Antimicrobial susceptibility testing of clinical isolates of Bordetella pertussis from northern California: report from the SENTRY Antimicrobial Surveillance Program

Macrolide Resistance in Bordetella pertussis: Current Situation and Future Challenges

Pertussis is a highly contagious respiratory infection caused by Bordetella pertussis bacterium. The mainstay of treatment is macrolide antibiotics that reduce transmissibility, shorten the duration of symptoms and decrease mortality in infants. Recently, the macrolide resistance of B. pertussis has been reported globally but is especially widespread in mainland China. In this review, we aim to summarise the current understanding of the epidemiology, resistance mechanisms and clinical implications of B. pertussis macrolide resistance. Since the first appearance of macrolide-resistant B. pertussis in Arizona, USA, in 1994, only sporadic cases have been reported outside China. In certain parts of China, on the other hand, up to 70-100% of the recent clinical isolates have been found to be macrolide resistant. Reasons for macrolide resistance being centred upon China during the last decade can only be speculated on, but the dominant B. pertussis lineage is different between China and most of the high-income countries. It seems evident that efforts to increase awareness, guide molecular epidemiological surveillance and carry out systematic screening of B. pertussis positive samples for macrolide resistance should be implemented globally. In addition, practices to improve the clinical care of infants with pertussis caused by resistant strains should be studied vigorously.

Missed pertussis diagnosis during co-infection with Bordetella holmesii

The purpose of this study is to identify predictive factors associated with missed diagnosis of B. pertussis-B. holmesii co-infection by assessing the analytical performance of a commercially available multiplexed PCR assay and by building a prediction model based on clinical signs and symptoms for detecting co-infections. This is a retrospective study on the electronic health records of all clinical samples that tested positive to either B. pertussis or B. holmesii from January 2015 to January 2018 at Geneva University Hospitals. Multivariate logistic regression was used to build a model for co-infection prediction based on the electronic health record chart review. Limit of detection was determined for all targets of the commercial multiplexed PCR assay used on respiratory samples. A regression model, developed from clinical symptoms and signs, predicted B. pertussis and B. holmesii co-infection with an accuracy of 82.9% (95% CI 67.9-92.8%, p value = .012), for respiratory samples positive with any of the two tested Bordetella species. We found that the LOD of the PCR reaction targeting ptxS1 is higher than that reported by the manufacturer by a factor 10. The current testing strategy misses B. pertussis and B. holmesii co-infections by reporting only B. holmesii infections. Thus, we advocate to perform serological testing for detecting a response against pertussis toxin whenever a sample is found positive for B. holmesii. These findings are important, both from a clinical and epidemiological point of view, as the former impacts the choice of antimicrobial drugs and the latter biases surveillance data, by underestimating B. pertussis infections during co-infections.

Pharmacotherapy for Bordetella pertussis infection. I. A synthesis of laboratory sciences

There is considerable history and practice experience both with laboratory susceptibility testing for Bordetella pertussis and clinical treatment. This two-part narrative review provides a synthesis of the laboratory and clinical sciences as they apply to this bacterium and the clinical consequences of treating infection. It is generally held that antibiotic susceptibility testing for B. pertussis is not sufficiently standardised, but there has not been an urgent need to consolidate the same given the lack global experience with major resistance profiles. Experience in China, however, has provided concern for high-level macrolide resistance. The nature of and frequency of such resistance has raised the bar for reconsideration of susceptibility testing given that first-line treatment may be regionally compromised. Disk diffusion and Etest susceptibility testing can be recommended for screening resistance among individual isolates of B. pertussis and on an ad hoc manner. Disk diffusion, Etest and/or critical agar dilution testing can be recommended for large-scale studies. Standards for inoculum, growth atmosphere, timing of interpretation, preferred testing media and controls can be extrapolated from the publications to date. Such methods should be able to detect high-level resistance to several antibiotics, but especially macrolides. Concern for intermediate-susceptible categories requires consideration as well as the correlation with bacteriological and clinical outcomes. Provisional standards can be applied at this time, and modification or fine-tuning of any such standards are open to future investigation.

In vitro activity and clinical efficacy of macrolides, cefoperazone-sulbactam and piperacillin/piperacillin-tazobactam against Bordetella pertussis and the clinical manifestations in pertussis patients due to these isolates: A single-centre study in Zhejiang Province, China

BACKGROUND AND OBJECTIVE

Macrolides are the recommended antibiotics for treating pertussis and preventing transmission. The causative bacterium, Bordetella pertussis, has high macrolide resistance and has recently circulated in China. The objective of this study was to find effective alternative antibiotics for treatment by assessing the in vitro activity and clinical efficacy of antibiotics against Bordetella pertussis.

METHODS

Bordetella pertussis was confirmed by agglutination with specific antisera and mass spectrometry. The MICs of antibiotics against isolates were determined using the Etest method. Treatment outcomes were clinically and microbiologically evaluated.

RESULTS

A total of 126 pertussis patients were diagnosed based on culture, 69.8% of whom were aged ≤6 months and 72.1% were treated with previous macrolides. Leucocytosis and lymphocytosis were observed in 29.4% and 54.8% of all patients, respectively. Both MIC₅₀ and MIC₉₀ of erythromycin, azithromycin, and clindamycin were >256mg/L, and 75.4% were highly macrolide resistant. The MIC₉₀ of trimethoprim-sulfamethoxazole, ampicillin, ampicillin-sulbactam, cefuroxime, ceftriaxone and cefoperazone-sulbactam were 0.38mg/L, 0.25mg/L, 0.19mg/L, 12mg/L, 0.19mg/L and 0.047mg/L, respectively. The MICs of piperacillin in all of the isolations were <0.016mg/L. Of the patients treated with single cefoperazone-sulbactam or piperacillin-tazobactam, 30 of 32 (93.8%) had significantly improved clinical symptoms and 24 of 25 (96%) had negative culture results after 2 weeks of therapy.

CONCLUSION

Macrolide resistance in Bordetella pertussis is a serious problem in Zhejiang Province, China. Piperacillin/piperacillin-tazobactam and cefoperazone-sulbactam have potent antibacterial activity in vitro and in vivo, and may become the alternative choice for treating pertussis caused by macrolide-resistant isolates.

Antimicrobial Susceptibility and Molecular Detection of Pertactin-producing and Pertactin-Deficient Bordetella pertussis

Resurgence of Bordetella pertussis in recent years in the United States has coincided with a dramatic rise in pertactin-deficient strains. Limited data exist on detectability by nucleic acid amplification testing and antimicrobial susceptibility of pertactin-deficient B. pertussis. This study compares 15 pertactin-producing and 15 pertactin-deficient B. pertussis isolates. Pertactin-producing and pertactin-deficient strains were equally detected by nucleic acid amplification testing and were susceptible to antibiotics.

Variation in Bordetella pertussis Susceptibility to Erythromycin and Virulence-Related Genotype Changes in China (1970-2014)

OBJECTIVES

To investigate changes in virulence-related genotypes and in the antimicrobial susceptibility of Bordetella pertussis isolates collected from the 1970s to 2014 in the northern part of China.

METHODS

A total of 124 B. pertussis isolates from three periods, the 1970s, 2000-2008, and May 2013-Sept 2014, were typed by multilocus sequence typing (MLST) and tested for antimicrobial susceptibility and virulence-related genes. A fragment of the 23S rRNA gene from each of the 99 isolates from 2013-2014 was amplified and sequenced.

RESULTS

All isolates from 2000-2008 and 2013-2014 were identified as ST2, whereas isolates from the 1970s were ST1. PtxA2/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2, which was the same as the vaccine strain, was the only type in the 1970s. During the 2000s and 2013-2014, the virulence type ptxA1/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2 was dominant, with frequencies of 68.4% and 91.9%, respectively. Nine ptxP3 strains, which were more virulent, were detected after 2000. All 124 isolates were susceptible to levofloxacin, sulphamethoxazole/trimethoprim and tetracycline. The isolates from the 1970s and 2000-2008 were susceptible to all tested macrolides, whereas 91.9% of the 2013-2014 isolates were highly resistant (minimal inhibitory concentration, MIC >256 μg/ml). No ptxP3 strain was resistant to macrolides. All erythromycin-resistant strains except for one had the A2047G mutation in the 23S rRNA gene.

CONCLUSIONS

Macrolide resistance of the B. pertussis population has been a serious problem in the northern part of China. Because most of the epidemic clone of the pathogen expresses the same antigen profiles as the vaccine strain, except ptxA, improvements in immunization strategies may prevent the spread of infection and drug resistance.

Emergence of quinolone-resistant Bordetella pertussis in Japan

Six Bordetella pertussis strains isolated from children in Japan from 2004 to 2006 showed high-level resistance to nalidixic acid (NAL; MIC, >256 microg/ml) and decreased susceptibilities to fluoroquinolones. All of the NAL-resistant strains had the same D87G mutation in gyrA.

Antimicrobial susceptibility testing of Bordetella pertussis in Taiwan prompted by a case of pertussis in a paediatric patient

In Taiwan, pertussis is a notifiable disease with a low incidence in recent years, and antimicrobial susceptibility testing for the causative agent, Bordetella pertussis, has not been reported to date. In May 2007, the Centers for Disease Control, Taiwan, was informed of a 1-month-old pertussis patient who did not respond to erythromycin treatment. In this study, we report the result of antimicrobial susceptibility testing performed for the suspected erythromycin-resistant isolate, as well as for an additional 27 B. pertussis clinical isolates that represented almost all epidemiologically unrelated isolates obtained throughout Taiwan between 2003 and 2007. All isolates were fully susceptible to azithromycin, erythromycin, clarithromycin and trimethoprim/sulfamethoxazole (MIC ≤0.047 μg ml−1). This result demonstrates the general susceptibility of B. pertussis to antimicrobial agents in vitro in Taiwan.

Clinical and economic effects of pertussis outbreaks

BACKGROUND

The reported incidence of pertussis is increasing, especially among the adolescent population. Current outbreak management strategies include investigating cases, contact follow-up, diagnostic testing, and antibiotic prophylaxis and treatment. The cost of these methods is substantial and can be attributed to the mobilization within public health departments to control the outbreaks.

METHODS

Through an extensive review of the literature, the clinical and economic effects of pertussis outbreaks in various nonhousehold settings are discussed.

RESULTS

The reported incidence of pertussis among adolescents and adults in the United States since the early 1980s continues to rise. The challenges of preventing and controlling pertussis outbreaks involve diagnosing pertussis in a timely, accurate, and standardized fashion and understanding the true burden of disease in different age and socioeconomic groups. The economic effects of pertussis have been demonstrated to be significant to individuals and communities, both locally and globally. Costs associated with pertussis often include diagnostic testing, hospitalization, emergency and/or medical office visits, antibiotic and symptomatic treatment, lost work days, and other reductions in productivity. In outbreak settings, increased surveillance, antibiotic prophylaxis, isolation of infected cases, and enhanced communication and education add to the economic burden of this disease. The potential opportunity to apply the use of pertussis booster vaccination to these populations, particularly among adolescents, likely would reduce the occurrence of pertussis and minimize the clinical and economic repercussions of pertussis outbreaks.

CONCLUSIONS

In the near future, it is anticipated that evaluating the effects of a licensed acellular pertussis booster vaccine in persons > or =10 years of age will become routine in pertussis prevention and outbreak-control activities.

Pharmacokinetics of intravenously administered azithromycin in pediatric patients

BACKGROUND

The objective of this study was to characterize the pharmacokinetics and tolerance of a single intravenous (IV) azithromycin dose in children.

METHODS

Subjects were stratified into 4 age groups: 0.5-2 years; >2-<6 years; 6-<12 years; and 12-<16 years. Each subject received a single 10 mg/kg dose (500 mg maximum) infused in 1 hour. Serial venous blood samples were obtained for a 168-hour period, and laboratory safety evaluations were performed immediately preceding azithromycin administration and at the conclusion of the study. Serum azithromycin concentrations were quantified with a validated high performance liquid chromatography method with mass spectrometric detection. Pharmacokinetic indices were calculated for each subject by noncompartmental techniques.

RESULTS

Thirty-two subjects (6.7 +/- 5.0 years, 11 boys) participated. Mean serum concentration-time data were comparable for the 4 age groups. For all subjects with evaluable data, the mean area under the curve from 0 to 72 hours (AUC0-72) was 8.2 microg . h/mL (n = 26), the maximum concentration (Cmax) was 2.4 microg/mL and the elimination half-life (t1/2) was 65.2 hours (n = 25). The AUC0-72 and Cmax were not associated with age. The dose was well-tolerated with no serious adverse events.

CONCLUSION

The disposition of azithromycin after a single 10-mg/kg IV dose (maximum labeled adult dose of 500 mg) is comparable in pediatric patients between 0.5 and 16 years of age. These pharmacokinetic data can be used to guide dose selection for future therapeutic trials of IV azithromycin in pediatric patients.