The Intracellular Survival and Growth of Gonococci in Human Phagocytes

Abstract

In a reassessment of previous tests for intracellular survival, results have been confirmed and additional evidence obtained indicating that some gonococci can survive and multiply in human phagocytes. Use was made of the ability of penicillin to penetrate phagocytes and to kill only actively growing organisms. In microscopic counts on 33 urethral exudate smears, an average of 49 % of gonococci were associated with polymorphonuclear phagocytes. The organisms were unevenly distributed amongst the phagocytes, with most cells uninfected and some containing large numbers. Many phagocytes also remained uninfected in tests in vitro with low gonococcal inocula although experiments with large inocula showed that most phagocytes could ingest gonococci. It is proposed that ingestion of one gonococcus may stimulate the phagocytes to take up more. Phagocytes were killed and disintegrated after ingesting large numbers of gonococci and a similar effect in vivo may be responsible for the large clumps of organisms seen in urethral exudate. These results underline the probable importance in the pathogenesis of gonorrhoea of intracellular survival in phagocytes.

Demonstration of Intracellular Growth of Gonococci in Human Phagocytes using Spectinomycin to Kill Extracellular Organisms

“…At higher penicillin concentrations there was substantial killing of intracellular organisms by penetration of the antibiotic into the phagocytes , as has been noted in phagocytosis tests with other bacteria and antibiotics (Patterson & Youmans, 1970;Frost et al, 1972;Hart, 1973;Cole & Brostoff, 1975). Even with 0-4pg penicillin ml-l some antibiotic apparently penetrated the phagocytes and the numbers of viable intracellular gonococci found after 4 to 6 h incubation were usually low (Veale et al, , 1979. However, these intracellular gonococci appeared to be growing, since they were killed by the addition of high concentrations of penicillin after 4 h incubation with lower concentrations (Veale et al, 1979); penicillin kills only growing organisms (Ghuysen, 1977), a property used recently in the demonstration of intracellular multiplication of Salmonella typhimuriurn (Lowrie et al, 1979).…”

“…gonorrhoea are associated with polymorphonuclear (PMN) phagocytes (Veale et al, 1979). Electron microscopic observations suggest that the majority of gonococci associated with PMN phagocytes are intracellular and that, judged morphologically, some of them are capable of surviving and dividing (Ward et al, 1972;Farzadegan & Roth, 1975;Novotny et al, 1975;Ovchinnikov et al, 1976).…”

“…Even with 0-4pg penicillin ml-l some antibiotic apparently penetrated the phagocytes and the numbers of viable intracellular gonococci found after 4 to 6 h incubation were usually low (Veale et al, , 1979. However, these intracellular gonococci appeared to be growing, since they were killed by the addition of high concentrations of penicillin after 4 h incubation with lower concentrations (Veale et al, 1979); penicillin kills only growing organisms (Ghuysen, 1977), a property used recently in the demonstration of intracellular multiplication of Salmonella typhimuriurn (Lowrie et al, 1979). Gonococci and phagocytes were mixed in a ratio of 20: 1 (expts 1 and 4) or 40: 1 (expts 2,3 and 5).…”

“…Until now, the most effective bactericidal medium for studying gonococcal survival in human phagocytes has been a mixture of penicillin (at low concentration; 0.2 to 0.4 pg ml-l) and fresh human serum; survival of gonococci for up to 15 h in human peripheral blood PMN phagocytes was demonstrated using this mixture (Veale et al, , 1979Witt et al, 1976). At higher penicillin concentrations there was substantial killing of intracellular organisms by penetration of the antibiotic into the phagocytes , as has been noted in phagocytosis tests with other bacteria and antibiotics (Patterson & Youmans, 1970;Frost et al, 1972;Hart, 1973;Cole & Brostoff, 1975).…”

“…In some tubes, the deposits were not incubated in medium containing spectinomycin but with penicillin (0.4 pg n1l-l) as used previously (Veale et al, 1979); the viable counts found in the phagocyte deposits after 6 h incubation (without extra addition of penicillin at 4 h) in experiments 1 , 2, 3, 4 and 5 were 5 ( < 2), 420 (< 2), 2200 ( c 2), < 2 ( < 2) and 85 ( < 2), respectively.…”