design

Antibiotics are essential agents that have greatly reduced human mortality due to infectious diseases. Their use, and sometimes overuse, have increased over the past several decades in humans, veterinary medicine and agriculture. However, the emergence of resistant pathogens is becoming an increasing problem that could result in the re-emergence of infectious diseases. Antibiotic prescription in human medicine plays a key role in this phenomenon. Under selection pressure, resistance can emerge in the commensal flora of treated individuals and disseminate to others. However, even if the effects of antimicrobial use on resistance is intuitively accepted, scientific rationales are required to convince physicians, legislators and public opinion to adopt appropriate behaviours and policies. With this review, we aim to provide an overview of different epidemiological study designs that are used to study the relationship between antibiotic use and the emergence and spread of resistance, as well as highlight their main strengths and weaknesses.

It's not easy being green: the viridans group streptococci, with a focus on pediatric clinical manifestations

The viridans group streptococci (VGS) are a heterogeneous group of organisms that can be human commensals, colonizing the gastrointestinal and genitourinary tracts in addition to the oral mucosa. VGS are generally considered to be of low pathogenic potential in immunocompetent individuals. However, in certain patient populations, VGS can cause invasive disease, such as endocarditis, intra-abdominal infection, and shock. Within the VGS, the rates and patterns of antimicrobial resistance vary greatly depending upon the species identification and the patient population. In general, Streptococcus mitis group organisms are resistant to more antimicrobial agents than the other VGS species. This review addresses current VGS taxonomy, in addition to the current methodologies being used in clinical microbiology laboratories for identification of VGS. Automated systems struggle overall with species level identification and susceptibility testing for VGS. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) identification is emerging as a potential alternative for organism identification. A review of recent pediatric-specific data regarding the clinical manifestations of VGS revealed that the Streptococcus anginosus group (SAG) organisms may be important pathogens in pediatric patients and that the VGS may contribute to disease in patients with cystic fibrosis. It also appears that rates of antimicrobial resistance in VGS in pediatric patients are surpassing those of the adult population.

Predictors of pain and/or fever at 3 to 7 days for children with acute otitis media not treated initially with antibiotics: a meta-analysis of individual patient data

OBJECTIVE

The goal was to determine the predictors of a prolonged course for children with acute otitis media.

METHODS

A meta-analysis of data with the observation groups of 6 randomized, controlled trials was performed. Participants were 824 children, 6 months to 12 years of age, with acute otitis media. The primary outcome was a prolonged course of acute otitis media, which was defined as fever and/or pain at 3 to 7 days.

RESULTS

Of the 824 included children, 303 had pain and/or fever at 3 to 7 days. Independent predictors of a prolonged course were age of < 2 years and bilateral acute otitis media. The absolute risk of pain and/or fever at 3 to 7 days for children < 2 years of age with bilateral acute otitis media (20% of all children) was 55%, and that for children > or = 2 years of age with unilateral acute otitis media (47% of all children) was 25%.

CONCLUSIONS

The risk of a prolonged course was 2 times higher for children < 2 years of age with bilateral acute otitis media than for children > or = 2 years of age with unilateral acute otitis media. Clinicians can use these features (ie, age of < 2 years and bilateral acute otitis media) to inform parents more explicitly about the expected course of their child's otitis media and to explain which features should prompt parents to contact their clinician for reexamination of the child.

Viridans Group Streptococcal Infections Among Children With Cancer and the Importance of Emerging Antibiotic Resistance

Viridans group streptococci (VGS) are major pathogens among children with cancer or receiving hematopoietic stem cell transplantation and are associated with considerable morbidity and mortality rates. The incidence and severity of VGS infections have increased during the past 15 years and account for as many as one third of all bacteremic episodes. Risk factors include severe neutropenia, mucositis, gastrointestinal toxicity, pneumonia, younger age, and high-intensity chemotherapy (especially cytosine arabinoside). VGS no longer can be assumed to be susceptible to penicillin because as many as 37 percent of VGS isolates harbor high levels of resistance (minimum inhibitory concentration >4 microg/mL). Furthermore, resistance to multiple classes of antibiotics, including beta-lactams and fluoroquinolones, has now been documented and is increasing in prevalence. In this article, we present a brief overview of VGS, describe the clinical spectrum of VGS-related diseases in children with cancer, and review the recent data regarding the incidence, clinical significance, and management of emerging antibiotic resistance among VGS.

Infection control, hospital epidemiology, and patient safety

Health care-acquired are a major risk for hospitalized children. Similar to adult patients, children are vulnerable to infections related to medical devices. Children also are at significant risk of nosocomial transmission of common pediatric viral illness, such as respiratory syncytial virus and varicella. In addition, pediatric patients have unique or incompletely developed immune system.

Pneumococcal vaccines: an update on current strategies

Streptococcus pneumoniae is a major cause of morbidity and mortality in infants, children and the elderly. Despite the availability of excellent antimicrobial therapy and adequate health care systems, respiratory diseases and invasive infections caused by pneumococci still comprise a major health problem. The emerging resistance to penicillin and other commonly used antibiotics underscores the importance of the development of novel vaccine strategies to combat pneumococcal disease. Although the 23-valent polysaccharide (PS) vaccine is immunogenic and protective in most adults and children over 5 years of age, they fail to protect children under 2 years of age. Fortunately, the recent conjugate vaccines have shown to be highly efficacious in preventing invasive diseases in this risk group. Moreover, promising results regarding prevention of pneumonia and acute otitis media have been published. Unfortunately, protection is raised against a limited number of pneumococcal serotypes, and serotype replacement and subsequent vaccine failure have become a serious concern. Currently, several pneumococcal surface proteins are considered as alternative vaccine candidates because of their serotype-independence. Thus far, pneumococcal surface adhesin A (PsaA) has proven to be highly protective against colonization in animal models. Moreover, pneumococcal surface protein A (PspA) and pneumolysin have shown to elicit protection against invasive diseases. Future research will elucidate their true potential in protecting humans. In this paper we discuss the present knowledge on pneumococcal vaccines and the current status of novel vaccine strategies.

Beta-lactamase-producing nontypeable Haemophilus influenzae fails to protect Streptococcus pneumoniae from amoxicillin during experimental acute otitis media

Acute otitis media (AOM) is the most common reason for outpatient antimicrobial therapy. Mixed infections pose a potential problem, since the first-line drug used for the treatment of AOM, amoxicillin, can be neutralized by beta-lactamase-producing pathogens of the upper respiratory tract. To study the effects of a 5-day course of amoxicillin on a mixed middle ear infection, rats were challenged with Streptococcus pneumoniae alone or in combination with beta-lactamase-producing nontypeable Haemophilus influenzae. Amoxicillin was introduced at the clinical peak of the infection. Local and systemic changes were monitored by otomicroscopy, bacterial culture, and analysis of histological changes and the expression of the transforming growth factor beta (TGF-beta) gene. beta-Lactamase-producing H. influenzae did not demonstrate an ability to protect S. pneumoniae. Amoxicillin eradicated the pneumococci in all treated animals but increased to some degree the ability of H. influenzae to persist at the site of infection. Thus, only an insignificant acceleration of the resolution of the AOM caused by a mixture of pathogens was observed during treatment. Moderate to major morphological changes could not be avoided by treatment of the mixed infections, but a slight downregulation of TGF-beta expression was observed. In contrast to infections caused by a single pathogen, the mixed infections induced white plaques in the tympanic membrane at a remarkably high frequency independent of treatment. These experimental findings constitute support for further studies of antimicrobial drugs and AOM caused by bacteria with and without mechanisms of antibiotic resistance.

Controlling healthcare-associated infections: the role of infection control and antimicrobial use practices

Healthcare-associated infections are a major cause of morbidity and mortality in pediatric patients in the United States and throughout the world. Overall rates of infection range widely depending on the pediatric population, with the highest rates being in patients in neonatal intensive care units, followed by those in pediatric intensive care units, immunocompromised patients, and those undergoing surgical procedures. Risk factors for healthcare-associated infection include intrinsic and extrinsic factors. The major intrinsic factors are age, birth weight, underlying diseases, and immune status. The major extrinsic factors are presence of invasive devices and procedures. The major risk factors for healthcare-associated infection caused by antimicrobial-resistant pathogens are either the transmission of pathogens from person to person (directly or indirectly, usually via the hands of healthcare workers) or the emergence of resistance after exposure to antimicrobials. Preventing healthcare-associated infections caused by antimicrobial-resistant pathogens requires a comprehensive approach that includes: 1) preventing infections through the use of vaccines and prophylaxis; 2) minimizing the use of invasive devices; 3) understanding and fully implementing (and complying with) current guideline recommendations for the prevention of infections; and 4) using antimicrobials judiciously. Implementing such a comprehensive program will reduce healthcare-associated infections, reduce the prevalence of antimicrobial-resistant pathogens, improve patient outcomes, and reduce health care costs.

Peritonsillar Abscess: A Study of 724 Cases in Japan

We reviewed the records of 724 patients diagnosed with peritonsillar abscess who had been admitted to our hospital between January 1988 and December 1999. We analyzed their clinical features, disease course, and treatment. The male:female ratio was 3:1, and approximately two-thirds of these patients were between 20 and 39 years of age. The most common aerobic bacteria cultured from patients’ pus were α-hemolytic streptococci. Severe complications—including deep neck infections and mediastinals—were seen in 13 patients (1.8%). This complication rate suggests that patients with peritonsillar abscess should undergo immediate incision and drainage rather than needle aspiration.

Effects of large dosages of amoxicillin/clavulanate or azithromycin on nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, nonpneumococcal alpha-hemolytic streptococci, and Staphylococcus aureus in children with acute otitis media

Prior use of antibiotics is associated with carriage of resistant bacteria. Colonization by Streptococcus pneumoniae, Haemophilus influenzae, nonpneumococcal alpha-hemolytic streptococci (NPAHS), and Staphylococcus aureus was evaluated in children receiving antibiotic therapy for acute otitis media and in untreated, healthy control subjects. Children were randomly assigned to receive either amoxicillin/clavulanate (90 mg/kg per day) or azithromycin. Swabs were obtained before initiating therapy and again 2 weeks and 2 months after initiating therapy. We also obtained swabs from control subjects at the time of enrollment and 2 weeks and 2 months after enrollment. The decrease in the rate of carriage of S. pneumoniae and H. influenzae at 2 weeks was significant only in the amoxicillin/clavulanate group (P<.001 and P=.005, respectively). The rate of nasopharyngeal colonization with NPAHS among treated patients increased from 23% to 39% at 2 months (P=.01). This increase was similar for both treatment groups. These results suggest that the competitive balance between organisms is altered by antibiotic therapy.

Association between antibiotic resistance and community prescribing: a critical review of bias and confounding in published studies

The reported association between antibiotic prescribing and resistance may be subject to bias or confounding. Bias describes any effect at any stage of investigation or inference tending to produce results that depart systematically from the true value. A confounding variable is one that is associated independently with both exposure and outcome. Confounding variables may create an apparent association or mask a real association. Pharmacoepidemiology is the study of the use and the effects of drugs in large numbers of people. We have used standard pharmacoepidemiological methods to investigate sources of bias and confounding in the association between prescribing and resistance. We conclude that the association is statistically valid and that the consistency of evidence supports a cause-effect relationship. Nonetheless, several important sources of bias and confounding must be taken into account in future studies that analyze the impact of prescribing policies on resistance.

Current approaches to otitis media

Acute otitis media is the most commonly diagnosed illness in children, and is one of the most common reasons for antibiotic prescription. In many countries, antibiotic resistance is increasing among the bacteria that are implicated in acute otitis media, particularly Streptococcus pneumoniae. This evolution should stimulate changes in the management of acute otitis media, particularly the following: improvement in diagnostic accuracy; reduction in antibiotic use; selection of the most appropriate drugs at the appropriate dosage; reduction in duration of treatment, when possible; and implementation of new vaccines.