  The line generated by two distinct points, $x$ and $y$, in a finite metric
space $M=(V,d)$, denoted by $\overline{xy}^M$, is the set of points given by
$$\overline{xy}^M:=\{z\in V: d(x,y)=|d(x,z)\pm d(z,y)|\}.$$ A 2-set $\{x,y\}$
such that $\overline{xy}^M=V$ is called a universal pair and its associated
line a universal line.
  Chen and Chv\'atal conjectured that in any finite metric space either there
is a universal line or there are at least $|V|$ different (non-universal)
lines. Chv\'atal proved that this is indeed the case when the metric space has
distances in the set $\{0,1,2\}$.
  Aboulker et al. proposed the following strengthening for Chen and Chv\'atal
conjecture in the context of metric spaces induced by finite graphs. The number
of lines plus the number of universal pairs is at least the number of point of
the space.
  In this work we first prove that metric spaces with distances in the set
$\{0,1,2\}$ satisfy this stronger conjecture. We also prove that for metric
spaces induced by bipartite graphs the number of lines plus the number of
bridges of the graph is at least the number its vertices, unless the graph is
$C_4$ or $K_{2,3}$.
