From the Intergalactic Journal of Biology and Mechanics
During the solar cycle of 14456, a replication study was conducted by our scientists at the Intergalactic Congress Laboratory. The study attempted to replicate an experiment from a previously published human study. The results were a conclusive replication indicating that the human mouth contains up to 200 species of microorganisms at a concentration of 1,000 to 1 billion on each dental protrusion (tooth).
Despite their out world classification as a class A-1 predator, on their own planet, they meet a low classification of a D-8 predator or a B-2 when factoring in their intelligence. For this reason, on their own planet, the humans are not considered to be venomous despite the need for immediate hospitalization upon receiving a bite from their own species.
Off planet, their nature as an A-1 apex predator gives them a subclass of a G-6 venom predator. Though their saliva is not dangerous when in contact with open skin or carapace, immediate medical attention is required if bitten or spit on. Areas of danger include the eyes nose mouth or any other orifice that allows access to the nervous system.
Additional literature on the subject indicates that bacterial presence is used as a catalyst for breaking down food in the mouth. Other bacteria exists within the gut to help with food processing. Without bacterial assistance, food processing would be almost impossible for a human. The nature of this mutualism inoculates the human against most off-world diseases.
A cautionary note: Species from the Gamma four sector are advised to keep clear of humans altogether as they are particularly susceptible to human venom*.+
*All non-human species are advised to avoid calling humans "Venomous" as it may be seen as an insult. Humans do not see themselves as a particular danger to others in this way.
***
At any other time, Krill might have been worried about their present predicament, but after months of shenanigans with the humans including almost dying more than once, the situation they were in now was almost laughable.
Once again human reckless stupidity had brought them to their knees before an angry group of Burg. Perhaps they would have made it out alive if the "sass" of the Captain hadn't inadvertently offended the leader of the ship; an offense, which punishment was immediate execution.
On their knees, the humans were almost as tall as the Burg, though of course the Burg were Octapeds, and would likely tower over the humans if they stood on their back-most set of legs.
"Ready yourself for your demise, Human." The Burg commander clicked through his quadra-segment mouth a sheen of base slime glittering over his body
The Captain raised an eyebrow, "Come on, I didn't mean it like that. In fact, ugly scorpion is a term of endearment on my planet."
With a roar, the Burg commander scuttled closer pincers clicking right in front of the human's face shining points ominously close to his one remaining eye. The human blinked and leaned back in a very unsettled sort of way. Despite this, Krill still saw the reaction as understated. He had death literally two inches from his face and he seemed more disturbed by the thing's segmented mouth than his own imminent doom.
"Ready the weapons!" the Burg called out. Beneath him, a light dusting of slime glistened in the low lighting. The entire ship smelled painfully sterile. Out of the corner of his eye, Krill could see the humans wincing as the smell assaulted their noses.
"I don't think you want to do that." The captain interjected as plasma rays were aimed towards his head.
The Burg gave a clicking laugh, "You are hardly in a place to be making threats."
"Oh really," Krill had spent enough time with the humans to know when they were bluffing, and the Captain was getting ready for a big whopper of a lie. Why he thought that would work mystified Krill, but he said nothing content with watching the horror unfold from a distance.
"Do you even know what a human is?" The man asked ominously
The commander laughed, "I do not care."
"Well, you should." The human shot back, "If you knew what we were capable of you would run screaming from this place."
"And why is that?" The creature asked in amusement
"Because, if I chose to, I could snap these chains with my bare hands and throttle you with them."
The creature laughed, but Krill kept silent. He sort of doubted that claim, but it honestly wouldn't surprise him if that was true.
"Than do it. If you can break the chains then do it, and take your freedom." When nothing happened, the creature gave a chuckle mandibles clicking in amusement.
"I am going to enjoy this, and once you're dead, I'm going to take my time with the rest of your crew. I am going to rip them to pieces bit by bit and sing along with their screams of agony.
Mistake.
Krill winced shrinking back as he watched the human's eyes narrow in rage.
The creature let off another clicking laugh, and then a terrible scream. Krill yelped in horror unsure what was happening as the group of creatures rushed in to help their commander who was on the ground underneath the captain's knees.
The man's teeth had torn a piece of carapace from the creature's shoulder.
As he was pulled away saliva and slime coated his chin and neck.
Where the saliva and slime made contact steam fizzed into the air.
The Commander once silent was now crying out in pain scratching at his torn carapace with terrifying fervor. Steam blasted from the slime-producing pours under his carapace as the slightly acidic human saliva met the base slime of the creature.
"IT BURNS!" He screamed. The steam was fading away now, and the spot was beginning to turn red.
Even the captain seemed surprised as the creature thrashed around on the floor its pinkish flesh growing redder and redder by the moment.
Whatever it was, it was spreading.
Even the Captain looked slightly surprised as the creature thrashed before him.
In acts of anger, the rest of the crew turned to face their weapons leveled. They kept at a distance. Whatever the human had done, it couldn't reach them here.
In an act of what must have been defiance or sheer dumb luck, one of the humans spit at the closest soldiers. Whatever it was, it happened to be a pretty good shot striking the creature in the face who immediately reared back roaring in pain as steam rolled off his carapace.
Looking back down at the commander, the redness had spread under his other plates which were even now beginning to wilt and blacken. Steam rose from his skin.
The captain backed away in shock eyes wide.
One of the other humans had appropriated a plasma weapon from the thrashing commander and shot the chains loose releasing the humans who made a point of growling at anyone who got too close retreating from the ship quickly.
The virulent reaction of the saliva was enough of a concern that, once the Intergalactic Assembly had caught wind, they demanded the humans be placed into quarantine as the ICDC examined the site. While conclusions were still being formed about what had happened, the running theory was that the slightly acidic nature of the human's saliva had reacted with the basic nature of the protective slime rendering it functionless as a protective agent. The bacteria were then able to slip in through the pores under the creature's armor and spread rapidly through its nervous system. It was unknown at this point why the bacteria had been so fast-acting, but it was theorized the structures of the human's versus the Burg somehow accommodated the spread of bacterial infection.
The eyes, requiring the basic slime to function had had their functioning burned away and allowed infections to set straight into the brain.
The Intergalactic council ruled the incident self-defense and mitigated other charges as the human had not known what the reaction would be.
However, from that day on, a law was set in place determining that human spitting at someone be a class one Felony charge, or in certain cases, attempted murder, while other precautions were put in place forcing human inmates to wear spit shields when placed into custody.
Despite themselves, the humans found the entire thing funny, never had they assumed another species would consider them venomous.
It was only bacteria after all, and venom and bacteria aren't the same things.