Hospital-based prospective study of pertussis in infants and close contacts in Tehran, Iran.

BACKGROUND: Pertussis remain a global health concern, especially in infants too young to initiate their vaccination. Effective vaccination and high coverage limit the circulation of the pathogen, yet duration of protection is limited and boosters are recommended during a lifetime. In Iran, boosters are given at 18 months and 6 years old using whole pertussis vaccines for which efficacy is not known, and pertussis surveillance is scant with only sporadic biological diagnosis. Burden of pertussis is not well understood and local data are needed. METHODS: Hospital-based prospective study implementing molecular laboratory testing in infants aged ≤6 months and presenting ≥5 days of cough associated to one pertussis-like symptom in Tehran. Household and non-household contact cases of positive infants were evaluated by comprehensive pertussis diagnosis (molecular testing and serology) regardless of clinical signs. Clinical evaluation and source of infection were described. RESULTS: A total of 247 infants and 130 contact cases were enrolled. Pertussis diagnosis result was obtained for 199 infants and 104 contact cases. Infant population was mostly < 3 months old (79.9%; 157/199) and unvaccinated (62.3%; 124/199), 20.1% (40/199) of them were confirmed having B. pertussis infection. Greater cough duration and lymphocyte counts were the only symptoms associated to positivity. Half of the contact cases (51.0%; 53/104) had a B. pertussis infection, median age was 31 years old. A proportion of 28.3% (15/53) positive contacts did not report any symptom. However, 67.9% (36/53) and 3.8% (2/53) of them reported cough at inclusion or during the study, including 20.8% (11/53) who started coughing ≥7 days before infant cough onset. Overall, only five samples were successfully cultured. CONCLUSION: These data evidenced the significant prevalence of pertussis infection among paucy or poorly symptomatic contacts of infants with pertussis infection. Widespread usage of molecular testing should be implemented to identify B. pertussis infections.

Genomic epidemiology of Iranian Bordetella pertussis: 50 years after the implementation of whole cell vaccine.

Pertussis caused by Bordetella pertussis, remains a public health problem worldwide, despite high vaccine coverage in infants and children in many countries. Iran has been using whole cell vaccine for the last 50 years with more than 95% vaccination rate since 1988 and has experienced pertussis resurgence in recent years. Here, we sequenced 55 B. pertussis isolates mostly collected from three provinces with the highest number of pertussis cases in Iran, including Tehran, Mazandaran, and Eastern-Azarbayjan from the period of 2008-2016. Most isolates carried ptxP3/prn2 alleles (42/55, 76%), the same genotype as isolates circulating in acellular vaccine-administrating countries. The second most frequent genotype was ptxP3/prn9 (8/55, 14%). Only three isolates (5%) were ptxP1. Phylogenetic analysis showed that Iranian ptxP3 isolates can be divided into eight clades (Clades 1-8) with no temporal association. Most of the isolates from Tehran grouped together as one distinctive clade (Clade 8) with six unique single nucleotide polymorphisms (SNPs). In addition, the prn9 isolates were grouped together as Clade 5 with 12 clade-supporting SNPs. No pertactin deficient isolates were found among the 55 Iranian isolates. Our findings suggest that there is an ongoing adaptation and evolution of B. pertussis regardless of the types of vaccine used.

Molecular detection of Bordetella holmesii in two infants with pertussis-like syndrome: the first report from Iran.

BACKGROUND AND OBJECTIVES: Bordetella holmesii is associated with a pertussis-like respiratory syndrome in healthy individuals and also a rare cause of septicaemia, endocarditis, pneumonia, and septic arthritis, mostly in immunocompromised patients. Culture technique and real-time PCR are 2 methods used to detect Bordetella spp. MATERIALS AND METHODS: In this study, 435 nasopharyngeal specimens of patients with suspected whooping cough were checked for the presence of B. holmesii using 2 methods of culture technique and real-time PCR. RESULTS: In this study, we detected hIS1001 and IS481 of B. holmesii in 2 infants suspected of having pertussis-like syndrome. CONCLUSION: Our observations demonstrate that accurate diagnosis is needed to discriminate between B. holmesii and B. pertussis infections among pertussis cases; otherwise, it could lead to misestimating pertussis rate and vaccine efficacy.

Comparison of culture and real-time PCR for detection of Bordetella pertussis isolated from patients in Iran.

BACKGROUND AND OBJECTIVE: Due to contagiousness of pertussis, a rapid and sensitive method for diagnosis is required to initiate the treatment and interrupt its transmission. MATERIALS AND METHODS: To detect B. pertussis strains, we used two real-time PCR targeting IS481 and BP283 sequences and compared factors influencing culture and real-time PCR results. RESULTS: Totally, 779 specimens were collected from patients among which 11 (1.4%) were culture positive. Using IS481 and BP283 primers, 122 (15.6%) and 100 (12.8%) were diagnosed as infected specimens respectively. There were significant relationships between the real-time PCR method for diagnosis of B. pertussis and age, sex and vaccination of patients before sampling. CONCLUSION: The real-time PCR is superior and much more sensitive than culture for diagnosis of B. pertussis. However, the sensitivity was improved when both IS481 and BP283 were used. Correct sampling and transportation of specimen also improved the detection rate in our research.