Haemophilus influenzae type b disease after rifampin prophylaxis in a day care center: possible reasons for its failure

Pharyngeal Colonization by Kingella kingae, Transmission, and Pathogenesis of Invasive Infections: A Narrative Review

With the appreciation of Kingella kingae as a prime etiology of osteoarticular infections in young children, there is an increasing interest in the pathogenesis of these diseases. The medical literature on K. kingae’s colonization and carriage was thoroughly reviewed. Kingella kingae colonizes the oropharynx after the second life semester, and its prevalence reaches 10% between the ages of 12 and 24 months, declining thereafter as children reach immunological maturity. Kingella kingae colonization is characterized by the periodic substitution of carried organisms by new strains. Whereas some strains frequently colonize asymptomatic children but are rarely isolated from diseased individuals, others are responsible for most invasive infections worldwide, indicating enhanced virulence. The colonized oropharyngeal mucosa is the source of child-to-child transmission, and daycare attendance is associated with a high carriage rate and increased risk of invasive disease. Kingella kingae elaborates a potent repeat-in-toxin (RTXA) that lyses epithelial, phagocytic, and synovial cells. This toxin breaches the epithelial barrier, facilitating bloodstream invasion and survival and the colonization of deep body tissues. Kingella kingae colonization and carriage play a crucial role in the person-to-person transmission of the bacterium, its dissemination in the community, and the pathogenesis of invasive infections.

Kingella kingae: carriage, transmission, and disease

Kingella kingae is a common etiology of pediatric bacteremia and the leading agent of osteomyelitis and septic arthritis in children aged 6 to 36 months. This Gram-negative bacterium is carried asymptomatically in the oropharynx and disseminates by close interpersonal contact. The colonized epithelium is the source of bloodstream invasion and dissemination to distant sites, and certain clones show significant association with bacteremia, osteoarthritis, or endocarditis. Kingella kingae produces an RTX (repeat-in-toxin) toxin with broad-spectrum cytotoxicity that probably facilitates mucosal colonization and persistence of the organism in the bloodstream and deep body tissues. With the exception of patients with endocardial involvement, children with K. kingae diseases often show only mild symptoms and signs, necessitating clinical acumen. The isolation of K. kingae on routine solid media is suboptimal, and detection of the bacterium is significantly improved by inoculating exudates into blood culture bottles and the use of PCR-based assays. The organism is generally susceptible to antibiotics that are administered to young patients with joint and bone infections. β-Lactamase production is clonal, and the local prevalence of β-lactamase-producing strains is variable. If adequately and promptly treated, invasive K. kingae infections with no endocardial involvement usually run a benign clinical course.

Outbreaks of Kingella kingae infections in daycare facilities

During the past decade, transmission of the bacterium Kingella kingae has caused clusters of serious infections, including osteomyelitis, septic arthritis, bacteremia, endocarditis, and meningitis, among children in daycare centers in the United States, France, and Israel. These events have been characterized by high attack rates of disease and prevalence of the invasive strain among asymptomatic classmates of the respective index patients, suggesting that the causative organisms benefitted from enhanced colonization fitness, high transmissibility, and high virulence. After prophylactic antibacterial drugs were administered to close contacts of infected children, no further cases of disease were detected in the facilities, although test results showed that some children still carried the bacterium. Increased awareness of this public health problem and use of improved culture methods and sensitive nucleic acid amplification assays for detecting infected children and respiratory carriers are needed to identify and adequately investigate outbreaks of K. kingae disease.

Outbreak of Haemophilus influenzae type b disease among fully vaccinated children in a day-care center

BACKGROUND

Two cases of invasive Haemophilus influenzae type b (Hib) infection were reported in immunized children in a day nursery within 1 week. Both cases were younger than 18 months of age, cared for in the same room. We aimed to characterize carriage of Hib and response to eradication therapy in this setting.

METHODS

Ninety-four children were enrolled in the nursery, cared for by 21 staff in 4 rooms, divided by age. Two children of a part time teacher also attended. Oropharyngeal swabs were taken to detect Hib carriage before introduction of rifampin prophylaxis (20 mg/kg/day for 4 days). A questionnaire addressing risk factors for colonization was administered to parents and staff. Carriage was reassessed in children and carers from the same room as the index cases 1 month later.

RESULTS

Eighty-nine children and all 21 staff were swabbed. Two additional Hib carriers, 1 child and 1 staff member, were identified from the same room as the cases. These isolates appeared identical with those causing invasive disease. Given the small numbers no clear risk factors for carriage could be confirmed. Compliance with rifampin prophylaxis was 97.4%. One month later no carriers were found among the 7 children and 3 staff tested from the room in which the cases were originally identified.

CONCLUSIONS

Although immunization against Hib has resulted in a reduction in the incidence of this disease in the UK, individual protection cannot be assumed to be infallible. The importance of timely chemoprophylaxis of close contacts of a child with invasive Hib disease is reinforced.

Chemoprophylaxis of meningitis

Chemoprophylaxis of meningitis caused by Neisseria meningitidis and Haemophilus influenzae may be determined by the epidemiology of transmission, the antibiotic susceptibility patterns of the organisms, and the usage of vaccines. A review of transmission in England distinguishes differences in sporadic and cluster meningococcal infections. Because of resistance to sulphadiazine, rifampicin and ciprofloxacin are prophylactic agents of choice. Vaccination can be a useful adjunct to antibiotic prophylaxis. Prophylaxis for meningitis due to H. influenzae type b can be provided by rifampicin and vaccination can also be an adjunct to antibiotic prophylaxis.

Risk of subsequent disease among day-care contacts of patients with systemic Hemophilus influenzae type B disease

There is controversy about whether to provide rifampin prophylaxis routinely to contacts in day-care facilities of a patient with a primary case of Hemophilus influenzae type b disease. We prospectively investigated primary cases of H. influenzae type b disease in day-care facilities in Dallas County, Texas, to determine the rate of subsequent disease among contacts. Ninety-one children with primary cases of H. influenzae type b disease who were attending day-care facilities were enrolled from October 1982 to October 1984. A total of 587 classroom contacts of these children under four years of age were not given rifampin. During 60 days of follow-up, there was one subsequent case in a classroom contact. Untreated children under two years of age who were directly exposed to a patient with a primary case were considered to be at highest risk of disease, but there were no subsequent cases in this group of 361 children. However, there were two cases in new enrollees who started attending day-care facilities during the 60-day follow-up period but who were not exposed to a patient with a primary case. At day-care centers in which there was a second case during the follow-up period, there was a high prevalence of colonization with H. influenzae type b in both patient and nonpatient groups of preschool children. These data indicate that the rate of subsequent disease in classroom contacts of patients in day-care facilities is lower than that reported in households (1 of 587 vs. 20 of 829, P = 0.001) and that this rate may be similar to the base rate of primary disease in day-care facilities. We conclude that rifampin prophylaxis may not be appropriate after the occurrence of a primary case of H. influenzae type b disease in a day-care facility in Dallas County.

Pharyngeal colonization with Haemophilus influenzae type b in children in a day care center without invasive disease

During an 18-month period, monthly pharyngeal cultures for Haemophilus influenzae type b (Hib) were obtained from 66 children and their caretakers in a day care center in which no systemic disease caused by Hib occurred. The average colonization rate for Hib was 10%, and ranged from 0% to 23% for a single month. Infants housed in a separate building with a cohorted staff were not colonized by Hib. However, 71% of the toddler group and 48% of the preschool group became colonized by Hib at some time during the 18-month-study. Of 89 Hib isolates, 93% were biotype 1 (Kilian), and 90% of these had a similar outer membrane protein profile, designated subtype 1L. This strain was recovered from children at the center for 15 of 18 months. No invasive disease occurred. Thus, Hib may be widespread among preschool children in a day care center and persist for longer than a year without resulting in systemic disease.

Prophylaxis for bacterial meningitis

Close contact of patients with bacterial meningitis that is caused by either Haemophilus influenzae type b or Neisseria meningitidis are at an increased risk of developing invasive infections with these bacteria. Chemoprophylaxis with rifampin and immunoprophylaxis with vaccines may prevent some secondary infections.

Prevention of central nervous system infections in patients at risk

Infections of the central nervous system in patients at risk are relatively uncommon when compared with pneumonia, bacteremia, and soft tissue infection. However, they carry serious morbidity and are frequently fatal. Each of the diverse conditions that can place a patient at risk for central nervous system infection is associated with a fairly predictable spectrum of etiologic organisms. Various forms of trauma (including blunt and penetrating injuries and neurosurgery, especially when a cerebrospinal fluid shunt is implanted) predispose to infection with common pathogenic bacteria. Defects of cellular immunity including congenital immune deficiencies, immunosuppressive drug therapy, leukemia, lymphoma, and the acquired immune deficiency syndrome are more likely to give rise to infection with a distinctive spectrum of opportunistic viruses, fungi, and protozoa. Other underlying conditions include sinus, ear, and mastoid infections, congenital heart disease, intrathoracic suppuration, endocarditis, and bacteremia, hypogammaglobulinemia, and complement deficiencies. Some preventive measures including vaccines, antibiotics, and surgical procedures are available. However, for many of these central nervous system infections, preventive measures are lacking or less effective than those for infections in other organs. In the future, opportunistic central nervous system infections will increase in frequency as the number of patients at risk continues to grow.