The relationship between pertussis symptomatology, incidence and serology in adolescents.

Adolescents have an unknown true incidence of pertussis and are important reservoirs of transmission. We evaluated the incidence of coughing illnesses, serologic evidence of recent infection and the relationship between symptomatology and serology in adolescents. A retrospective respiratory questionnaire and anti-pertussis toxin immunoglobulin G measurement was undertaken in a convenience sample of adolescents and was repeated one year later. The US Centers for Disease Control clinical case definition of pertussis was used. At least a third of coughing illnesses met the CDC clinical case definition. Symptoms correlated with serology. Pertussis was endemic with a high annual incidence of new infections.

Cough symptoms in children aged 5-14 years in Sydney, Australia: non-specific cough or unrecognized pertussis?

OBJECTIVE: The aim of this study was to estimate the community prevalence of coughing symptoms, consistent with surveillance definitions for pertussis, and doctor-diagnosed pertussis in children aged 5-14 years. METHODOLOGY: A telephone survey of a cross-sectional community sample of parents regarding their child's cough symptoms in the previous 12 months was undertaken in a representative Australian urban region. RESULTS: In 2020 interviews, parents reported that 22% of children had a cough lasting 2 weeks or longer in the preceding 12 months, and 14% (283) had additional symptoms meeting the Centers for Disease Control (CDC) case definition for pertussis. A cough meeting the case definition was significantly more commonly reported by parents of children aged 5-9 years (17%; P < 0.001) but reported exposure to diagnosed pertussis in such cases was significantly more common in children aged 10-14 years (4.3%; odds ratio 12.8; P < 0.01). Parents of 90% of children meeting the CDC case definition sought medical advice. A diagnosis of pertussis was reported in only 1.2% of cases, which extrapolates to an annual incidence of doctor-diagnosed pertussis of 347/100,000 (95% confidence interval, 140-714 per 100,000). This contrasts with 29/100,000 notified cases in the same age group, time period and geographic area. CONCLUSION: Cough episodes meeting a clinical case definition for pertussis commonly used in surveillance are reported by a high proportion of carers of school-aged children in Australia. The majority of children who met the CDC and Australian case definitions for pertussis and sought medical attention were not identified as potentially having pertussis, suggesting underdiagnosis of pertussis. Even if less than half of this is true pertussis, the potential impact in terms of transmission of pertussis in the community is likely to be high. The reported incidence of doctor-diagnosed disease estimated from this survey was at least five and up to 20 times the official notification rate. More work needs to be done in raising awareness among medical practitioners of pertussis as a differential diagnosis in older children and adolescents with cough.

Biochemical and functional characterisation of secreted phospholipase activities from Cryptococcus neoformans in their naturally occurring state.

A recent study demonstrated that phospholipase B (PLB), lysophospholipase (LPL) and lysophopholipase transacylase (LPTA) are secreted by Cryptococcus neoformans var. neoformans and showed that the amount of enzyme production correlated with virulence in mice. The present study characterised the extracellular enzyme activities further by radiometric assays and 31P nuclear magnetic resonance spectroscopy (NMR). All three enzymes were most active between 25 and 40 degrees C. Bovine lung surfactant and its major lipid components, disaturated phosphatidylcholine and phosphatidylglycerol, were the optimal substrates for PLB. Lysophosphatidylcholine was the favoured substrate for LPL and LPTA. PLB and LPL/LPTA were differentially affected by Triton X-100, and palmitoyl carnitine was a potent inhibitor of the three phospholipases. LPL and PLB activities were inhibited by dithiothreitol; N-ethylmaleimide inhibited LPL and LPTA activities. None of the enzymes was inhibited by N-bromosuccinimide or p-bromophenacyl bromide. Cellular disruption experiments indicated that >85% of the phospholipase activities were cell-associated, with LPL and LPTA being more easily released than PLB. At pH 5.5 and 7.0, the heat-inactivated secreted enzyme preparations decreased the viability of human neutrophils. This effect was attenuated by active supernates. The relative activities of the PLB, LPL and LPTA in the environment of neutrophils are likely to determine the fate of these cells in vivo. Both phospholipases and heat-stable substances secreted by C. neoformans at 37 degrees C could contribute to membrane degradation and virulence.