Is Klebsiella pneumoniae found in the throat of healthy people?
Klebsiella species, including pneumoniae, are normal members of the healthy human oral microbiome.
Saliva microbiomes from 6 healthy adults were analyzed by 16S sequencing over a starvation timecourse, where oral microbes were cultured in minimal medium (PBS or 1:1 PBS:cell-free saliva). Figure 1 shows that the genus Klebsiella is initially low abundance in the healthy oral microbiome, but the proportion of Klebsiella increases over the starvation timecourse in the two media tested. An excerpt from the results:
At day 1, several species of Streptococcus were recovered, as were Gamella sanguinis, Klebsiella pneumoniae, and Klebsiella oxytoca. At day 20, K. pneumoniae, K. oxytoca, Enterobacter homaechei, and Providencia alcalifaciens were the only recoverable species. Finally, at day 84 and day 100, only K. pneumoniae and P. alcalifaciens were recoverable under the conditions tested
Given the proximity of the mouth to the throat, I think it's fair to say that K. pneumoniae is likely a member of the healthy human throat.
If that's not convincing, you can check the supplemental data from this paper, which looked at 16S data associated with throat tissue samples from 29 patients with laryngeal carcinoma and 31 control patients with vocal cord polyps. Looking at the relative abundance of different phyla, they found that Proteobacteria (the phylum containing the genus Klebsiella) accounts for 11% of the recovered 16S reads on average for all patients (range 0–67.1%). The authors claim to have recovered 218 genera and >3000 unique OTUs at 97% similarity, though they only report the ~30 most abundant genera in their differential abundance analyses, and it doesn't look like they included the full dataset in this publication.