Gram staining of the sample may demonstrate bacteria in bacterial meningitis, but absence of bacteria does not exclude bacterial meningitis as they are only seen in 60% of cases; this figure is reduced by a further 20% if antibiotics were administered before the sample was taken.
Bojenje po Gramu uzorka može dokazati prisustvo bakterija u bakterijskom meningitisu, ali nedokazivanje bakterija ne isključuje da se radi o bakterijskom meningitisu, jer se one vide u samo 60 % slučajeva; ovaj se postotak smanjuje za dodatnih 20 % u slučajevima primjene antibiotika prije izvođenja lumbalne punkcije.